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Sample records for optical spacer layers

  1. Investigation of optical spacer layers from solution based precursors for polymer solar cells using X-ray reflectometry

    DEFF Research Database (Denmark)

    Andersen, Philip Hvidthøft Delff; Skårhøj, Jakob; Andreasen, Jens Wenzel

    2009-01-01

    Optical spacer layers based on titaniumalkoxide precursor solutions were prepared by spin-coating on top of bulk heterojunction layers based on poly-3-hexylthiophene (P3HT) and phenyl-C61-butyric acid methylester (PCBM). Models and experiment have shown that the performance of polymer solar cells...

  2. Stable inverted small molecular organic solar cells using a p-doped optical spacer.

    Science.gov (United States)

    Lee, Sang-Hoon; Seo, Ji-Won; Lee, Jung-Yong

    2015-01-07

    We report inverted small molecular organic solar cells using a doped window layer as an optical spacer. The optical spacer was used to shift the optical field distribution inside the active layers, generating more charge carriers from sunlight. In this report, N,N,N',N'-tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD) was doped with 2,2-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ), a p-type dopant material. P-doped MeO-TPD was adopted as an optical spacer because it has a large energy band gap, and its conductivity can be increased by several orders of magnitude through a doping process. As a result, a power conversion efficiency of 4.15% was achieved with the doped window layer of optimized thickness. Lastly, we present significantly improved stability of the inverted devices with the MeO-TPD layer.

  3. Solution-processed organic tandem solar cells with embedded optical spacers

    NARCIS (Netherlands)

    Hadipour, Afshin; de Boer, Bert; Blom, Paul W. M.

    2007-01-01

    We demonstrate a solution-processed polymer tandem solar cell in which the two photoactive single cells are separated by an optical spacer. The use of an optical spacer allows for an independent optimization of both the electronic and optical properties of the tandem cell. The optical transmission

  4. Very strong antiferromagnetic interlayer exchange coupling with iridium spacer layer for perpendicular magnetic tunnel junctions

    Science.gov (United States)

    Yakushiji, Kay; Sugihara, Atsushi; Fukushima, Akio; Kubota, Hitoshi; Yuasa, Shinji

    2017-02-01

    We systematically studied the interlayer exchange coupling (IEC) in a perpendicular synthetic antiferromagnetically coupled structure having an Ir spacer layer for perpendicular magnetic tunnel junctions (p-MTJs). We found a broader peak in IEC energy density (Jex) versus spacer thickness (tIr) compared with the case of using a Ru spacer. The highest IEC energy density was 2.6 erg/cm2 at a tIr of about 5 nm. The p-MTJ nanopillars had a high magnetoresistance ratio (131%) as well as a high spin-transfer torque (STT) switching efficiency (about 2). An Ir spacer can be used to make a stable reference layer for STT magnetoresistive random access memory.

  5. Improvement in the Photocurrent of Inverted Organic Solar Cells Using MoO(x)-Doped TAPC as a P-Type Optical Spacer.

    Science.gov (United States)

    Song, Jiyun; Song, Hyung-Jun; Kim, Jun Young; Lee, Yeonkyung; Park, Myeongjin; Kwon, Yongwon; Ko, Youngjun; Lee, Changhee

    2016-05-01

    In this work, we demonstrate enhancement in the short-circuit current of inverted organic photovoltaic cells (OPVs) using a p-type optical spacer. The p-type optical spacer, which consists of molybdenum oxide (MoO(x))-doped 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), shows improved transmittance at visible light with high electrical conductivity. The electrical field distribution of incident light at the active layer of OPVs can be controlled by tuning the thickness of the optical spacer in the OPVs. Specifically, the incorporation of the 20-nm optical spacer layer in the OPV leads to enhanced spectral response of the device in the wavelength range of 400-600 nm, which is consistent with the combined results of improved optical absorption and better charge transport characteristics. As a result, the OPV with a 20-nm p-type optical spacer shows improvement in the short-circuit current compared with a device with 10 nm of embedded MoO(x).

  6. Effect of spacer layer on the magnetization dynamics of permalloy/rare-earth/permalloy trilayers

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Chen, E-mail: ronanluochen@gmail.com; Yin, Yuli; Zhang, Dong; Jiang, Sheng; Yue, Jinjin; Zhai, Ya, E-mail: yazhai@seu.edu.cn [Physics Department, Southeast University, Nanjing 211189 (China); Du, Jun; Zhai, Hongru [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-05-07

    The permalloy/rare-earth/permalloy trilayers with different types (Gd and Nd) and thicknesses of spacer layer are investigated using frequency dependence of ferromagnetic resonance (FMR) measurements at room temperature, which shows different behaviors with different rare earth spacer layers. By fitting the frequency dependence of the FMR resonance field and linewidth, we find that the in-plane uniaxial anisotropy retains its value for all samples, the perpendicular anisotropy remains almost unchanged for different thickness of Gd layer but the values are tailored by different thicknesses of Nd layer. The Gilbert damping is almost unchanged with different thicknesses of Gd; however, the Gilbert damping is significantly enhanced from 8.4×10{sup −3} to 20.1×10{sup −3} with 6 nm of Nd and then flatten out when the Nd thickness rises above 6 nm.

  7. Effect of the spacer group nature on the optical and electrical properties of confined poly( p-phenylene vinylene) derivatives

    Science.gov (United States)

    Benzarti-Ghédira, Maha; Zahou, Imen; Hrichi, Haikel; Jaballah, Nejmeddine; Ben Chaâbane, Rafik; Majdoub, Mustapha; Ben Ouada, Hafedh

    2015-09-01

    This study is an investigation about the effect of chemical modification on the morphological, optical and electrical properties of semiconducting organic thin films. Two confined poly( p-phenylene vinylene) (PPV)-type polymers containing different spacer groups were studied: P1 has an isopropylidene spacer group and P2 with hexafluoroisopropylidene spacer. The UV-Vis absorption and PL analysis showed a stronger π- π interaction in the P1 film; in P2, the π-stacking is limited by the introduction of a bulky trifluoromethyl (CF3) groups on the spacer units. The P2 exhibits a better film quality as illustrated by the atomic force microscopy. The HOMO and LUMO energy levels and electrochemical band gap of the polymers were determinate by the cyclic voltammetry. The electrical properties of ITO/PPV derivative/Al diodes were investigated by means of current-voltage and show a space-charge-limited current conduction mechanism with higher mobility in the P2 thin layer. The impedance spectra of the devices can be discussed in terms of an equivalent circuit model designed as a parallel resistance ( R p) and capacitance ( C p) network in series with a resistance.

  8. Visible light dynamical diffraction in a 1-D photonic crystal-based interferometer with an extremely thin spacer layer

    Science.gov (United States)

    Prudnikov, I. R.

    2016-01-01

    Properties of light diffraction in a Fabry-Pérot-like interferometer composed of two 1-D photonic crystals and a nanometer-thick spacer layer are analytically investigated. It is shown that the resonant enhancement of light wave intensity in such a layer is possible because of light dynamical diffraction from the photonic crystals of the interferometer. Numerical simulations of (i) light reflectivity and transmittance curves of the interferometer having an ultra-thin spacer layer (its thickness changes from less than 1 nm to about 10 nm) and (ii) the resonant distribution of the light wave intensity in the vicinity of the layer are performed. Based on the numerical simulations, potentialities for the determination of the structural parameters (e.g., thicknesses and refraction indexes) of ultra-thin spacer films are discussed. A difference is found to appear in resonant intensity enhancements inside the ultra-thin spacer layers between s- and p-polarized light waves.

  9. Graphene as a spacer to layer-by-layer assemble electrochemically functionalized nanostructures for molecular bioelectronic devices.

    Science.gov (United States)

    Wang, Xiang; Wang, Jingfang; Cheng, Hanjun; Yu, Ping; Ye, Jianshan; Mao, Lanqun

    2011-09-06

    This study demonstrates the capability of graphene as a spacer to form electrochemically functionalized multilayered nanostructures onto electrodes in a controllable manner through layer-by-layer (LBL) chemistry. Methylene green (MG) and positively charged methylimidazolium-functionalized multiwalled carbon nanotubes (MWNTs) were used as examples of electroactive species and electrochemically useful components for the assembly, respectively. By using graphene as the spacer, the multilayered nanostructures of graphene/MG and graphene/MWNT could be readily formed onto electrodes with the LBL method on the basis of the electrostatic and/or π-π interaction(s) between graphene and the electrochemically useful components. Scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-vis), and cyclic voltammetry (CV) were used to characterize the assembly processes, and the results revealed that nanostructure assembly was uniform and effective with graphene as the spacer. Electrochemical studies demonstrate that the assembled nanostructures possess excellent electrochemical properties and electrocatalytic activity toward the oxidation of NADH and could thus be used as electronic transducers for bioelectronic devices. This potential was further demonstrated by using an alcohol dehydrogenase-based electrochemical biosensor and glucose dehydrogenase-based glucose/O(2) biofuel cell as typical examples. This study offers a simple route to the controllable formation of graphene-based electrochemically functionalized nanostructures that can be used for the development of molecular bioelectronic devices such as biosensors and biofuel cells.

  10. 3D laser inspection of fuel assembly grid spacers for nuclear reactors based on diffractive optical elements

    Science.gov (United States)

    Finogenov, L. V.; Lemeshko, Yu A.; Zav'yalov, P. S.; Chugui, Yu V.

    2007-06-01

    Ensuring the safety and high operation reliability of nuclear reactors takes 100% inspection of geometrical parameters of fuel assemblies, which include the grid spacers performed as a cellular structure with fuel elements. The required grid spacer geometry of assembly in the transverse and longitudinal cross sections is extremely important for maintaining the necessary heat regime. A universal method for 3D grid spacer inspection using a diffractive optical element (DOE), which generates as the structural illumination a multiple-ring pattern on the inner surface of a grid spacer cell, is investigated. Using some DOEs one can inspect the nomenclature of all produced grids. A special objective has been developed for forming the inner surface cell image. The problems of diffractive elements synthesis, projecting optics calculation, adjusting methods as well as calibration of the experimental measuring system are considered. The algorithms for image processing for different constructive elements of grids (cell, channel hole, outer grid spacer rim) and the experimental results are presented.

  11. The effects of strain and spacer layer in CdSe/CdS/ZnS and CdSe/ZnS/CdS core/shell quantum dots

    Science.gov (United States)

    Pisheh, Hadi S.; Gheshlaghi, Negar; Ünlü, Hilmi

    2017-01-01

    The effects of lattice mismatch induced interface strain on the structural, optical and dielectric properties of CdSe based Cd(Zn)S shell and Cd(Zn)S/Zn(Cd)S multishell quantum dots (QDs) is studied. Introducing Zn(Cd)S spacer layer to the CdSe/Cd(Zn)S core/shell structure is found to influence induced interfacial strain through changing the lattice parameter, band gap and band offset of core/shell nanostructure. Lattice parameter of spacer layer affected by outer shell, changes the interface strain in the core region. Theoretically obtained strain in the core/shell(multishell) is used in the effective mass approximation (EMA) to determine the capped core diameter. We show that introducing ZnS spacer layer to the CdSe/CdS core/shell QDs rises the amount of strain and cause more decrease in the core size in CdSe/ZnS/CdS. Furthermore, CdS sandwiched between CdSe/ZnS decreases the amount of strain in crystal and suppresses the size decrease of the core in the CdSe/ZnS. Good agreement is found between the strain included EMA core size predictions in core/shell and multishell and observed size image from transmission electron microscopy (TEM) measurements of bare CdSe core nanocrystals.

  12. Controlling the exciton emission of gold coated GaAs-AlGaAs core-shell nanowires with an organic spacer layer

    Science.gov (United States)

    Kaveh, M.; Gao, Q.; Jagadish, C.; Ge, J.; Duscher, G.; Wagner, H. P.

    2016-12-01

    Excitons are the most prominent optical excitations and controlling their emission is an important step towards new optical devices. We have investigated the exciton emission from uncoated and gold/aluminum quinoline (Alq3) coated GaAs-AlGaAs-GaAs core-shell nanowires (NWs) using temperature-, intensity- and polarization dependent photoluminescence (PL). Plasmonic GaAs-AlGaAs-GaAs NWs with a ˜10 nm thick Au coating but without an Alq3 spacer layer reveal a significant reduction of the PL intensity of the exciton emission compared with the uncoated NW sample. Plasmonic NW samples with the same nominal Au coverage and an additional Alq3 interlayer of 3 or 6 nm thickness show a clearly stronger PL intensity which increases with rising Alq3 spacer thickness. Time-resolved (TR) PL measurements reveal an increase of the exciton decay rate by a factor of up to two with decreasing Alq3 spacer thickness suggesting the presence of Förster energy transfer from NW excitons to plasmon oscillations in the gold film. The weak change of the decay time, however, indicates that Förster energy-transfer is only partially responsible for the PL quenching in the gold coated NWs. The main reason for the reduction of the PL emission is attributed to a gold induced band-bending in the GaAs NW core which causes exciton dissociation. With increasing Alq3 spacer thickness the band-bending decreases leading to a reduction of the exciton dissociation and PL quenching. Our interpretation is supported by electron energy loss spectroscopy measurements which show a signal reduction and blue shift of defect (possibly EL2) transitions when gold particles are deposited on NWs compared with bare or Alq3 coated NWs.

  13. A More Uniform Electric Field Distribution on Surge Arresters through the Optimal Design of Spacer and Fiber Glass Layer

    Directory of Open Access Journals (Sweden)

    M.R. Aghaebrahimi

    2013-04-01

    Full Text Available In this study, the optimal design of spacers and fiber glass layer of a metal oxide surge arrester is presented in order to achieve a more uniform electric field distribution, inside and outside the arrester. This is done by using intelligent algorithms and numerical analysis, i.e., Finite Element Method (FEM. The introduced method can be used in order to determine the optimal dimensions of spacers and fiber glass layer so that the electric field distribution is optimized and the lifetime of highly stressed ZnO blocks in the vicinity of HV electrode is increased. In order to verify the results, Differential Evolution (DE and Particle Swarm Optimization (PSO algorithms are used.

  14. Effect of inter-layer strain interaction on the optical properties of Ge/Si(001) island multi-layers

    Institute of Scientific and Technical Information of China (English)

    M. De Seta; G. Capellini; F. Evangelieti; C. Ferrari; L. Lazzarini; G. Salviati; R. W. Peng; S. S.Jiang

    2007-01-01

    In this paper we present a study on the influence of the number and the thickness of silicon spacer layer on the optical properties of single- and multi-layers of self assembled Ge/Si (001) islands performed by means of cathodoluminescence spectroscopy, high resolution X-ray diffraction and transmission electron microscopy. In single-layer sample, we do not evidence dependence of the island no-phonon emission peak position on the silicon cap-layer thickness. In multi-layer samples having a thin (33 nm) silicon spacer layer the no-phonon emission energyvalue progressively blue-shifts for an increasing number of island layers. This is interpreted as an enhanced intermixing driven by the strain interaction existing between island layers. On the contrary, island emission energy position is independent on the number of layers in the sample series having a thicker spacer layer (60 nm). These findings are consistent with the X-ray diffraction observation that islands belonging to different layers have the same composition. As a consequence we can conclude that multilayers with 60-nm spaced islands layer are more homogeneous and ordered.

  15. Low temperature tunneling magnetoresistance on (La,Sr)MnO3/Co junctions with organic spacer layers

    Science.gov (United States)

    Vinzelberg, H.; Schumann, J.; Elefant, D.; Gangineni, R. B.; Thomas, J.; Büchner, B.

    2008-05-01

    This paper concerns with giant magnetoresistance (MR) effects in organic spin valves, which are realized as layered (La,Sr)MnO3 (LSMO)-based junctions with tris-(8, hydroxyquinoline) aluminum (Alq3)-spacer and ferromagnetic top layers. The experimental work was focused on the understanding of the transport behavior in this type of magnetic switching elements. The device preparation was carried out in an ultrahigh vacuum chamber equipped with a mask changer by evaporation and sputtering on SrTiO3 substrates with LSMO stripes deposited by pulsed laser technique. The field and temperature dependences of the MR of the prepared elements are studied. Spin-valve effects at 4.2K have been observed in a broad resistance interval from 50Ω to MΩ range, however, without systematic dependence on spacer layer thickness and device area. In some samples, the MR changes sign as a function of the bias voltage. The observed similarity in the bias voltages dependences of the MR in comparison with conventional magnetic tunnel junctions with oxide barriers suggests a description of the found effects within the classical tunneling concept. This assumption is also confirmed by a similar switching behavior observed on ferromagnetically contacted carbon nanotube devices. The proposed model implies the realization of the transport via local Co chains embedded in the Alq3 layer and spin dependent tunneling over barriers at the interface Co grains/Alq3/LSMO. The existence of conducting Co chains within the organics is supported by transmission electron microscopic/electron energy loss spectroscopic studies on cross-sectional samples from analogous layer stacks.

  16. Mapping bound plasmon propagation on a nanoscale stripe waveguide using quantum dots: influence of spacer layer thickness

    Directory of Open Access Journals (Sweden)

    Chamanei S. Perera

    2015-10-01

    Full Text Available In this paper we image the highly confined long range plasmons of a nanoscale metal stripe waveguide using quantum emitters. Plasmons were excited using a highly focused 633 nm laser beam and a specially designed grating structure to provide stronger incoupling to the desired mode. A homogeneous thin layer of quantum dots was used to image the near field intensity of the propagating plasmons on the waveguide. We observed that the photoluminescence is quenched when the QD to metal surface distance is less than 10 nm. The optimised spacer layer thickness for the stripe waveguides was found to be around 20 nm. Authors believe that the findings of this paper prove beneficial for the development of plasmonic devices utilising stripe waveguides.

  17. Optical modulator including grapene

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ming; Yin, Xiaobo; Zhang, Xiang

    2016-06-07

    The present invention provides for a one or more layer graphene optical modulator. In a first exemplary embodiment the optical modulator includes an optical waveguide, a nanoscale oxide spacer adjacent to a working region of the waveguide, and a monolayer graphene sheet adjacent to the spacer. In a second exemplary embodiment, the optical modulator includes at least one pair of active media, where the pair includes an oxide spacer, a first monolayer graphene sheet adjacent to a first side of the spacer, and a second monolayer graphene sheet adjacent to a second side of the spacer, and at least one optical waveguide adjacent to the pair.

  18. Cross-layer design in optical networks

    CERN Document Server

    Brandt-Pearce, Maïté; Demeester, Piet; Saradhi, Chava

    2013-01-01

    Optical networks have become an integral part of the communications infrastructure needed to support society’s demand for high-speed connectivity.  Cross-Layer Design in Optical Networks addresses topics in optical network design and analysis with a focus on physical-layer impairment awareness and network layer service requirements, essential for the implementation and management of robust scalable networks.  The cross-layer treatment includes bottom-up impacts of the physical and lambda layers, such as dispersion, noise, nonlinearity, crosstalk, dense wavelength packing, and wavelength line rates, as well as top-down approaches to handle physical-layer impairments and service requirements.

  19. Use of optical spacers to enhance infrared Mueller ellipsometry sensitivity: application to the characterization of organic thin films.

    Science.gov (United States)

    Ndong, Gerald; Lizana, Angel; Garcia-Caurel, Enric; Paret, Valerie; Melizzi, Géraldine; Cattelan, Denis; Pelissier, Bernard; Tortai, Jean-Hervé

    2016-04-20

    Mueller ellipsometry in the mid-infrared (IR) spectral range can be used to obtain information about chemical composition through the vibrational spectra of samples. In the case of very thin films (thin film made of a known material which is between the substrate and the layer of interest. We show that, when the thickness of the two layers fulfills a given condition, the spectral features due to vibrational absorptions are enhanced. We explain the enhancement effect in terms of the Airy formula. The theoretical discussion is illustrated with two examples. We analyzed polystyrene thin films deposited on silicon wafers. Some of the wafers were covered by a thin film of thermal silicon dioxide (SiO2), which was used as a spacer. The results show the suitability of the proposed technique to overcome the lack of sensitivity in ellipsometric measurements when it comes to working with either very thin films or materials with low absorption.

  20. Asymmetric underlap spacer layer enabled nanoscale double gate MOSFETs for design of ultra-wideband cascode amplifiers

    Science.gov (United States)

    Roy, Debapriya; Biswas, Abhijit

    2017-10-01

    Using extensive numerical analysis we investigate effects of asymmetric sidewall spacers on various device parameters of 20-nm double gate MOSFETs associated with analog/RF applications. Our studies show that the device with underlap drain-side spacer length LED of 10 nm and source-side spacer length LES of 5 nm shows improvement in terms of the peak value of transconductance efficiency, voltage gain Av, unity-gain cut-off frequency fT and maximum frequency of oscillations fMAX by 8.6%, 51.7%, 5% and 10.3%, respectively compared to the symmetric 5 nm underlap spacer device with HfO2 spacer of dielectric constant k = 22. Additionally, a higher spacer dielectric constant increases the peak Av while decreasing both peak fT and fMAX. The detailed physical insight is exploited to design a cascode amplifier which yields an ultra-wide gain bandwidth of 2.48 THz at LED = 10 nm with a SiO2 spacer.

  1. In-situ biofouling assessment in spacer filled channels using optical coherence tomography (OCT): 3D biofilm thickness mapping

    KAUST Repository

    Fortunato, Luca

    2017-01-13

    Membrane systems for water purification can be seriously hampered by biofouling. The use of optical coherence tomography (OCT) to investigate biofilms in membrane systems has recently increased due to the ability to do the characterization in-situ and non-destructively The OCT biofilm thickness map is presented for the first time as a tool to assess biofilm spatial distribution on a surface. The map allows the visualization and evaluation of the biofilm formation and growth in membrane filtration systems through the use of a false color scale. The biofilm development was monitored with OCT to evaluate the suitability of the proposed approach. A 3D time series analysis of biofilm development in a spacer filled channel representative of a spiral-wound membrane element was performed. The biofilm thickness map enables the time-resolved and spatial-resolved evaluation and visualization of the biofilm deposition pattern in-situ non-destructively.

  2. Effect of Ti seed and spacer layers on structure and magnetic properties of FeNi thin films and FeNi-based multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Svalov, A.V., E-mail: andrey.svalov@ehu.es [Departamento de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), 48080 Bilbao (Spain); Department of Magnetism and Magnetic Nanomaterials, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Larrañaga, A. [SGIker, Servicios Generales de Investigación, Universidad del País Vasco (UPV/EHU), 48080 Bilbao (Spain); Kurlyandskaya, G.V. [Departamento de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), 48080 Bilbao (Spain); Department of Magnetism and Magnetic Nanomaterials, Ural Federal University, 620002 Ekaterinburg (Russian Federation)

    2014-10-15

    Highlights: • Fe{sub 19}Ni{sub 81} films and FeNi-based multilayers were prepared by magnetron sputtering. • The samples were deposited onto glass substrates at room temperature. • Ti/FeNi films exhibit good (1 1 1) texture and crystallinity. • The thick Cu seed increases the coercive force of the magnetic layer. • The thin Ti spacer restores the magnetic softness of the Cu/Ti/FeNi multilayers. - Abstract: The microstructure and magnetic properties of sputtered permalloy films and FeNi-based multilayers prepared by magnetron sputtering have been studied. X-ray diffraction measurements indicate that Ti/FeNi films exhibit good (1 1 1) texture and crystallinity. Ti/FeNi bilayers with high crystallographic quality have relatively low resistivity. The Ti seed layer does not influence the magnetic properties of FeNi film in Ti/FeNi bilayers, but the thick Cu seed layer leads to an increase of the coercive force of the magnetic layer. For the FeNi films deposited on thick Cu seed layer, the (0 1 0) and (0 0 2) diffraction peaks of hcp nickel were clearly observed. The thin Ti spacer between Cu and FeNi layers prevents the formation of the nickel phase and restores the magnetic softness of the FeNi layer in the Cu/Ti/FeNi sample. Obtained results can be important for the development of multilayer sensitive elements for giant magnetoimpedance or magnetoresistance detectors.

  3. Transverse optical plasmons in layered superconductors.

    NARCIS (Netherlands)

    vanderMarel, D; Tsvetkov, A

    1996-01-01

    We discuss the possible existance of transverse optical plasma modes in superlattices consisting of Josephson coupled superconducting layers. These modes appear as resonances in the current-current correlation function, as opposed to the usual plasmons which are poles in the density-density channel.

  4. Nonlinear optical properties of ultrathin metal layers

    DEFF Research Database (Denmark)

    Lysenko, Oleg

    2016-01-01

    . The optical characterization of the plasmonic waveguides is performed using femtosecond and picosecond optical pulses. Two nonlinear optical effects in the strip plasmonic waveguides are experimentally observed and reported. The first effect is the nonlinear power transmission of the plasmonic mode......-order nonlinear susceptibility of the plasmonic mode in the gold strip waveguides significantly depends on the metal layer thickness and laser pulse duration. This dependence is explained in detail in terms of the free-electron temporal dynamics in gold. The third-order nonlinear susceptibility of the gold layer...... duration dependence of the third-order nonlinear susceptibility of gold is calculated in the broad range from tens of femtoseconds to tens of picoseconds using the two-temperature model of the free-electron temporal dynamics of gold, and shows the saturation of the thirdorder nonlinear susceptibility...

  5. Optical modulators with 2D layered materials

    Science.gov (United States)

    Sun, Zhipei; Martinez, Amos; Wang, Feng

    2016-04-01

    Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that 2D layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this Review, we cover the state of the art of optical modulators based on 2D materials, including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as 2D heterostructures, plasmonic structures, and silicon and fibre integrated structures. We also take a look at the future perspectives and discuss the potential of yet relatively unexplored mechanisms, such as magneto-optic and acousto-optic modulation.

  6. Anisotropic Optical Properties of Layered Germanium Sulfide

    CERN Document Server

    Tan, Dezhi; Wang, Feijiu; Mohamed, Nur Baizura; Mouri, Shinichiro; Sandhaya, Koirala; Zhang, Wenjing; Miyauchi, Yuhei; Ohfuchi, Mari; Matsuda, Kazunari

    2016-01-01

    Two-dimensional (2D) layered materials, transition metal dichalcogenides and black phosphorus, have attracted much interest from the viewpoints of fundamental physics and device applications. The establishment of new functionalities in anisotropic layered 2D materials is a challenging but rewarding frontier, owing to their remarkable optical properties and prospects for new devices. Here, we report the anisotropic optical properties of layered 2D monochalcogenide of germanium sulfide (GeS). Three Raman scattering peaks corresponding to the B3g, A1g, and A2g modes with strong polarization dependence are demonstrated in the GeS flakes, which validates polarized Raman spectroscopy as an effective method for identifying the crystal orientation of anisotropic layered GeS. Photoluminescence (PL) is observed with a peak at around 1.66 eV that originates from the direct optical transition in GeS at room temperature. Moreover, determination of the polarization dependent characteristics of the PL and absorption reveals...

  7. Enhancement of perpendicular magnetic anisotropy and transmission of spin-Hall-effect-induced spin currents by a Hf spacer layer in W/Hf/CoFeB/MgO layer structures

    Energy Technology Data Exchange (ETDEWEB)

    Pai, Chi-Feng; Nguyen, Minh-Hai; Vilela-Leão, Luis Henrique; Buhrman, R. A., E-mail: rab8@cornell.edu [Cornell University, Ithaca, New York 14853 (United States); Belvin, Carina [Department of Physics, Wellesley College, Massachusetts 02481 (United States); Ralph, D. C. [Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell, Ithaca, New York 14853 (United States)

    2014-02-24

    We report that strong perpendicular magnetic anisotropy of the ferromagnetic layer in a W/CoFeB/MgO multilayer structure can be established by inserting a Hf layer as thin as 0.25 nm between the W and CoFeB layers. The Hf spacer also allows transmission of spin currents generated by an in-plane charge current in the W layer to apply strong spin torque on the CoFeB, thereby enabling current-driven magnetic switching. The antidamping-like and field-like components of the spin torque exerted on a 1 nm CoFeB layer are of comparable magnitudes in this geometry. Both components originate from the spin Hall effect in the underlying W layer.

  8. Layer-by-layer introduction of poly(phenylenevinylene) onto microspheres and probing the influence from the weak/strong polyanion spacer-layers.

    Science.gov (United States)

    Song, Jing; Qiu, Tian; Chen, Yun; Zhang, Wei; Fan, Li-Juan

    2015-08-15

    The layer-by-layer (LBL) technique was employed for preparing fluorescent microspheres with a core-shell structure by the alternating adsorption of positively charged poly(p-phenylenevinylene) precursor (pre-PPV) and the polyanions onto polymer substrate spheres, followed by the thermal elimination to convert pre-PPV into fluorescent poly(p-phenylenevinylene) (PPV). Weak polyelectrolytes poly(acrylic acid) (PAA) (usually in a partly ionized form) and strong polyelectrolytes poly(sodium-p-styrenesulfonate) (PSS) were used as the anions to space the PPV layers and reduce the fluorescence self-quenching. Flow cytometry, combined with spectroscopy and microscopy, were used to study the structure and photophysical properties of the resulting microspheres. Optimization of the processing factors was carried out. PAA and PSS as weak and strong polyelectrolytes, respectively, displayed very different influence on the final emission of the spheres. Such difference was attributed to different inherent characteristics of PAA and PSS after detailed investigation in many aspects. In addition, the fluorescent spheres were found to have excellent photostability and thermal stability. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Enhancement of current-perpendicular-to-plane giant magnetoresistance in Heusler-alloy based pseudo spin valves by using a CuZn spacer layer

    Energy Technology Data Exchange (ETDEWEB)

    Furubayashi, T., E-mail: furubayashi.takao@nims.go.jp; Takahashi, Y. K.; Sasaki, T. T.; Hono, K. [National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2015-10-28

    Enhancement of magnetoresistance output was attained in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices by using a bcc CuZn alloy for the spacer. Pseudo spin valves that consisted of the Co{sub 2}Fe(Ga{sub 0.5}Ge{sub 0.5}) Heusler alloy for ferromagnetic layers and CuZn alloy with the composition of Cu{sub 52.4}Zn{sub 47.6} for a spacer showed the large change of the resistance-area products, ΔRA, up to 8 mΩ·μm{sup 2} for a low annealing temperature of 350 °C. The ΔRA value is one of the highest reported so far for the CPP-GMR devices for the low annealing temperature, which is essential for processing read heads for hard disk drives. We consider that the enhancement of ΔRA is produced from the spin-dependent resistance at the Co{sub 2}Fe(Ga{sub 0.5}Ge{sub 0.5})/CuZn interfaces.

  10. Spatially-resolved in-situ quantification of biofouling using optical coherence tomography (OCT) and 3D image analysis in a spacer filled channel

    KAUST Repository

    Fortunato, Luca

    2016-11-21

    The use of optical coherence tomography (OCT) to investigate biomass in membrane systems has increased with time. OCT is able to characterize the biomass in-situ and non-destructively. In this study, a novel approach to process three-dimensional (3D) OCT scans is proposed. The approach allows obtaining spatially-resolved detailed structural biomass information. The 3D biomass reconstruction enables analysis of the biomass only, obtained by subtracting the time zero scan to all images. A 3D time series analysis of biomass development in a spacer filled channel under representative conditions (cross flow velocity) for a spiral wound membrane element was performed. The flow cell was operated for five days with monitoring of ultrafiltration membrane performance: feed channel pressure drop and permeate flux. The biomass development in the flow cell was detected by OCT before a performance decline was observed. Feed channel pressure drop continuously increased with increasing biomass volume, while flux decline was mainly affected in the initial phase of biomass accumulation. The novel OCT imaging approach enabled the assessment of spatial biomass distribution in the flow cell, discriminating the total biomass volume between the membrane, feed spacer and glass window. Biomass accumulation was stronger on the feed spacer during the early stage of biofouling, impacting the feed channel pressure drop stronger than permeate flux.

  11. An Electrochemical Experiment Using an Optically Transparent Thin Layer Electrode

    Science.gov (United States)

    DeAngelis, Thomas P.; Heineman, William R.

    1976-01-01

    Describes a unified experiment in which an optically transparent thin layer electrode is used to illustrate the techniques of thin layer electrochemistry, cyclic voltammetry, controlled potential coulometry, and spectroelectrochemistry. (MLH)

  12. Dependency of anti-ferro-magnetic coupling strength on Ru spacer thickness of [Co/Pd]{sub n}-synthetic-anti-ferro-magnetic layer in perpendicular magnetic-tunnel-junctions fabricated on 12-inch TiN electrode wafer

    Energy Technology Data Exchange (ETDEWEB)

    Chae, Kyo-Suk [MRAM Center, Department of Electronics, Hanyang University, Seoul 133-791 (Korea, Republic of); Samsung Electronics Co., Ltd., San #16 Banwol-dong, Hwasung-City, Gyeonggi-Do 445-701 (Korea, Republic of); Shim, Tae-Hun; Park, Jea-Gun, E-mail: parkjgL@hanyang.ac.kr [MRAM Center, Department of Electronics, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2014-07-21

    We investigated the Ru spacer-thickness effect on the anti-ferro-magnetic coupling strength (J{sub ex}) of a [Co/Pd]{sub n}-synthetic-anti-ferro-magnetic layer fabricated with Co{sub 2}Fe{sub 6}B{sub 2}/MgO based perpendicular-magnetic-tunneling-junction spin-valves on 12-in. TiN electrode wafers. J{sub ex} peaked at a certain Ru spacer-thickness: specifically, a J{sub ex} of 0.78 erg/cm{sup 2} at 0.6 nm, satisfying the J{sub ex} criteria for realizing the mass production of terra-bit-level perpendicular-spin-transfer-torque magnetic-random-access-memory. Otherwise, J{sub ex} rapidly degraded when the Ru spacer-thickness was less than or higher than 0.6 nm. As a result, the allowable Ru thickness variation should be controlled less than 0.12 nm to satisfy the J{sub ex} criteria. However, the Ru spacer-thickness did not influence the tunneling-magneto-resistance (TMR) and resistance-area (RA) of the perpendicular-magnetic-tunneling-junction (p-MTJ) spin-valves since the Ru spacer in the synthetic-anti-ferro-magnetic layer mainly affects the anti-ferro-magnetic coupling efficiency rather than the crystalline linearity of the Co{sub 2}Fe{sub 6}B{sub 2} free layer/MgO tunneling barrier/Co{sub 2}Fe{sub 6}B{sub 2} pinned layer, although Co{sub 2}Fe{sub 6}B{sub 2}/MgO based p-MTJ spin-valves ex-situ annealed at 275 °C achieved a TMR of ∼70% at a RA of ∼20 Ω μm{sup 2}.

  13. Antenna Effect on the Organic Spacer-Modified Eu-Doped Layered Gadolinium Hydroxide for the Detection of Vanadate Ions over a Wide pH Range.

    Science.gov (United States)

    Jeong, Heejin; Lee, Byung-Il; Byeon, Song-Ho

    2016-05-04

    The excitation of the adsorbed vanadate group led to the red emission arising from the efficient energy transfer to Eu-doped layered gadolinium hydroxide (LGdH:Eu). This light-harvesting antenna effect allowed LGdH:Eu to detect selectively a vanadate in aqueous solution at different pHs. Because vanadate exists in various forms by extensive oligomerization and protonation reactions in aqueous solution depending on pH, it is important to detect a vanadate regardless of its form over a wide pH range. In particular, spacer molecules with long alkyl chains greatly facilitated access of a vanadate antenna into the interlayer surface of LGdH:Eu. The concomitant increase in adsorption capacity of LGdH:Eu achieved a strong antenna effect of vanadate on the red emission from Eu(3+). When a suspension containing LGdH:Eu nanosheets (1.0 g/L) was used, the vanadate concentration down to 1 × 10(-5) M could even be visually monitored, and the detection limit based on the (5)D0 → (7)F2 emission intensity could reach 4.5 × 10(-8) M.

  14. Physical-layer network coding in coherent optical OFDM systems.

    Science.gov (United States)

    Guan, Xun; Chan, Chun-Kit

    2015-04-20

    We present the first experimental demonstration and characterization of the application of optical physical-layer network coding in coherent optical OFDM systems. It combines two optical OFDM frames to share the same link so as to enhance system throughput, while individual OFDM frames can be recovered with digital signal processing at the destined node.

  15. Electron stimulated desorption of cations from C sub 6 H sub 6 and C sub 6 H sub 1 sub 2 molecules adsorbed on Pt(1 1 1) and Ar spacer layer

    CERN Document Server

    Kawanowa, H; Hanatani, K; Gotoh, Y; Souda, R

    2003-01-01

    Mechanisms of electron stimulated cation desorption have been investigated for adsorbed C sub 6 H sub 6 and C sub 6 H sub 1 sub 2 molecules on the Pt(1 1 1) surface and the Ar spacer layer formed on it. The ion yields from the molecules adsorbed on the Ar spacer layer are highly enhanced at the smallest coverage and decay steeply with increasing coverage. No such enhancement was observed when they are adsorbed directly on the Pt(1 1 1) substrate. This behavior is explained in terms of the Coulombic repulsion of cations confined in nanoclusters, together with the delocalization of valence holes on the Pt(1 1 1) substrate as well as in the multilayer hydrocarbons. The holes in the C sub 6 H sub 6 molecule are more delocalized than those in the C sub 6 H sub 1 sub 2 molecule due to the overlap of pi orbitals.

  16. Significant enhancement of yellow-green light emission of TiO2 thin films using Au localized surface plasmons: effect of dielectric MgO spacer layer thickness.

    Science.gov (United States)

    Zhang, Cen; Liu, Weizhen; Xu, Haiyang; Ma, Jiangang; Liu, Yichun

    2014-05-01

    TiO2/MgO/Au composite thin films with different MgO spacer layer thicknesses (0-41 nm) were fabricated on c-sapphire substrates by sputtering and pulsed laser deposition. Through optimizing the thickness of MgO spacer layer, which can effectively prevent nonradiative Förster resonant energy transfer and charge transfer between Au and TiO2, defect-related yellow-green light emission of TiO2 thin film was greatly enhanced - 12 times. The enhancement mechanism is attributed to the efficient increase of luminescence efficiency of deep levels in TiO2 induced by resonant coupling between localized surface plasmons in Au nanoparticles and electron-hole pairs in defect-related levels of TiO2.

  17. Optical and structural investigations of self-assembled Ge/Si bi-layer containing Ge QDs

    Energy Technology Data Exchange (ETDEWEB)

    Samavati, Alireza, E-mail: alireza.samavati@yahoo.com [Ibn Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia); Othaman, Z., E-mail: zulothaman@gmail.com [Ibn Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia); Ghoshal, S.K.; Dousti, M.R. [Advanced Optical Material Research Group, Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)

    2014-10-15

    We report the influence of Si spacer thickness variation (10–40 nm) on structural and optical properties of Ge quantum dots (QDs) in Ge/Si(1 0 0) bi-layer grown by radio frequency magnetron sputtering. AFM images reveal the spacer dependent width, height, root mean square roughness and number density of QDs vary in the range of ∼12–25 nm, ∼2–6 nm, ∼1.95–1.05 nm and ∼0.55×10{sup 11}–2.1×10{sup 11} cm{sup −2}, respectively. XRD patterns exhibit the presence of poly-oriented structures of Ge with preferred growth along (1 1 1) direction accompanied by a reduction in strain from 4.9% to 1.2% (estimated from Williamson–Hall plot) due to bi-layering. The room temperature luminescence displays strong blue–violet peak associated with a blue shift as much as 0.05 eV upon increasing the thickness of Si spacer. This shift is attributed to the quantum size effect, the material intermixing and the strain mediation. Raman spectra for both mono and bi-layer samples show intense Ge–Ge optical phonon mode that is shifted towards higher frequency. Furthermore, the first order features of Raman spectra affirm the occurrence of interfacial intermixing and phase formation during deposition. The excellent features of the results suggest that our systematic method may constitute a basis for the tunable growth of Ge QDs suitable in nanophotonics. - Highlights: • High quality bilayered hetero-structure Ge/Si using economic and easy rf magnetron sputtering fabrication method. • The role of phonon-confinement and strain relaxation mechanisms. • Influence of bilayering on evolutionary growth dynamics. • Band gap shift of visible PL upon bilayering.

  18. Layered Polymeric Optical Systems Using Continuous Coextrusion

    Science.gov (United States)

    2009-01-01

    band[13]. The possibility of fabricating tunable photonic crystals was explored using thermoplastic polyurethane (TPU, n = 1.55) layered against Pebax... losses within the cavity reflection band. Typical emission spectra are shown in Figure 9. The thickness of the dielectric layer determines the spacing...fabrication of refractive index patterns, including gradients and superlattices. The periodic dielectric nature leads to interference effects

  19. Advanced optical modelling of dynamically deposited silicon nitride layers

    Science.gov (United States)

    Borojevic, N.; Hameiri, Z.; Winderbaum, S.

    2016-07-01

    Dynamic deposition of silicon nitrides using in-line plasma enhanced chemical vapor deposition systems results in non-uniform structure of the dielectric layer. Appropriate analysis of such layers requires the optical characterization to be performed as a function of the layer's depth. This work presents a method to characterize dynamically deposited silicon nitride layers. The method is based on the fitting of experimental spectroscopic ellipsometry data via grading of Tauc-Lorentz optical parameters through the depth of the layer. When compared with the standard Tauc-Lorentz fitting procedure, used in previous studies, the improved method is demonstrating better quality fits to the experimental data and revealing more accurate optical properties of the dielectric layers. The most significant advantage of the method is the ability to extract the depth profile of the optical properties along the direction of the layer normal. This is enabling a better understanding of layers deposited using dynamic plasma enhanced chemical vapor deposition systems frequently used in the photovoltaic industry.

  20. Optical devices featuring textured semiconductor layers

    Science.gov (United States)

    Moustakas, Theodore D.; Cabalu, Jasper S.

    2011-10-11

    A semiconductor sensor, solar cell or emitter, or a precursor therefor, has a substrate and one or more textured semiconductor layers deposited onto the substrate. The textured layers enhance light extraction or absorption. Texturing in the region of multiple quantum wells greatly enhances internal quantum efficiency if the semiconductor is polar and the quantum wells are grown along the polar direction. Electroluminescence of LEDs of the invention is dichromatic, and results in variable color LEDs, including white LEDs, without the use of phosphor.

  1. Characteristics and optimization of 4H-SiC MESFET with a novel p-type spacer layer incorporated with a field-plate structure based on improved trap models

    Institute of Scientific and Technical Information of China (English)

    Song Kun; Chai Changchun; Yang Yintang; Jia Hujun; Zhang Xianjun; Chen Bin

    2011-01-01

    A novel structure of 4H-SiC MESFETs is proposed that focuses on surface trap suppression.Characteristics of the device have been investigated based on physical models for material properties and improved trap models.By comparing with the performance of the well-utilized buried-gate incorporated with a field-plate (BG-FP) structure,it is shown that the proposed structure improves device properties in comprehensive aspects.A p-type spacer layer introduced in the channel layer suppresses the surface trap effect and reduces the gate-drain capacitance (Cgd) under a large drain voltage.A p-type spacer layer incorporated with a field-plate improves the electric field distribution on the gate edge while the spacer layer induces less Cgd than a conventional FP.For microwave applications,4H-SiC MESFET for the proposed structure has a larger gate-lag ratio in the saturation region due to better surface trap isolation from the conductive channel.For high power applications,the proposed structure is able to endure higher operating voltage as well.The maximum saturation current density of 460 mA/mm is yielded.Also,the gate-lag ratio under a drain voltage of 20 V is close to 90%.In addition,5% and 17.8% improvements in fT and fmax are obtained compared with a BG-FP MESFET in AC simulation,respectively.Parameters and dimensions of the proposed structure are optimized to make the best of the device for microwave applications and to provide a reference for device design.

  2. Characteristics and optimization of 4H-SiC MESFET with a novel p-type spacer layer incorporated with a field-plate structure based on improved trap models

    Energy Technology Data Exchange (ETDEWEB)

    Song Kun; Chai Changchun; Yang Yintang; Jia Hujun; Zhang Xianjun; Chen Bin, E-mail: sk88205853@sina.com [Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices of the Ministry of Education, School of Microelectronics, Xidian University, Xi' an 710071 (China)

    2011-07-15

    A novel structure of 4H-SiC MESFETs is proposed that focuses on surface trap suppression. Characteristics of the device have been investigated based on physical models for material properties and improved trap models. By comparing with the performance of the well-utilized buried-gate incorporated with a field-plate (BG-FP) structure, it is shown that the proposed structure improves device properties in comprehensive aspects. A p-type spacer layer introduced in the channel layer suppresses the surface trap effect and reduces the gate-drain capacitance (C{sub gd}) under a large drain voltage. A p-type spacer layer incorporated with a field-plate improves the electric field distribution on the gate edge while the spacer layer induces less C{sub gd} than a conventional FP. For microwave applications, 4H-SiC MESFET for the proposed structure has a larger gate-lag ratio in the saturation region due to better surface trap isolation from the conductive channel. For high power applications, the proposed structure is able to endure higher operating voltage as well. The maximum saturation current density of 460 mA/mm is yielded. Also, the gate-lag ratio under a drain voltage of 20 V is close to 90%. In addition, 5% and 17.8% improvements in f{sub T} and f{sub max} are obtained compared with a BG-FP MESFET in AC simulation, respectively. Parameters and dimensions of the proposed structure are optimized to make the best of the device for microwave applications and to provide a reference for device design. (semiconductor devices)

  3. Phase-Change Optical Disk Having a Nitride Interface Layer

    Science.gov (United States)

    Yamada, Noboru; Otoba, Mayumi; Kawahara, Katsumi; Miyagawa, Naoyasu; Ohta, Hiroyuki; Akahira, Nobuo; Matsunaga, Toshiyuki

    1998-04-01

    A thin nitride layer formed at the interface of a Ge Sb Te recording layer and a ZnS SiO2 protective layer successfully suppresses the phenomenon that reflectivity or signal amplitude becomes markedly small due to repeated overwrites. Based on secondary ion mass spectrometry (SIMS) observations, the 5-nm-thick interface layer was found to restrain sulfur atoms in the ZnS SiO2 layer from diffusing into the Ge Sb Te layer and from changing the optical characteristics of the layer. Among several nitride materials, germanium nitride (Ge N) sputtered film is found to have the most suitable properties as an interface layer: high barrier effect and good adhesiveness with Ge Sb Te and ZnS SiO2 layers. The optical disk having the Ge N interface layer achieves more than 5×105 cycles of overwrites with almost no changes in signal amplitude, reflectivity and jitter based on DVD-RAM specifications. The disk shows no degradation such as cracking, peeling, and corrosion after exposure to accelerated environmental conditions of 90°C and 80% RH for 200 h.

  4. Optical coherence tomography segmentation reveals ganglion cell layer pathology after optic neuritis.

    Science.gov (United States)

    Syc, Stephanie B; Saidha, Shiv; Newsome, Scott D; Ratchford, John N; Levy, Michael; Ford, E'tona; Crainiceanu, Ciprian M; Durbin, Mary K; Oakley, Jonathan D; Meyer, Scott A; Frohman, Elliot M; Calabresi, Peter A

    2012-02-01

    Post-mortem ganglion cell dropout has been observed in multiple sclerosis; however, longitudinal in vivo assessment of retinal neuronal layers following acute optic neuritis remains largely unexplored. Peripapillary retinal nerve fibre layer thickness, measured by optical coherence tomography, has been proposed as an outcome measure in studies of neuroprotective agents in multiple sclerosis, yet potential swelling during the acute stages of optic neuritis may confound baseline measurements. The objective of this study was to ascertain whether patients with multiple sclerosis or neuromyelitis optica develop retinal neuronal layer pathology following acute optic neuritis, and to systematically characterize such changes in vivo over time. Spectral domain optical coherence tomography imaging, including automated retinal layer segmentation, was performed serially in 20 participants during the acute phase of optic neuritis, and again 3 and 6 months later. Imaging was performed cross-sectionally in 98 multiple sclerosis participants, 22 neuromyelitis optica participants and 72 healthy controls. Neuronal thinning was observed in the ganglion cell layer of eyes affected by acute optic neuritis 3 and 6 months after onset (P optica, with and without a history of optic neuritis, when compared with healthy controls (P optica and a history of optic neuritis exhibited the greatest reduction in ganglion cell layer thickness. Results from our in vivo longitudinal study demonstrate retinal neuronal layer thinning following acute optic neuritis, corroborating the hypothesis that axonal injury may cause neuronal pathology in multiple sclerosis. Further, these data provide evidence of subclinical disease activity, in both participants with multiple sclerosis and with neuromyelitis optica without a history of optic neuritis, a disease in which subclinical disease activity has not been widely appreciated. No pathology was seen in the inner or outer nuclear layers of eyes with optic

  5. Optical modulators with two-dimensional layered materials

    CERN Document Server

    Sun, Zhipei; Wang, Feng

    2016-01-01

    Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that two-dimensional layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this review, we cover the state-of-the-art of optical modulators based on two-dimensional layered materials including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as two-dimensional heterostructures, plasmonic structures, and silicon/fibre integrated structures. We also take a look at future perspectives and discuss the potential of yet relatively unexplored mechanisms such as magneto-optic and acousto-optic modulation.

  6. Generalized approach to design multi-layer stacks for enhanced optical detectability of ultrathin layers

    Science.gov (United States)

    Hutzler, A.; Matthus, C. D.; Rommel, M.; Frey, L.

    2017-01-01

    The optical detectability of ultrathin conductive films (down to one atomic layer) can be enhanced by choosing distinct layer-stacks. A simple analytical approach using the transfer matrix method is applied for calculating the reflectance of arbitrary multi-layer stack systems with and without the ultrathin layer of interest on top in a wide wavelength range, including both the visible spectrum and the ultraviolet spectrum. Then, the detectability defined by the Michelson contrast was calculated. Performing these calculations for thickness variations of the individual layers in the stack allows determining optimum layer thicknesses, e.g., maximum overall contrast or maximum contrast for a given wavelength. To demonstrate the validity of the methodology, two thin film stacks were investigated, which use p-type silicon as a substrate material and partially covered by a single-layer graphene as a top layer. For each stack, two samples with different layer thicknesses were fabricated and their experimentally determined reflectance was compared to the calculated values. The first system consists of a single SiO2 layer with a thickness of 147 nm and 304 nm, respectively, and the second is a double layer stack consisting of a Si3N4 layer with a thickness of 54 nm and 195 nm, respectively, on top of an 11 nm SiO2 film. The Michelson contrast of single-layer graphene flakes on the latter layer stacks becomes very high (absolute value of more than 0.3) in the visible wavelength range. Additionally, in the UV-B range a large difference in the reflection of selected SiO2 layer thicknesses on silicon substrates with and without single-layer graphene on top is found with a decrease in the measured reflectance of up to 33%. The measured and calculated values showed a high conformity suggesting this approach usable for the calculation of reflectance and transmittance properties of arbitrary layer stack systems including thin conductive layers.

  7. Vibrational and quantum-chemical study of push-pull chromophores for second-order nonlinear optics from rigidified thiophene-based pi-conjugating spacers.

    Science.gov (United States)

    Ruiz Delgado, Mari Carmen; Hernández, Víctor; Casado, Juan; López Navarrete, Juan T; Raimundo, Jean-Manuel; Blanchard, Philippe; Roncali, Jean

    2003-08-04

    Two types of push-pull chromophores built around thiophene-based pi-conjugating spacers rigidified by either covalent bonds or noncovalent intramolecular interactions have been analysed by means of IR and Raman spectroscopical measurements in the solid state as well as in a variety of solvents. Comparison of the Raman features of NLO-phores based on a covalently rigidified dithienylene (DTE) spacer with those of their open chain DTE analogues shows that the bridging of the central double bond of DTE with the nearest beta-positions of the thienyl units through two ethylene bridges significantly improves the intramolecular charge transfer. This also occurs for NLO-phores based on a 2,2'-bi(3,4-ethylenedioxythiophene) (BEDOT) spacer as compared with their corresponding parent compounds based on an unsubstituted bithiophene (BT) spacer. For NLO-phores based on a BEDOT spacer, noncovalent intramolecular interactions between sulfur and oxygen atoms are responsible for the rigidification of the spacer. The Raman spectra of these NLO-phores obtained in the form of solutes in dilute solutions reveal two different behaviours: i) chromophores based on covalently bridged or open chain DTE spacers display Raman spectral profiles in solution quite similar to those of the corresponding solids, with a very little dependence on the polarity of the solvent, while ii) larger spectral changes are noticed for NLO-phores built around BEDOT or BT spacers on going from solids to solutions. In the second case, spectral changes must be ascribed not solely to conformational distortions of the donor and acceptor end groups with respect to the pi-conjugated backbone mean-square-plane (as for the DTE-based NLO-phores) but also to distortions of the thienyl units of the pi-conjugating spacer from coplanarity. The insertion of vinylenic bridges between the thienyl units of the pi-conjugating spacer and between the spacer and the donor and acceptor end groups is a suitable strategy to reach a

  8. Optical characterization of epitaxial semiconductor layers

    CERN Document Server

    Richter, Wolfgang

    1996-01-01

    The last decade has witnessed an explosive development in the growth of expitaxial layers and structures with atomic-scale dimensions. This progress has created new demands for the characterization of those stuctures. Various methods have been refined and new ones developed with the main emphasis on non-destructive in-situ characterization. Among those, methods which rely on the interaction of electromagnetic radiation with matter are particularly valuable. In this book standard methods such as far-infrared spectroscopy, ellipsometry, Raman scattering, and high-resolution X-ray diffraction are presented, as well as new advanced techniques which provide the potential for better in-situ characterization of epitaxial structures (such as reflection anistropy spectroscopy, infrared reflection-absorption spectroscopy, second-harmonic generation, and others). This volume is intended for researchers working at universities or in industry, as well as for graduate students who are interested in the characterization of ...

  9. Layer compression and enhanced optical properties of few-layer graphene nanosheets induced by ion irradiation

    CERN Document Server

    Tan, Yang; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng

    2016-01-01

    Graphene has been recognized as an attractive two-dimensional material for fundamental research and wide applications in electronic and photonic devices owing to its unique properties. The technologies to modulate the properties of graphene are of continuous interest to researchers in multidisciplinary areas. Herein, we report on the first experimental observation of the layer-to-layer compression and enhanced optical properties of few-layer graphene nanosheets by applying the irradiation of energetic ion beams. After the irradiation, the space between the graphene layers was reduced, resulting in a tighter contact between the few-layer graphene nanosheet and the surface of the substrate. This processing also enhanced the interaction between the graphene nanosheets and the evanescent-field wave near the surface, thus reinforcing the polarization-dependent light absorption of the graphene layers (with 3-fold polarization extinction ratio increment). Utilizing the ion-irradiated graphene nanosheets as saturable...

  10. NEAR INFRARED ELECTROCHROMIC VARIABLE OPTICAL ATTENUATOR FABRICATED BY LAYER-BY-LAYER ASSEMBLY*

    Institute of Scientific and Technical Information of China (English)

    Jia Zheng; Yi-jun Zheng; Xin-hua Wan

    2011-01-01

    An electrochromic variable optical attenuator (ECVOA) was fabricated by layer-by-layer (LBL) assembly of disodium N,N-bis(p-sulfonatophenyl)naphthalenedicarboximide (Naph-SO3Na) and common cationic polymer poly(diallyldimethylammonium) chloride (PDDA). The UV-Vis absorption spectra of the multilayer films revealed that approximately an equal amount of Naph-SO3Na was assembled in each deposition cycle. Upon one-electron reduction, multilayer films exhibited intense absorption around 452 nm and also a broad absorption band from 1200 nm to 1900 nm. Owing to the improved ionic conductivity, the optical attenuation at 1550 nm of the films showed rapid response time and reached 1.3 dB/μm within 5 s. These results indicate that layer-by-layer assembly could be an effective method for the preparation of ECVOA operating in near infrared region.

  11. Optical measurements of degradation in aircraft boundary layers

    Science.gov (United States)

    Kelsall, D.

    1980-01-01

    Visible wavelength measurements of the degradation of optical beams when transmitted through the thin aerodynamic boundary layers around an aircraft are reviewed. The measured results indicated degradation levels for the KC-135 airplanes between 0.10 to 0.13 lambda increasing to 0.18 lambda (rms wavefront distortion). For the Lear Jet, degradation with a 25 mm diameter optics was roughly 0.07 lambda. The corresponding infinite aperture degradation levels are also calculated. The corresponding measured correlation lengths of roughly 12 mm for the KC-135 aircraft and 6 mm for the Lear Jet scale to roughly 20 and 25 mm, respectively, for infinite apertures. These boundary layer correlation lengths do not appear to reflect the different boundary layer thicknesses on the two different aircraft.

  12. Photonic layer security in fiber-optic networks and optical OFDM transmission

    Science.gov (United States)

    Wang, Zhenxing

    Currently the Internet is experiencing an explosive growth in the world. Such growth leads to an increased data transmission rate demand in fiber-optical networks. Optical orthogonal frequency multiplexing (OFDM) is considered as a promising solution to achieve data rate beyond 100Gb/s per wavelength channel. In the meanwhile, because of extensive data transmission and sharing, data security has become an important problem and receives considerable attention in current research literature. This thesis focuses on data security issues at the physical layer of optical networks involving code-division multiple access (CDMA) systems and steganography methods. The thesis also covers several implementation issues in optical OFDM transmission. Optical CDMA is regarded as a good candidate to provide photonic layer security in multi-access channels. In this thesis we provide a systematic analysis of the security performance of incoherent optical CDMA codes. Based on the analysis, we proposed and experimentally demonstrated several methods to improve the security performance of the optical CDMA systems, such as applying all-optical encryption, and code hopping using nonlinear wavelength conversion. Moreover, we demonstrate that the use of wireless CDMA codes in optical systems can enhance the security in one single-user end-to-end optical channel. Optical steganography is another method to provide photonic data security and involves hiding the existence of data transmissions. In the thesis, we demonstrate that an optical steganography channel can exist in phase modulated public channels as well as traditional on-off-keying (OOK) modulated channels, without data synchronization. We also demonstrate an optical steganography system with enhanced security by utilizing temporal phase modulation techniques. Additionally, as one type of an overlay channel, the optical steganography technology can carry the sensor data collected by wireless sensor network on top of public optical

  13. Nonlocal optical properties in periodic lattice of graphene layers.

    Science.gov (United States)

    Chern, Ruey-Lin; Han, Dezhuan

    2014-02-24

    Based on the effective medium model, nonlocal optical properties in periodic lattice of graphene layers with the period much less than the wavelength are investigated. Strong nonlocal effects are found in a broad frequency range for TM polarization, where the effective permittivity tensor exhibits the Lorentzian resonance. The resonance frequency varies with the wave vector and coincides well with the polaritonic mode. Nonlocal features are manifest on the emergence of additional wave and the occurrence of negative refraction. By examining the characters of the eigenmode, the nonlocal optical properties are attributed to the excitation of plasmons on the graphene surfaces.

  14. Physical layer secret key generation for fiber-optical networks.

    Science.gov (United States)

    Kravtsov, Konstantin; Wang, Zhenxing; Trappe, Wade; Prucnal, Paul R

    2013-10-07

    We propose and experimentally demonstrate a method for generating and sharing a secret key using phase fluctuations in fiber optical links. The obtained key can be readily used to support secure communication between the parties. The security of our approach is based on a fundamental asymmetry associated with the optical physical layer: the sophistication of tools needed by an eavesdropping adversary to subvert the key establishment is significantly greater and more costly than the complexity needed by the legitimate parties to implement the scheme. In this sense, the method is similar to the classical asymmetric algorithms (Diffie-Hellman, RSA, etc.).

  15. Structural Stator Spacers

    DEFF Research Database (Denmark)

    Rasmussen, Peter Omand; Andreasen, Jens H.; Pijanowski, J. M.

    2001-01-01

    This paper presents a powerful new design aspect to reduce acoustic noise and vibration of electro-magnetic origin for electrical machines, by introducing improved slot wedges referred to as "Structural Stator Spacers". These spacers, by using a very stiff dielectric and non magnetic material...... drawbacks usually associated with other noise reduction methods or interdict other noise control methods. Design models and practical prototypes are detailed which are used to verify the effectiveness of the spacers......., a modified shape and small modifications to the stator laminations not only secure the windings and reduce windage losses but also make it possible to increase the stiffness of the stator structure significantly thereby reducing the generation of audible noise. This new method does not incur the significant...

  16. Interaction of excitons with optical phonons in layer crystals

    Science.gov (United States)

    Nitsovich, Bohdan M.; Zenkova, C. Y.; Kramar, N. K.

    2002-02-01

    The investigation is concerned with layer crystals of the GaSe, InSe, GaTe, MoS2-type and other inorganic semiconductors, whose phonon spectrum has a great number of peculiarities, among them the availability of low-energy optical phonons. In this case the dispersion of these phonons can be essential and vary in character. The mass operator of the exciton-phonon system and the light absorption coefficient for different dispersion laws of optical phonons have been calculated. The influence of the sign of the phonon 'effective mass' on the exciton absorption band of layer crystals, which causes the opposite in sign dynamics of the absorption maximum shift, and the change of the absorption curve asymmetry have been determined.

  17. Tailoring optical forces for nanoparticle manipulation on layered substrates

    Science.gov (United States)

    Salary, Mohammad M.; Mosallaei, Hossein

    2016-07-01

    Optical forces can be used to manipulate small particles through various mechanisms. In this paper, we present a comprehensive analysis of optical forces acting on the nanoparticles located over a substrate using different manipulation techniques, as well as the conditions of the optimization of these forces. In particular, we study optical trapping, acceleration, and binding. Calculations are carried out using the exact multipole expansion method combined with Maxwell stress tensor formalism, providing a general framework to study optical forces on particles for arbitrary incident fields using closed-form expressions. The method takes into account multiple scattering between the particles and substrate and allows clear predictive abilities well beyond the dipole model. We consider the interaction of dielectric and metallic nanoparticles with various substrates. The presence of substrate is shown to have a significant impact on the nanoparticles' resonances and provides an additional degree of freedom in tailoring the optical forces. We explore different physical processes contributing to the optical force and their interplay on the mobility of the particle. It is established that engineering layered substrates can broaden the scope of trapping and acceleration and enhance the binding forces. It can also provide a high tunability of the acceleration direction. The analysis presented in this paper provides key physical insights to identify optimum setup for nanoparticles manipulation in various applications.

  18. Quantum optical effective-medium theory for layered metamaterials

    CERN Document Server

    Amooghorban, Ehsan

    2016-01-01

    The quantum optics of metamaterials starts with the question whether the same effective-medium theories apply as in classical optics. In general the answer is negative. For active plasmonics but also for some passive metamaterials, we show that an additional effective-medium parameter is indispensable besides the effective index, namely the effective noise-photon distribution. Only with the extra parameter can one predict how well the quantumness of states of light is preserved in the metamaterial. The fact that the effective index alone is not always sufficient and that one additional effective parameter suffices in the quantum optics of metamaterials is both of fundamental and practical interest. Here from a Lagrangian description of the quantum electrodynamics of media with both linear gain and loss, we compute the effective noise-photon distribution for quantum light propagation in arbitrary directions in layered metamaterials, thereby detailing and generalizing our recent work [ E. Amooghorban et al., Ph...

  19. Diamond-based protective layer for optical biosensors

    Science.gov (United States)

    Majchrowicz, D.; Ficek, M.; Baran, T.; WÄ sowicz, M.; Struk, P.; Jedrzejewska-Szczerska, M.

    2016-09-01

    Optical biosensors have become a powerful alternative to the conventional ways of measurement owing to their great properties, such as high sensitivity, high dynamic range, cost effectiveness and small size. Choice of an optical biosensor's materials is an important factor and impacts the quality of the obtained spectra. Examined biological objects are placed on a cover layer which may react with samples in a chemical, biological and mechanical way, therefore having a negative impact on the measurement reliability. Diamond, a metastable allotrope of carbon with sp3 hybridization, shows outstanding properties such as: great chemical stability, bio-compatibility, high thermal conductivity, wide bandgap and optical transparency. Additionally it possesses great mechanical durability, which makes it a long-lasting material. The protective diamond thin films were deposited on the substrate using Microwave Plasma Assisted Chemical Vapor Deposition (MW PA CVD) system. The surface morphology and roughness was assessed with atomic force microscopy and profilometry. We have performed a series of measurements to assess the biocompatibility of diamond thin films with whole blood. The results show that thin diamond protective layer does not affect the red blood cells, while retaining the sensors high resolution and dynamic range of measurement. Therefore, we conclude that diamond thin films are a viable protective coating for optical biosensors, which allows to examine many biological elements. We project that it can be particularly useful not only for biological objects but also under extreme conditions like radioactive or chemically aggressive environments and high temperatures.

  20. Tunable multiple layered Dirac cones in optical lattices.

    Science.gov (United States)

    Lan, Z; Celi, A; Lu, W; Öhberg, P; Lewenstein, M

    2011-12-16

    We show that multiple layered Dirac cones can emerge in the band structure of properly addressed multicomponent cold fermionic gases in optical lattices. The layered Dirac cones contain multiple copies of massless spin-1/2 Dirac fermions at the same location in momentum space, whose different Fermi velocity can be tuned at will. On-site microwave Raman transitions can further be used to mix the different Dirac species, resulting in either splitting of or preserving the Dirac point (depending on the symmetry of the on-site term). The tunability of the multiple layered Dirac cones allows us to simulate a number of fundamental phenomena in modern physics, such as neutrino oscillations and exotic particle dispersions with E~p(N) for arbitrary integer N.

  1. Free-space optical channel estimation for physical layer security.

    Science.gov (United States)

    Endo, Hiroyuki; Fujiwara, Mikio; Kitamura, Mitsuo; Ito, Toshiyuki; Toyoshima, Morio; Takayama, Yoshihisa; Takenaka, Hideki; Shimizu, Ryosuke; Laurenti, Nicola; Vallone, Giuseppe; Villoresi, Paolo; Aoki, Takao; Sasaki, Masahide

    2016-04-18

    We present experimental data on message transmission in a free-space optical (FSO) link at an eye-safe wavelength, using a testbed consisting of one sender and two receiver terminals, where the latter two are a legitimate receiver and an eavesdropper. The testbed allows us to emulate a typical scenario of physical-layer (PHY) security such as satellite-to-ground laser communications. We estimate information-theoretic metrics including secrecy rate, secrecy outage probability, and expected code lengths for given secrecy criteria based on observed channel statistics. We then discuss operation principles of secure message transmission under realistic fading conditions, and provide a guideline on a multi-layer security architecture by combining PHY security and upper-layer (algorithmic) security.

  2. Free-space optical channel estimation for physical layer security

    Science.gov (United States)

    Endo, Hiroyuki; Fujiwara, Mikio; Kitamura, Mitsuo; Ito, Toshiyuki; Toyoshima, Morio; Takayama, Yoshihisa; Takenaka, Hideki; Shimizu, Ryosuke; Laurenti, Nicola; Vallone, Giuseppe; Villoresi, Paolo; Aoki, Takao; Sasaki, Masahide

    2016-04-01

    We present experimental data on message transmission in a free-space optical (FSO) link at an eye-safe wavelength, using a testbed consisting of one sender and two receiver terminals, where the latter two are a legitimate receiver and an eavesdropper. The testbed allows us to emulate a typical scenario of physical-layer (PHY) security such as satellite-to-ground laser communications. We estimate information-theoretic metrics including secrecy rate, secrecy outage probability, and expected code lengths for given secrecy criteria based on observed channel statistics. We then discuss operation principles of secure message transmission under realistic fading conditions, and provide a guideline on a multi-layer security architecture by combining PHY security and upper-layer (algorithmic) security.

  3. Optical stability of silicon nitride MIS inversion layer solar cells

    Science.gov (United States)

    Jaeger, K.; Hezel, R.

    1985-09-01

    For MIS inversion layer solar cells with silicon nitride as an AR coating, accelerated optical stress tests were performed. Degradation of the cell characteristics occurred which was found to be caused by photons with energies equal to or greater than 3.7 eV (wavelength of 335 nm or less). Generation of interface states at the silicon-insulator interface by UV light is shown to be the mechanism responsible. The original cell data could be completely restored by heat treatment (activation energy 0.5 eV) and partially by illumination with short-wavelength light. As the most striking result, however, it is demonstrated that the UV light-induced instability can be drastically improved by incorporation of cesium ions into the silicon nitride layer. An interpretation is given for this effect.

  4. `imaka - a ground-layer adaptive optics system on Maunakea

    CERN Document Server

    Chun, Mark; Toomey, Douglas; Lu, Jessica; Service, Max; Baranec, Christoph; Thibault, Simon; Brousseau, Denis; Hayano, Yutaka; Oya, Shin; Santi, Shane; Kingery, Christopher; Loss, Keith; Gardiner, John; Steele, Brad

    2016-01-01

    We present the integration status for `imaka, the ground-layer adaptive optics (GLAO) system on the University of Hawaii 2.2-meter telescope on Maunakea, Hawaii. This wide-field GLAO pathfinder system exploits Maunakea's highly confined ground layer and weak free-atmosphere to push the corrected field of view to ~1/3 of a degree, an areal field approaching an order of magnitude larger than any existing or planned GLAO system, with a FWHM ~ 0.33 arcseconds in the visible and near infrared. We discuss the unique design aspects of the instrument, the driving science cases and how they impact the system, and how we will demonstrate these cases on the sky.

  5. Optical and electrical properties of bi-layers organic devices

    Science.gov (United States)

    Trad, Hager; Rouis, Ahlem; Davenas, Jöel; Majdoub, Mustapha

    2014-10-01

    The influence of interfacial charges on the device characteristics of bi-layers structure LEDs with poly[5-methoxy-2-octyloxy-1,4-phenylenevinylene] (MO-PPV) as active polymer layer is investigated. The concept to improve device performance is presented using: a diacetate cellulose (DAC) and a new synthetized 5-{2-(2-chloroethoxy)ethoxy}-2-{(E)-(2-pyridyl)azo}phenol (PDEG) components. The DAC and mixed (DAC+PDEG) layers were inserted between indium tin oxide (ITO) and MO-PPV polymer. The optical properties (UV-Vis) of MO-PPV, PDEG and mixed (DAC+PDEG) in solutions were studied and compared to those on thin films. Detailed current-voltage measurements of the bi-layers devices showed improvements of the threshold voltage (Vth) of the ITO/(DAC+PDEG)/MO-PPV/Al device attributed to the enhancement of carriers injection and transport resulted from the modified electrode structures. Conduction mechanisms of structure LEDs were matched with space-charge-limited current (SCLC) one. The impedance spectra for all devices can be discussed in terms of an equivalent circuit model designed as a parallel resistor Rp and capacitor Cp network in series with resistor Rs. The ITO/(DAC+PDEG)/MO-PPV/Al device showed the lowest impedance attributed to the removal of contaminants and to changes in the work function of ITO. The frequency-dependent electrical properties of the ITO/(DAC+PDEG)/MO-PPV/Al structure is analyzed by impedance spectroscopy as function of bias. We have extracted numerical values of the equivalent circuit model parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution.

  6. Optical Gratings Coated with Thin Si3N4 Layer for Efficient Immunosensing by Optical Waveguide Lightmode Spectroscopy

    Directory of Open Access Journals (Sweden)

    Lorena Diéguez

    2012-04-01

    Full Text Available New silicon nitride coated optical gratings were tested by means of Optical Waveguide Lightmode Spectroscopy (OWLS. A thin layer of 10 nm of transparent silicon nitride was deposited on commercial optical gratings by means of sputtering. The quality of the layer was tested by x-ray photoelectron spectroscopy and atomic force microscopy. As a proof of concept, the sensors were successfully tested with OWLS by monitoring the concentration dependence on the detection of an antibody-protein pair. The potential of the Si3N4 as functional layer in a real-time biosensor opens new ways for the integration of optical waveguides with microelectronics.

  7. Adaptive-optic approach to mitigating aero-optic disturbances for a forced shear layer

    Science.gov (United States)

    Nightingale, Alice M.

    Non-uniform, variable-density fields, resulting from compressibility effects in turbulent flows, are the source of aero-optical distortions which cause significant reductions in optical system performance. As a laser beam transverses through an optically active medium, containing index-of-refraction variations, several optical phenomena occur including beam wander, image distortion, and beam defocus. When encountering a variation in the index field, light waves refract causing an otherwise planar wavefront of a laser beam to become aberrated, contributing to the adverse effects mentioned above. Adaptive-Optics (AO) is a technique used to correct for such spatially and temporally varying aberrations on an optical beam by applying a conjugate waveform correction prior to the beams transmission through the flow. Conventional AO systems are bandwidth limited by real-time processing issues and wavefront sensor limitations. Therefore, an alternative to the conventional AO approach has been proposed, developed and evaluated with the goal of overcoming such bandwidth limitations. The alternative AO system, presented throughout this document, consists of two main features; feed-forward flow control and a phase-locked-loop AO control strategy. Initially irregular, unpredictable large-scale structures within a shear layer are regularized using flow control. Subsequently, the resulting optical wavefront, and corresponding optical signal, emerging from the regularized flow becomes more periodic and predictable effectively reducing the bandwidth necessary to make real-time corrections. A phase-lock-loop controller is then used to perform real-time corrections. Wavefront corrections are estimated based upon the regularized flow, while two small aperture laser beams provide a non-intrusive means of acquiring amplitude and phase error measurements. The phase-lock-loop controller uses these signals as feedback to synchronize the deformable mirror's waveform to that of the shear

  8. THz - ToF Optical Layer Analysis (OLA) to determine optical properties of dielectric materials

    Science.gov (United States)

    Spranger, Holger; Beckmann, Jörg

    2017-02-01

    Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. The knowledge of the base materials shape and optical properties is essential for a proper reconstruction result. To obtain these properties a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric characteristics. The Optical Layer Analysis (OLA) is able to fulfill these requirements. A short description why the optical properties are crucial for meaningful SAFT reconstruction results will be given first. Afterwards the OLA will be derived and applied on representative samples to discuss and evaluate its benefits and limits.

  9. Instrumentation in Support of Research on Bio-optical Thin Layers in Coastal Waters

    Science.gov (United States)

    1997-09-30

    INSTRUMENTATION IN SUPPORT OF RESEARCH ON BIO -OPTICAL THIN LAYERS IN COASTAL WATERS Dian J. Gifford Graduate School of Oceanography University of...SUBTITLE Instrumentation in Support of Research on Bio -optical Thin Layers in Coastal Waters 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...Because the layers scatter both sound and light, they are important in a number of other disciplinary areas in ocean including bio -optics and acoustics

  10. Cyanobacterial ecotypes in different optical microenvironments of a 68 C hot spring mat community revealed by 16S-23S rRNA internal transcribed spacer region variation

    DEFF Research Database (Denmark)

    Ferris, Mike J.; Kühl, Michael; Wieland, Andrea

    2003-01-01

    We examined the population of unicellular cyanobacteria (Synechococcus) in the upper 3-mm vertical interval of a 68°C region of a microbial mat in a hot spring effluent channel (Yellowstone National Park, Wyoming). Fluorescence microscopy and microsensor measurements of O2 and oxygenic photosynth......We examined the population of unicellular cyanobacteria (Synechococcus) in the upper 3-mm vertical interval of a 68°C region of a microbial mat in a hot spring effluent channel (Yellowstone National Park, Wyoming). Fluorescence microscopy and microsensor measurements of O2 and oxygenic...... distinct populations over the vertical interval. We were unable to identify patterns in genetic variation in Synechococcus 16S rRNA sequences that correlate with different vertically distributed populations. However, patterns of variation at the internal transcribed spacer locus separating 16S and 23S r...

  11. LISA telescope spacer design investigations

    Science.gov (United States)

    Sanjuan, Josep; Mueller, Guido; Livas, Jeffrey; Preston, Alix; Arsenovic, Petar; Castellucci, Kevin; Generie, Joseph; Howard, Joseph; Stebbins, Robin

    The Laser Interferometer Space Antenna (LISA) is a space-based gravitational wave observa-tory with the goal of observing Gravitational Waves (GWs) from astronomical sources in a frequency range from 30 µHz to 0.1 Hz. The detection of GWs at such low frequency requires measurements of distances at the pico-meter level between bodies separated by 5 million kilo-meters. The LISA mission consists of three identical spacecraft (SC) separated by 5 × 106 km forming an equilateral triangle. Each SC contains two optical assemblies and two vacuum en-closures housing one proof mass (PM) in geodesic (free fall) motion each. The two assemblies on one SC are each pointing towards an identical assembly on each of the other two SC to form a non-equal arm interferometer. The measurement of the GW strain is done by measuring the change in the length of the optical path between the PMs of one arm relative to the other arms caused by the pass of a GW. An important element of the Interferometric Measurement System (IMS) is the telescope which, on one hand, gathers the light coming from the far SC (˜100 pW) and, on the other hand, expands and collimates the small outgoing beam ( 1 W) and sends it to the far SC. Due to the very demanding sensitivity requirements care must be taken in the design and validation of the telescope not to degrade the IMS performance. For instance, the diameter of the telescope sets the the shot noise of the IMS and depends critically on the diameter of the primary and the divergence angle of the outgoing beam. As the telescope is rather fast telescope, the divergence angle is a critical function of the overall separation between the primary and secondary. Any long term changes of the distance of more than a a few micro-meter would be detrimental to the LISA mission. Similarly challenging are the requirements on the in-band path-length noise for the telescope which has to be kept below 1 pm Hz-1/2 in the LISA band. Different configurations (on-axis/off axis

  12. An experimental study of aero-optical aberration and dithering of supersonic mixing layer via BOS

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The optical performance of supersonic mixing layer is heavily deteriorated by the aero-optical aberration and dithering of coherent structures, but current measuring methods limit the spatiotemporal resolution in relevant studies. A high resolution whole-field aero-optical aberration and dithering measuring method based on the Background Orient Schlieren (BOS) technique was studied. The systematic structure, sensitivity and resolution of BOS are analyzed in this paper. The aero-optical aberration and dithering of streamwise structures in supersonic mixing layers were quantificationally studied with BOS. The aberration field of spanwise structures revealed the ribbon-like aberration structures, which heavily restrict the optical performance of a mixing layer. The quantifications of aero-optical aberration and dithering are very important in studying aero-optical performance of supersonic mixing layer.

  13. Effects of optical layer impairments on 2.5 Gb/s optical CDMA transmission.

    Science.gov (United States)

    Feng, H; Mendez, A; Heritage, J; Lennon, W

    2000-07-03

    We conducted a computer simulation study to assess the effects of optical layer impairments on optical CDMA (O-CDMA) transmission of 8 asynchronous users at 2.5 Gb/s each user over a 214-km link. It was found that with group velocity dispersion compensation, two other residual effects, namely, the nonzero chromatic dispersion slope of the single mode fiber (which causes skew) and the non-uniform EDFA gain (which causes interference power level to exceed signal power level of some codes) degrade the signal to multi-access interference (MAI) ratio. In contrast, four wave mixing and modulation due to the Kerr and Raman contributions to the fiber nonlinear refractive index are less important. Current wavelength-division multiplexing (WDM) technologies, including dispersion management, EDFA gain flattening, and 3 rd order dispersion compensation, are sufficient to overcome the impairments to the O-CDMA transmission system that we considered.

  14. Enhanced Faraday Rotation via Resonant Tunnelling in Tri-Layers Containing Magneto-Optical Metals

    CERN Document Server

    Moccia, Massimo; Galdi, Vincenzo; Alu', Andrea; Engheta, Nader

    2013-01-01

    We study resonant tunnelling effects that can occur in tri-layer structures featuring a dielectric layer sandwiched between two magneto-optical-metal layers. We show that the resonance splitting associated with these phenomena can be exploited to enhance Faraday rotation at optical frequencies. Our results indicate that, in the presence of realistic loss levels, a tri-layer structure of sub-wavelength thickness is capable of yielding sensible (~10{\\deg}) Faraday rotation with transmittance levels that are an order of magnitude larger than those attainable with a standalone slab of magneto-optical metal of same thickness.

  15. ERDA study of H incorporated into lithium niobate optical layers

    CERN Document Server

    Budnev, N M; Pelicon, P; Spirkova-Hradilova, J; Kolarova-Nekvindova, P; Turcicova, H

    2000-01-01

    Hydrogen concentration depth profiles in the proton-exchange treated LiNbO/sub 3/ samples were determined by means of the ERDA (elastic recoil detection analysis) method. The ERDA measurements with 1.8 MeV helium ions were performed using reflection geometry with Al foils used for the separation of the recoiled nuclei from the scattered projectiles. The study clearly showed that the substitutional (H:Li) mechanism, which prevails in the Z-cuts, is accompanied by interstitial diffusion of H into the substrates for the X-cuts. It was also confirmed that the post-exchange annealing not only stabilized the optical properties of the samples, but enlarged the differences between both crystallographically different types of the wafers, leading to more diffused H-profiles for the Z-cuts than for the X-cuts. Plasma treatment of the Z-cut leads to shallower hydrogen containing layers than those in the APE (annealed proton exchange) ones. (7 refs).

  16. Silver hollow optical fibers with acrylic silicone resin coating as buffer layer for sturdy structure

    Science.gov (United States)

    Iwai, Katsumasa; Takaku, Hiroyuki; Miyagi, Mitsunobu; Shi, Yi-Wei; Zhu, Xiao-Song; Matsuura, Yuji

    2016-03-01

    For sturdy silver hollow optical fibers, acrylic silicone resin is newly used as a buffer layer between an inner silver layer and a silica capillary. This acrylic silicone resin film prevents the glass surface from chemical and mechanical micro damages during silver plating process, which deteriorate mechanical strength of the hollow fibers. In addition, it keeps high adhesion of the silver layer with the glass surface. We discuss improvement of mechanical strength of the hollow glass fibers without deterioration of optical properties.

  17. Optical layer development for thin films thermal conductivity measurement by pulsed photothermal radiometry

    Energy Technology Data Exchange (ETDEWEB)

    Martan, J., E-mail: jmartan@ntc.zcu.cz [New Technologies Research Centre, University of West Bohemia, Univerzitní 8, 306 14 Plzeň (Czech Republic)

    2015-01-15

    Measurement of thermal conductivity and volumetric specific heat of optically transparent thin films presents a challenge for optical-based measurement methods like pulsed photothermal radiometry. We present two approaches: (i) addition of an opaque optical layer to the surface and (ii) approximate correction of the mathematical model to incorporate semitransparency of the film. Different single layer and multilayer additive optical layers were tested. The materials of the optical layers were chosen according to analysis and measurement of their optical properties: emissivity and absorption coefficient. Presented are thermal properties’ measurement results for 6 different thin films with wide range of thermal conductivity in three configurations of surface: as deposited, added Ti layer, and added Ti/TiAlSiN layer. Measurements were done in dependence on temperature from room temperature to 500 °C. The obtained thermal effusivity evolution in time after the laser pulse shows different effects of the surface layers: apparent effusivity change and time delay. Suitability of different measurement configurations is discussed and results of high temperature testing of different optical layers are presented.

  18. Radiation Hard Multi-Layer Optical Coatings Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Next generation space telescopes require advanced optical coatings to provide low loss transmission of light in a variety of spectral ranges and protect optical...

  19. Facile preparation, optical and electrochemical properties of layer-by-layer V2O5 quadrate structures

    Science.gov (United States)

    Zhang, Yifu; Zheng, Jiqi; Wang, Qiushi; Hu, Tao; Tian, Fuping; Meng, Changgong

    2017-03-01

    Layer-by-layer V2O5 structures self-assembly by quadrate sheets like "multilayer cake" were successfully synthesized using NH4VO3 as the vanadium sources by a facile hydrothermal route and combination of the calcination. The structure and composition were characterized by field emission scanning electron microscopy, energy-dispersive X-ray spectrometer, X-ray powder diffraction, Raman and Fourier transform infrared spectroscopy. The optical properties of the as-obtained V2O5 layer-by-layer structures were investigated by the Ultraviolet-visible spectroscopy and photoluminescence spectrum. The electrochemical properties of the as-obtained V2O5 layer-by-layer structures as electrodes in supercapacitor device were measured by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) both in the aqueous and organic electrolyte. The specific capacitance is 347 F g-1 at 1 A g-1 in organic electrolyte, which is improved by 46% compared with 238 F g-1 in aqueous electrolyte. During the cycle performance, the specific capacitances of V2O5 layer-by-layer structures after 100 cycles are 30% and 82% of the initial discharge capacity in the aqueous and organic electrolyte, respectively, indicating the cycle performance is significantly improved in organic electrolyte. Our results turn out that layer-by-layer V2O5 structures are an ideal material for supercapacitor electrode in the present work.

  20. Retinal nerve fiber layer thickness is associated with lesion length in acute optic neuritis

    DEFF Research Database (Denmark)

    Kallenbach, K; Simonsen, Helle Juhl; Sander, B;

    2010-01-01

    BACKGROUND: Acute optic neuritis occurs with and without papillitis. The presence of papillitis has previously been thought to imply an anterior location of the neuritis, but imaging studies seeking to test this hypothesis have been inconclusive. METHODS: This prospective observational cohort study...... included 41 patients with unilateral optic neuritis and 19 healthy volunteers. All patients were evaluated and examined within 28 days of onset of symptoms. The peripapillary retinal nerve fiber layer thickness (RNFLT), an objective quantitative measure of optic nerve head edema, was measured by optical...... in the development of optic nerve head edema in optic neuritis....

  1. Retinal nerve fiber layer thickness is associated with lesion length in acute optic neuritis

    DEFF Research Database (Denmark)

    Kallenbach, K; Simonsen, Helle Juhl; Sander, B

    2010-01-01

    included 41 patients with unilateral optic neuritis and 19 healthy volunteers. All patients were evaluated and examined within 28 days of onset of symptoms. The peripapillary retinal nerve fiber layer thickness (RNFLT), an objective quantitative measure of optic nerve head edema, was measured by optical...... coherence tomography and the length and location of the inflammatory optic nerve lesion were evaluated using MRI. RESULTS: Ophthalmoscopically, 34% of the patients had papillitis. The retinal nerve fiber layer in affected eyes (mean 123.1 microm) was higher during the acute phase than that of fellow eyes...... (mean 98.1 microm, p eyes (mean 97.1 microm, p

  2. Properites of ultrathin films appropriate for optics capping layers in extreme ultraviolet lithography (EUVL)

    Energy Technology Data Exchange (ETDEWEB)

    Bajt, S; Edwards, N V; Madey, T E

    2007-06-25

    The contamination of optical surfaces by irradiation shortens optics lifetime and is one of the main concerns for optics used in conjunction with intense light sources, such as high power lasers, 3rd and 4th generation synchrotron sources or plasma sources used in extreme ultraviolet lithography (EUVL) tools. This paper focuses on properties and surface chemistry of different materials, which as thin layers, could be used as capping layers to protect and extend EUVL optics lifetime. The most promising candidates include single element materials such as ruthenium and rhodium, and oxides such as TiO{sub 2} and ZrO{sub 2}.

  3. Silk protein as a new optically transparent adhesion layer for an ultra-smooth sub-10 nm gold layer

    Science.gov (United States)

    Min, Kyungtaek; Umar, Muhammad; Ryu, Shinyoung; Lee, Soonil; Kim, Sunghwan

    2017-03-01

    Ultra-thin and ultra-smooth gold (Au) films are appealing for photonic applications including surface plasmon resonances and transparent contacts. However, poor adhesion at the Au–dielectric interface prohibits the formation of a mechanically stable, ultra-thin, and ultra-smooth Au film. A conventional solution is to use a metallic adhesion layer, such as titanium and chromium, however such layers cause the optical properties of pure Au to deteriorate. Here we report the use of silk protein to enhance the adhesion at the Au–dielectric interface, thus obtaining ultra-smooth sub-10 nm Au films. The Au films that were deposited onto the silk layer exhibited superior surface roughness to those deposited on SiO2, Si, and poly(methyl methacrylate), along with improved adhesion, electrical conductivity, and optical transparency. Additionally, we confirm that a metal–insulator–metal optical resonator can be successfully generated using a silk insulating layer without the use of a metallic adhesion layer.

  4. STUDY ON STRATEGY OF DYNAMIC JOINT ROUTING AND RESOURCE ALLOCATION IN LAYERED OPTICAL TRANSPORT NETWORKS

    Institute of Scientific and Technical Information of China (English)

    Su Yang; Xu Zhanqi; Zhao Ruiqin; Liu Zengji

    2008-01-01

    A layered network model for optical transport networks is proposed in this paper, which involves Internet Protocol (IP), Synchronous Digital Hierarchy (SDH) and Wavelength Division Multiplexing (WDM) layers. The strategy of Dynamic Joint Routing and Resource Allocation (DJRRA) and its algorithm description are also presented for the proposed layered network model. DJRRA optimizes the bandwidth usage of interface links between different layers and the logic links inside all layers. The simulation results show that DJRRA can reduce the blocking probability and increase network throughput effectively, which is in contrast to the classical separate sequential routing and resource allocation solutions.

  5. Optical limiting of layered transition metal dichalcogenide semiconductors

    CERN Document Server

    Dong, Ningning; Feng, Yanyan; Zhang, Saifeng; Zhang, Xiaoyan; Chang, Chunxia; Fan, Jintai; Zhang, Long; Wang, Jun

    2015-01-01

    Nonlinear optical property of transition metal dichalcogenide (TMDC) nanosheet dispersions, including MoS2, MoSe2, WS2, and WSe2, was performed by using Z-scan technique with ns pulsed laser at 1064 nm and 532 nm. The results demonstrate that the TMDC dispersions exhibit significant optical limiting response at 1064 nm due to nonlinear scattering, in contrast to the combined effect of both saturable absorption and nonlinear scattering at 532 nm. Selenium compounds show better optical limiting performance than that of the sulfides in the near infrared. A liquid dispersion system based theoretical modelling is proposed to estimate the number density of the nanosheet dispersions, the relationship between incident laser fluence and the size of the laser generated micro-bubbles, and hence the Mie scattering-induced broadband optical limiting behavior in the TMDC dispersions.

  6. Radiation Hard Multi-Layer Optical Coatings Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Next-generation space telescopes require advanced optical coatings to provide low-loss polarization-preserving transmission/reflection of light in a variety of...

  7. High quality ZnO layers with adjustable refractive indices for integrated optics applications

    NARCIS (Netherlands)

    Heideman, R.G.; Lambeck, P.V.; Gardeniers, J.G.E.

    1995-01-01

    Thin ( 1 μm) crystalline ZnO films with a good optical quality and good (0002) texture are grown under two considerably different process parameter sets using a r.f. planar magnetron sputtering unit. The optical parameters of the two corresponding ZnO layers are distinctly different: high refractive

  8. High quality ZnO layers with adjustable refractive indices for integrated optics applications

    NARCIS (Netherlands)

    Heideman, Rene; Lambeck, Paul; Gardeniers, Johannes G.E.

    1995-01-01

    Thin (approx. 1 μm) crystalline ZnO films with a good optical quality and a good (0002) texture are grown under two considerably different process parameter sets using a r.f. planar magnetron sputtering unit. The optical parameters of the two corresponding ZnO layers are distinctly different: high

  9. Unidirectional light propagation through two-layer nanostructures based on optical near-field interactions

    CERN Document Server

    Naruse, Makoto; Ishii, Satoshi; Drezet, Aurélien; Huant, Serge; Hoga, Morihisa; Ohyagi, Yasuyuki; Matsumoto, Tsutomu; Tate, Naoya; Ohtsu, Motoichi

    2014-01-01

    We theoretically demonstrate direction-dependent polarization conversion efficiency, yielding unidirectional light transmission, through a two-layer nanostructure by using the angular spectrum representation of optical near-fields. The theory provides results that are consistent with electromagnetic numerical simulations. This study reveals that optical near-field interactions among nanostructured matter can provide unique optical properties, such as the unidirectionality observed here, and offers fundamental guiding principles for understanding and engineering nanostructures for realizing novel functionalities.

  10. Practical Privacy in WDM Networks with All-Optical Layered Encryption

    OpenAIRE

    Engelmann, Anna; Jukan, Admela

    2016-01-01

    Privacy in form of anonymous communication could be comparably both faster and harder to break in optical routers than in today's anonymous IP networks based on The Onion Routing (Tor). Implementing the practical privacy alloptically,however, is not straightforward, as it requires key generation in each anonymization node to avoid distribution of long keys, and layered encryption, both at the optical line rate. Due to the unavailability of cryptographically strong optical key generation and e...

  11. Optic nerve head and fibre layer imaging for diagnosing glaucoma

    Science.gov (United States)

    Michelessi, Manuele; Lucenteforte, Ersilia; Oddone, Francesco; Brazzelli, Miriam; Parravano, Mariacristina; Franchi, Sara; Ng, Sueko M; Virgili, Gianni

    2016-01-01

    Background The diagnosis of glaucoma is traditionally based on the finding of optic nerve head (ONH) damage assessed subjectively by ophthalmoscopy or photography or by corresponding damage to the visual field assessed by automated perimetry, or both. Diagnostic assessments are usually required when ophthalmologists or primary eye care professionals find elevated intraocular pressure (IOP) or a suspect appearance of the ONH. Imaging tests such as confocal scanning laser ophthalmoscopy (HRT), optical coherence tomography (OCT) and scanning laser polarimetry (SLP, as used by the GDx instrument), provide an objective measure of the structural changes of retinal nerve fibre layer (RNFL) thickness and ONH parameters occurring in glaucoma. Objectives To determine the diagnostic accuracy of HRT, OCT and GDx for diagnosing manifest glaucoma by detecting ONH and RNFL damage. Search methods We searched several databases for this review. The most recent searches were on 19 February 2015. Selection criteria We included prospective and retrospective cohort studies and case-control studies that evaluated the accuracy of OCT, HRT or the GDx for diagnosing glaucoma. We excluded population-based screening studies, since we planned to consider studies on self-referred people or participants in whom a risk factor for glaucoma had already been identified in primary care, such as elevated IOP or a family history of glaucoma. We only considered recent commercial versions of the tests: spectral domain OCT, HRT III and GDx VCC or ECC. Data collection and analysis We adopted standard Cochrane methods. We fitted a hierarchical summary ROC (HSROC) model using the METADAS macro in SAS software. After studies were selected, we decided to use 2 × 2 data at 0.95 specificity or closer in meta-analyses, since this was the most commonly-reported level. Main results We included 106 studies in this review, which analysed 16,260 eyes (8353 cases, 7907 controls) in total. Forty studies (5574

  12. VLBA Teams With Optical Interferometer to Study Star's Layers

    Science.gov (United States)

    2007-05-01

    Structure of S Ori (Artist's Impression) "Astronomers are like medical doctors, who use various instruments to examine different parts of the human body," said co-author David Boboltz. "While the mouth can be checked with a simple light, a stethoscope is required to listen to the heart beat. Similarly the heart of the star can be observed in the optical, the molecular and dust layers can be studied in the infrared and the maser emission can be probed with radio instruments. Only the combination of the three gives us a more complete picture of the star and its envelope." The maser emission comes from silicon monoxide (SiO) molecules and can be used to image and track the motion of gas clouds in the stellar envelope roughly 10 times the size of the Sun. The astronomers observed S Ori with two of the largest interferometric facilities available: the ESO Very Large Telescope Interferometer (VLTI) at Paranal, observing in the near- and mid-infrared, and the NRAO-operated Very Long Baseline Array (VLBA), that takes measurements in the radio wave domain. Because the star's luminosity changes periodically, the astronomers observed it simultaneously with both instruments, at several different epochs. The first epoch occurred close to the stellar minimum luminosity and the last just after the maximum on the next cycle. ESO PR Photo 25c/07 ESO PR Photo 25c/07 S Ori to Scale (Artist's Impression) The astronomers found the star's diameter to vary between 7.9 milliarcseconds and 9.7 milliarcseconds. At the distance of S Ori, this corresponds to a change of the radius from about 1.9 to 2.3 times the distance between the Earth and the Sun, or between 400 and 500 solar radii! As if such sizes were not enough, the inner dust shell is found to be about twice as big. The maser spots, which also form at about twice the radius of the star, show the typical structure of partial to full rings with a clumpy distribution. Their velocities indicate that the gas is expanding radially, moving away at a

  13. Metallic wave-impedance matching layers for broadband terahertz optical systems.

    Science.gov (United States)

    Kröll, Josef; Darmo, Juraj; Unterrainer, Karl

    2007-05-28

    We examine the potential of ultra-thin metallic layers for broadband wave-impedance matching in the terahertz frequency range. The metallic layer is modeled using Fresnel formulae for stratified optical medium. Experimental data for chromium and indium-tin-oxide layers, measured using time-domain terahertz spectroscopy over the frequency range 0.4 - 4.5 THz, are compared with theoretical results.

  14. Twenty-Layer Optical Disc Fabricated by Web Coating and Lamination

    Science.gov (United States)

    Mikami, Tatsuo; Mochizuki, Hidehiro; Sasaki, Toshio; Kitahara, Toshiyuki; Tsuyama, Hiroaki; Inoue, Kenichirou; Ito, Masaharu

    2013-09-01

    We developed a new fabrication method for multilayer optical discs for the high-throughput production of such discs. We used web coating and lamination to prepare a stacked unit. The stacked unit was a layered structure consisting of a recording layer, a UV resin layer, a recording layer, and a pressure-sensitive adhesive layer. We obtained a 20-layer disc simply by laminating the stacked units 10 times. The transmittance of the 20 recording layers was 87% owing to the high transparency of the two-photon recording material. A scanning electron microscopy (SEM) image of the disc showed a clear multilayer structure. The recording layers of the disc were recorded using a pulse laser without interlayer cross write. The thickness variation of the transparent part of the disc was within +/-2 µm, and the tilt angles of the disc satisfied the Blu-ray disc (BD) specifications.

  15. Investigating the effects of capping layer on optical gain of nitride based semiconductor nanostructure lasers

    Science.gov (United States)

    Annabi Milani, E.; Mohadesi, V.; Asgari, A.

    2017-04-01

    In this study, the effects of GaN capping layer on the behaviour of AlGaN/GaN nanostructure based laser is considered. We have employed the self-consistent solution of Poisson and Schrodinger equations for calculation of the energy levels, wave functions and conduction and valance bands profile. The impact of different thicknesses of the capping layer has been studied for sheet carrier density, then on optical gain. The results indicate that, by increasing the thickness of the cap layer, the optical gain decreases.

  16. Comprehensive optical studies on SnS layers synthesized by chemical bath deposition

    Science.gov (United States)

    Gedi, Sreedevi; Minnam Reddy, Vasudeva Reddy; Park, Chinho; Chan-Wook, Jeon; Ramakrishna Reddy, K. T.

    2015-04-01

    A simple non-vacuum and cost effective wet chemical technique, chemical bath deposition was used to prepare tin sulphide (SnS) layers on glass substrates. The layers were formed by varying bath temperature in the range, 40-80 °C, keeping other deposition parameters as constant. An exhaustive investigation on their optical properties with bath temperature was made using the transmittance and reflectance measurements. The absorption coefficient was evaluated from the optical transmittance data utilizing Lambert's principle and is >104 cm-1 for all the as-prepared layers. The energy band gap of the layers was determined from the differential reflectance spectra that varied from 1.41 eV to 1.30 eV. Consequently, refractive index and extinction coefficient were obtained from Pankov relations and dispersion constants were calculated using Wemple-Didomenico method. In addition, other optical parameters such as the optical conductivity, dielectric constants, dissipation factor, high frequency dielectric constant and relaxation time were also calculated. Finally electrical parameters such as resistivity, carrier mobility and carrier density of as-prepared layers were estimated using optical data. A detailed analysis of the dependence of all above mentioned parameters on bath temperature is reported and discussed for a clean understanding of electronic characteristics of SnS layers.

  17. Hydrogen-induced electrical and optical switching in Pd capped Pr nanoparticle layers

    Indian Academy of Sciences (India)

    Shubhra Kala; B R Mehta

    2008-06-01

    In this study, modification in the properties of hydrogen-induced switchable mirror based on Pr nanoparticle layers is reported. The reversible changes in hydrogen-induced electrical and optical properties of Pd capped Pr nanoparticle layers have been studied as a function of hydrogenation time and compared with the conventional device based on Pd capped Pr thin films. Faster electrical and optical response, higher optical contrast and presence of single absorption edge corresponding to Pr trihydride state in hydrogen loaded state have been observed in the case of nanoparticle layers. The improvement in the electrical and optical properties have been explained in terms of blue shift in the absorption edge due to quantum confinement effect, larger number of interparticle boundaries, presence of defects, loose adhesion to the substrate and enhanced surface to volume atom ratio at nanodimension.

  18. Optical extinction in a single layer of nanorods

    CERN Document Server

    Ghenuche, Petru; Laroche, Marine; Bardou, Nathalie; Haïdar, Riad; Pelouard, Jean-Luc; Collin, Stéphane

    2012-01-01

    We demonstrate that almost 100 % of incident photons can interact with a monolayer of scatterers in a symmetrical environment. Nearly-perfect optical extinction through free-standing transparent nanorod arrays has been measured. The sharp spectral opacity window, in the form of a characteristic Fano resonance, arises from the coherent multiple scattering in the array. In addition, we show that nanorods made of absorbing material exhibit a 25-fold absorption enhancement per unit volume compared to unstructured thin film. These results open new perspectives for light management in high-Q, low volume dielectric nanostructures, with potential applications in optical systems, spectroscopy, and optomechanics.

  19. Transport of Optically Active Particles from the Surface Mixed Layer

    Science.gov (United States)

    2005-09-30

    aragonite in the form of abundant coccoliths and coccospheres, and occasional forams, pteropods and larval gastropods . The δ18O signature of the 2003... APPLICATIONS These experiments were designed to identify the major loss terms of optically-active particles. This indeed was accomplished. Such

  20. Strong THz and Infrared Optical Forces on a Suspended Single-Layer Graphene Sheet

    CERN Document Server

    Mousavi, S Hossein; Wang, Zheng

    2014-01-01

    Single-layer graphene exhibits exceptional mechanical properties attractive for optomechanics: it combines low mass density, large tensile modulus, and low bending stiffness. However, at visible wavelengths, graphene absorbs weakly and reflects even less, thereby inadequate to generate large optical forces needed in optomechanics. Here, we numerically show that a single-layer graphene sheet is sufficient to produce strong optical forces under terahertz or infrared illumination. For a system as simple as graphene suspended atop a uniform substrate, high reflectivity from the substrate is crucial in creating a standing-wave pattern, leading to a strong optical force on graphene. This force is readily tunable in amplitude and direction by adjusting the suspension height. In particular, repellent optical forces can levitate graphene to a series of stable equilibrium heights above the substrate. One of the key parameters to maximize the optical force is the excitation frequency: peak forces are found near the scat...

  1. Isotropy of optical excitations in few-layer graphenes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.H. [Department of Physics, National Cheng Kung University, 701 Tainan, Taiwan (China); Shyu, F.L. [Department of Physics, R.O.C. Military Academy, 830 Kaohsiung, Taiwan (China); Chiu, C.W., E-mail: giorgio@fonran.com.t [Department of Physics, National Cheng Kung University, 701 Tainan, Taiwan (China); Lin, M.F., E-mail: mflin@mail.ncku.edu.t [Department of Physics, National Cheng Kung University, 701 Tainan, Taiwan (China)

    2010-07-26

    The geometric and the most band structures of monolayer and AB-stacked bilayer graphenes exhibit strong anisotropy. Nevertheless, the absorption spectra are isotropic for the polarization vector on graphene plane. The velocity matrix elements dominate this property. These results suggest that AA- and AB-stacked few-layer graphenes and graphites manifest this feature.

  2. The Effect of Optic Disc Center Displacement on Retinal Nerve Fiber Layer Measurement Determined by Spectral Domain Optical Coherence Tomography

    Science.gov (United States)

    Uhm, Ki Bang; Sung, Kyung Rim; Kang, Min Ho; Cho, Hee Yoon; Seong, Mincheol

    2016-01-01

    Purpose To investigate the effect of optic disc center displacement on retinal nerve fiber layer (RNFL) measurement determined by spectral domain optical coherence tomography (SD-OCT). Methods The optic disc center was manipulated at 1-pixel intervals in horizontal, vertical, and diagonal directions. According to the manipulated optic disc center location, the RNFL thickness data were resampled: (1) at a 3.46-mm diameter circle; and (2) between a 2.5-mm diameter circle and 5.4-mm square. Error was calculated between the original and resampled RNFL measurements. The tolerable error threshold of the optic disc center displacement was determined by considering test-retest variability of SD-OCT. The unreliable zone was defined as an area with 10% or more variability. Results The maximum tolerable error thresholds of optic disc center displacement on the RNFL thickness map were distributed from 0.042 to 0.09 mm in 8 directions. The threshold shape was vertically elongated. Clinically important unreliable zones were located: (1) at superior and inferior region in the vertical displacement; (2) at inferotemporal region in the horizontal displacement, and (3) at superotemporal or inferotemporal region in the diagonal displacement. The unreliable zone pattern and threshold limit varied according to the direction of optic disc displacement. Conclusions Optic disc center displacement had a considerable impact on whole RNFL thickness measurements. Understanding the effect of optic disc center displacement could contribute to reliable RNFL measurements. PMID:27783663

  3. Nanoparticle-Based Brachytherapy Spacers for Delivery of Localized Combined Chemoradiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Rajiv, E-mail: r.kumar@neu.edu [Nanomedicine Science and Technology Center, Northeastern University, Boston, Massachusetts (United States); Department of Radiation Oncology, Brigham and Women' s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts (United States); Belz, Jodi [Nanomedicine Science and Technology Center, Northeastern University, Boston, Massachusetts (United States); Markovic, Stacey [Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts (United States); Jadhav, Tej; Fowle, William [Nanomedicine Science and Technology Center, Northeastern University, Boston, Massachusetts (United States); Niedre, Mark [Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts (United States); Cormack, Robert; Makrigiorgos, Mike G. [Department of Radiation Oncology, Brigham and Women' s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts (United States); Sridhar, Srinivas [Nanomedicine Science and Technology Center, Northeastern University, Boston, Massachusetts (United States); Department of Radiation Oncology, Brigham and Women' s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts (United States)

    2015-02-01

    Purpose: In radiation therapy (RT), brachytherapy-inert source spacers are commonly used in clinical practice to achieve high spatial accuracy. These implanted devices are critical technical components of precise radiation delivery but provide no direct therapeutic benefits. Methods and Materials: Here we have fabricated implantable nanoplatforms or chemoradiation therapy (INCeRT) spacers loaded with silica nanoparticles (SNPs) conjugated containing a drug, to act as a slow-release drug depot for simultaneous localized chemoradiation therapy. The spacers are made of poly(lactic-co-glycolic) acid (PLGA) as matrix and are physically identical in size to the commercially available brachytherapy spacers (5 mm × 0.8 mm). The silica nanoparticles, 250 nm in diameter, were conjugated with near infrared fluorophore Cy7.5 as a model drug, and the INCeRT spacers were characterized in terms of size, morphology, and composition using different instrumentation techniques. The spacers were further doped with an anticancer drug, docetaxel. We evaluated the in vivo stability, biocompatibility, and biodegradation of these spacers in live mouse tissues. Results: The electron microscopy studies showed that nanoparticles were distributed throughout the spacers. These INCeRT spacers remained stable and can be tracked by the use of optical fluorescence. In vivo optical imaging studies showed a slow diffusion of nanoparticles from the spacer to the adjacent tissue in contrast to the control Cy7.5-PLGA spacer, which showed rapid disintegration in a few days with a burst release of Cy7.5. The docetaxel spacers showed suppression of tumor growth in contrast to control mice over 16 days. Conclusions: The imaging with the Cy7.5 spacer and therapeutic efficacy with docetaxel spacers supports the hypothesis that INCeRT spacers can be used for delivering the drugs in a slow, sustained manner in conjunction with brachytherapy, in contrast to the rapid clearance of the drugs when

  4. UV optical properties of thin film oxide layers deposited by different processes.

    Science.gov (United States)

    Pellicori, Samuel F; Martinez, Carol L

    2011-10-01

    UV optical properties of thin film layers of compound and mixed oxide materials deposited by different processes are presented. Japan Electron Optics Laboratory plasma ion assisted deposition (JEOL PIAD), electron beam with and without IAD, and pulsed DC magnetron sputtering were used. Comparisons are made with published deposition process data. Refractive indices and absorption values to as short as 145 nm were measured by spectroscopic ellipsometry (SE). Electronic interband defect states are detected that are deposition-process dependent. SE might be effective in identifying UV optical film quality, especially in defining processes and material composition beneficial for high-energy excimer laser applications and environments requiring stable optical properties.

  5. Optical characteristics of a-Si:H layers deposited by PACVD at various temperatures

    Science.gov (United States)

    Jaglarz, Janusz; Jurzecka-Szymacha, Maria; Tkacz-Śmiech, Katarzyna; Sahraoui, Bouchta

    2015-01-01

    Amorphous a-Si:H layers fabricated by plasma assisted chemical vapour deposition are studied. The layers were grown on monocrystalline silicon at various temperatures, ranging from the room temperature to 400 °C. Structure and chemical composition (hydrogen content) of the layers were characterized by use of fourier transform infrared spectroscopy (FTIR). A main attention in the studies was focused on optical properties of the layers. The respective measurements were made by variable angle spectroscopic ellipsometry within 170-1900 nm spectral range, at room temperature and during post-annealing the sample up to 400 °C. The Kramers-Krönig optical model was matched to the ellipsometric angle spectra, Ψ(λ) and Δ(λ), and hence the layers' thicknesses and optical indices were calculated. The band gap of the studied materials was calculated from the Tauc expression for the extinction index near the band edge. The results show that the layers deposited at 150 °C have similar properties. Their growth rate is higher than 0.1 nm/s and hydrogen content does not exceed 10 at.%. All they have relatively high refractive index within visible light range. The highest refractive index is for the layer deposited at 400 °C and reaches almost 4.0 at 460 nm. The band gap of all layers deposited at 150 °C and above exceeds 2 eV but is not higher than 2.4 eV. The band gap of the layers deposited below 150 °C is less than 2 eV. Post-annealing of the layers for 40 min at 400 °C does not change their optical indices but clearly reduces the depolarization.

  6. Optical behavior of silver nanoparticles embedded in polymer thin film layers

    Science.gov (United States)

    Carlberg, M.; Pourcin, F.; Margeat, O.; Le Rouzo, J.; Berginc, G.; Sauvage, R.-M.; Ackermann, J.; Escoubas, L.

    2016-09-01

    The study of metal nanoparticles (NPs) is challenging for the control of the light matter interaction phenomena. In this context, our work is focused on optical characterization and modeling of polymer thin films layers with inclusions of previously chemically synthesized NPs. Through the presence of metallic NPs in polymer thin films, the optical properties are assumed to become tunable. Thin film layers with inclusions of differently shaped and sized silver NPs, such as nanospheres and nanoprisms, are optically characterized to get the scattering, the reflection and the absorption of the layers. One step and two step seed based methods of silver ions reduction are used for the chemical synthesis of nanospheres and nanoprisms. The plasmonic resonance peaks of these colloidal solutions range from 360 to 1300 nm. A poly vinyl pyrrolidone (PVP) polymer matrix is chosen for its light non-absorbing and NP-stabilizing properties. Knowledge on the shape and size of the NPs embedded in the spin coated layers is obtained by transmission electron microscopy (TEM) imaging. The optical properties include spectrophotometry and spectroscopic ellipsometry (SE) measurements to get the reflectance, the transmittance, the absorptance and the optical indices n and k of the heterogeneous layers. A redshift in absorption is measured between deposited nanospheres and other shaped NPs. FDTD simulations allow calculation of far and near field properties. The visualization of the NP interactions and the electric field enhancement, on and around the NPs, are studied to improve the understanding of the far field properties.

  7. Control of Boundary Layers for Aero-optical Applications

    Science.gov (United States)

    2015-06-23

    fluctuating density cause initially planar optical wavefronts passing through them to be distorted ( Gladstone & Dale, 1863; Liepmann, 1952; Tatarski...8217),,( tyxOPLtyxOPLtyxOPD dytzyxKtyxOPL b a GD −= = ∫ ρ (1.1) where KGD is the Gladstone -Dale constant, the integration is...Ross, 2009; Porter, et al. 2013) Sutton ( 1969 ) introduced the most widely cited theoretical formulation for calculating the effect of turbulent

  8. Enhancement of Magneto-Optic Effect in Optical Isolator with Semiconductor Guiding Layer by Selective Oxidation of AlInAs

    Institute of Scientific and Technical Information of China (English)

    Takashi; Sakai; Yuya; Shoji; Hideki; Yokoi; Tetsuya; Mizumoto

    2003-01-01

    Selective oxidation of an AlInAs layer was investigated for enhancement of magneto-optic effect in an optical isolator. Twelve times nonreciprocal phase shift enhancement was estimated from a measured AlInAs-oxide refractive index.

  9. Hierarchical Supervisor and Agent Routing Algorithm in LEO/MEO Double-layered Optical Satellite Network

    Science.gov (United States)

    Li, Yongjun; Zhao, Shanghong

    2016-09-01

    A novel routing algorithm (Hierarchical Supervisor and Agent Routing Algorithm, HSARA) for LEO/MEO (low earth orbit/medium earth orbit) double-layered optical satellite network is brought forward. The so-called supervisor (MEO satellite) is designed for failure recovery and network management. LEO satellites are grouped according to the virtual managed field of MEO which is different from coverage area of MEO satellite in RF satellite network. In each LEO group, one LEO satellite which has maximal persistent link with its supervisor is called the agent. A LEO group is updated when this optical inter-orbit links between agent LEO satellite and the corresponding MEO satellite supervisor cuts off. In this way, computations of topology changes and LEO group updating can be decreased. Expense of routing is integration of delay and wavelength utilization. HSARA algorithm simulations are implemented and the results are as follows: average network delay of HSARA can reduce 21 ms and 31.2 ms compared with traditional multilayered satellite routing and single-layer LEO satellite respectively; LEO/MEO double-layered optical satellite network can cover polar region which cannot be covered by single-layered LEO satellite and throughput is 1% more than that of single-layered LEO satellite averagely. Therefore, exact global coverage can be achieved with this double-layered optical satellite network.

  10. Optical Detection Using Four-Layer Semiconductor Structures

    Science.gov (United States)

    2005-06-01

    analog considers the thyristor, specifically in this case a Shockley diode, as two Bipolar Junction Transistors (BJTs), one npn and one pnp, con- 15...appropriate BJT layer: emitter (E), base (B) and collector (C). The subscript pnp or npn is used to distinguish between the two transistors . It must be...both transistors in the active mode. The holes gathering in the pnp collector (P2) and the electrons in npn collector (N1) have no external escape

  11. LOCO: Characterization of Phytoplankton in Thin Optical Layers

    Science.gov (United States)

    2008-01-01

    this process is that compatible gametes must be successful in finding each other in a dilute, watery environment. We have hypothesized that the...close proximity of cells in a dense thin layer should facilitate this process. Consistent with these ideas, male gamete formation, as well as auxospores...various stages of male gamete formation. CytoSense Evaluation. Our CytoSense scanning, in-line flow cytometer was specifically designed to study the

  12. Decreased retinal nerve fibre layer thickness detected by optical coherence tomography in patients with ethambutol‐induced optic neuropathy

    Science.gov (United States)

    Chai, Samantha J; Foroozan, Rod

    2007-01-01

    Background It is difficult to assess the degree of optic nerve damage in patients with ethambutol‐induced optic neuropathy, especially just after the onset of visual loss, when the optic disc typically looks normal. Aim To evaluate changes in retinal nerve fibre layer thickness (RNFLT) using optical coherence tomography (OCT) in patients with optic neuropathy within 3 months of cessation of ethambutol treatment. Design A retrospective observational case series from a single neuro‐ophthalmology practice. Methods 8 patients with a history of ethambutol‐induced optic neuropathy were examined within 3 months after stopping ethambutol treatment. All patients underwent a neuro‐ophthalmologic examination, including visual acuity, colour vision, visual fields and funduscopy. OCT was performed on both eyes of each patient using the retinal nerve fibre layer analysis protocol. Results The interval between cessation of ethambutol treatment and the initial visit ranged from 1 week to 3 months. All patients had visual deficits characteristic of ethambutol‐induced optic neuropathy at their initial visit, and the follow‐up examination was performed within 12 months. Compared with the initial RNFLT, there was a statistically significant decrease in the mean RNFLT of the temporal, superior and nasal quadrants (p = 0.009, 0.019 and 0.025, respectively), with the greatest decrease in the temporal quadrant (mean decrease 26.5 μm). Conclusions A decrease in RNFLT is observed in all quadrants in patients with ethambutol‐induced optic neuropathy who have recently discontinued the medication. This decrease is most pronounced in the temporal quadrant of the optic disc. PMID:17215265

  13. The Physics of Boundary-Layer Aero-Optic Effects

    Science.gov (United States)

    2012-09-01

    index-of refraction in turn depends on the media density, ρ, via a Gladstone -Dale relation, [1], ’)1( nKnK GDGD =−=ρ , where KGD is a Gladstone -Dale...6. References [1] Gladstone , J. H., Dale, T. P. 1863 “Researches on the Refraction, Dispersion, and Sensitiveness of Liquids”, Philosophical...AIAA J, 7 9 ( 1969 ), pp. 1737–1743. [9] R.J. Hugo and E.J. Jumper, ”Applicability of the Aero-Optic Linking Equation to a Highly Coherent

  14. Optical Phased Array Using Guided Resonance with Backside Reflectors

    Science.gov (United States)

    Horie, Yu (Inventor); Arbabi, Amir (Inventor); Faraon, Andrei (Inventor)

    2016-01-01

    Methods and systems for controlling the phase of electromagnetic waves are disclosed. A device can consist of a guided resonance grating layer, a spacer, and a reflector. A plurality of devices, arranged in a grid pattern, can control the phase of reflected electromagnetic phase, through refractive index control. Carrier injection, temperature control, and optical beams can be applied to control the refractive index.

  15. Extraction of optical scattering parameters and attenuation compensation in optical coherence tomography images of multi-layered tissue structures

    DEFF Research Database (Denmark)

    Thrane, Lars; Frosz, Michael Henoch; Tycho, Andreas

    2004-01-01

    A recently developed analytical optical coherence tomography (OCT) model [Thrane et al., J. Opt. Soc. Am. A 17, 484 (2000)] allows the extraction of optical scattering parameters from OCT images, thereby permitting attenuation compensation in those images. By expanding this theoretical model, we...... have developed a new method for extracting optical scattering parameters from multilayered tissue structures in vivo. To verify this, we used a Monte Carlo (MC) OCT model as a numerical phantom to simulate the OCT signal for het-erogeneous multilayered tissue. Excellent agreement between the extracted...... values of the optical scattering properties of the different layers and the corresponding input reference values of the MC simulation was obtained, which demonstrates the feasibility of the method for in vivo applications. This is to our knowledge the first time such verification has been obtained...

  16. Mask specification guidelines in spacer patterning technology

    Science.gov (United States)

    Hashimoto, Kohji; Mukai, Hidefumi; Miyoshi, Seiro; Yamaguchi, Shinji; Mashita, Hiromitsu; Kobayashi, Yuuji; Kawano, Kenji; Hirano, Takashi

    2008-11-01

    We have studied both the mask CD specification and the mask defect specification for spacer patterning technology (SPT). SPT has the possibility of extending optical lithography to below 40nm half-pitch devices. Since SPT necessitates somewhat more complicated wafer process flow, the CD error and mask defect printability on wafers involve more process factors compared with conventional single-exposure process (SEP). This feature of SPT implies that it is very important to determine mask-related specifications for SPT in order to select high-end mask fabrication strategies; those are for mask writing tools, mask process development, materials, inspection tools, and so on. Our experimental studies reveal that both mask CD specification and mask defect specification are somehow relaxed from those in ITRS2007. This is most likely because SPT reduces mask CD error enhanced factor (MEF) and the reduction of line-width roughness (LWR).

  17. Aerosols optical properties in Titan's Detached Haze Layer

    Science.gov (United States)

    Seignovert, Benoit; Rannou, Pascal; Lavvas, Panayotis; West, Robert

    2016-10-01

    Titan's Detached Haze Layer (DHL) was first observed in 1983 by Rages and Pollack during the Voyager 2 is a consistent spherical haze feature surrounding Titan's upper atmosphere and detached from the main haze. Since 2005, the Imaging Science Subsystem (ISS) instrument on board the Cassini mission performs a continuous survey of the Titan's atmosphere and confirmed its persistence at 500 km up to the equinox (2009) before its drop and disappearance in 2012 (West et al. 2011). Previous analyses showed, that this layer corresponds to the transition area between small spherical aerosols and large fractal aggregates and play a key role in the aerosols formation in Titan's atmosphere (Rannou et al. 2000, Lavvas et al. 2009, Cours et al. 2011).In this talk we will present the UV photometric analyses based on radiative transfer inversion to retrieve aerosols particles properties in the DHL (bulk and monomer radius and local density) performed on ISS observations taken from 2005 to 2007.References:- Rages and Pollach, Icarus 55 (1983)- West, et al., Icarus 38 (2011)- Rannou, et al., Icarus 147 (2000)- Lavvas, et al., Icarus 201 (2009)- Cours, et al., ApJ Lett. 741 (2015)

  18. Optical characteristics of silicon nanowires grown from tin catalyst layers on silicon coated glass

    KAUST Repository

    Ball, Jeremy

    2012-08-20

    The optical characteristics of silicon nanowires grown on Si layers on glass have been modeled using the FDTD (Finite Difference Time Domain) technique and compared with experimental results. The wires were grown by the VLS (vapour-liquid-solid) method using Sn catalyst layers and exhibit a conical shape. The resulting measured and modeled absorption, reflectance and transmittance spectra have been investigated as a function of the thickness of the underlying Si layer and the initial catalyst layer, the latter having a strong influence on wire density. High levels of absorption (>90% in the visible wavelength range) and good agreement between the modeling and experiment have been observed when the nanowires have a relatively high density of ∼4 wires/μ m2. The experimental and modeled results diverge for samples with a lower density of wire growth. The results are discussed along with some implications for solar cell fabrication. © 2012 Optical Society of America.

  19. Near-field optical microscopy and spectroscopy of few-layer black phosphorous

    Science.gov (United States)

    Frenzel, A. J.; Tran, S.; Hinton, J. P.; Sternbach, A. J.; Yang, J.; Gillgren, N.; Lau, C. N.; Basov, D. N.

    Few-layer black phosphorous is a recent addition to the family of two-dimensional (2D) materials which exhibits strongly anisotropic transport and optical properties due to its puckered honeycomb structure. It was recently predicted that this intrinsic anisotropy should manifest in the plasmon dispersion. Additionally, tuning layer number and carrier density can control the dispersion of these collective modes. Scanning near-field optical microscopy (SNOM) has been demonstrated as a powerful method to probe electronic properties, including propagating collective modes, in layered 2D materials. We used SNOM to investigate anisotropic carrier response in few-layer black phosphorous encapsulated by hexagonal boron nitride. In addition to exploring gate-voltage tunability of the electronic response, we demonstrate effective modulation of the near-field signal by ultrafast photoexcitation.

  20. Current status and challenges in optical turbulence simulations in various layers of the Earth's atmosphere

    Science.gov (United States)

    He, Ping; Nunalee, Christopher G.; Basu, Sukanta; Vorontsov, Mikhail A.; Fiorino, Steven T.

    2014-10-01

    In this study, we present a brief review on the existing approaches for optical turbulence estimation in various layers of the Earth's atmosphere. The advantages and disadvantages of these approaches are also discussed. An alternative approach, based on mesoscale modeling with parameterized turbulence, is proposed and tested for the simulation of refractive index structure parameter (C2n ) in the atmospheric boundary layer. The impacts of a few atmospheric flow phenomena (e.g., low-level jets, island wake vortices, gravity waves) on optical turbulence are discussed. Consideration of diverse geographic settings (e.g., flat terrain, coastal region, ocean islands) makes this study distinct.

  1. Simultaneous measurement of aero-optical distortion and turbulent structure in a heated boundary layer

    Science.gov (United States)

    Saxton-Fox, Theresa; McKeon, Beverley; Smith, Adam; Gordeyev, Stanislav

    2014-11-01

    This study examines the relationship between turbulent structures and the aero-optical distortion of a laser beam passing through a turbulent boundary layer. Previous studies by Smith et al. (AIAA, 2014--2491) have found a bulk convection velocity of 0 . 8U∞ for aero-optical distortion in turbulent boundary layers, motivating a comparison of the distortion with the outer boundary layer. In this study, a turbulent boundary layer is developed over a flat plate with a moderately-heated section of length 25 δ . Density variation in the thermal boundary layer leads to aero-optical distortion, which is measured with a Malley probe (Smith et al., AIAA, 2013--3133). Simultaneously, 2D PIV measurements are recorded in a wall-normal, streamwise plane centered on the Malley probe location. Experiments are run at Reθ = 2100 and at a Mach number of 0.03, with the heated wall 10 to 20°C above the free stream temperature. Correlations and conditional averages are carried out between Malley probe distortion angles and flow features in the PIV vector fields. Aero-optical distortion in this study will be compared to distortion in higher Mach number flows studied by Gordeyev et al. (J. Fluid Mech., 2014), with the aim of extending conclusions into compressible flows. This research is made possible by the Department of Defense through the National Defense & Engineering Graduate Fellowship (NDSEG) Program and by the Air Force Office of Scientific Research Grant # FA9550-12-1-0060.

  2. Optical control of graphene plasmon using liquid crystal layer 29K New One

    Science.gov (United States)

    2017-03-01

    the basic research and establishes possible optical ways to control the surface plasmon polariton in graphene layer. A system comprises the graphene...Project main idea The project is devoted to the basic research and establishes possible optical ways to control the surface plasmon polariton in...H H E     (5) Demanding the boundary conditions (5) to be satisfied we obtain after some algebraic transformations a dispersion equation for

  3. Magneto-optical characteristics of layered Epsilon-Near-Zero metamaterials

    Science.gov (United States)

    Abdi-Ghaleh, Reza; Suldozi, Reza

    2016-09-01

    The transmittance magneto-optical (MO) characteristics of Epsilon-Near-Zero (ENZ) metamaterials are studied, using 4 by 4 transfer matrix method. The considered structures are a free standing ENZ-MO slab, and a microcavity type multi-layer structure containing an ENZ-MO layer. The transmittance coefficients of the right- and left-handed circular polarizations for the slab are analytically obtained and numerically investigated. Furthermore, these characteristics are numerically studied for the multi-layer structure. In addition, the Faraday rotations of both structures are investigated. The results reveal the circular polarization filtering effects.

  4. Optical properties of PZT thin films deposited on a ZnO buffer layer

    OpenAIRE

    Schneider, T.; Leduc, D; Cardin, J.; LUPI, C; Barreau, N; Gundel, H.

    2007-01-01

    International audience; The optical properties of lead zirconate titanate (PZT) thin films deposited on ZnO were studied by m-lines spectroscopy. In order to retrieve the refractive index and the thickness of both layers from the m-lines spectra, we develop a numerical algorithm for the case of a two-layer system and show its robustness in the presence of noise. The sensitivity of the algorithm of the two-layer model allows us to relate the observed changes in the PZT refractive index to the ...

  5. Optical properties of PZT thin films deposited on a ZnO buffer layer

    OpenAIRE

    Schneider, T.; Leduc, D; Cardin, J.; LUPI, C; Barreau, N; Gundel, H.

    2015-01-01

    The optical properties of lead zirconate titanate (PZT) thin films deposited on ZnO were studied by m-lines spectroscopy. In order to retrieve the refractive index and the thickness of both layers from the m-lines spectra, we develop a numerical algorithm for the case of a two-layer system and show its robustness in the presence of noise. The sensitivity of the algorithm of the two-layer model allows us to relate the observed changes in the PZT refractive index to the PZT structural change du...

  6. Optical properties of silica fibers and layered dielectric mirrors

    Energy Technology Data Exchange (ETDEWEB)

    Cooke, D.W.; Farnum, E.H.; Clinard, F.W. Jr.; Bennett, B.L. [Los Alamos National Lab., NM (United States); Portis, A.M. [Univ. of California, Berkeley, CA (United States)

    1996-04-01

    Radioluminescence (RL) from virgin and neutron-irradiated (10{sup 23} n-m{sup -2}) silica fibers has been measured in the temperature interval 4 to 300 K. Unirradiated specimens exhibit a decrease in RL intensity with increasing temperature such that the intensity is extremely weak at room temperature. The luminescence is well described by a barrier-limited exciton mechanism. in contrast, the heavily-irradiated samples show an increase in RL with elevated temperatures such that the intensity at room temperature is about twice that measured at 4 K. Neutron irradiation presumably produces many luminescence centers that act as radiative sites for exciton decay. Absolute specular reflectance of a series of neutron irradiated, layered dielectric mirrors was also measured. In addition to structural damage that has already been reported, we typically found approximately 10% reduction in the reflectance following irradiation. These results suggest that neither fibers nor dielectric mirrors are well suited for use near the high radiation area of the ITER plasma.

  7. Analysis of physical layer performance of hybrid optical-wireless access network

    Science.gov (United States)

    Shaddad, R. Q.; Mohammad, A. B.; Al-hetar, A. M.

    2011-09-01

    The hybrid optical-wireless access network (HOWAN) is a favorable architecture for next generation access network. It is an optimal combination of an optical backhaul and a wireless front-end for an efficient access network. In this paper, the HOWAN architecture is designed based on a wavelengths division multiplexing/time division multiplexing passive optical network (WDM/TDM PON) at the optical backhaul and a wireless fidelity (WiFi) technology at the wireless front-end. The HOWAN is proposed that can provide blanket coverage of broadband and flexible connection for end-users. Most of the existing works, based on performance evaluation are concerned on network layer aspects. This paper reports physical layer performance in terms of the bit error rate (BER), eye diagram, and signal-to-noise ratio (SNR) of the communication system. It accommodates 8 wavelength channels with 32 optical network unit/wireless access points (ONU/APs). It is demonstrated that downstream and upstream of 2 Gb/s can be achieved by optical backhaul for each wavelength channel along optical fiber length of 20 km and a data rate of 54 Mb/s per ONU/AP along a 50 m outdoor wireless link.

  8. Relationship Between Optic Nerve Appearance and Retinal Nerve Fiber Layer Thickness as Explored with Spectral Domain Optical Coherence Tomography

    Science.gov (United States)

    Aleman, Tomas S.; Huang, Jiayan; Garrity, Sean T.; Carter, Stuart B.; Aleman, Wendy D.; Ying, Gui-shuang; Tamhankar, Madhura A.

    2014-01-01

    Purpose To study the relationship between the appearance of the optic nerve and the retinal nerve fiber layer (RNFL) thickness determined by spectral domain optical coherence tomography (OCT). Methods Records from patients with spectral domain-OCT imaging in a neuro-ophthalmology practice were reviewed. Eyes with glaucoma/glaucoma suspicion, macular/optic nerve edema, pseudophakia, and with refractive errors > 6D were excluded. Optic nerve appearance by slit lamp biomicroscopy was related to the RNFL thickness by spectral domain-OCT and to visual field results. Results Ninety-one patients (176 eyes; mean age: 49 ± 15 years) were included. Eighty-three eyes (47%) showed optic nerve pallor; 89 eyes (50.6%) showed RNFL thinning (sectoral or average peripapillary). Average peripapillary RNFL thickness in eyes with pallor (mean ± SD = 76 ± 17 μm) was thinner compared to eyes without pallor (91 ± 14 μm, P < 0.001). Optic nerve pallor predicted RNFL thinning with a sensitivity of 69% and a specificity of 75%. Optic nerve appearance predicted RNFL thinning (with a sensitivity and specificity of 81%) when RNFL had thinned by ∼ 40%. Most patients with pallor had RNFL thinning with (66%) or without (25%) visual field loss; the remainder had normal RNFL and fields (5%) or with visual field abnormalities (4%). Conclusions Optic nerve pallor as a predictor of RNFL thinning showed fair sensitivity and specificity, although it is optimally sensitive/specific only when substantial RNFL loss has occurred. Translational Relevance Finding an acceptable relationship between the optic nerve appearance by ophthalmoscopy and spectral domain-OCT RNFL measures will help the clinician's interpretation of the information provided by this technology, which is gaining momentum in neuro-ophthalmic research. PMID:25374773

  9. Optical coherence tomography layer thickness characterization of a mock artery during angioplasty balloon deployment

    Science.gov (United States)

    Azarnoush, Hamed; Vergnole, Sébastien; Boulet, Benoît; Lamouche, Guy

    2011-03-01

    Optical coherence tomography (OCT) is used to study the deformation of a mock artery in an angioplasty simulation setup. An OCT probe integrated in a balloon catheter provides intraluminal real-time images during balloon inflation. Swept-source OCT is used for imaging. A 4 mm semi-compliant polyurethane balloon is used for experiments. The balloon is inflated inside a custom-built multi-layer artery phantom. The phantom has three layers to mock artery layers, namely, intima, media and adventitia. Semi-automatic segmentation of phantom layers is performed to provide a detailed assessment of the phantom deformation at various inflation pressures. Characterization of luminal diameter and thickness of different layers of the mock artery is provided for various inflation pressures.

  10. Designing Two-Layer Optical Networks with Statistical Multiplexing

    Science.gov (United States)

    Addis, B.; Capone, A.; Carello, G.; Malucelli, F.; Fumagalli, M.; Pedrin Elli, E.

    The possibility of adding multi-protocol label switching (MPLS) support to transport networks is considered an important opportunity by telecom carriers that want to add packet services and applications to their networks. However, the question that arises is whether it is suitable to have MPLS nodes just at the edge of the network to collect packet traffic from users, or also to introduce MPLS facilities on a subset of the core nodes in order to exploit packet switching flexibility and multiplexing, thus providing induction of a better bandwidth allocation. In this article, we address this complex decisional problem with the support of a mathematical programming approach. We consider two-layer networks where MPLS is overlaid on top of transport networks-synchronous digital hierarchy (SDH) or wavelength division multiplexing (WDM)-depending on the required link speed. The discussions' decisions take into account the trade-off between the cost of adding MPLS support in the core nodes and the savings in the link bandwidth allocation due to the statistical multiplexing and the traffic grooming effects induced by MPLS nodes. The traffic matrix specifies for each point-to-point request a pair of values: a mean traffic value and an additional one. Using this traffic model, the effect of statistical multiplexing on a link allows the allocation of a capacity equal to the sum of all the mean values of the traffic demands routed on the link and only the highest additional one. The proposed approach is suitable to solve real instances in reasonable time.

  11. Low-loss as-grown germanosilicate layers for optical waveguides

    NARCIS (Netherlands)

    Ay, Feridun; Aydinli, Atilla; Agan, Sedat

    2003-01-01

    We report on systematic growth and characterization of low-loss germanosilicate layers for use in optical waveguide technology. The films were deposited by plasma-enhanced chemical vapor deposition technique using silane, germane, and nitrous oxide as precursor gases. Fourier transform infrared spec

  12. OPTICAL COMPUTING: Analysis of the tomographic contrast during the immersion bleaching of layered biological tissues

    Science.gov (United States)

    Prokhorov, I. V.; Yarovenko, I. P.

    2010-01-01

    The control of optical properties of biological tissues irradiated by a cw laser source is considered. Within the framework of the stationary model of the radiation transfer, basic factors affecting the tomographic contrast of a layered medium are revealed theoretically and numerically, when immersion liquids, decreasing the radiation scattering level in a medium, are used.

  13. Ultra-Short Optical Pulse Generation with Single-Layer Graphene

    CERN Document Server

    Lee, C -C; Bunch, J S; Schibli, T R

    2010-01-01

    Pulses as short as 260 fs have been generated in a diode-pumped low-gain Er:Yb:glass laser by exploiting the nonlinear optical response of single-layer graphene. The application of this novel material to solid-state bulk lasers opens up a way to compact and robust lasers with ultrahigh repetition rates.

  14. Interband magneto-optical transitions in a layer of semiconductor nano-rings

    NARCIS (Netherlands)

    Voskoboynikov, O.; Wijers, C.M.J.; Liu, J.L.; Lee, C.P.

    2005-01-01

    We have developed a quantitative theory of the collective electromagnetic response of layers of semiconductor nano-rings. The response can be controlled by means of an applied magnetic field through the optical Aharonov-Bohm effect and is ultimately required for the design of composite materials. We

  15. Optical bandgap of single- and multi-layered amorphous germanium ultra-thin films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Pei; Zaslavsky, Alexander [Department of Physics and School of Engineering, Brown University, 182-184 Hope St., Providence, Rhode Island 02912 (United States); Longo, Paolo [Gatan, Inc., 5794 W Las Positas Blvd., Pleasanton, California 94588 (United States); Pacifici, Domenico, E-mail: Domenico-Pacifici@brown.edu [School of Engineering, Brown University, 184 Hope St., Providence, Rhode Island 02912 (United States)

    2016-01-07

    Accurate optical methods are required to determine the energy bandgap of amorphous semiconductors and elucidate the role of quantum confinement in nanometer-scale, ultra-thin absorbing layers. Here, we provide a critical comparison between well-established methods that are generally employed to determine the optical bandgap of thin-film amorphous semiconductors, starting from normal-incidence reflectance and transmittance measurements. First, we demonstrate that a more accurate estimate of the optical bandgap can be achieved by using a multiple-reflection interference model. We show that this model generates more reliable results compared to the widely accepted single-pass absorption method. Second, we compare two most representative methods (Tauc and Cody plots) that are extensively used to determine the optical bandgap of thin-film amorphous semiconductors starting from the extracted absorption coefficient. Analysis of the experimental absorption data acquired for ultra-thin amorphous germanium (a-Ge) layers demonstrates that the Cody model is able to provide a less ambiguous energy bandgap value. Finally, we apply our proposed method to experimentally determine the optical bandgap of a-Ge/SiO{sub 2} superlattices with single and multiple a-Ge layers down to 2 nm thickness.

  16. Optical bandgap of single- and multi-layered amorphous germanium ultra-thin films

    Science.gov (United States)

    Liu, Pei; Longo, Paolo; Zaslavsky, Alexander; Pacifici, Domenico

    2016-01-01

    Accurate optical methods are required to determine the energy bandgap of amorphous semiconductors and elucidate the role of quantum confinement in nanometer-scale, ultra-thin absorbing layers. Here, we provide a critical comparison between well-established methods that are generally employed to determine the optical bandgap of thin-film amorphous semiconductors, starting from normal-incidence reflectance and transmittance measurements. First, we demonstrate that a more accurate estimate of the optical bandgap can be achieved by using a multiple-reflection interference model. We show that this model generates more reliable results compared to the widely accepted single-pass absorption method. Second, we compare two most representative methods (Tauc and Cody plots) that are extensively used to determine the optical bandgap of thin-film amorphous semiconductors starting from the extracted absorption coefficient. Analysis of the experimental absorption data acquired for ultra-thin amorphous germanium (a-Ge) layers demonstrates that the Cody model is able to provide a less ambiguous energy bandgap value. Finally, we apply our proposed method to experimentally determine the optical bandgap of a-Ge/SiO2 superlattices with single and multiple a-Ge layers down to 2 nm thickness.

  17. Giant magneto-optical Raman effect in a layered transition metal compound.

    Science.gov (United States)

    Ji, Jianting; Zhang, Anmin; Fan, Jiahe; Li, Yuesheng; Wang, Xiaoqun; Zhang, Jiandi; Plummer, E W; Zhang, Qingming

    2016-03-01

    We report a dramatic change in the intensity of a Raman mode with applied magnetic field, displaying a gigantic magneto-optical effect. Using the nonmagnetic layered material MoS2 as a prototype system, we demonstrate that the application of a magnetic field perpendicular to the layers produces a dramatic change in intensity for the out-of-plane vibrations of S atoms, but no change for the in-plane breathing mode. The distinct intensity variation between these two modes results from the effect of field-induced broken symmetry on Raman scattering cross-section. A quantitative analysis on the field-dependent integrated Raman intensity provides a unique method to precisely determine optical mobility. Our analysis is symmetry-based and material-independent, and thus the observations should be general and inspire a new branch of inelastic light scattering and magneto-optical applications.

  18. Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition

    Directory of Open Access Journals (Sweden)

    Adib Abou Chaaya

    2013-10-01

    Full Text Available A study of transmittance and photoluminescence spectra on the growth of oxygen-rich ultra-thin ZnO films prepared by atomic layer deposition is reported. The structural transition from an amorphous to a polycrystalline state is observed upon increasing the thickness. The unusual behavior of the energy gap with thickness reflected by optical properties is attributed to the improvement of the crystalline structure resulting from a decreasing concentration of point defects at the growth of grains. The spectra of UV and visible photoluminescence emissions correspond to transitions near the band-edge and defect-related transitions. Additional emissions were observed from band-tail states near the edge. A high oxygen ratio and variable optical properties could be attractive for an application of atomic layer deposition (ALD deposited ultrathin ZnO films in optical sensors and biosensors.

  19. Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition.

    Science.gov (United States)

    Abou Chaaya, Adib; Viter, Roman; Bechelany, Mikhael; Alute, Zanda; Erts, Donats; Zalesskaya, Anastasiya; Kovalevskis, Kristaps; Rouessac, Vincent; Smyntyna, Valentyn; Miele, Philippe

    2013-01-01

    A study of transmittance and photoluminescence spectra on the growth of oxygen-rich ultra-thin ZnO films prepared by atomic layer deposition is reported. The structural transition from an amorphous to a polycrystalline state is observed upon increasing the thickness. The unusual behavior of the energy gap with thickness reflected by optical properties is attributed to the improvement of the crystalline structure resulting from a decreasing concentration of point defects at the growth of grains. The spectra of UV and visible photoluminescence emissions correspond to transitions near the band-edge and defect-related transitions. Additional emissions were observed from band-tail states near the edge. A high oxygen ratio and variable optical properties could be attractive for an application of atomic layer deposition (ALD) deposited ultrathin ZnO films in optical sensors and biosensors.

  20. Flexo-dielectro-optical spectroscopy of PDLC films modified by nano-rubbed PTFE layers

    Science.gov (United States)

    Popova, Lidia T.

    2016-02-01

    The electro-optical (EO) response of planar single layers of polymer-dispersed liquid crystal (PDLC) composites of relatively large nematic microdroplets modified by layers of teflon (PTFE), was studied. The PDLC films were prepared from liquid crystal E7 and photopolymer NOA-65 in cells assembled with parallel or orthogonal PTFE-covered glass plates. The influence of nanostructured PTFE polymer nanolayers on both the polarized and depolarized component of laser light transmitted through PDLC cells of both geometry of layer rubbing directions was determined. Flexo-dielectro-optical spectroscopy in the range of 10 Hz - 1 kHz was applied to examine the amplitude-frequency EO modulation by PTFE-modified PDLCs in dependence on the applied alternating-current electric field. Specific fall-downs in the frequency spectra of the first and second harmonic EO modulation by PTFE-modified PDLCs were observed, that could be tuned by the driving electric field.

  1. Tunable Optical Nanocavity of Iron-garnet with a Buried Metal Layer

    Directory of Open Access Journals (Sweden)

    Alexey N. Kuz'michev

    2015-05-01

    Full Text Available We report on the fabrication and characterization of a novel magnetophotonic structure designed as iron garnet based magneto-optical nanoresonator cavity constrained by two noble metal mirrors. Since the iron garnet layer requires annealing at high temperatures, the fabrication process can be rather challenging. Special approaches for the protection of metal layers against oxidation and morphological changes along with a special plasma-assisted polishing of the iron garnet layer surface were used to achieve a 10-fold enhancement of the Faraday rotation angle (up to 10.8\\(^{\\circ}/\\mu\\m within a special resonance peak of 12 nm (FWHM linewidth at a wavelength of 772 nm, in the case of a resonator with two silver mirrors. These structures are promising for tunable nanophotonics applications, in particular, they can be used as magneto-optical (MO metal-insulator-metal waveguides and modulators.

  2. Investigation of radiative effects of the optically thick dust layer over the Indian tropical region

    Energy Technology Data Exchange (ETDEWEB)

    Das, S.K.; Chen, J.P. [National Taiwan Univ. (China). Dept. of Atmospheric Sciences; Ratnam, M. Venkat; Jayaraman, A. [National Atmospheric Research Laboratory, Tirupati (India)

    2013-06-01

    Optical and physical properties of aerosols derived from multi-satellite observations (MODIS-Aqua, OMI-Aura, MISR-Terra, CALIOP-CALIPSO) have been used to estimate radiative effects of the dust layer over southern India. The vertical distribution of aerosol radiative forcing and heating rates are calculated with 100m resolution in the lower atmosphere, using temperature and relative humidity data from balloon-borne radiosonde observations. The present study investigates the optically thick dust layer of optical thickness 0.18 {+-} 0.06 at an altitude of 2.5 {+-} 0.7 km over Gadanki, transported from the Thar Desert, producing radiative forcing and heating rate of 11.5 {+-} 3.3 W m{sup -2} and 0.6 {+-} 0.26 K day{sup -1}, respectively, with a forcing efficiency of 43 W m{sup -2} and an effective heating rate of 4Kday-1 per unit dust optical depth. Presence of the dust layer increases radiative forcing by 60% and heating rate by 60 times at that altitude compared to nondusty cloud-free days. Calculation shows that the radiative effects of the dust layer strongly depend on the boundary layer aerosol type and mass loading. An increase of 25% of heating by the dust layer is found over relatively cleaner regions than urban regions in southern India and further 15% of heating increases over the marine region. Such heating differences in free troposphere may have significant consequences in the atmospheric circulation and hydrological cycle over the tropical Indian region. (orig.)

  3. Optical measurements of absorption changes in two-layered diffusive media

    Energy Technology Data Exchange (ETDEWEB)

    Fabbri, Francesco [Department of Biomedical Engineering, Bioengineering Center, Tufts University, 4 Colby Street, Medford, MA 02155 (United States); Sassaroli, Angelo [Department of Biomedical Engineering, Bioengineering Center, Tufts University, 4 Colby Street, Medford, MA 02155 (United States); Henry, Michael E [McLean Hospital and Department of Psychiatry, Harvard Medical School, 115 Mill Street, Belmont, MA 02478 (United States); Fantini, Sergio [Department of Biomedical Engineering, Bioengineering Center, Tufts University, 4 Colby Street, Medford, MA 02155 (United States)

    2004-04-07

    We have used Monte Carlo simulations for a two-layered diffusive medium to investigate the effect of a superficial layer on the measurement of absorption variations from optical diffuse reflectance data processed by using: (a) a multidistance, frequency-domain method based on diffusion theory for a semi-infinite homogeneous medium; (b) a differential-pathlength-factor method based on a modified Lambert-Beer law for a homogeneous medium and (c) a two-distance, partial-pathlength method based on a modified Lambert-Beer law for a two-layered medium. Methods (a) and (b) lead to a single value for the absorption variation, whereas method (c) yields absorption variations for each layer. In the simulations, the optical coefficients of the medium were representative of those of biological tissue in the near-infrared. The thickness of the first layer was in the range 0.3-1.4 cm, and the source-detector distances were in the range 1-5 cm, which is typical of near-infrared diffuse reflectance measurements in tissue. The simulations have shown that (1) method (a) is mostly sensitive to absorption changes in the underlying layer, provided that the thickness of the superficial layer is {approx}0.6 cm or less; (2) method (b) is significantly affected by absorption changes in the superficial layer and (3) method (c) yields the absorption changes for both layers with a relatively good accuracy of {approx}4% for the superficial layer and {approx}10% for the underlying layer (provided that the absorption changes are less than 20-30% of the baseline value). We have applied all three methods of data analysis to near-infrared data collected on the forehead of a human subject during electroconvulsive therapy. Our results suggest that the multidistance method (a) and the two-distance partial-pathlength method (c) may better decouple the contributions to the optical signals that originate in deeper tissue (brain) from those that originate in more superficial tissue layers.

  4. Spacer lock of roof bolting

    Energy Technology Data Exchange (ETDEWEB)

    Shirokov, A.P.; Boronov, N.N.; Isachenko, V.M.; Kuntsevich, V.I.

    1980-04-05

    The object of the invention is a spacer joint of anchor bolting, which includes a wedge-shaped head and half-coupling, which are beveled on the inner side of the walls, and have ribs on the outer sides of the walls. It is characterized in that in order to reduce cost of the joint by reducing the amount of steel and manufacturing costs, the walls of the half-couplings hae identical thickness lengthwise, and the ribs are of varying height with corresponding projections on the inner side of the half-couplings.

  5. Layered ACO-OFDM for intensity-modulated direct-detection optical wireless transmission.

    Science.gov (United States)

    Wang, Qi; Qian, Chen; Guo, Xuhan; Wang, Zhaocheng; Cunningham, David G; White, Ian H

    2015-05-04

    Layered asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) with high spectral efficiency is proposed in this paper for optical wireless transmission employing intensity modulation with direct detection. In contrast to the conventional ACO-OFDM, which only utilizes odd subcarriers for modulation, leading to an obvious spectral efficiency loss, in layered ACO-OFDM, the subcarriers are divided into different layers and modulated by different kinds of ACO-OFDM, which are combined for simultaneous transmission. In this way, more subcarriers are used for data transmission and the spectral efficiency is improved. An iterative receiver is also proposed for layered ACO-OFDM, where the negative clipping distortion of each layer is subtracted once it is detected so that the signals from different layers can be recovered. Theoretical analysis shows that the proposed scheme can improve the spectral efficiency by up to 2 times compared with conventional ACO-OFDM approaches with the same modulation order. Meanwhile, simulation results confirm a considerable signal-to-noise ratio gain over ACO-OFDM at the same spectral efficiency.

  6. Security risk assessment of the primary layer of wavelength division multiplexing passive optical network

    Science.gov (United States)

    Koudelka, Petr; Siska, Petr; Latal, Jan; Poboril, Radek; Hajek, Lukas; Kepak, Stanislav; Vasinek, Vladimir

    2015-01-01

    Next-generation passive optical access networks come to the fore nowadays. These optical next-generation networks are the response to the increasing qualitative requirements from end users. Technologies using Time Division Multiplexing include NG-PON (XG-PON 1 and XG-PON 2) and 10GEPON. Their advantage is the applicability to older topologies, which are operated by the original technology of passive optical access networks. Wavelength Division Multiplexing Passive Optical Network (WDM-PON) is an alternative also belonging to next-generation networks. Time Division Multiplexing is in this case replaced by Wavelength Division Multiplexing. Certain variants of WDM-PON use a combination of broadband light source, optical circulator, optical phased array and tunable FP laser. Construction of the terminal units (ONU) is advantageous because it can always tune in to the appropriate wavelength in the given optical DWDM channel (100 GHz). The disadvantage is the increased security risk on the primary layer due to channel crosstalk in an optical phased array (AWG). The aim of this paper is to assess the degree of security risk in real conditions. The article includes both simulation and real measurements in C + L bands with 100 GHz DWDM spacing.

  7. Probing the electric field in organic double layer-system by optical second harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Eunju; Shibata, Yoshinori; Manaka, Takaaki [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan); Iwamoto, Mitsumasa, E-mail: iwamoto@ome.pe.titech.ac.j [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan)

    2009-11-30

    Optical electric field induced second harmonic generation (EFISHG) measurements were employed to probe the electric field in the active layer of organic field effect transistors (OFETs) and organic light emitting diodes (OLEDs). The OFETs used were double-layered with an active layer of pentacene/poly (3-hexyl thiophene) P3HT on SiO{sub 2} gate insulator with Au source and drain electrodes. It was shown that SHG from the P3HT bottom layer could be selectively probed at a wavelength of 450 nm. Similarly, by using OLEDs comprised of a double layer of Tris(8-hydroxyquinolinato) aluminium (Alq{sub 3}) and N'-di(1-naphthyl)-N,N'-diphenylbenzidine ({alpha}-NPD) with a device structure of indium-zinc oxide (IZO)/{alpha}-NPD/Alq{sub 3}/Al, it was shown that EFISHG from the Alq{sub 3} layer could be selectively probed at a wavelength of 1000 nm by reflective laser beam irradiation from IZO-side. The results show that the spectroscopic nature of materials allows us to selectively probe the electric field distribution in each layer of multi-layer in organic devices.

  8. High-sensitivity four-layer polymer fiber-optic evanescent wave sensor.

    Science.gov (United States)

    Xin, Xin; Zhong, Nianbing; Liao, Qiang; Cen, Yanyan; Wu, Ruohua; Wang, Zhengkun

    2017-05-15

    We present a novel four-layer structure consisting of bottom, second, third, and surface layers in the sensing region, for a D-shaped step-index fiber-optic evanescent wave (FOEW) sensor. To reduce the background noise, the surface of the longitudinal section in the D-shaped region is coated with a light-absorbing film. We check the morphologies of the second and surface layers, examine the refractive indices (RIs) of the third and surface layers, and analyze the composition of the surface layer. We also investigate the effects of the thicknesses and RIs of the third and surface layers and the LA film on the light transmission and sensitivity of the FOEW sensors. The results highlight the very good sensitivity of the proposed FOEW sensor with a four-layer structure, which reached -0.077 (μg/l)(-1) in the detection of the target antibody; the sensitivity of the novel FOEW sensor was 7.60 and 1.52 times better than that of a conventional sensor with a core-cladding structure and an FOEW sensor with a three-layer structure doped with GeO2. The applications of this high-sensitivity FOEW sensor can be extended to biodefense, disease diagnosis, and biomedical and biochemical analysis.

  9. CRISPR interference directs strand specific spacer acquisition.

    Directory of Open Access Journals (Sweden)

    Daan C Swarts

    Full Text Available BACKGROUND: CRISPR/Cas is a widespread adaptive immune system in prokaryotes. This system integrates short stretches of DNA derived from invading nucleic acids into genomic CRISPR loci, which function as memory of previously encountered invaders. In Escherichia coli, transcripts of these loci are cleaved into small RNAs and utilized by the Cascade complex to bind invader DNA, which is then likely degraded by Cas3 during CRISPR interference. RESULTS: We describe how a CRISPR-activated E. coli K12 is cured from a high copy number plasmid under non-selective conditions in a CRISPR-mediated way. Cured clones integrated at least one up to five anti-plasmid spacers in genomic CRISPR loci. New spacers are integrated directly downstream of the leader sequence. The spacers are non-randomly selected to target protospacers with an AAG protospacer adjacent motif, which is located directly upstream of the protospacer. A co-occurrence of PAM deviations and CRISPR repeat mutations was observed, indicating that one nucleotide from the PAM is incorporated as the last nucleotide of the repeat during integration of a new spacer. When multiple spacers were integrated in a single clone, all spacer targeted the same strand of the plasmid, implying that CRISPR interference caused by the first integrated spacer directs subsequent spacer acquisition events in a strand specific manner. CONCLUSIONS: The E. coli Type I-E CRISPR/Cas system provides resistance against bacteriophage infection, but also enables removal of residing plasmids. We established that there is a positive feedback loop between active spacers in a cluster--in our case the first acquired spacer--and spacers acquired thereafter, possibly through the use of specific DNA degradation products of the CRISPR interference machinery by the CRISPR adaptation machinery. This loop enables a rapid expansion of the spacer repertoire against an actively present DNA element that is already targeted, amplifying the

  10. Few layers graphene as thermally activated optical modulator in the visible-near IR spectral range.

    Science.gov (United States)

    Benítez, J L; Hernández-Cordero, Juan; Muhl, S; Mendoza, D

    2016-01-01

    We report the temperature modulation of the optical transmittance of a few layers of graphene (FLG). The FLG was heated either by the Joule effect of the current flowing between coplanar electrodes or by the absorption of a continuous-wave 532 nm laser. The optical signals used to evaluate the modulation of the FLG were at 633, 975, and 1550 nm; the last wavelengths are commonly used in optical communications. We also evaluated the effect of the substrate on the modulation effect by comparing the performance of a freely suspended FLG sample with one mounted on a glass substrate. Our results show that the modulation of the optical transmittance of FLG can be from millihertz to kilohertz.

  11. Optical bistability with film-coupled metasurfaces.

    Science.gov (United States)

    Huang, Zhiqin; Baron, Alexandre; Larouche, Stéphane; Argyropoulos, Christos; Smith, David R

    2015-12-01

    Metasurfaces comprising arrays of film-coupled, nanopatch antennas are a promising platform for low-energy, all-optical switches. The large field enhancements that can be achieved in the dielectric spacer region between the nanopatch and the metallic substrate can substantially enhance optical nonlinear processes. Here we consider a dielectric material that exhibits an optical Kerr effect as the spacer layer and numerically calculate the optical bistability of a metasurface using the finite element method (FEM). We expect the proposed method to be highly accurate compared with other numerical approaches, such as those based on graphical post-processing techniques, because it self-consistently solves for both the spatial field distribution and the intensity-dependent refractive index distribution of the spacer layer. This method offers an alternative approach to finite-difference time-domain (FDTD) modeling. We use this numerical tool to design a metasurface optical switch and our optimized design exhibits exceptionally low switching intensity of 33  kW/cm2, corresponding to switching energy on the order of tens of attojoules per resonator, a value much smaller than those found for most devices reported in the literature. We propose our method as a tool for designing all-optical switches and modulators.

  12. Optical Band Gap and Thermal Diffusivity of Polypyrrole-Nanoparticles Decorated Reduced Graphene Oxide Nanocomposite Layer

    Directory of Open Access Journals (Sweden)

    Amir Reza Sadrolhosseini

    2016-01-01

    Full Text Available A polypyrrole-nanoparticles reduced graphene oxide nanocomposite layer was prepared using electrochemical method. The prepared samples were characterized using Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and UV-visible spectroscopy. The band gap of nanocomposite layers was calculated from UV-visible spectra and the thermal diffusivity of layers was measured using a photoacoustic technique. As experimental results, the optical band gap was in the range between 3.580 eV and 3.853 eV, and thermal diffusivity was increased with increasing the layer thickness from 2.873 cm2/s to 12.446 cm2/s.

  13. Development of a High Performance Spacer Grid

    Energy Technology Data Exchange (ETDEWEB)

    Song, Kee Nam; Song, K. N.; Yoon, K. H. (and others)

    2007-03-15

    A spacer grid in a LWR fuel assembly is a key structural component to support fuel rods and to enhance the heat transfer from the fuel rod to the coolant. In this research, the main research items are the development of inherent and high performance spacer grid shapes, the establishment of mechanical/structural analysis and test technology, and the set-up of basic test facilities for the spacer grid. The main research areas and results are as follows. 1. 18 different spacer grid candidates have been invented and applied for domestic and US patents. Among the candidates 16 are chosen from the patent. 2. Two kinds of spacer grids are finally selected for the advanced LWR fuel after detailed performance tests on the candidates and commercial spacer grids from a mechanical/structural point of view. According to the test results the features of the selected spacer grids are better than those of the commercial spacer grids. 3. Four kinds of basic test facilities are set up and the relevant test technologies are established. 4. Mechanical/structural analysis models and technology for spacer grid performance are developed and the analysis results are compared with the test results to enhance the reliability of the models.

  14. Design and analysis of optically pumped semiconductor VECSEL with ANECz optical control layer

    Institute of Scientific and Technical Information of China (English)

    Yuqi Zhou; Dapeng Zhao; Yajuan Li; Qingxin Yang

    2008-01-01

    Through the reversible isomerization of trans-cis-trans under the linear polarization light, the molecules of azo materials have the same tropism which is vertical to the polarization of light. This means that azo materials have photo-induced birefringence which is related to optical power and polarization angle of the light. Based on the photo-induced birefringence of azo materials, we design a new type of optically pumped semiconductor vertical external cavity surface emitting laser (OPS-VECSEL) which can control the polarization and frequency of the ejection laser. The functional molecules of azo materials are [3-azo- (4'nitro)]-(9-ethyl)-carbazole (ANECz).

  15. Aero-optic analysis of anisotropic turbulent boundary layer by direct integration

    Science.gov (United States)

    Taylor, S.; Price, J.; Chen, C. P.; Pond, John E.; Sutton, G. W.

    2013-09-01

    Aero-optic aberrations that effect optical sensor performance and laser beam propagation, can be caused by changes in the index-of-refraction field as the optical wave traverses a compressible non-uniform, turbulent flowfield. Mean flowfield non-uniformities cause bore sight error and blurring and, if the mean flowfield is unsteady, jitter. Turbulence causes blurring and high frequency jitter. Blurring also causes the signal-to-noise ratio to decrease and image distortion, and adversely affects centroid location for precision tracking. The objective of this study is to develop an unified approach for whole-field aero-optics prediction using hybrid LES/RANS (Large Eddy Simulation/Reynolds Average Navier-Stokes) turbulence modeling in combination with a newly formulated optical Modulation Transfer Function (MTF). The whole field turbulence includes the near-vehicle boundary layer mean and turbulence, as well as far-field atmospheric turbulence. A flat plate compressible boundary layer case is used to demonstrate the methodology. the abstract two lines below author names and addresses.

  16. Sputtered-silica defect layer in artificial opals: tunability of highly transmitted and reflected optical modes

    CERN Document Server

    Hong, Phan Ngoc; Coolen, Laurent; Maître, Agnès; Schwob, Catherine

    2013-01-01

    We propose an original and efficient method to engineer a defect between two well-ordered silica opals by sputtering silica on the top of the first one. As the amount of sputtered silica can be well controlled, it is also the case for the thickness of the layer and consequently for the spectral position of the defect mode. The optical response of these sandwich structures is studied in terms of specular reflection and transmission spectroscopy. Tunable highly transmitted and reflected optical modes are evidenced. The very good agreement between the experimental results and the simulations, run without fitting parameters, demonstrates the almost perfect order of the synthesized structures.

  17. Near-band edge optical properties of exfoliated h-BN layers.

    OpenAIRE

    Loyza, J.; Barjon, J; Pierret, A.; Betz, A.; Placais, B.; Ducastelle, F.; Loiseau, A.

    2013-01-01

    Luminescence properties of h-BN are governed, in the energy range 5.5 { 6 eV, by strong Frenkel-type excitonic e ects, highly sensitive to structural defects [1-3]. Nowadays, BN meets a growing interest for graphene engineering. It is therefore highly desirable to better know optical and electronic properties of thin layers, in correlation with their structural properties. We carry out optical and structural characterizations of this material by combining CL at 4K in the UV range and TEM. Thi...

  18. High quality ZnO layers with adjustable refractive indices for integrated optics applications

    OpenAIRE

    Heideman, R.G.; Lambeck, P.V.; Gardeniers, J.G.E.

    1995-01-01

    Thin ( 1 μm) crystalline ZnO films with a good optical quality and good (0002) texture are grown under two considerably different process parameter sets using a r.f. planar magnetron sputtering unit. The optical parameters of the two corresponding ZnO layers are distinctly different: high refractive index ( 2.0 at λ = 632.8 nm) ZnO films resembling the single crystal form, and ZnO films with considerably lower (typical difference 0.05) refractive indices. The refractive index of the latter Zn...

  19. Influence of a thin metal layer on a beam propagation in a biconical optical fibre taper

    Science.gov (United States)

    Stasiewicz, K. A.; Moś, J. E.

    2016-12-01

    The paper presents results of a simulation of the plasmon effect achieved between a thin precious metal layer and a biconical optical fibre taper, manufactured on a standard single mode fibre. Gold, silver and titanium were used as a metal which fulfilled a cladding function for a small diameter structure. For simulation Mode Solution software was used on which modal and frequency analyses of a wavelength were provided in the range of 800-1700 nm. A displacement of a plasmon pick in dependence of thickness of a deposited precious layer for the highest plasmon effects was observed.

  20. Optical Tamm state polaritons in a quantum well microcavity with gold layers

    Institute of Scientific and Technical Information of China (English)

    Zhang Wei-Li; Rao Yun-Jiang

    2012-01-01

    A new type of cavity polariton,the optical Tamm state(OTS)polariton,is proposed to be realized by sandwiching a quantum well(QW)between a gold layer and a distributed Bragg reflector(DBR).It is shown that OTS polaritons can be generated from the strong couplings between the QW excitons and the free OTSs.In addition,ff a second gold layer is introduced into the bottom of the DBR,two independent free OTSs can interact strongly with the Q W excitons to produce extra OTS polaritons.

  1. Synthesis and Characterization of Layered Double Hydroxides Containing Optically Active Transition Metal Ion

    Science.gov (United States)

    Tyagi, S. B.; Kharkwal, Aneeta; Nitu; Kharkwal, Mamta; Sharma, Raghunandan

    2017-01-01

    The acetate intercalated layered double hydroxides of Zn and Mn, have been synthesized by chimie douce method. The materials were characterized by XRD, TGA, CHN, IR, XPS, SEM-EDX and UV-visible spectroscopy. The photoluminescence properties was also studied. The optical properties of layered hydroxides are active transition metal ion dependent, particularly d1-10 system plays an important role. Simultaneously the role of host - guest orientation has been considered the basis of photoluminescence. Acetate ion can be exchanged with iodide and sulphate ions. The decomposed product resulted the pure phase Mn doped zinc oxide are also reported.

  2. Silicon electro-optic modulator with high-permittivity gate dielectric layer

    Institute of Scientific and Technical Information of China (English)

    Mengxia Zhu; Zhiping Zhou; Dingshan Gao

    2009-01-01

    A high-permittivity (high-k) material is applied as the gate dielectric layer in a silicon metal-oxidesemiconductor (MOS) capacitor to form a special electro-optic (EO) modulator.Both induced charge density and modulation efficiency in the proposed modulator are improved due to the special structure design and the application of the high-k material.The device has an ultra-compact dimension of 691 μm in length.

  3. Macular Microcysts in Mitochondrial Optic Neuropathies: Prevalence and Retinal Layer Thickness Measurements.

    Directory of Open Access Journals (Sweden)

    Michele Carbonelli

    Full Text Available To investigate the thickness of the retinal layers and to assess the prevalence of macular microcysts (MM in the inner nuclear layer (INL of patients with mitochondrial optic neuropathies (MON.All patients with molecularly confirmed MON, i.e. Leber's Hereditary Optic Neuropathy (LHON and Dominant Optic Atrophy (DOA, referred between 2010 and 2012 were enrolled. Eight patients with MM were compared with two control groups: MON patients without MM matched by age, peripapillary retinal nerve fiber layer (RNFL thickness, and visual acuity, as well as age-matched controls. Retinal segmentation was performed using specific Optical coherence tomography (OCT software (Carl Zeiss Meditec. Macular segmentation thickness values of the three groups were compared by one-way analysis of variance with Bonferroni post hoc corrections.MM were identified in 5/90 (5.6% patients with LHON and 3/58 (5.2% with DOA. The INL was thicker in patients with MON compared to controls regardless of the presence of MM [133.1±7μm vs 122.3±9μm in MM patients (p<0.01 and 128.5±8μm vs. 122.3±9μm in no-MM patients (p<0.05], however the outer nuclear layer (ONL was thicker in patients with MM (101.4±1mμ compared to patients without MM [77.5±8mμ (p<0.001] and controls [78.4±7mμ (p<0.001]. ONL thickness did not significantly differ between patients without MM and controls.The prevalence of MM in MON is low (5-6%, but associated with ONL thickening. We speculate that in MON patients with MM, vitreo-retinal traction contributes to the thickening of ONL as well as to the production of cystic spaces.

  4. Optical Effects in the Active Layer of Organic Solar Cells with Embedded Noble Metal Nanoparticles

    OpenAIRE

    Supachai Sompech; Sukhontip Thaomola; Thananchai Dasri

    2016-01-01

    The optical properties of organic solar cells with noble metal nanoparticles such as Ag and Au embedded in the active layer were investigated. The Discrete Dipole Approximation theory was used to analyze the light scattering and absorption efficiencies. The results show that the size, refractive index of medium and amount of the metal nanoparticles are key factors that directly influence the plasmonic enhancements in the devices. These parameters were adjusted for the light scattering and abs...

  5. Structure and Optical Properties of the Atmospheric Boundary Layer over Dusty Hot Deserts

    Science.gov (United States)

    Chalermthai, B.; Al Marzooqi, M.; Basha, G.; Ouarda, T.; Armstrong, P.; Molini, A.

    2014-12-01

    Strong sensible heat fluxes and deep turbulent mixing - together with marked dustiness and a low substrate water content - represent a characteristic signature of the atmospheric boundary layer (ABL) over hot deserts, resulting in "thicker" mixing layers and peculiar optical properties. Beside these main common features however, desert boundary layers present extremely complex local structures that have been scarcely addressed in the literature, and whose understanding is essential in modeling processes such as transport and deposition of dust and pollutants, local wind fields, turbulent fluxes and their impacts on the sustainable development, human health and solar energy harvesting in these regions. In this study, we explore the potential of the joint usage of Lidar Ceilometer backscattering profiles and sun-photometer optical depth retrievals to quantitatively determine the vertical aerosol profile over dusty hot desert regions. Toward this goal, we analyze a continuous record of observations of the atmospheric boundary layer height from a single lens LiDAR ceilometer operated at Masdar Institute Field Station (24.4425N 54.6163E, Abu Dhabi, United Arab Emirates), starting March 2013, and the concurrent measurements of aerosol optical depth derived independently from the Masdar Institute AERONET sun-photometer. The main features of the desert ABL are obtained from the ceilometer range corrected backscattering profiles through bi-dimensional clustering technique we developed as a modification of the recently proposed single-profile clustering method, and therefore "directly" and "indirectly" calibrated to obtain a full diurnal cycle climatology of the aerosol optical depth and aerosol profiles. The challenges and the advantages of applying a similar methodology to the monitoring of aerosols and dust over hyper-arid regions are also discussed, together with the issues related to the sensitivity of commercial ceilometers to changes in the solar background.

  6. Macular Microcysts in Mitochondrial Optic Neuropathies: Prevalence and Retinal Layer Thickness Measurements

    Science.gov (United States)

    Carbonelli, Michele; La Morgia, Chiara; Savini, Giacomo; Cascavilla, Maria Lucia; Borrelli, Enrico; Chicani, Filipe; do V. F. Ramos, Carolina; Salomao, Solange R.; Parisi, Vincenzo; Sebag, Jerry; Bandello, Francesco; Sadun, Alfredo A.; Carelli, Valerio; Barboni, Piero

    2015-01-01

    Purpose To investigate the thickness of the retinal layers and to assess the prevalence of macular microcysts (MM) in the inner nuclear layer (INL) of patients with mitochondrial optic neuropathies (MON). Methods All patients with molecularly confirmed MON, i.e. Leber’s Hereditary Optic Neuropathy (LHON) and Dominant Optic Atrophy (DOA), referred between 2010 and 2012 were enrolled. Eight patients with MM were compared with two control groups: MON patients without MM matched by age, peripapillary retinal nerve fiber layer (RNFL) thickness, and visual acuity, as well as age-matched controls. Retinal segmentation was performed using specific Optical coherence tomography (OCT) software (Carl Zeiss Meditec). Macular segmentation thickness values of the three groups were compared by one-way analysis of variance with Bonferroni post hoc corrections. Results MM were identified in 5/90 (5.6%) patients with LHON and 3/58 (5.2%) with DOA. The INL was thicker in patients with MON compared to controls regardless of the presence of MM [133.1±7μm vs 122.3±9μm in MM patients (p<0.01) and 128.5±8μm vs. 122.3±9μm in no-MM patients (p<0.05)], however the outer nuclear layer (ONL) was thicker in patients with MM (101.4±1mμ) compared to patients without MM [77.5±8mμ (p<0.001)] and controls [78.4±7mμ (p<0.001)]. ONL thickness did not significantly differ between patients without MM and controls. Conclusion The prevalence of MM in MON is low (5-6%), but associated with ONL thickening. We speculate that in MON patients with MM, vitreo-retinal traction contributes to the thickening of ONL as well as to the production of cystic spaces. PMID:26047507

  7. A 130 GHz Electro-Optic Ring Modulator with Double-Layer Graphene

    Directory of Open Access Journals (Sweden)

    Lei Wu

    2017-02-01

    Full Text Available The optical absorption coefficient of graphene will change after injecting carriers. Based on this principle, a high-speed double-layer graphene electro-optic modulator with a ring resonator structure was designed in this paper. From the numerical simulations, we designed a modulator. Its optical bandwidth is larger than 130 GHz, the switching energy is 0.358 fJ per bit, and the driven voltage is less than 1.2 V. At the same time, the footprint of the proposed modulator is less than 10 microns squared, which makes the process compatible with the Complementary Metal Oxide Semiconductors (CMOS process. This will provide the possibility for the on-chip integration of the photoelectric device.

  8. Optical Properties and Band Gap of Single- and Few-Layer MoTe2 Crystals

    Science.gov (United States)

    Aslan, Ozgur Burak; Ruppert, Claudia; Heinz, Tony

    2015-03-01

    Single- and few-layer crystals of exfoliated MoTe2 have been characterized spectroscopically by photoluminescence, Raman scattering, and optical absorption measurements. We find that MoTe2 in the monolayer limit displays strong photoluminescence. On the basis of complementary optical absorption results, we conclude that monolayer MoTe2 is a direct-gap semiconductor with an optical band gap of 1.10 eV. This new monolayer material extends the spectral range of atomically thin direct-gap materials from the visible to the near-infrared. Supported by the NSF through Grant DMR-1124894 for sample preparation and characterization by the O?ce of Naval Research for analysis. C.R. acknowledges support from the Alexander von Humboldt Foundation.

  9. Reference Architecture for Multi-Layer Software Defined Optical Data Center Networks

    Directory of Open Access Journals (Sweden)

    Casimer DeCusatis

    2015-09-01

    Full Text Available As cloud computing data centers grow larger and networking devices proliferate; many complex issues arise in the network management architecture. We propose a framework for multi-layer; multi-vendor optical network management using open standards-based software defined networking (SDN. Experimental results are demonstrated in a test bed consisting of three data centers interconnected by a 125 km metropolitan area network; running OpenStack with KVM and VMW are components. Use cases include inter-data center connectivity via a packet-optical metropolitan area network; intra-data center connectivity using an optical mesh network; and SDN coordination of networking equipment within and between multiple data centers. We create and demonstrate original software to implement virtual network slicing and affinity policy-as-a-service offerings. Enhancements to synchronous storage backup; cloud exchanges; and Fibre Channel over Ethernet topologies are also discussed.

  10. Microcystic Changes in the Retinal Internal Nuclear Layer Associated with Optic Atrophy: A Prospective Study

    Directory of Open Access Journals (Sweden)

    Benjamin Wolff

    2014-01-01

    Full Text Available Purpose. This study aimed at assessing the prevalence of pathologies presenting retinal inner nuclear layer (RINL microcystic perimacular changes associated with optic nerve atrophy (OA. The charts of patients presenting a significant defect of the Retinal Nerve Fiber Layer (RNFL were included prospectively in this study. Patients were classified according to the etiology of the RNFL defect. Two hundred and one eyes of 138 patients were enrolled in this analysis. Retinal images obtained showed the typical hyporeflective perifoveal crescent-shaped lesion composed of small round hyporeflective microcysts confined to the RINL in 35.3% of the eyes. Those findings were found in 75% of eyes presenting hereditary OA, 50% of eyes presenting ischemic optic neuritis, 50% of eyes with drusen of the optic nerve (ON, 44.4% of eyes presenting a compressive OA, 32% of eyes presenting inflammatory optic neuropathy from multiple sclerosis, 18.5% of eyes presenting OA from undetermined origin, and 17.6% of eyes having primary open-angle glaucoma. This study demonstrates that microcystic changes in RINL are not specific to a disease but are found in OA of various etiologies. Moreover, their incidence was found to be dependent upon the cause of OA, with the highest incidence occurring in genetic OA.

  11. Laser Patterning of Optically Reconfigurable Transistor Channels in a Photochromic Diarylethene Layer.

    Science.gov (United States)

    Tsuruoka, Tohru; Hayakawa, Ryoma; Kobashi, Kazuyoshi; Higashiguchi, Kenji; Matsuda, Kenji; Wakayama, Yutaka

    2016-12-14

    Optical switching organic field-effect transistors (OFETs) provide a new direction for optoelectronics based on photochromic molecules. However, the patterning of OFETs is difficult because conventional fabrication processes, including lithography and ion etching, inevitably cause severe damage to organic molecules. Here, we demonstrate laser patterning of one-dimensional (1D) channels on an OFET with a photochromic diarylethene (DAE) layer. The main findings are (i) a number of 1D channels can be repeatedly written and erased in the DAE layer by scanning focused ultraviolet and visible light laser beams alternately between the source and drain electrodes, (ii) the conductivity (or resistivity) of the 1D channel can be controlled by the illumination conditions, such as the laser power density and the scan speed, and (iii) it is possible to draw an analogue adder circuit by optically writing 1D channels so that a portion of the channels overlaps and to perform optical summing operations by local laser illumination of the respective channels. These findings will open new possibilities for realizing various optically reconfigurable, low-dimensional organic transistor circuits, which are not possible with conventional thin film OFETs.

  12. Broadband ultraviolet-visible optical property measurement in layered turbid media

    Science.gov (United States)

    Wang, Quanzeng; Le, Du; Ramella-Roman, Jessica; Pfefer, Joshua

    2012-01-01

    The ability to accurately measure layered biological tissue optical properties (OPs) may improve understanding of spectroscopic device performance and facilitate early cancer detection. Towards these goals, we have performed theoretical and experimental evaluations of an approach for broadband measurement of absorption and reduced scattering coefficients at ultraviolet-visible wavelengths. Our technique is based on neural network (NN) inverse models trained with diffuse reflectance data from condensed Monte Carlo simulations. Experimental measurements were performed from 350 to 600 nm with a fiber-optic-based reflectance spectroscopy system. Two-layer phantoms incorporating OPs relevant to normal and dysplastic mucosal tissue and superficial layer thicknesses of 0.22 and 0.44 mm were used to assess prediction accuracy. Results showed mean OP estimation errors of 19% from the theoretical analysis and 27% from experiments. Two-step NN modeling and nonlinear spectral fitting approaches helped improve prediction accuracy. While limitations and challenges remain, the results of this study indicate that our technique can provide moderately accurate estimates of OPs in layered turbid media. PMID:22741070

  13. A Novel Analytical Approach for Multi-Layer Diaphragm-Based Optical Microelectromechanical-System Pressure Sensors

    Institute of Scientific and Technical Information of China (English)

    LI Ming; WANG Ming; RONG Hua; LI Hong-Pu

    2006-01-01

    @@ An optical microelectromechanical-system (MEMS) pressure sensor based on multi-layer circular diaphragm is described and analysed by using the proposed novel analytical approach and the traditional transfer matrix method. The analytical expressions of the deflection of multi-layer diaphragm and absolute optical reflectance are derived respectively. The influence of residual stress on the deflection of diaphragm is also analysed. Simulation results given by the finite element method are consistent with the ones which are analysed by using the analytical approach. The analytical approach will be helpful to design and fabricate the optical MEMS pressure sensors with multi-layer diaphragm based on Fabry-Perot interferometry.

  14. Application of Thin ZnO ALD Layers in Fiber-Optic Fabry-Pérot Sensing Interferometers

    OpenAIRE

    Daria Majchrowicz; Marzena Hirsch; Paweł Wierzba; Michael Bechelany; Roman Viter; Małgorzata Jędrzejewska‑Szczerska

    2016-01-01

    In this paper we investigated the response of a fiber-optic Fabry-Pérot sensing interferometer with thin ZnO layers deposited on the end faces of the optical fibers forming the cavity. Standard telecommunication single-mode optical fiber (SMF-28) segments were used with the thin ZnO layers deposited by Atomic Layer Deposition (ALD). Measurements were performed with the interferometer illuminated by two broadband sources operating at 1300 nm and 1550 nm. Reflected interference signal was acqui...

  15. Growth and optical properties of ZnO nanostructures grown on ZnO seed layers

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Yong; Feneberg, Martin; Reiser, Anton; Tischer, Ingo; Wiedenmann, Michael; Frey, Reinhard; Roeder, Uwe; Sauer, Rolf; Thonke, Klaus [Institut fuer Halbleiterphysik, Universitaet Ulm (Germany)

    2009-07-01

    Using a ZnO seed layer, we grow well-aligned ZnO nanopillars on different substrates including a-plane sapphire, c-plane GaN, and (100) silicon. We use Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) to characterize the morphology of the ZnO seed layers and of the ZnO nanopillars. Layers and nanopillars were also investigated by optical spectroscopy. For all kinds of substrates used, we find well-faceted nanopillars which are uniform along the whole length. The data indicate that they grow via the vapour-solid (VS) mechanism under well-controlled growth conditions. The photoluminescence of the ZnO nanopillars shows sharp near-band-edge luminescence and nearly no green or yellow band luminescence, indicating very low contamination.

  16. Double layers liquid-crystal microlens arrays used in optical switches

    Science.gov (United States)

    Wang, Cheng; Fan, Di; Zhang, Bo; Tong, Qing; Luo, Jun; Lei, Yu; Zhang, Xinyu; Xie, Changsheng

    2015-12-01

    Based on our previous works in liquid-crystal microlens arrays (LCMAs), a new kind of optical switches using the 24×24 fiber arrays coupled with the LCMAs, which have a key dual-mode function of the switches about on and off state and work in visible and infrared range, is proposed and fabricated in this paper. Different with other common LCMAs, this new kind of dual-mode LCMAs includes two layers of control electrodes deposited directly over the surface of the top glass substrate in LC microcavity fabricated. The first layer is the patterned electrode, which is designed into basic circular holes with suitable diameter, and the second is the planar electrode. Both layered electrodes are effectively separated by a thin SiO2 film with a typical thickness of about several micrometers, and then the dual-mode microlenses are driven by applied electrical signals with different root mean square (rms) voltage.

  17. Buffer layer between a planar optical concentrator and a solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Solano, Manuel E. [Departamento de Ingeniería Matemática and CI" 2 MA, Universidad de Concepción, Concepción, Casilla 160-C (Chile); Barber, Greg D. [Penn State Institute of Energy and the Environment, Pennsylvania State University, University Park, PA 16802 (United States); Department of Chemistry, Pennsylvania State University, University Park, PA 16802 (United States); Lakhtakia, Akhlesh [Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802 (United States); Faryad, Muhammad [Department of Physics, Lahore University of Management Sciences, Lahore 54792 (Pakistan); Monk, Peter B. [Department of Mathematical Sciences, University of Delaware, Newark, DE 19716 (United States); Mallouk, Thomas E. [Department of Chemistry, Pennsylvania State University, University Park, PA 16802 (United States)

    2015-09-15

    The effect of inserting a buffer layer between a periodically multilayered isotropic dielectric (PMLID) material acting as a planar optical concentrator and a photovoltaic solar cell was theoretically investigated. The substitution of the photovoltaic material by a cheaper dielectric material in a large area of the structure could reduce the fabrication costs without significantly reducing the efficiency of the solar cell. Both crystalline silicon (c-Si) and gallium arsenide (GaAs) were considered as the photovoltaic material. We found that the buffer layer can act as an antireflection coating at the interface of the PMLID and the photovoltaic materials, and the structure increases the spectrally averaged electron-hole pair density by 36% for c-Si and 38% for GaAs compared to the structure without buffer layer. Numerical evidence indicates that the optimal structure is robust with respect to small changes in the grating profile.

  18. Fiber optic distributed temperature sensing for the determination of the nocturnal atmospheric boundary layer height

    Directory of Open Access Journals (Sweden)

    C. A. Keller

    2010-06-01

    Full Text Available A new method for measuring air temperature profiles in the atmospheric boundary layer at high spatial and temporal resolution is presented. The measurements are based on Raman scattering distributed temperature sensing (DTS with a fiber optic cable attached to a tethered balloon. These data were used to estimate the height of the stable nocturnal boundary layer. The experiment was successfully deployed during a two-day campaign in September 2009, providing evidence that DTS is well suited for this atmospheric application. Observed stable temperature profiles exhibit an exponential shape confirming similarity concepts of the temperature inversion close to the surface. The atmospheric mixing height (MH was estimated to vary between 5 m and 50 m as a result of the nocturnal boundary layer evolution. This value is in good agreement to the MH derived from concurrent Radon-222 (222Rn measurements and in previous studies.

  19. Fiber optic distributed temperature sensing for the determination of the nocturnal atmospheric boundary layer height

    Directory of Open Access Journals (Sweden)

    C. A. Keller

    2011-02-01

    Full Text Available A new method for measuring air temperature profiles in the atmospheric boundary layer at high spatial and temporal resolution is presented. The measurements are based on Raman scattering distributed temperature sensing (DTS with a fiber optic cable attached to a tethered balloon. These data were used to estimate the height of the stable nocturnal boundary layer. The experiment was successfully deployed during a two-day campaign in September 2009, providing evidence that DTS is well suited for this atmospheric application. Observed stable temperature profiles exhibit an exponential shape confirming similarity concepts of the temperature inversion close to the surface. The atmospheric mixing height (MH was estimated to vary between 5 m and 50 m as a result of the nocturnal boundary layer evolution. This value is in good agreement with the MH derived from concurrent Radon-222 (222Rn measurements and in previous studies.

  20. Structural, optical, and electrical-transport properties of Al-P-O inorganic layer coated on flexible stainless steel substrate

    Science.gov (United States)

    Kim, Moojin; Min, Jinhyuk; Kwak, Yongsu; Kim, Doori; Kim, Kyoung-Bo; Song, Jonghyun

    2017-03-01

    We coated inorganic layer containing oxygen, aluminium, phosphorus, and negligible sodium (APO) on stainless steel (STS) by using slot-die coating method and studied its application prospects as a substrate for flexible devices. The APO layer was compositionally uniform in overall area with an amorphous crystal structure. Surface morphology characterization of STS exhibited an improved flatness after the APO layer coating process. The optical property characterization of the APO film carried out by measuring optical reflectance spectrum and refractive index. We also investigated the electrical-transport mechanism in the APO layer. These experimental observations imply the possibility of potential application of APO-STS as a substrate for flexible devices.

  1. High diffraction efficiency of three-layer diffractive optics designed for wide temperature range and large incident angle.

    Science.gov (United States)

    Mao, Shan; Cui, Qingfeng; Piao, Mingxu; Zhao, Lidong

    2016-05-01

    A mathematical model of diffraction efficiency and polychromatic integral diffraction efficiency affected by environment temperature change and incident angle for three-layer diffractive optics with different dispersion materials is put forward, and its effects are analyzed. Taking optical materials N-FK5 and N-SF1 as the substrates of multilayer diffractive optics, the effect on diffraction efficiency and polychromatic integral diffraction efficiency with intermediate materials POLYCARB is analyzed with environment temperature change as well as incident angle. Therefore, three-layer diffractive optics can be applied in more wide environmental temperature ranges and larger incident angles for refractive-diffractive hybrid optical systems, which can obtain better image quality. Analysis results can be used to guide the hybrid imaging optical system design for optical engineers.

  2. Analysis of Retinal Layer Thicknesses and Their Clinical Correlation in Patients with Traumatic Optic Neuropathy.

    Directory of Open Access Journals (Sweden)

    Ju-Yeun Lee

    Full Text Available The aims of this study were 1 To evaluate retinal nerve fiber layer (fRNFL thickness and ganglion cell layer plus inner plexiform layer (GCIPL thickness at the fovea in eyes affected with traumatic optic neuropathy (TON compared with contralateral normal eyes, 2 to further evaluate these thicknesses within 3 weeks following trauma (defined as "early TON", and 3 to investigate the relationship between these retinal layer thicknesses and visual function in TON eyes. Twenty-nine patients with unilateral TON were included. Horizontal and vertical spectral-domain optical coherence tomography (SD-OCT scans of the fovea were taken in patients with unilateral TON. The main outcome measure was thickness of the entire retina, fRNFL, and GCIPL in eight areas. Thickness of each retinal layer was compared between affected and unaffected eyes. The correlation between the thickness of each retinal layer and visual function parameters, including best corrected visual acuity, color vision, P100 latency, and P100 amplitude in visual evoked potential (VEP, mean deviation (MD and visual field index (VFI in Humphrey visual field analysis in TON eyes was analyzed. Thicknesses of the entire retina, fRNFL, and GCIPL in SD-OCT were significantly thinner (3-36% in all measurement areas of TON eyes compared to those in healthy eyes (all p<0.05. Whereas, only GCIPL in the outer nasal, superior, and inferior areas was significantly thinner (5-10% in the early TON eyes than that in the control eyes (all p<0.01. A significant correlation was detected between retinal layer thicknesses and visual function parameters including color vision, P100 latency and P100 amplitude in VEP, MD, and VFI (particularly P100 latency, MD, and VFI (r = -0.70 to 0.84. Among the retinal layers analyzed in this study, GCIPL (particularly in the superior and inferior areas was most correlated with these five visual function parameters (r = -0.70 to 0.71. Therefore, evaluation of morphological change

  3. Improved properties of phosphor-filled luminescent down-shifting layers: reduced scattering, optical model, and optimization for PV application

    Science.gov (United States)

    Solodovnyk, Anastasiia; Lipovšek, Benjamin; Forberich, Karen; Stern, Edda; Krč, Janez; Batentschuk, Miroslaw; Topič, Marko; Brabec, Christoph J.

    2015-12-01

    We studied the optical properties of polymer layers filled with phosphor particles in two aspects. First, we used two different polymer binders with refractive indices n = 1.46 and n = 1.61 (λ = 600 nm) to decrease Δn with the phosphor particles (n = 1.81). Second, we prepared two particle size distributions D50 = 12 μm and D50 = 19 μm. The particles were dispersed in both polymer binders in several volume concentrations and coated onto glass with thicknesses of 150 - 600 μm. We present further a newly developed optical model for simulation and optimization of such luminescent down-shifting (LDS) layers. The model is developed within the ray tracing framework of the existing optical simulator CROWM (Combined Ray Optics / Wave Optics Model), which enables simulation of standalone LDS layers as well as complete solar cells (including thick and thin layers) enhanced by the LDS layers for an improved solar spectrum harvesting. Experimental results and numerical simulations show that the layers of the higher refractive index binder with larger particles result in the highest optical transmittance in the visible light spectrum. Finally we proved that scattering of the phosphor particles in the LDS layers may increase the overall light harvesting in the solar cell. We used numerical simulations to determine optimal layer composition for application in realistic thin-film photovoltaic devices. Surprisingly LDS layers with lower measured optical transmittance are more efficient when applied onto the solar cells due to graded refractive index and efficient light scattering. Therefore, our phosphor-filled LDS layers could possibly complement other light-coupling techniques in photovoltaics.

  4. Photoluminescence properties of Bi/Al-codoped silica optical fiber based on atomic layer deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Jianxiang, E-mail: wenjx@shu.edu.cn [Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072 (China); Wang, Jie; Dong, Yanhua; Chen, Na [Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072 (China); Luo, Yanhua; Peng, Gang-ding [Photonics & Optical Communications, School of Electrical Engineering & Telecommunications, University of New South Wales, Sydney 2052, NSW (Australia); Pang, Fufei; Chen, Zhenyi [Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072 (China); Wang, Tingyun, E-mail: tywang@mail.shu.edu.cn [Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072 (China)

    2015-09-15

    Highlights: • We report on a new fabrication method of producing Bi/Al-codoped silica optical fibers. • There are obvious Bi-type ions absorption peaks at 520, 700 and 800 nm. • The fluorescence peaks are 1130 and 1145 nm with 489 and 705 nm excitations, respectively. • Their fluorescence lifetimes are 701 and 721 μs, respectively. • And then there are obvious fluorescence bands in 600–850 and 900–1650 nm with 532 nm pump exciting. • There is a maximum fluorescence intensity peak at 1120 nm, and its full wave at half maximum (FWHM) is approximately 180 nm. • These may mainly result from the interaction between Bi and Al ions. • The Bi/Al-codoped silica optical fibers would be used in high power or broadly tunable laser sources, and optical fiber amplifier in the optical communication fields. - Abstract: The Bi/Al-codoped silica optical fibers are fabricated by atomic layer deposition (ALD) doping technique combing with conventional modified chemical vapor deposition (MCVD) process. Bi{sub 2}O{sub 3} and Al{sub 2}O{sub 3} are induced into silica optical fiber core layer by ALD technique, with Bis (2,2,6,6-tetra-methyl-3,5-heptanedionato) Bismuth(III) (Bi(thd){sub 3}) and H{sub 2}O as Bi and O precursors, and with Al(CH{sub 3}){sub 3} (TMA) as Al precursor, respectively. The structure features and optical properties of Bi/Al-codoped silica optical fibers are investigated. Bi{sub 2}O{sub 3} stoichiometry is confirmed by X-ray photoelectron spectroscopy (XPS). The valence state of Bi element is +3. Concentration distribution of Si, Ge and O elements is approximately 24–33, 9 and 66 mol%, respectively, in fiber preform core and cladding layer region. Bi and Al ions have been also slightly doped approximately 150–180 and 350–750 ppm in fiber preform core, respectively. Refractive index difference of the Bi/Al-codoped fiber is approximately 0.58% using optical fiber refractive index profiler analyzer. There are obvious Bi-type ions absorption

  5. Optical coherence tomography evaluation of retinal nerve fiber layer in longitudinally extensive transverse myelitis

    Directory of Open Access Journals (Sweden)

    Frederico C. Moura

    2011-02-01

    Full Text Available OBJECTIVE: To compare optical coherence tomography (OCT measurements on the retinal nerve fiber layer (RNFL of healthy controls and patients with longitudinally extensive transverse myelitis (LETM without previous optic neuritis. METHOD: Twenty-six eyes from 26 patients with LETM and 26 control eyes were subjected to automated perimetry and OCT for comparison of RNFL measurements. RESULTS: The mean deviation values from perimetry were significantly lower in patients with LETM than in controls (p<0.0001. RNFL measurements in the nasal quadrant and in the 3-o'clock segment were significantly smaller in LETM eyes than in controls. (p=0.04 and p=0.006, respectively. No significantly differences in other RNFL measurements were found. CONCLUSION: Patients with LETM may present localized RNFL loss, particularly on the nasal side of the optic disc, associated with slight visual field defects, even in the absence of previous episodes of optic neuritis. These findings emphasize the fact that patients with LETM may experience attacks of subclinical optic nerve damage.

  6. Growth and optical characteristics of high-quality ZnO thin films on graphene layers

    Directory of Open Access Journals (Sweden)

    Suk In Park

    2015-01-01

    Full Text Available We report the growth of high-quality, smooth, and flat ZnO thin films on graphene layers and their photoluminescence (PL characteristics. For the growth of high-quality ZnO thin films on graphene layers, ZnO nanowalls were grown using metal-organic vapor-phase epitaxy on oxygen-plasma treated graphene layers as an intermediate layer. PL measurements were conducted at low temperatures to examine strong near-band-edge emission peaks. The full-width-at-half-maximum value of the dominant PL emission peak was as narrow as 4 meV at T = 11 K, comparable to that of the best-quality films reported previously. Furthermore, the stimulated emission of ZnO thin films on the graphene layers was observed at the low excitation energy of 180 kW/cm2 at room temperature. Their structural and optical characteristics were investigated using X-ray diffraction, transmission electron microscopy, and PL spectroscopy.

  7. Evaluation of Retinal Nerve Fiber Layer and Ganglion Cell Complex in Patients with Optic Neuritis or Neuromyelitis Optica Spectrum Disorders Using Optical Coherence Tomography in a Chinese Cohort

    OpenAIRE

    Guohong Tian; Zhenxin Li; Guixian Zhao; Chaoyi Feng; Mengwei Li; Yongheng Huang; Xinghuai Sun

    2015-01-01

    We evaluate a cohort of optic neuritis and neuromyelitis optica (NMO) spectrum disorders patients in a territory hospital in China. The peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell complex (GCC) were measured using spectral-domain OCT after 6 months of acute onset. The results showed that both the peripapillary RNFL and macular GCC were significantly thinner in all optic neuritis subtypes compared to controls. In addition, the recurrent optic neuritis and NMO group...

  8. Determining the imaging plane of a retinal capillary layer in adaptive optical imaging

    Science.gov (United States)

    Yang, Le-Bao; Hu, Li-Fa; Li, Da-Yu; Cao, Zhao-Liang; Mu, Quan-Quan; Ma, Ji; Xuan, Li

    2016-09-01

    Even in the early stage, endocrine metabolism disease may lead to micro aneurysms in retinal capillaries whose diameters are less than 10 μm. However, the fundus cameras used in clinic diagnosis can only obtain images of vessels larger than 20 μm in diameter. The human retina is a thin and multiple layer tissue, and the layer of capillaries less than 10 μm in diameter only exists in the inner nuclear layer. The layer thickness of capillaries less than 10 μm in diameter is about 40 μm and the distance range to rod&cone cell surface is tens of micrometers, which varies from person to person. Therefore, determining reasonable capillary layer (CL) position in different human eyes is very difficult. In this paper, we propose a method to determine the position of retinal CL based on the rod&cone cell layer. The public positions of CL are recognized with 15 subjects from 40 to 59 years old, and the imaging planes of CL are calculated by the effective focal length of the human eye. High resolution retinal capillary imaging results obtained from 17 subjects with a liquid crystal adaptive optics system (LCAOS) validate our method. All of the subjects’ CLs have public positions from 127 μm to 147 μm from the rod&cone cell layer, which is influenced by the depth of focus. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174274, 11174279, 61205021, 11204299, 61475152, and 61405194).

  9. Optic Disc and Retinal Nerve Fiber Layer Thickness Evaluation of the Fellow Eyes in Non-Arteritic Ischemic Optic Neuropathy

    Directory of Open Access Journals (Sweden)

    Medine Yılmaz Dağ

    2015-05-01

    Full Text Available Objectives: To examine the fellow eyes in unilateral non-arteritic ischemic optic neuropathy (NAION and to compare their optic disc parameters and peripapillary retinal nerve fiber layer (RNFL thickness with age-and refraction-matched normal controll subjects, using Heidelberg Retinal Tomograph 2 (HRT II. Materials and Methods: The fellow eyes of 40 patients with typical unilateral NAION (study group and one randomly chosen eye of 42 age-, sex-, and refraction-matched normal control subjects were enrolled in the study. Optic disc morphologic features (average disc area, cup area, rim area, disc volume, rim volume, cup/disc area ratio, cup depth and peripapillary RNFL thickness were evaluated using HRT II, a confoal scanning ophtalmoscopy. Results: In the study group, there were 26 (65% men and 14 (35% women, whereas there were 27 (64% men and 15 (36% women in the control group (Chi square test, p=0.89. Mean age of the patients in the study and control groups was 59.4±10.3 and 57.7±9.1 years, respectively (T test, p=0.72. There was not any statistically significant difference regarding mean spheric equivalent between the two groups (Mann-Whitney U-test, p=0.203. The NAION unaffected fellow eyes had significantly smaller disc areas, cup areas, cup volumes, cup-disc area ratios (vertical and lineer, and cup depths than the control eyes (Mann-Whitney U-test; p<0.05, whereas there was no significant difference in the RNFL thickness between the two. Conclusion: A comparison of the fellow eyes in patients with unilateral NAION and the control eyes showed a significant difference in optic disc parameters and the morphology of RNFL. These differences could be important in the pathogenesis of NAION and needs to have further investigated. (Turk J Ophthalmol 2015; 45: 111-114

  10. Stellate figure in the macula: visualization in the Henle fiber layer on optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Makino S

    2014-01-01

    Full Text Available Shinji Makino, Meri Watanabe, Hironobu TampoDepartment of Ophthalmology, Jichi Medical University, Shimotsuke, Tochigi, JapanAbstract: A 21-year-old woman complaining of a sudden visual disturbance in her left eye was referred to our hospital. The best-corrected visual acuity (BCVA in the left eye was 0.3. Fundus examination revealed tortuous retinal veins, soft exudates, and retinal edema. Optical coherence tomography showed that the macular thickness was increased to 685 µm. We diagnosed the condition as a central retinal vein occlusion. Systemic administration of an antiplatelet agent was initiated. The BCVA improved to 0.6, the retinal edema dramatically resolved, and the macular thickness was reduced to 318 µm 1 week later. Furthermore, the reduced retinal edema had transformed to many spokes in a wheel of exudates, a so-called “stellate figure”s, in the macula. On optical coherence tomography, hyper-reflective substances were detected in the Henle fiber layer. One month later, the BCVA improved to 1.0. Changes in microstructural findings and visual acuity were analogous during the recovery of macular edema in our patient.Keywords: stellate figure in the macula, Henle fiber layer, central retinal vein occlusion, macular edema, optical coherence tomography

  11. Enhancement of optical nonlinearity of LCs with gold-nanoparticle-doped alignment layers

    Science.gov (United States)

    Lin, Hui-Chi; Fuh, Andy Y. G.; Lin, Ci-Yong; Li, Ming-Shian

    2013-05-01

    In this study, the optical nonlinearity of LCs with cell substrates coated with gold-nanoparticle (AuNP) -doped PVA alignment layers were examined using the Z-scan technique. The results show that the nonlinear refractive index n2 of the sample is enhanced by the gold nanoparticles doped in the alignment layers, because of the thermal effect of the absorption by the surface of the sample through the localized surface plasmon resonance (LSPR) of the gold nanoparticles. As the concentration of AuNPs in the alignment layers of the LC sample increases, the thermal effect of the LSPR increases, and |n2| observably increases. Furthermore, the self-defocusing effect (n2<0) of the sample can be modulated by the application of an external voltage, and a self-focusing effect (n2<0) can be observed when samples are illuminated by a high-intensity laser with the application of a high voltage. Therefore, the magnitude and the sign of n2 of the sample can be modulated by combining the applied electric field and the optical field.

  12. Dependences of optical properties of spherical two-layered nanoparticles on parameters of gold core and material shell

    Science.gov (United States)

    Pustovalov, V. K.; Astafyeva, L. G.; Zharov, V. P.

    2013-12-01

    Modeling of nonlinear dependences of optical properties of spherical two-layered gold core and some material shell nanoparticles (NPs) placed in water on parameters of core and shell was carried out on the basis of the extended Mie theory. Efficiency cross-sections of absorption, scattering and extinction of radiation with wavelength 532 nm by core-shell NPs in the ranges of core radii r00=5-40 nm and of relative NP radii r1/r00=1-8 were calculated (r1-radius of two-layered nanoparticle). Shell materials were used with optical indexes in the ranges of refraction n1=0.2-1.5 and absorption k1=0-3.5 for the presentation of optical properties of wide classes of shell materials (including dielectrics, metals, polymers, vapor shell around gold core). Results show nonlinear dependences of optical properties of two-layered NPs on optical indexes of shell material, core r00 and relative NP r1/r00 radii. Regions with sharp decrease and increase of absorption, scattering and extinction efficiency cross-sections with changing of core and shell parameters were investigated. These dependences should be taken into account for applications of two-layered NPs in laser nanomedicine and optical diagnostics of tissues. The results can be used for experimental investigation of shell formation on NP core and optical determination of geometrical parameters of core and shell of two-layered NPs.

  13. SDOCT Thickness Measurements of Various Retinal Layers in Patients with Autosomal Dominant Optic Atrophy due to OPA1 Mutations

    Directory of Open Access Journals (Sweden)

    Andrea M. Schild

    2013-01-01

    Full Text Available Purpose. To specify thickness values of various retinal layers on macular spectral domain Optical Coherence Tomography (SDOCT scans in patients with autosomal dominant optic atrophy (ADOA compared to healthy controls. Methods. SDOCT volume scans of 7 patients with ADOA (OPA-1 mutation and 14 healthy controls were quantitatively analyzed using manual grading software. Mean thickness values for the ETDRS grid subfields 5–8 were calculated for the spaces neurosensory retina, retinal nerve fiber layer (RNFL, ganglion cell layer (GCL, a combined space of inner plexiform layer/outer plexiform layer/inner nuclear layer (IPL+INL+OPL, and a combined space of outer nuclear layer/photoreceptor layers (ONL+PL. Results. ADOA patients showed statistically significant lower retinal thickness values than controls (. RNFL ( and GCL thicknesses ( were significantly lower in ADOA patients. There was no difference in IPL+INL+OPL and in ONL+PL thickness. Conclusion. Manual subanalysis of macular SDOCT volume scans allowed detailed subanalysis of various retinal layers. Not only RNFL but also GCL thicknesses are reduced in the macular area of ADOA patients whereas subjacent layers are not involved. Together with clinical findings, macular SDOCT helps to identify patients with suspicion for hereditary optic neuropathy before genetic analysis confirms the diagnosis.

  14. Electrochemical and optical characterizations of anodic porous n-InP(1 0 0) layers

    Energy Technology Data Exchange (ETDEWEB)

    Santinacci, Lionel, E-mail: santinacci@cinam.univ-mrs.f [Institut Lavoisier de Versailles (UMR CNRS 8180), University of Versailles Saint-Quentin, 45 avenue des Etats-Unis, F-78000 Versailles (France); Goncalves, Anne-Marie; Simon, Nathalie; Etcheberry, Arnaud [Institut Lavoisier de Versailles (UMR CNRS 8180), University of Versailles Saint-Quentin, 45 avenue des Etats-Unis, F-78000 Versailles (France)

    2010-12-30

    In this paper, electrochemical and optical characterizations of anodic porous n-InP(1 0 0) are reported. The direct relation between the observed pore morphology and the physical properties is demonstrated using electrochemical methods such as cyclic voltammetry and impedance spectroscopy as well as optical techniques like photocurrent spectroscopy and photoluminescence measurements. An enhancement of the interfacial capacitance, proportional to the anodic charge, is revealed by voltammetry and Mott-Schottky analysis. It is related to the drastic increase of the area of the porous electrode. However, when the porous samples are sufficiently reverse-biased, the capacitance enlargement disappears because the nanosized pore walls are fully depleted and the electroactive area recovers its initial value. Photocurrent spectroscopy and photoluminescence measurements show the porous film behaves like an absorbent layer. This effect is also ascribed to the specific geometry of the space charge layer within the pore walls. A model based on the absorption coefficient and the effective optical path length is thus used to describe the phenomenon. However the model is not sufficient to depict the phenomenon and the charge recombination in the additional surface states created during the pore formation and the long transit time of electrons in the porous matrix are also significant. Additional effects such as the initial enhancement of the photocurrent response and the redshift of the absorption edge of the photocurrent spectra are observed. Inversely, no shift of the photoluminescence peak is detected. However an exponential quenching of the photoluminescence is also attributed to an absorbent behavior of the porous layer.

  15. In vivo quantitative evaluation of the rat retinal nerve fiber layer with optical coherence tomography.

    Science.gov (United States)

    Nagata, Atsushi; Higashide, Tomomi; Ohkubo, Shinji; Takeda, Hisashi; Sugiyama, Kazuhisa

    2009-06-01

    To determine whether optical coherence tomography (OCT) is useful for quantitative evaluation of the thickness of the rat retinal nerve fiber layer (RNFL) in an optic nerve crush model. An OCT system was developed with a modified commercial time-domain OCT and a superluminescent diode with a bandwidth of 150 nm. Optical components were optimized to acquire rat retinal images. The right optic nerve was crushed intraorbitally with a clip. The left eye served as the untreated control. Circumpapillary OCT scans with a circle diameter of 500 microm centered on the optic disc were performed before and 1, 2, and 4 weeks after the crush. Repeatability and reproducibility of RNFL thickness measurements were evaluated. The RNFL thicknesses at 400, 500, and 600 microm from the center of the optic disc determined by linear vertical OCT scans were compared with thicknesses in retinal sections. The mean RNFL thicknesses in circumpapillary OCT scans were 27.9 +/- 1.8, 29.2 +/- 2.4, 19.9 +/- 2.3, and 4.5 +/- 3.6 microm before and 1, 2, and 4 weeks after the crush, respectively. RNFL thickness was unchanged 1 week after the crush, but then decreased significantly and progressively after the second week (P < 0.01). Coefficients of repeatability and reproducibility were less than 10% except for the crushed eyes at 4 weeks. RNFL thicknesses in OCT images correlated significantly with thicknesses determined histologically (r = 0.90, P < 0.001). OCT is a useful and valuable tool for quantitative evaluation of rat RNFL thickness.

  16. Optical and structural investigation of a-plane GaN layers on r-plane sapphire with nucleation layer optimization

    Institute of Scientific and Technical Information of China (English)

    Zhang Jin-Feng; Xu Sheng-Rui; Zhang Jin-Cheng; Hao Yue

    2011-01-01

    Nonpolar a-plane GaN epilayers are grown on several r-plane sapphire substrates by metal organic chemical vapour deposition using different nucleation layers: (A) a GaN nucleation layer deposited at low temperature (LT); (B) an A1N nucleation layer deposited at high temperature; or (C) an LT thin A1N nucleation layer with an A1N layer and an AIN/AlGaN superlattice both subsequently deposited at high temperature. The samples have been characterized by Xray diffraction (XRD), atomic force microscopy and photoluminescence. The GaN layers grown using nucleation layers B and C show narrower XRD rocking curves than that using nucleation layer A, indicating a reduction in crystal defect density. Furthermore, the GaN layer grown using nucleation layer C exhibits a surface morphology with triangular defect pits eliminated completely. The improved optical property, corresponding to the enhanced crystal quality, is also confirmed by temperature-dependent and excitation power-dependent photoluminescence measurements.

  17. Application of Radar and Optical Images to Create Copernicus High Resolution Layers: Case Studies in Hungary

    Science.gov (United States)

    Surek, Gyorgy; Nador, Gizella; Friedl, Zoltan; Gyimesi, Balint; Rada, Matyas; Akos Gera, David; Hubik, Iren; Rotterne Kulesar, Aniko; Totok, Cecilia

    2016-08-01

    Injection of SAR imagery based information in the production of Copernicus High Resolution Layers can help to refine information served by optical satellite imagery, together with a-priori knowledge it may overcome the gaps caused by the cloud cover issue. However, this requires a methodological adaptation, given the different nature of SAR as compared to optical data. The methodological adaptation shall allow for an operational implementation, and shall help reducing the elapsed time between available satellite imagery. This requires the analysis of the potential use of SAR based imagery in the COPERNICUS land context, supported with case studies. In this paper the contribution of radar polarimetry for distinguishing land cover categories is evaluated.

  18. Persistent photoconductivity and optical quenching of photocurrent in GaN layers under dual excitation

    Science.gov (United States)

    Ursaki, V. V.; Tiginyanu, I. M.; Ricci, P. C.; Anedda, A.; Hubbard, S.; Pavlidis, D.

    2003-09-01

    Persistent photoconductivity (PPC) and optical quenching (OQ) of photoconductivity (PC) were investigated in a variety of n-GaN layers characterized by different carrier concentrations, luminescence characteristics, and strains. The relation between PPC and OQ of PC was studied by exciting the samples with two beams of monochromatic radiation of various wavelengths and intensities. The PPC was found to be excited by the first beam with a threshold at 2.0 eV, while the second beam induces OQ of PC in a wide range of photon energies with a threshold at 1.0 eV. The obtained results are explained on the basis of a model combining two previously put forward schemes with electron traps playing the main role in PPC and hole traps inducing OQ of PC. The possible nature of the defects responsible for optical metastability of GaN is discussed.

  19. Coherent control of the optical absorption in a plasmonic lattice coupled to a luminescent layer

    CERN Document Server

    Pirruccio, Giuseppe; Rodriguez, Said Rahimzadeh-Kalaleh; Rivas, Jaime Gomez

    2016-01-01

    We experimentally demonstrate the coherent control, i.e., phase-dependent enhancement and suppression, of the optical absorption in an array of metallic nanoantennas covered by a thin lu- minescent layer. The coherent control is achieved by using two collinear, counter-propagating and phase-controlled incident waves with wavelength matching the absorption spectrum of dye molecules coupled to the array. Symmetry arguments shed light on the relation between the relative phase of the incident waves and the excitation efficiency of the optical resonances of the system. This coherent control is associated with a phase-dependent distribution of the electromagnetic near-fields in the structure which enables a significant reduction of the unwanted dissipation in the metallic structures.

  20. Improved optical sintering efficiency at the contacts of silver nanowires encapsulated by a graphene layer.

    Science.gov (United States)

    Yang, Seung-Bok; Choi, HongKyw; Lee, Da Som; Choi, Choon-Gi; Choi, Sung-Yool; Kim, Il-Doo

    2015-03-18

    Graphene/silver nanowire (AgNWs) stacked electrodes, i.e., graphene/AgNWs, are fabricated on a glass substrate by air-spray coating of AgNWs followed by subsequent encapsulation via a wet transfer of single-layer graphene (SLG) and multilayer graphene (MLG, reference specimen) sheets. Here, graphene is introduced to improve the optical sintering efficiency of a xenon flash lamp by controlling optical transparency and light absorbing yield in stacked graphene/AgNW electrodes, facilitating the fusion at contacts of AgNWs. Intense pulsed light (IPL) sintering induced ultrafast (sintering is an efficient way to provide fast welding of Ag wire-to-wire junctions in stacked electrodes of graphene/AgNWs, leading to enhanced conductivity as well as superior long-term stability under oxygen and sulfur atmospheres. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Application of double-layered skin phantoms for optical flow imaging during laser tattoo treatments

    Science.gov (United States)

    Lee, Byeong-il; Song, Woosub; Kim, Hyejin; Kang, Hyun Wook

    2016-05-01

    The feasible application of double-layered skin phantoms was evaluated to identify artificial blood flow with a Doppler optical coherence tomography (DOCT) system for laser tattoo treatments. Polydimethylsiloxane (PDMS) was used to fabricate the artificial phantoms with flow channels embedded. A double-integrating sphere system with an inverse adding-doubling method quantified both the absorption and the reduced scattering coefficients for epidermis and dermis phantoms. Both OCT and caliper measurements confirmed the double-layered phantom structure (epidermis = 136 ± 17 µm vs. dermis = 3.0 ± 0.1 mm). The DOCT method demonstrated that high flow rates were associated with high image contrast, visualizing the position and the shape of the flow channel. Application of the channel-embedded skin phantoms in conjunction with DOCT can be a reliable technique to assess dynamic variations in the blood flow during and after laser tattoo treatments.

  2. Photocurrent switching method based on photoisomerization of diarylethene layer for nondestructive readout of photochromic optical memory.

    Science.gov (United States)

    Tsujioka, Tsuyoshi; Onishi, Itaru; Natsume, Daisuke

    2010-07-10

    We report on photocurrent switching based on photoisomerization for the nondestructive readout of photochromic optical memory. The photoisomerization of a diarylethene (DAE) memory layer switched the photocurrent generated in a light-absorbing phthalocyanine layer upon irradiation of a laser light. This switching is based on the ionization potential change of the DAE molecules. Switching characteristics of the photocurrent were investigated for the laser light with a wavelength of 410 nm, 630 nm, or 780 nm. Excellent on-off ratios of the photocurrent were achieved by irradiation at 630 nm and 780 nm. When the pulsed laser light with a wavelength of 780 nm was repeatedly irradiated to the colored and uncolored memory devices, no change of the photocurrent signal levels was observed, even after 8 x 10(5) cycles, indicating a successful demonstration of the nondestructive readout.

  3. Integrated Survivability Strategies of IP/GMPLS/Optical Multi-layer Network

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ji-jun; JI Yue-feng; XU Da-xiong

    2003-01-01

    In last decade,due to that the popularity of the internet, data-central traffic kept growing,some emerging networking requirements have been posed on the today's telecommunication networks,especially in the area of network survivability.Obviously,as a key networking problem,network reliability will be more and more important.The integration of different technologies such as ATM,SDH,and WDM in multilayer transport networks raises many questions regarding the coordination of the individual network layers.This problem is referred as multilayer network survivability.The integrated multilayer network survivability is investingated as well as the representation of an interworking strategy between different single layer survivability schemes in IP via generalized multi-protocol label switching over optical network.

  4. LOLAS: an optical turbulence profiler in the atmospheric boundary layer with extreme altitude-resolution

    CERN Document Server

    Avila, R; Wilson, R W; Chun, M; Butterley, T; Carrasco, E

    2008-01-01

    We report the development and first results of an instrument called Low Layer Scidar (LOLAS) which is aimed at the measurement of optical-turbulence profiles in the atmospheric boundary layer with high altitude-resolution. The method is based on the Generalized Scidar (GS) concept, but unlike the GS instruments which need a 1- m or larger telescope, LOLAS is implemented on a dedicated 40-cm telescope, making it an independent instrument. The system is designed for widely separated double-star targets, which enables the high altitude-resolution. Using a 20000-separation double- star, we have obtained turbulence profiles with unprecedented 12-m resolution. The system incorporates necessary novel algorithms for autoguiding, autofocus and image stabilisation. The results presented here were obtained at Mauna Kea Observatory. They show LOLAS capabilities but cannot be considered as representative of the site. A forthcoming paper will be devoted to the site characterisation. The instrument was built as part of the ...

  5. Simulation of a ground-layer adaptive optics system for the Kunlun Dark Universe Survey Telescope

    Institute of Scientific and Technical Information of China (English)

    Peng Jia; Sijiong Zhang

    2013-01-01

    Ground Layer Adaptive Optics (GLAO) is a recently developed technique extensively applied to ground-based telescopes,which mainly compensates for the wavefront errors induced by ground-layer turbulence to get an appropriate point spread function in a wide field of view.The compensation results mainly depend on the turbulence distribution.The atmospheric turbulence at Dome A in the Antarctic is mainly distributed below 15 meters,which is an ideal site for applications of GLAO.The GLAO system has been simulated for the Kunlun Dark Universe Survey Telescope,which will be set up at Dome A,and uses a rotating mirror to generate several laser guide stars and a wavefront sensor with a wide field of view to sequentially measure the wavefronts from different laser guide stars.The system is simulated on a computer and parameters of the system are given,which provide detailed information about the design of a practical GLAO system.

  6. Prospective Study on Retinal Nerve Fibre Layer Thickness Changes in Isolated Unilateral Retrobulbar Optic Neuritis

    Directory of Open Access Journals (Sweden)

    Gordon S. K. Yau

    2013-01-01

    Full Text Available Purpose. To investigate the retinal nerve fibre layer (RNFL thickness after unilateral acute optic neuritis using optical coherence tomography (OCT. Patients and Methods. This prospective cohort study recruited consecutive patients with a first episode of isolated, unilateral acute optic neuritis. RNFL thickness and visual acuity (VA of the attack and normal fellow eye were measured at presentation and 3 months in both the treatment and nontreatment groups. Results. 11 subjects received systemic steroids and 9 were treated conservatively. The baseline RNFL thickness was similar in the attack and fellow eye (P≥0.4. At 3 months, the attack eye had a thinner temporal (P=0.02 and average (P=0.05 RNFL compared to the fellow eye. At 3 months, the attack eye had significant RNFL thinning in the 4 quadrants and average thickness (P≤0.0002 compared to baseline. The RNFL thickness between the treatment and nontreatment groups was similar at baseline and 3 months (P≥0.1. Treatment offered better VA at 3 months (0.1 ± 0.2 versus 0.3 ± 0.2 LogMAR, P=0.04. Conclusion. Generalized RNFL thinning occurred at 3 months after a first episode of acute optic neuritis most significantly in the temporal quadrant and average thickness. Visual improvement with treatment was independent of RNFL thickness.

  7. Evaluation of peripapillary choroidal and retinal nerve fiber layer thickness in eyes with tilted optic disc

    Directory of Open Access Journals (Sweden)

    Muammer Ozcımen

    2014-12-01

    Full Text Available Purpose: This study was performed to evaluate the retinal nerve fiber layer (RNFL and peripapillary choroidal thickness in eyes with tilted optic disc in order to identify characteristic RNFL and peripapillary choroid patterns verified by optical coherence tomography (OCT. Methods: Twenty-nine eyes of 29 patients with tilted optic discs were studied with spectral-domain (SD-OCT and compared with age and sex-matched control subjects in a prospective design. The imaging of RNFL was performed using circular scans of a diameter of 3.4 mm around the optic disc using OCT. For measurements of peripapillary choroidal thickness, the standar d protocol for RNFL assessment was performed. Results: SD-OCT indicated significantly lower superotemporal (p<0.001, superonasal (p=0.001, and global (p=0.005 RNFL thicknesses in the tilted disc group than those of the control group. Peripapillary choroid was significantly thicker at the site of the elevated rim of eyes with tilted disc (p<0.001. Conclusion: This study demonstrated a clinical characterization of the main tilted disc morphologies that may be helpful in differentiating a tilted disc from other altered disc morphologies. Further studies are recommended to study the comparison between glaucoma and tilted disc groups.

  8. The Retinal Nerve Fiber Layer Defects in Patients with Anterior Ischemic Optic Neuropathy

    Institute of Scientific and Technical Information of China (English)

    HaiLu; QiZang

    1995-01-01

    Purpose:To demonstrate the effects of optic nerve ischemia on retinal nerve fiber layer(RNFL)and the associated visual dysfunction.Methods:23patients(25eyes)wits anterior ischemic optic neuropathy(AION)un derwent fundus fluorescein angiography(FFA),and then red-foree light pic-tures were taken via SE-40exceiter filter.All pictures were printed for RNAFL analysis,Humphrey central field analysis was conducted.All dataobtained fromFFA and visual field defects were analysed statistically.Results:The RNFL defects and the corresponding visual field edfects were pre-sented in 23of 25eyes(92%),The optic disc filling defects,RNAL edfects and visual field defects were found to be highly correspondent to each other.The RNFL defects were mainly the local losses of RNFL which were correspondent to the ischemic regions.Conclusion:The poor optic disc filling or ischemia can result in the RNFL defects which cause the associated visual dysfunction.Because RNFLdefects are irrever-siable changes,the potential values in predicting the prognosis of visual field de-fects caused by RNFL damages were suggested.Eye Science1995;11:165-167.

  9. Optical implementation of a single-layer finite impulse response neural network

    Science.gov (United States)

    Silveira, Paulo E. X.; Pati, G. S.; Wagner, Kelvin H.

    2000-05-01

    This paper demonstrates a space integrating optical implementation of a single-layer FIRNN. A scrolling spatial light modulator is used for representing the spatio-temporal input plane, while the weights are implemented by the adaptive grating formation in a photorefractive crystal. Differential heterodyning is used for low-noise bipolar output detection and an active stabilization technique using a lock-in amplifier and a piezo-electric actuator is adopted for long term interferometric stability. Simulations and initial experimental results for adaptive sonar broadband beamforming are presented.

  10. Use of a gold reflecting-layer in optical antenna substrates for increase of photoluminescence enhancement.

    Science.gov (United States)

    Fernandez-Garcia, Roberto; Rahmani, Mohsen; Hong, Minghui; Maier, Stefan A; Sonnefraud, Yannick

    2013-05-20

    We report on a straightforward way to increase the photoluminescence enhancement of nanoemitters induced by optical nanotantennas. The nanoantennas are placed above a gold film-silica bilayer, which produces a drastic increase of the scattered radiation power and near field enhancement. We demonstrate this increase via photoluminescence enhancement using an organic emitter of low quantum efficiency, Tetraphenylporphyrin (TPP). An increase of the photoluminescence enhancement by a factor larger than three is observed compared to antennas without the reflecting-layer. In addition, we study the possibility of influencing the polarization of the light emitted by utilizing asymmetry of dimer antennas.

  11. Light comfort zones of mesopelagic acoustic scattering layers in two contrasting optical environments

    KAUST Repository

    Røstad, Anders

    2016-03-31

    We make a comparison of the mesopelagic sound scattering layers (SLs) in two contrasting optical environments; the clear Red Sea and in murkier coastal waters of Norway (Masfjorden). The depth distributions of the SL in Masfjorden are shallower and narrower than those of the Red Sea. This difference in depth distribution is consistent with the hypothesis that the organisms of the SL distribute according to similar light comfort zones (LCZ) in the two environments. Our study suggest that surface and underwater light measurements ranging more than10 orders of magnitude is required to assess the controlling effects of light on SL structure and dynamics.

  12. Ray tracing simulation of aero-optical effect using multiple gradient index layer

    Science.gov (United States)

    Yang, Seul Ki; Seong, Sehyun; Ryu, Dongok; Kim, Sug-Whan; Kwon, Hyeuknam; Jin, Sang-Hun; Jeong, Ho; Kong, Hyun Bae; Lim, Jae Wan; Choi, Jong Hwa

    2016-10-01

    We present a new ray tracing simulation of aero-optical effect through anisotropic inhomogeneous media as supersonic flow field surrounds a projectile. The new method uses multiple gradient-index (GRIN) layers for construction of the anisotropic inhomogeneous media and ray tracing simulation. The cone-shaped projectile studied has 19° semi-vertical angle; a sapphire window is parallel to the cone angle; and an optical system of the projectile was assumed via paraxial optics and infrared image detector. The condition for the steady-state solver conducted through computational fluid dynamics (CFD) included Mach numbers 4 and 6 in speed, 25 km altitude, and 0° angle of attack (AoA). The grid refractive index of the flow field via CFD analysis and Gladstone-Dale relation was discretized into equally spaced layers which are parallel with the projectile's window. Each layer was modeled as a form of 2D polynomial by fitting the refractive index distribution. The light source of ray set generated 3,228 rays for varying line of sight (LOS) from 10° to 40°. Ray tracing simulation adopted the Snell's law in 3D to compute the paths of skew rays in the GRIN layers. The results show that optical path difference (OPD) and boresight error (BSE) decreases exponentially as LOS increases. The variation of refractive index decreases, as the speed of flow field increases the OPD and its rate of decay at Mach number 6 in speed has somewhat larger value than at Mach number 4 in speed. Compared with the ray equation method, at Mach number 4 and 10° LOS, the new method shows good agreement, generated 0.33% of relative root-mean-square (RMS) OPD difference and 0.22% of relative BSE difference. Moreover, the simulation time of the new method was more than 20,000 times faster than the conventional ray equation method. The technical detail of the new method and simulation is presented with results and implication.

  13. Excitonic optical nonlinearities and transport in the layered compound semiconductor GaSe

    DEFF Research Database (Denmark)

    Mizeikis, V.; Vadim, Lyssenko; Østergaard, John Erland;

    1995-01-01

    Dephasing and transient grating experiments in the direct excitonic absorption region of GaSe at low temperatures show that a fast relaxation within the one-dimensionally disordered excitonic band results in band filling being the dominant mechanism of the optical nonlinearity. Correspondingly, we...... observe a blueshift of the nonlinear signal with excitation density. The temperature dependence of the exciton diffusion constant measured in directions parallel to the GaSe layer planes indicates that temperature-independent scattering (trapping) and scattering by acoustic phonons determine the exciton...

  14. Computational Combination of the Optical Properties of Fenestration Layers at High Directional Resolution

    Directory of Open Access Journals (Sweden)

    Lars Oliver Grobe

    2017-03-01

    Full Text Available Complex fenestration systems typically comprise co-planar, clear and scattering layers. As there are many ways to combine layers in fenestration systems, a common approach in building simulation is to store optical properties separate for each layer. System properties are then computed employing a fast matrix formalism, often based on a directional basis devised by JHKlems comprising 145 incident and 145 outgoing directions. While this low directional resolution is found sufficient to predict illuminance and solar gains, it is too coarse to replicate the effects of directionality in the generation of imagery. For increased accuracy, a modification of the matrix formalism is proposed. The tensor-tree format of RADIANCE, employing an algorithm subdividing the hemisphere at variable resolutions, replaces the directional basis. The utilization of the tensor-tree with interfaces to simulation software allows sharing and re-use of data. The light scattering properties of two exemplary fenestration systems as computed employing the matrix formalism at variable resolution show good accordance with the results of ray-tracing. Computation times are reduced to 0.4% to 2.5% compared to ray-tracing through co-planar layers. Imagery computed employing the method illustrates the effect of directional resolution. The method is supposed to foster research in the field of daylighting, as well as applications in planning and design.

  15. Note: Non-invasive optical method for rapid determination of alignment degree of oriented nanofibrous layers

    Energy Technology Data Exchange (ETDEWEB)

    Pokorny, M.; Rebicek, J. [R& D Department, Contipro Biotech s.r.o., 561 02 Dolni Dobrouc (Czech Republic); Klemes, J. [R& D Department, Contipro Pharma a.s., 561 02 Dolni Dobrouc (Czech Republic); Kotzianova, A. [R& D Department, Contipro Pharma a.s., 561 02 Dolni Dobrouc (Czech Republic); Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, CZ-62500 Brno (Czech Republic); Velebny, V. [R& D Department, Contipro Biotech s.r.o., 561 02 Dolni Dobrouc (Czech Republic); R& D Department, Contipro Pharma a.s., 561 02 Dolni Dobrouc (Czech Republic)

    2015-10-15

    This paper presents a rapid non-destructive method that provides information on the anisotropic internal structure of nanofibrous layers. A laser beam of a wavelength of 632.8 nm is directed at and passes through a nanofibrous layer prepared by electrostatic spinning. Information about the structural arrangement of nanofibers in the layer is directly visible in the form of a diffraction image formed on a projection screen or obtained from measured intensities of the laser beam passing through the sample which are determined by the dependency of the angle of the main direction of polarization of the laser beam on the axis of alignment of nanofibers in the sample. Both optical methods were verified on Polyvinyl alcohol (PVA) nanofibrous layers (fiber diameter of 470 nm) with random, single-axis aligned and crossed structures. The obtained results match the results of commonly used methods which apply the analysis of electron microscope images. The presented simple method not only allows samples to be analysed much more rapidly and without damaging them but it also makes possible the analysis of much larger areas, up to several square millimetres, at the same time.

  16. Intra-retinal layer segmentation of 3D optical coherence tomography using coarse grained diffusion map.

    Science.gov (United States)

    Kafieh, Raheleh; Rabbani, Hossein; Abramoff, Michael D; Sonka, Milan

    2013-12-01

    Optical coherence tomography (OCT) is a powerful and noninvasive method for retinal imaging. In this paper, we introduce a fast segmentation method based on a new variant of spectral graph theory named diffusion maps. The research is performed on spectral domain (SD) OCT images depicting macular and optic nerve head appearance. The presented approach does not require edge-based image information in localizing most of boundaries and relies on regional image texture. Consequently, the proposed method demonstrates robustness in situations of low image contrast or poor layer-to-layer image gradients. Diffusion mapping applied to 2D and 3D OCT datasets is composed of two steps, one for partitioning the data into important and less important sections, and another one for localization of internal layers. In the first step, the pixels/voxels are grouped in rectangular/cubic sets to form a graph node. The weights of the graph are calculated based on geometric distances between pixels/voxels and differences of their mean intensity. The first diffusion map clusters the data into three parts, the second of which is the area of interest. The other two sections are eliminated from the remaining calculations. In the second step, the remaining area is subjected to another diffusion map assessment and the internal layers are localized based on their textural similarities. The proposed method was tested on 23 datasets from two patient groups (glaucoma and normals). The mean unsigned border positioning errors (mean ± SD) was 8.52 ± 3.13 and 7.56 ± 2.95 μm for the 2D and 3D methods, respectively.

  17. Coordinated Multi-layer Multi-domain Optical Network (COMMON) for Large-Scale Science Applications (COMMON)

    Energy Technology Data Exchange (ETDEWEB)

    Vokkarane, Vinod [University of Massachusetts

    2013-09-01

    We intend to implement a Coordinated Multi-layer Multi-domain Optical Network (COMMON) Framework for Large-scale Science Applications. In the COMMON project, specific problems to be addressed include 1) anycast/multicast/manycast request provisioning, 2) deployable OSCARS enhancements, 3) multi-layer, multi-domain quality of service (QoS), and 4) multi-layer, multidomain path survivability. In what follows, we outline the progress in the above categories (Year 1, 2, and 3 deliverables).

  18. Investigation of a double barrier resonant tunnelling structure which incorporates an optical window layer in the top contact

    Energy Technology Data Exchange (ETDEWEB)

    Henini, M.; Eaves, L.; Maude, D.K.; Hughes, O.H. (Dept. of Physics, Univ. of Nottingham (UK)); White, C.R.H. (Dept. of Physics, Univ. of Nottingham (UK) RSRE, Great Malvern (UK)); Simmonds, P.E. (Royal Signals and Radar Establishment, Great Malvern (UK) Dept. of Physics, Univ. of Nottingham (UK)); Skolnick, M.S. (Royal Signals and Radar Establishment, Great Malvern (UK)); Portal, J.C. (SNCI-CNRS, 38 - Grenoble (France) LPS-INSA, 31 - Toulouse (France))

    1991-05-01

    The electrical and optical properties of a double barrier resonant tunnelling device based on n-GaAs/(AlGa)As and incorporating a heavily doped (AlGa)As window layer are described. The window layer is located between the quantum well and the top surface and has a band gap which exceeds the energy of the quantum well photoluminescence. The incorporation of this layer does not impair the electrical properties of the device. (orig.).

  19. Structural, optical, and adsorption properties of ZnO(2)/poly(acrylic acid) hybrid thin porous films prepared by ionic strength controlled layer-by-layer method.

    Science.gov (United States)

    Pál, Edit; Sebok, Dániel; Hornok, Viktória; Dékány, Imre

    2009-04-01

    ZnO(2)/poly(acrylic acid) sandwich structures were prepared by layer-by-layer (LbL) self-assembly. The structure and optical behavior of the hybrid films were controlled by changing the surface charge and conformation of the poly(acrylic acid). The buildup of the films was followed by UV-vis absorption and reflection spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), and quartz crystal microbalance (QCM) measurements. It was found that the ionic strength of the polymer solution had a great influence on the film thickness which, in turn, affected the optical properties. The water vapor adsorption isotherms of the films determined by QCM showed an adsorption hysteresis characteristic of porous thin layer structures. The adsorption of water molecules inside the films changed the effective refractive index resulting in a change of the reflection properties. This phenomenon is shown to be exploited for the application of the films as optical sensors. The polarizability of water molecules in the adsorption layer was also determined. It was found that polarization of water molecules in the adsorption layer is much lower than in the liquid water when the surface coverage (Theta) is low.

  20. Optical Tagging of Ion Beams Accelerated by Double Layers in Laboratory Plasma

    Science.gov (United States)

    Good, Timothy; Aguirre, Evan; Thompson, Derek; Scime, Earl

    2016-10-01

    Experiments in helicon sources that investigate plasma expansion into weakly magnetized, low density regions reveal the production of supersonic ion beams attributed to acceleration by spatially localized double layer structures. Current efforts are aimed at mapping the ion velocity flow field utilizing 2D spatially scanning laser induced fluorescence (LIF) probes that yield metastable ion velocity distribution functions (IVDF) for velocities along and perpendicular to the flow. Observation of metastable ion beams by LIF renders plausible a Lagrangian approach to studying the field-ion interaction via optical tagging. We propose a tagging scheme in which metastable state ion populations are modulated by optical pumping upstream of the double layer and the synchronous detection of LIF at the ion beam velocity is recorded downstream. Besides the unambiguous identification of the source of beam ions, this method can provide detailed dynamical information through time of flight analysis. Preliminary results will be presented. Please include this poster in session that includes poster authored by Evan Aguirre et al.

  1. Nondestructive and in situ determination of graphene layers using optical fiber Fabry-Perot interference

    Science.gov (United States)

    Li, Cheng; Peng, Xiaobin; Liu, Qianwen; Gan, Xin; Lv, Ruitao; Fan, Shangchun

    2017-02-01

    Thickness measurement plays an important role for characterizing optomechanical behaviors of graphene. From the view of graphene-based Fabry-Perot (F-P) sensors, a simple, nondestructive and in situ method of determining the thickness of nanothick graphene membranes was demonstrated by using optical fiber F-P interference. Few-layer/multilayer graphene sheets were suspendedly adhered onto the endface of a ferrule with a 125 µm inner diameter by van der Waals interactions to construct micro F-P cavities. Along with the Fresnel’s law and complex index of refraction of the membrane working as a light reflector of an F-P interferometer, the optical reflectivity of graphene was modeled to investigate the effects of light wavelength and temperature. Then the average thickness of graphene membranes were extracted by F-P interference demodulation, and yielded a very strong cross-correlation coefficient of 99.95% with the experimental results observed by Raman spectrum and atomic force microscope. The method could be further extended for determining the number of layers of other 2D materials.

  2. Correlation between Retinal Nerve Fiber Layer Thickness by Optical Coherence Tomography and Perimetric Parameters in Optic Atrophy

    Directory of Open Access Journals (Sweden)

    Mostafa Soltan-Sanjari

    2008-12-01

    Full Text Available

    PURPOSE: To investigate the correlation between retinal nerve fiber layer (RNFL thickness determined by optical coherence tomography (OCT and visual field (VF parameters in patients with optic atrophy. METHODS: This study was performed on 35 eyes of 28 patients with optic atrophy. RNFL thickness was measured by OCT (Carl Zeiss, Jena, Germany and automated perimetry was performed using the Humphrey Field Analyzer (Carl Zeiss, Jena, Germany. The correlation between RNFL thickness and VF parameters was evaluated. RESULTS: Mean global RNFL thickness was 44.9±27.5 µm which was significantly correlated with mean deviation score on automated perimetry (r=0.493, P=0.003; however, no significant correlation was observed between visual field pattern standard deviation and the corresponding quadrantic RNFL thickness. In a similar manner, no significant association was found between visual acuity and RNLF thickness. CONCLUSION: Mean global RNFL thickness as determined by OCT seems to be correlated with VF defect depth as represented by the mean deviation score on Humphrey VF testing. OCT may be used as an objective diagnostic tool in the evaluation of patients with optic atrophy.

  3. Optical properties of embedded ZnTe nanocrystals in SiO{sub 2} thin layer

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, F.; Naciri, A.E. [Universite Paul Verlaine-Metz, Laboratoire LPMD, 1 Bd Arago, 57078 Metz (France); Grob, J.J. [InESS, 23 rue du Loess-B20, 67037 Strasbourg Cedex 2 (France)

    2010-07-15

    We have studied the optical properties of ZnTe nanocrystals (ZnTe-nc) embedded in a SiO{sub 2} matrix by spectroscopic ellipsometry. The ZnTe-nc are embedded in a SiO{sub 2} matrix by ion implantation technique. The dose of 2.9 x 10{sup 16} cm{sup -2} of tellurium and zinc ions are implanted in a 250 nm thick SiO{sub 2} layer thermally grown on Si with respective implantation energies of 180 and 115 keV. Subsequent thermal treatments at 700 C lead to the formation of ZnTe-nc. Their size is characterized by transmission electron microscopy. Variable angle ellipsometric measurements are performed in air at room temperature at angles of incidence of 55, 60, and 65 . By taking into account defects caused by ion implantation in silica matrix, the critical points (CPs) dispersion model is used in order to extract the optical responses of the ZnTe-nc. The determined dielectric function spectra reveals distinct structures attributed to direct band gap and optical transition at higher energy. The observed structures are analyzed by fitting second derivative spectrum of the imaginary part of dielectric function with analytic CP line shapes. Results show good agreement with CPs data. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  4. Effect of Media Opacity on Retinal Nerve Fiber Layer Thickness Measurements by Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Dae Woong Lee

    2010-01-01

    Full Text Available Purpose: To assess the effect of ocular media opacity on retinal nerve fiber layer (RNFL thickness measurements by optical coherence tomography (OCT. Methods: In this prospective, non-randomized clinical study, ocular examinations and OCT measurements were performed on 77 cataract patients, 80 laser refractive surgery patients and 90 patients whose signal strength on OCT was different on two consecutive measurements. None of the eyes had preexisting retinal or optic nerve pathology, including glaucoma. Cataracts were classified according to the Lens Opacity Classification System III (LOCS III. All eyes were scanned with the Stratus OCT using the Fast RNFL program before and three months after surgery. Internal fixation was used during scanning and all eyes underwent circular scans around the optic disc with a diameter of 3.4 mm. Results: Average RNFL thickness, quadrant thickness and signal strength significantly increased after cataract surgery (P<0.05. Cortical and posterior subcapsular cataracts, but not nuclear cataracts, had a significant influence on RNFL thickness measurements (P<0.05. There was no significant difference between OCT parameters before and after laser refractive surgery. In eyes for which different signal strengths were observed, significantly larger RNFL thickness values were obtained on scans with higher signal strengths. Conclusion: OCT parameters are affected by ocular media opacity because of changes in signal strength; cortical cataracts have the most significant effect followed by posterior subcapsular opacities. Laser refractive procedures do not seem to affect OCT parameters significantly.

  5. Ultraviolet optical properties of aluminum fluoride thin films deposited by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hennessy, John, E-mail: john.j.hennessy@jpl.nasa.gov; Jewell, April D.; Balasubramanian, Kunjithapatham; Nikzad, Shouleh [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)

    2016-01-15

    Aluminum fluoride (AlF{sub 3}) is a low refractive index material with promising optical applications for ultraviolet (UV) wavelengths. An atomic layer deposition process using trimethylaluminum and anhydrous hydrogen fluoride has been developed for the deposition of AlF{sub 3} at substrate temperatures between 100 and 200 °C. This low temperature process has resulted in thin films with UV-optical properties that have been characterized by ellipsometric and reflection/transmission measurements at wavelengths down to 200 nm. The optical loss for 93 nm thick films deposited at 100 °C was measured to be less than 0.2% from visible wavelengths down to 200 nm, and additional microstructural characterization demonstrates that the films are amorphous with moderate tensile stress of 42–105 MPa as deposited on silicon substrates. X-ray photoelectron spectroscopy analysis shows no signature of residual aluminum oxide components making these films good candidates for a variety of applications at even shorter UV wavelengths.

  6. Inner nuclear layer thickening is inversley proportional to retinal ganglion cell loss in optic neuritis.

    Directory of Open Access Journals (Sweden)

    Megha Kaushik

    Full Text Available AIM: To examine the relationship between retinal ganglion cell loss and changes in the inner nuclear layer (INL in optic neuritis (ON. METHODS: 36 multiple sclerosis (MS patients with a history of ON and 36 age and sex-matched controls underwent Optical Coherence Tomography. The paramacular retinal nerve fiber layer (RNFL, combined ganglion cell and inner plexiform layers (GCL/IPL and inner nuclear layer (INL thickness were measured at 36 points around the fovea. To remove inter-subject variability, the difference in thickness of each layer between the ON and fellow eye of each patient was calculated. A topographic analysis was conducted. RESULTS: The INL of the ON patients was thicker than the controls (42.9µm versus 39.6µm, p=0.002. ON patients also had a thinner RNFL (27.8µm versus 32.2µm, p<0.001 and GCL/IPL (69.3µm versus 98.1µm, p<0.001. Among the controls, there was no correlation between RNFL and GCL/IPL as well as RNFL and INL, but a positive correlation was seen between GCL/IPL and INL (r=0.65, p<0.001. In the ON group, there was a positive correlation between RNFL and GCL/IPL (r=0.80, p<0.001 but a negative correlation between RNFL and INL (r=-0.61, p<0.001 as well as GCL/IPL and INL (r=-0.44, p=0.007. The negative correlation between GCL/IPL and INL strengthened in the ON group when inter-subject variability was removed (r=-0.75, p<0.001. Microcysts within the INL were present in 5 ON patients, mainly in the superior and infero-nasal paramacular regions. While patients with microcysts lay at the far end of the correlation curve between GCL/IPL and INL (i.e. larger INL and smaller GCL/IPL compared to other patients, their exclusion did not affect the correlation (r= -0.76, p<0.001. CONCLUSIONS: INL enlargement in MS-related ON is associated with the severity of GCL loss. This is a continuous relationship and patients with INL microcysts may represent the extreme end of the scale.

  7. Inner nuclear layer thickening is inversley proportional to retinal ganglion cell loss in optic neuritis.

    Science.gov (United States)

    Kaushik, Megha; Wang, Chen Yu; Barnett, Michael H; Garrick, Raymond; Parratt, John; Graham, Stuart L; Sriram, Prema; Yiannikas, Con; Klistorner, Alexandr

    2013-01-01

    To examine the relationship between retinal ganglion cell loss and changes in the inner nuclear layer (INL) in optic neuritis (ON). 36 multiple sclerosis (MS) patients with a history of ON and 36 age and sex-matched controls underwent Optical Coherence Tomography. The paramacular retinal nerve fiber layer (RNFL), combined ganglion cell and inner plexiform layers (GCL/IPL) and inner nuclear layer (INL) thickness were measured at 36 points around the fovea. To remove inter-subject variability, the difference in thickness of each layer between the ON and fellow eye of each patient was calculated. A topographic analysis was conducted. The INL of the ON patients was thicker than the controls (42.9µm versus 39.6µm, p=0.002). ON patients also had a thinner RNFL (27.8µm versus 32.2µm, p<0.001) and GCL/IPL (69.3µm versus 98.1µm, p<0.001). Among the controls, there was no correlation between RNFL and GCL/IPL as well as RNFL and INL, but a positive correlation was seen between GCL/IPL and INL (r=0.65, p<0.001). In the ON group, there was a positive correlation between RNFL and GCL/IPL (r=0.80, p<0.001) but a negative correlation between RNFL and INL (r=-0.61, p<0.001) as well as GCL/IPL and INL (r=-0.44, p=0.007). The negative correlation between GCL/IPL and INL strengthened in the ON group when inter-subject variability was removed (r=-0.75, p<0.001). Microcysts within the INL were present in 5 ON patients, mainly in the superior and infero-nasal paramacular regions. While patients with microcysts lay at the far end of the correlation curve between GCL/IPL and INL (i.e. larger INL and smaller GCL/IPL compared to other patients), their exclusion did not affect the correlation (r= -0.76, p<0.001). INL enlargement in MS-related ON is associated with the severity of GCL loss. This is a continuous relationship and patients with INL microcysts may represent the extreme end of the scale.

  8. Advantages of the AlGaN spacer in InAlN high-electron-mobility transistors grown using metalorganic vapor phase epitaxy

    Science.gov (United States)

    Yamada, Atsushi; Ishiguro, Tetsuro; Kotani, Junji; Tomabechi, Shuichi; Nakamura, Norikazu; Watanabe, Keiji

    2016-05-01

    We demonstrate the advantages of an AlGaN spacer layer in an InAlN high-electron-mobility transistor (HEMT). We investigated the effects of the growth parameters of the spacer layer on electron mobility in InAlN HEMTs grown by metalorganic vapor phase epitaxy, focusing on the surface roughness of the spacer layer and sharpness of the interface with the GaN channel layer. The electron mobility degraded, as evidenced by the formation of a graded AlGaN layer at the top of the GaN channel layer and the surface roughness of the AlN spacer layer. We believe that the short migration length of aluminum atoms is responsible for the observed degradation. An AlGaN spacer layer was employed to suppress the formation of the graded AlGaN layer and improve surface morphology. A high electron mobility of 1550 cm2 V-1 s-1 and a low sheet resistance of 211 Ω/sq were achieved for an InAlN HEMT with an AlGaN spacer layer.

  9. Surface acoustic wave characterization of optical sol-gel thin layers.

    Science.gov (United States)

    Fall, Dame; Compoint, François; Duquennoy, Marc; Piombini, Hervé; Ouaftouh, Mohammadi; Jenot, Frédéric; Piwakowski, Bogdan; Belleville, Philippe; Ambard, Chrystel

    2016-05-01

    Controlling the thin film deposition and mechanical properties of materials is a major challenge in several fields of application. We are more particularly interested in the characterization of optical thin layers produced using sol-gel processes to reduce laser-induced damage. The mechanical properties of these coatings must be known to control and maintain optimal performance under various solicitations during their lifetime. It is therefore necessary to have means of characterization adapted to the scale and nature of the deposited materials. In this context, the dispersion of ultrasonic surface waves induced by a micrometric layer was studied on an amorphous substrate (fused silica) coated with a layer of ormosil using a sol-gel process. Our ormosil material is a silica-PDMS mixture with a variable polydimethylsiloxane (PDMS) content. The design and implementation of Surface Acoustic Wave InterDigital Transducers (SAW-IDT) have enabled quasi-monochromatic Rayleigh-type SAW to be generated and the dispersion phenomenon to be studied over a wide frequency range. Young's modulus and Poisson's ratio of coatings were estimated using an inverse method.

  10. Fluorooxoborates: Beryllium-Free Deep-Ultraviolet Nonlinear Optical Materials without Layered Growth.

    Science.gov (United States)

    Zhang, Bingbing; Shi, Guoqiang; Yang, Zhihua; Zhang, Fangfang; Pan, Shilie

    2017-03-27

    Deep-ultraviolet nonlinear optical (DUV NLO) crystals are the key materials to extend the output range of solid-state lasers to below 200 nm. The only practical material KBe2 BO3 F2 suffers high toxicity through beryllium and strong layered growth. Herein, we propose a beryllium-free material design and synthesis strategy for DUV NLO materials. Introducing the (BO3 F)(4-) , (BO2 F2 )(3-) , and (BOF3 )(2-) groups in borates could break through the fixed 3D B-O network that would produce a larger birefringence without layering and simultaneously keep a short cutoff edge down to DUV. The theoretical and experimental studies on a series of fluorooxoborates confirm this strategy. Li2 B6 O9 F2 is identified as a DUV NLO material with a large second harmonic generation efficiency (0.9×KDP) and a large predicted birefringence (0.07) without layering. This study provides a feasible way to break down the DUV wall for NLO materials. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Estimation of optical constants of a bio-thin layer (onion epidermis), using SPR spectroscopy

    Science.gov (United States)

    Rehman, Saif-ur-; Mumtaz, Huma; Hayashi, Shinji; Shaukat, S. F.; Sekkat, Zouheir

    2014-12-01

    We estimate the optical constants of a biological thin layer (Allium cepa) by surface plasmon resonance (SPR) spectroscopy. For this study, the fresh inner thin epidermis of an onion bulb was used and stacked directly on gold (Au) and silver (Ag) film surfaces in order to identify the shift in SPR mode of each metal film at an operating wavelength of 632.8 nm. The thickness and dielectric constants of the biological thin layer were determined by matching the experimental SPR curves to theoretical ones. The thickness and roughness of bare Au and Ag thin films were also measured by atomic force microscopy (AFM); the results of which are in good agreement with those obtained through experiment. Due to the high surface roughness of the natural onion epidermis layer, AFM could not measure the exact thickness of an onion epidermis. It is estimated that the value of the real part of the dielectric constant of an onion epidermis is between the dielectric constants of water and air.

  12. Investigation and analysis of dual-k spacer with different materials and spacer lengths for nanowire-FET performance

    Science.gov (United States)

    Ko, Hyungwoo; Kim, Jongsu; Kang, Myounggon; Shin, Hyungcheol

    2017-10-01

    In this work, dual-k spacer structures are investigated using a variety of materials along the high-k spacer length in detail. It is known that not only the higher permittivity materials of high-k spacer boost the on-current but also lower permittivity materials of low-k spacer effectively reduce the off-current. By compared the results of other various single spacers and dual-k spacers, it is HfO2/Vacuum dual-k spacer that shows relatively higher ION, ION/IOFF, better immunity of short channel effects and outstanding device performances.

  13. Optical and Electrical Characteristics of Graphene Double Layer Formed by a Double Transfer of Graphene Single Layers.

    Science.gov (United States)

    Kim, Young Jun; Bae, Gi Yoon; Chun, Sungwoo; Park, Wanjun

    2016-03-01

    We demonstrate formation of double layer graphene by means of a double transfer using two single graphene layers grown by a chemical vapor deposition method. It is observed that shiftiness and broadness in the double-resonance of Raman scattering are much weaker than those of bilayer graphene formed naturally. Transport characteristics examined from transmission line measurements and field effect transistors show the similar behavior with those of single layer graphene. It indicates that interlayer separation, in electrical view, is large enough to avoid correlation between layers for the double layer structure. It is also observed from a transistor with the double layer graphene that molecules adsorpted on two inner graphene surfaces in the double layered structure are isolated and conserved from ambient environment.

  14. Fabrication and Analysis of Three-Layer All-Silicon Interference Optical Filter with Sub-Wavelength Structure toward High Performance Terahertz Optics

    CERN Document Server

    Makitsubo, Hironobu; Kataza, Hirokazu; Mita, Makoto; Suzuki, Toyoaki; Yamamoto, Keita

    2016-01-01

    We propose an all-silicon multi-layer interference filter composed solely of silicon with sub-wavelength structure (SWS) in order to realize high performance optical filters operating in the THz frequency region with robustness against cryogenic thermal cycling and mechanical damage. We demonstrate fabrication of a three-layer prototype using well-established common micro-electro-mechanical systems (MEMS) technologies as a first step toward developing practical filters. The measured transmittance of the three-layer filter agrees well with the theoretical transmittances calculated by a simple thin-film calculation with effective refractive indices as well as a rigorous coupled-wave analysis simulation. We experimentally show that SWS layers can work as homogeneous thin-film interference layers with effective refractive indices even if there are multiple SWS layers in a filter.

  15. Measurement of optical loss variation on thickness of InGaN optical confinement layers of blue-violet-emitting laser diodes

    Science.gov (United States)

    Son, J. K.; Lee, S. N.; Paek, H. S.; Sakong, T.; Kim, H. K.; Park, Y.; Ryu, H. Y.; Nam, O. H.; Hwang, J. S.; Cho, Y. H.

    2008-05-01

    An optical loss of GaN-based blue-violet laser diodes (BV-LDs) was measured by taking the intensity decay of edge emitting luminescence with respect to the distance from cleaved edge of a wafer to the position where an excitation laser was focused. Amplified spontaneous emission (ASE) was also investigated by tuning the power of an excitation laser on BV-LD wafers. Measurements were performed on wafers with different thicknesses of InGaN optical confinement layers (OCLs). The threshold power of ASE intensity was minimized at an optimum thickness of InGaN OCL. We also found that optical loss of wafers was determined by absorption of an InGaN layer in thicker OCL structure. From experimental data and fittings, we obtained 40 cm-1 for InGaN absorption at 405 nm. The optical field confined in OCL region was reasonably high enough to affect the overall modal loss in devices. Therefore, the optical losses still remained even though the Mg-doped GaN regions are far enough from the active layers. The crystal quality of an InGaN layer should be an important aspect to improve the performance of BV-LDs.

  16. Characterization of retinal nerve fiber layer thickness changes associated with Leber’s hereditary optic neuropathy by optical coherence tomography

    Science.gov (United States)

    ZHANG, YIXIN; HUANG, HOUBIN; WEI, SHIHUI; QIU, HUAIYU; GONG, YAN; LI, HONGYANG; DAI, YANLI; JIANG, ZHAOCAI; LIU, ZIHAO

    2014-01-01

    In the present study, the changes in the retinal nerve fiber layer (RNFL) thickness associated with Leber’s hereditary optic neuropathy (LHON) were examined by Cirrus high definition-optical coherence tomography (OCT), and the correlation between the RNFL thickness and the best corrected visual acuity (BCVA) was evaluated. A cross-sectional study was performed. Sixty-eight eyes from patients with LHON and 30 eyes from healthy individuals were scanned. Affected eyes were divided into 5 groups according to disease duration: Group 1, ≤3 months; group 2, 4–6 months; group 3, 7–9 months; group 4, 10–12 months; and group 5, >12 months. The RNFL thickness of the temporal, superior, nasal and inferior quadrants and the 360° average were compared between the LHON groups and the control group. The eyes in groups 1 and 2 were observed to have a thicker RNFL in the superior, nasal and inferior quadrants and a higher 360°-average RNFL thickness compared with those of the control group (P<0.05), the RNFL was observed to be thinner in the temporal quadrant in groups 1 and 2. The eyes in groups 3 and 4 showed a thinner RNFL in the temporal (P=0.001), superior and inferior (both P<0.05) quadrants, and a lower 360°-average RNFL thickness as compared with controls (P=0.001). No significant correlation was identified between BCVA and RNFL thickness. RNFL thickness was observed to undergo a unique process from thickening to thinning in the patients with LHON. Changes in different quadrants occurred at different time periods and the BCVA was not found to be correlated with RNFL thickness. PMID:24396430

  17. Characterization of retinal nerve fiber layer thickness changes associated with Leber's hereditary optic neuropathy by optical coherence tomography.

    Science.gov (United States)

    Zhang, Yixin; Huang, Houbin; Wei, Shihui; Qiu, Huaiyu; Gong, Yan; Li, Hongyang; Dai, Yanli; Jiang, Zhaocai; Liu, Zihao

    2014-02-01

    In the present study, the changes in the retinal nerve fiber layer (RNFL) thickness associated with Leber's hereditary optic neuropathy (LHON) were examined by Cirrus high definition-optical coherence tomography (OCT), and the correlation between the RNFL thickness and the best corrected visual acuity (BCVA) was evaluated. A cross-sectional study was performed. Sixty-eight eyes from patients with LHON and 30 eyes from healthy individuals were scanned. Affected eyes were divided into 5 groups according to disease duration: Group 1, ≤3 months; group 2, 4-6 months; group 3, 7-9 months; group 4, 10-12 months; and group 5, >12 months. The RNFL thickness of the temporal, superior, nasal and inferior quadrants and the 360° average were compared between the LHON groups and the control group. The eyes in groups 1 and 2 were observed to have a thicker RNFL in the superior, nasal and inferior quadrants and a higher 360°-average RNFL thickness compared with those of the control group (P<0.05), the RNFL was observed to be thinner in the temporal quadrant in groups 1 and 2. The eyes in groups 3 and 4 showed a thinner RNFL in the temporal (P=0.001), superior and inferior (both P<0.05) quadrants, and a lower 360°-average RNFL thickness as compared with controls (P=0.001). No significant correlation was identified between BCVA and RNFL thickness. RNFL thickness was observed to undergo a unique process from thickening to thinning in the patients with LHON. Changes in different quadrants occurred at different time periods and the BCVA was not found to be correlated with RNFL thickness.

  18. The ribosomal gene spacer region in archaebacteria

    Science.gov (United States)

    Achenbach-Richter, L.; Woese, C. R.

    1988-01-01

    Sequences for the spacer regions that separate the 16S and 23S ribosomal RNA genes have been determined for four more (strategically placed) archaebacteria. These confirm the general rule that methanogens and extreme halophiles have spacers that contain a single tRNAala gene, while tRNA genes are not found in the spacer region of the true extreme thermophiles. The present study also shows that the spacer regions from the sulfate reducing Archaeglobus and the extreme thermophile Thermococcus (both of which cluster phylogenetically with the methanogens and extreme halophiles) contain each a tRNAala gene. Thus, not only all methanogens and extreme halophiles show this characteristic, but all organisms on the "methanogen branch" of the archaebacterial tree appear to do so. The finding of a tRNA gene in the spacer region of the extreme thermophile Thermococcus celer is the first known phenotypic property that links this organism with its phylogenetic counterparts, the methanogens, rather than with its phenotypic counterparts, the sulfur-dependent extreme thermophiles.

  19. Layer-controlled band alignment, work function and optical properties of few-layer GeSe

    Science.gov (United States)

    Song, Xiufeng; Zhou, Wenhan; Liu, Xuhai; Gu, Yu; Zhang, Shengli

    2017-08-01

    The electronic properties, such as the layer-dependent behavior of the band structure, band gap, work function alignment and dielectric properties of the few-layer GeSe are systematically investigated via gradient-corrected density functional theory computations, inspired by the experimentally observation of two-dimension materials such as graphene, phosphorene, MoS2 and BN. The results indicate that the few-layer GeSe presents a robust direct band gap, which decreases with increasing the thickness from bilayer (1.15 eV) to six-layer (1.00 eV) around the X point. Furthermore, the work function increases rapidly from monolayer (4.44 eV) to trilayer (4.95 eV). The robust direct band gap characteristics and the layer-dependent band gap suggest that the few-layer GeSe is a promising material for efficient solar energy harvesting applications. The layer dependence of the GeSe work function offers a practical route to tune the Schottky barrier in GeSe based electronic devices. Our results provide new insights on utilizing the layer-controlled band gap of the atomic layers of GeSe.

  20. Optical constants and dynamic conductivities of single layer MoS2, MoSe2, and WSe2

    Science.gov (United States)

    Morozov, Yurii V.; Kuno, Masaru

    2015-08-01

    The complex optical constants of single layer MoS2, MoSe2, and WSe2 transition metal dichalcogenides (TMDCs) have been measured using concerted frequency-dependent transmittance and reflectance measurements. Absolute absorptivities as well as complex refractive indices and dielectric permittivities have been extracted. Comparisons to associated bulk responses reveal differences due to increased electron-hole interactions in single layer TMDCs. In parallel, corresponding complex optical conductivities (σ) have been determined. For MoS2, extracted σ-values qualitatively agree with recent theoretical estimates. Significant differences exist, though, between experiment and theory regarding the imaginary part of σ. In all cases, the current approach distinguishes itself to other measurements of single layer TMDC optical constants in which it does not rely on Kramers-Kronig transformations of reflectance data.

  1. Evaluation of Retinal Nerve Fiber Layer and Ganglion Cell Complex in Patients with Optic Neuritis or Neuromyelitis Optica Spectrum Disorders Using Optical Coherence Tomography in a Chinese Cohort

    Directory of Open Access Journals (Sweden)

    Guohong Tian

    2015-01-01

    Full Text Available We evaluate a cohort of optic neuritis and neuromyelitis optica (NMO spectrum disorders patients in a territory hospital in China. The peripapillary retinal nerve fiber layer (RNFL and macular ganglion cell complex (GCC were measured using spectral-domain OCT after 6 months of acute onset. The results showed that both the peripapillary RNFL and macular GCC were significantly thinner in all optic neuritis subtypes compared to controls. In addition, the recurrent optic neuritis and NMO groups showed more severe damage on the RNFL and GCC pattern.

  2. Evaluation of Retinal Nerve Fiber Layer and Ganglion Cell Complex in Patients with Optic Neuritis or Neuromyelitis Optica Spectrum Disorders Using Optical Coherence Tomography in a Chinese Cohort.

    Science.gov (United States)

    Tian, Guohong; Li, Zhenxin; Zhao, Guixian; Feng, Chaoyi; Li, Mengwei; Huang, Yongheng; Sun, Xinghuai

    2015-01-01

    We evaluate a cohort of optic neuritis and neuromyelitis optica (NMO) spectrum disorders patients in a territory hospital in China. The peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell complex (GCC) were measured using spectral-domain OCT after 6 months of acute onset. The results showed that both the peripapillary RNFL and macular GCC were significantly thinner in all optic neuritis subtypes compared to controls. In addition, the recurrent optic neuritis and NMO groups showed more severe damage on the RNFL and GCC pattern.

  3. Low-loss as-grown germanosilicate layers for optical waveguides

    Science.gov (United States)

    Ay, Feridun; Aydinli, Atilla; Agan, Sedat

    2003-12-01

    We report on systematic growth and characterization of low-loss germanosilicate layers for use in optical waveguide technology. The films were deposited by plasma-enhanced chemical vapor deposition technique using silane, germane, and nitrous oxide as precursor gases. Fourier transform infrared spectroscopy was used to monitor the compositional properties of the samples. It was found that addition of germane leads to decreasing of N-H- and O-H-related bonds. The propagation loss values of the planar waveguides were correlated with the decrease in the hydrogen-related bonds of the as-deposited waveguides and resulted in very low values, eliminating the need for high-temperature annealing as is usually done.

  4. Study of electronic and optical properties of two-layered hydrogenated aluminum nitrate nanosheet

    Science.gov (United States)

    Faghihzadeh, Somayeh; Shahtahmasebi, Nasser; Rezaee Roknabadi, Mahmood

    2017-09-01

    First principle calculations based on density functional theory using GW approximation and two particle Bethe-Salpeter equation with electron-hole effect were performed to investigate electronic structure and optical properties of two-layered hydrogenated AlN. According to many body green function due to decrease in dimension and considering electron-electron effect, direct (indirect) band gap change from 2 (1.01) eV to 4.83 (3.62) eV. The first peak in imaginary part of dielectric function was observed in parallel direction to a plane obtaining 3.4 was achieved by bound exciton states possess 1.39 eV. The first absorption peak was seen in two parallel and perpendicular directions to a plane which are in UV region.

  5. Registration of adaptive optics corrected retinal nerve fiber layer (RNFL) images.

    Science.gov (United States)

    Ramaswamy, Gomathy; Lombardo, Marco; Devaney, Nicholas

    2014-06-01

    Glaucoma is the leading cause of preventable blindness in the western world. Investigation of high-resolution retinal nerve fiber layer (RNFL) images in patients may lead to new indicators of its onset. Adaptive optics (AO) can provide diffraction-limited images of the retina, providing new opportunities for earlier detection of neuroretinal pathologies. However, precise processing is required to correct for three effects in sequences of AO-assisted, flood-illumination images: uneven illumination, residual image motion and image rotation. This processing can be challenging for images of the RNFL due to their low contrast and lack of clearly noticeable features. Here we develop specific processing techniques and show that their application leads to improved image quality on the nerve fiber bundles. This in turn improves the reliability of measures of fiber texture such as the correlation of Gray-Level Co-occurrence Matrix (GLCM).

  6. Quantification of cell-free layer thickness and cell distribution of blood by optical coherence tomography

    Science.gov (United States)

    Lauri, Janne; Bykov, Alexander; Fabritius, Tapio

    2016-04-01

    A high-speed optical coherence tomography (OCT) with 1-μm axial resolution was applied to assess the thickness of a cell-free layer (CFL) and a spatial distribution of red blood cells (RBC) next to the microchannel wall. The experiments were performed in vitro in a plain glass microchannel with a width of 2 mm and height of 0.2 mm. RBCs were suspended in phosphate buffered saline solution at the hematocrit level of 45%. Flow rates of 0.1 to 0.5 ml/h were used to compensate gravity induced CFL. The results indicate that OCT can be efficiently used for the quantification of CFL thickness and spatial distribution of RBCs in microcirculatory blood flow.

  7. Ab initio calculations of optical constants of GaSe and InSe layered crystals

    Science.gov (United States)

    Sarkisov, S. Yu.; Kosobutsky, A. V.; Brudnyi, V. N.; Zhuravlev, Yu. N.

    2015-09-01

    The dielectric functions, refractive indices, and extinction coefficients of GaSe and InSe layered crystals have been calculated within the density functional theory. The calculations have been performed for the values of theoretical structural parameters optimized using the exchange-correlation functional, which allows one to take into account the dispersion interactions. It has been found that optical functions are characterized by the most pronounced polarization anisotropy in the range of photon energies of ˜4-7 eV. The frequency dependences for InSe compound in the range up to 4 eV demonstrate the more pronounced anisotropy as compared to GaSe. The results obtained for GaSe crystal agree better with the experimental data as compared to the previous calculations.

  8. Rhombohedral polytypes of the layered honeycomb delafossites with optical brilliance in the visible.

    Science.gov (United States)

    Roudebush, John H; Sahasrabudhe, Girija; Bergman, Susanna L; Cava, R J

    2015-04-06

    We report the synthesis of the Delafossite honeycomb compounds Cu3Ni2SbO6 and Cu3Co2SbO6 via a copper topotactic reaction from the layered α-NaFeO2-like precursors Na3Ni2SbO6 and Na3Co2SbO6. The low-temperature exchange reaction exclusively produces the rhombahedral 3R polytype subcell, whereas only the hexagonal 2H polytype subcell has been made by conventional synthesis. The thus-synthesized 3R variants are visually striking; they are bright lime-green (Ni variant) and terracotta-orange (Co variant), while both of the conventionally synthesized 2H variants have a burnt-red color. The new structures are characterized by powder X-ray diffraction and Rietveld analysis as well as magnetic susceptibility, X-ray photoelectron spectroscopy (XPS), and diffuse-reflectance optical spectroscopy. Using thermogravimetric analysis, we identify a second order 3R → 2H phase transition as well as a first-order structural transition associated with rearrangement of the honeycomb stacking layers. The optical absorbance spectra of the samples show discrete edges that correlate well to their visual colors. Exposing Cu3Ni2SbO6 to O2 and heat causes the sample to change color. XPS confirms the presence of Cu(2+) in these samples, which implies that the difference in color between the polytypes is due to oxygen intercalation resulting from their different synthetic routes.

  9. High-power AlInGaN-based violet laser diodes with InGaN optical confinement layers

    Science.gov (United States)

    Lee, Sung-Nam; Son, J. K.; Paek, H. S.; Sung, Y. J.; Kim, K. S.; Kim, H. K.; Kim, H.; Sakong, T.; Park, Y.; Ha, K. H.; Nam, O. H.

    2008-09-01

    InGaN optical confinement layers (OCLs) were introduced into blue-violet AlInGaN-based laser diodes (LDs), resulting in the drastic improvements of lasing performance. Comparing with conventional LD structure, the lowest threshold current density of 2.3kA/cm2 has been achieved by adding 100-nm-thick InGaN OCLs which represented maximum optical confinement factor. Additionally, we observed the high quantum efficiency and the uniform emission intensity distribution of InGaN quantum wells grown on lower InGaN OCL than on typical GaN layer. Upper InGaN OCL can reduce Mg diffusion from p-type layers to InGaN active region by separating the distance between InGaN quantum wells and p-type layers.

  10. Optical characterization of two-layered turbid media for non-invasive, absolute oximetry in cerebral and extracerebral tissue.

    Directory of Open Access Journals (Sweden)

    Bertan Hallacoglu

    Full Text Available We introduce a multi-distance, frequency-domain, near-infrared spectroscopy (NIRS method to measure the optical coefficients of two-layered media and the thickness of the top layer from diffuse reflectance measurements. This method features a direct solution based on diffusion theory and an inversion procedure based on the Levenberg-Marquardt algorithm. We have validated our method through Monte Carlo simulations, experiments on tissue-like phantoms, and measurements on the forehead of three human subjects. The Monte Carlo simulations and phantom measurements have shown that, in ideal two-layered samples, our method accurately recovers the top layer thickness (L, the absorption coefficient (µ a and the reduced scattering coefficient (µ' s of both layers with deviations that are typically less than 10% for all parameters. Our method is aimed at absolute measurements of hemoglobin concentration and saturation in cerebral and extracerebral tissue of adult human subjects, where the top layer (layer 1 represents extracerebral tissue (scalp, skull, dura mater, subarachnoid space, etc. and the bottom layer (layer 2 represents cerebral tissue. Human subject measurements have shown a significantly greater total hemoglobin concentration in cerebral tissue (82±14 µM with respect to extracerebral tissue (30±7 µM. By contrast, there was no significant difference between the hemoglobin saturation measured in cerebral tissue (56%±10% and extracerebral tissue (62%±6%. To our knowledge, this is the first time that an inversion procedure in the frequency domain with six unknown parameters with no other prior knowledge is used for the retrieval of the optical coefficients and top layer thickness with high accuracy on two-layered media. Our absolute measurements of cerebral hemoglobin concentration and saturation are based on the discrimination of extracerebral and cerebral tissue layers, and they can enhance the impact of NIRS for cerebral hemodynamics and

  11. Optic nerve atrophy and retinal nerve fibre layer thinning following optic neuritis: evidence that axonal loss is a substrate of MRI-detected atrophy.

    Science.gov (United States)

    Trip, S Anand; Schlottmann, Patricio G; Jones, Stephen J; Li, Wai-Yung; Garway-Heath, David F; Thompson, Alan J; Plant, Gordon T; Miller, David H

    2006-05-15

    Magnetic resonance imaging (MRI) measures of brain atrophy are often considered to be a marker of axonal loss in multiple sclerosis (MS) but evidence is limited. Optic neuritis is a common manifestation of MS and results in optic nerve atrophy. Retinal nerve fibre layer (RNFL) imaging is a non-invasive way of detecting axonal loss following optic neuritis. We hypothesise that if the optic nerve atrophy that develops following optic neuritis is contributed to by axonal loss, it will correlate with thinning of the RNFL. Twenty-five patients were studied at least 1 year after a single unilateral attack of optic neuritis without recurrence, with a selection bias towards incomplete recovery. They had MR quantification of optic nerve cross-sectional area and optic nerve lesion length, as well as optical coherence tomography (OCT) measurement of mean RNFL thickness and macular volume, quantitative visual testing, and visual evoked potentials (VEPs). Fifteen controls were also studied. Significant optic nerve atrophy (mean decrease 30% versus controls), RNFL thinning (mean decrease 33% versus controls), and macular volume loss occurred in patients' affected eyes when compared with patients' unaffected eyes and healthy controls. The optic nerve atrophy was correlated with the RNFL thinning, macular volume loss, visual acuity, visual field mean deviation, and whole field VEP amplitude but not latency. These findings suggest that axonal loss contributes to optic nerve atrophy following a single attack of optic neuritis. By inference, axonal loss due to other post-inflammatory brain lesions is likely to contribute to the global MRI measure of brain atrophy in multiple sclerosis.

  12. Genotype-phenotype heterogeneity of ganglion cell and inner plexiform layer deficit in autosomal-dominant optic atrophy

    DEFF Research Database (Denmark)

    Rönnbäck, Cecilia; Nissen, Claus; Almind, Gitte J;

    2015-01-01

    PURPOSE: To describe the thickness of the combined ganglion cell and inner plexiform layers (GC-IPL) and the peripapillary retinal nerve fibre layer (RNFL) in patients with OPA1 c.983A>G or c.2708_2711delTTAG autosomal-dominant optic atrophy (ADOA). METHODS: The study included 20 individuals with c...... measurement and high-definition optical coherence tomography. RESULTS: There was overlap in GC-IPL thickness in subjects younger than 20-30 years between the two new groups of ADOA patients and controls. Numerical decreases in GC-IPL thickness with age did not reach statistical significance in individuals...

  13. Broadband atomic-layer MoSsub>2sub> optical modulators for ultrafast pulse generations in the visible range.

    Science.gov (United States)

    Zhang, Yuxia; Yu, Haohai; Zhang, Rui; Zhao, Gang; Zhang, Huaijin; Chen, Yanxue; Mei, Liangmo; Tonelli, Mauro; Wang, Jiyang

    2017-02-01

    Visible lasers are a fascinating regime, and their significance is illustrated by the 2014 Noble prizes in physics and chemistry. With the development of blue laser diodes (LDs), the LD-pumped solid-state visible lasers become a burgeoning direction today. Constrained by the scarce visible optical modulators, the solid-state ultrafast visible lasers are rarely realized. Based on the bandgap structure and optoelectronic properties of atomic-layer MoSsub>2sub>, it can be proposed that MoSsub>2sub> has the potential as a visible optical modulator. Here, by originally revealing layer-dependent nonlinear absorption of the atomic-layer MoSsub>2sub> in the visible range, broadband atomic-layer MoSsub>2sub> optical modulators for the visible ultrafast pulse generation are developed and selected based on the proposed design criteria for novel two-dimensional (2D) optical modulators. By applying the selected MoSsub>2sub> optical modulators in the solid-state praseodymium lasers, broadband mode-locked ultrafast lasers from 522 to 639 nm are originally realized. We believe that this Letter should promote the development of visible ultrafast photonics and further applications of 2D optoelectronic materials.

  14. Application of Thin ZnO ALD Layers in Fiber-Optic Fabry-Pérot Sensing Interferometers.

    Science.gov (United States)

    Majchrowicz, Daria; Hirsch, Marzena; Wierzba, Paweł; Bechelany, Michael; Viter, Roman; Jędrzejewska-Szczerska, Małgorzata

    2016-03-22

    In this paper we investigated the response of a fiber-optic Fabry-Pérot sensing interferometer with thin ZnO layers deposited on the end faces of the optical fibers forming the cavity. Standard telecommunication single-mode optical fiber (SMF-28) segments were used with the thin ZnO layers deposited by Atomic Layer Deposition (ALD). Measurements were performed with the interferometer illuminated by two broadband sources operating at 1300 nm and 1550 nm. Reflected interference signal was acquired by an optical spectrum analyzer while the length of the air cavity was varied. Thickness of the ZnO layers used in the experiments was 50 nm, 100 nm, and 200 nm. Uncoated SMF-28 fiber was also used as a reference. Based on the results of measurements, the thickness of the ZnO layers and the length of the cavity were selected in order to achieve good visibility. Following, the interferometer was used to determine the refractive index of selected liquids.

  15. Application of Thin ZnO ALD Layers in Fiber-Optic Fabry-Pérot Sensing Interferometers

    Directory of Open Access Journals (Sweden)

    Daria Majchrowicz

    2016-03-01

    Full Text Available In this paper we investigated the response of a fiber-optic Fabry-Pérot sensing interferometer with thin ZnO layers deposited on the end faces of the optical fibers forming the cavity. Standard telecommunication single-mode optical fiber (SMF-28 segments were used with the thin ZnO layers deposited by Atomic Layer Deposition (ALD. Measurements were performed with the interferometer illuminated by two broadband sources operating at 1300 nm and 1550 nm. Reflected interference signal was acquired by an optical spectrum analyzer while the length of the air cavity was varied. Thickness of the ZnO layers used in the experiments was 50 nm, 100 nm, and 200 nm. Uncoated SMF-28 fiber was also used as a reference. Based on the results of measurements, the thickness of the ZnO layers and the length of the cavity were selected in order to achieve good visibility. Following, the interferometer was used to determine the refractive index of selected liquids.

  16. Layer-by-layer growth of high-optical-quality ZnO film on atomically smooth and lattice relaxed ZnO buffer layer

    OpenAIRE

    2003-01-01

    The growth mode of ZnO thin films can be well regulated in a molecular layer-by-layer growth by employing a ZnO buffer layer deposited on a lattice-matched ScAlMgO4 substrate and annealed at high temperature. The annealed buffer layer has atomically flat surface and relaxed (strain-free) crystal structure. The intensity oscillation of reflection high-energy electron diffraction persisted for more than a 100-nm film deposition under optimized conditions on such a buffer layer. Thus prepared th...

  17. An Optical Wavefront Sensor Based on a Double Layer Microlens Array

    Directory of Open Access Journals (Sweden)

    Hsiang-Chun Wei

    2011-10-01

    Full Text Available In order to determine light aberrations, Shack-Hartmann optical wavefront sensors make use of microlens arrays (MLA to divide the incident light into small parts and focus them onto image planes. In this paper, we present the design and fabrication of long focal length MLA with various shapes and arrangements based on a double layer structure for optical wavefront sensing applications. A longer focal length MLA could provide high sensitivity in determining the average slope across each microlens under a given wavefront, and spatial resolution of a wavefront sensor is increased by numbers of microlenses across a detector. In order to extend focal length, we used polydimethysiloxane (PDMS above MLA on a glass substrate. Because of small refractive index difference between PDMS and MLA interface (UV-resin, the incident light is less refracted and focused in further distance. Other specific focal lengths could also be realized by modifying the refractive index difference without changing the MLA size. Thus, the wavefront sensor could be improved with better sensitivity and higher spatial resolution.

  18. Optical nonlinearities in Ag/BaTiO{sub 3} multi-layer nanocomposite films

    Energy Technology Data Exchange (ETDEWEB)

    Yang Guang [Wuhan National Laboratory for Optoelectronics and School of Optoelectronics Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)], E-mail: gyang@hust.edu.cn; Zhou Youhua [Wuhan National Laboratory for Optoelectronics and School of Optoelectronics Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Physics and Information Engineering, Jianghan University, Wuhan 430056 (China); Long Hua; Li Yuhua; Yang Yifa [Wuhan National Laboratory for Optoelectronics and School of Optoelectronics Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2007-07-31

    The multi-layer structure of barium titanate composite thin films containing Ag nanoparticles were grown on MgO (100) substrates using pulsed laser deposition technique under the nitrogen pressure of 7.4 Pa. The X-ray photoelectron spectroscopy analysis indicated that the samples were composed of metal Ag embedded in the BaTiO{sub 3} matrices. The optical absorption properties were measured from 300 nm to 800 nm, and the absorption peaks due to the surface plasmon resonance of Ag particles were observed. With the increasing of Ag concentration in composite films, the peak absorption increased and shifted to longer wavelength (red-shift). Furthermore, the third-order optical nonlinearities of the films were determined by z-scan method and the nonlinear refractive index, n{sub 2}, and nonlinear absorption coefficient, {beta}, were determined to be about - 1.91 x 10{sup -13} m{sup 2}/W and - 5.80 x 10{sup -7} m/W, respectively.

  19. Physical-layer security analysis of PSK quantum-noise randomized cipher in optically amplified links

    Science.gov (United States)

    Jiao, Haisong; Pu, Tao; Xiang, Peng; Zheng, Jilin; Fang, Tao; Zhu, Huatao

    2017-08-01

    The quantitative security of quantum-noise randomized cipher (QNRC) in optically amplified links is analyzed from the perspective of physical-layer advantage. Establishing the wire-tap channel models for both key and data, we derive the general expressions of secrecy capacities for the key against ciphertext-only attack and known-plaintext attack, and that for the data, which serve as the basic performance metrics. Further, the maximal achievable secrecy rate of the system is proposed, under which secrecy of both the key and data is guaranteed. Based on the same framework, the secrecy capacities of various cases can be assessed and compared. The results indicate perfect secrecy is potentially achievable for data transmission, and an elementary principle of setting proper number of photons and bases is given to ensure the maximal data secrecy capacity. But the key security is asymptotically perfect, which tends to be the main constraint of systemic maximal secrecy rate. Moreover, by adopting cascaded optical amplification, QNRC can realize long-haul transmission with secure rate up to Gb/s, which is orders of magnitude higher than the perfect secrecy rates of other encryption systems.

  20. Crystal structure and switchable optical properties of yttrium hydride films covered by palladium layer

    Institute of Scientific and Technical Information of China (English)

    张文魁; 甘永平; 杨晓光; 黄辉; 余厉阳

    2003-01-01

    The palladium/yttrium films were prepared using magnetron sputtering technique.The changes of crystal structure,morphology and optical properties of the films during the hydrogen absorption/desorption process were investigated.The results of SEM and AFM analysis show that yttrium films have columnar structure,and the Pd cover layers on the surface of the yttrium films are composed of nanometer-sized Pd particles,which contain a large amount of smaller crystalline grains.During the gas hydrogen absorption/desorption process,YH3 and YH2 hydrides form on the sites of Pd grains contacting with Y grains.Upon hydrogenation,YH3 hydride forms and the switchable optical properties can be observed.The light transparency of the films increases with the increasing of hydrogen loading time and the light wavelength,and the absorption limitation occurs at λ=400 nm.Upon dehydrogenation,YH3 hydride dissociates into YH2 hydride,and the maximum transparency occurs at λ=689 nm.

  1. Longitudinal optical and spin Hall conductivities of Rashba conducting strips coupled to ferromagnetic and antiferromagnetic layers

    Science.gov (United States)

    Riera, José A.

    2017-01-01

    A system composed of a conducting planar strip with Rashba spin-orbit coupling (RSOC), magnetically coupled to a layer of localized magnetic moments, at equilibrium, is studied within a microscopic Hamiltonian with numerical techniques at zero temperature in the clean limit. In particular, transport properties for the cases of ferromagnetic (FM) and antiferromagnetic (AFM) coupled layers are computed in linear response on strips of varying width. Some behaviors observed for these properties are consistent with the ones observed for the corresponding Rashba helical currents. The case of uncoupled Rashba strips is also studied for comparison. In the case of Rashba strips coupled to an AFM localized order, results for the longitudinal dc conductivity, for small strip widths, suggest the proximity to a metal-insulator transition. More interesting, in the proximity of this transition, and in general at intermediate values of the RSOC, a large spin Hall conductivity is observed that is two orders of magnitude larger than the one for the FM order for the same values of the RSOC and strip widths. There are clearly two different regimes for small and for large RSOC, which is also present in the behavior of Rashba helical currents. Different contributions to the optical and the spin Hall conductivities, according to a new classification of inter- or intraband origin proposed for planar strips in the clean limit, or coming from the hopping or spin-orbit terms of the Hamiltonian, are examined. Finally, the effects of different orientation of the coupled magnetic moments will be also studied.

  2. Optical and Electrochemical Properties of Layered Crystals GaSe Intercalated by the Nickel

    Directory of Open Access Journals (Sweden)

    S.G. Barbutsa

    2013-10-01

    Full Text Available The presented results of the investigations of the optical and electrochemical properties indicate the possibility of intercalation of layered GaSe crystals with nickel ions. Established that the electrochemical introduction of Ni leads to a monotonic growth in electrode potential of layered semiconductors GaSe when a concentration of intercalants nNi  1018-1020сm – 3. In consequence of intercalation of nickel in GaSe crystal at T  293 K, occurred ncreases in the energy position of the exciton peak Eeks 6 meV (from 2.008 to 2.014 eV and the half-width of the exciton absorption bands of H by 5.2 meV. At a temperature T  77 K was detected non- monotonous concentration dependence of the excitonic maximum energy location for Еeks NiGaSe compounds. The dependence Еeks(nNi for these compounds are explained as a result of the introduction of competition between contributions of inter - and intralayer deformations which have the opposite signs of deformation potential.

  3. Structural, electrical and optical characterization of InGaN layers grown by MOVPE

    Institute of Scientific and Technical Information of China (English)

    Ylldlz A; (O)ztürk M Kemal; Bosi M; (O)z(c)elik S; Kasap M

    2009-01-01

    We present a study on n-type ternary InGaN layers grown by atmospheric pressure metalorganic vapour phase epitaxy (MOVPE) on GaN template/(0001) sapphire substrate. An investigation of the different growth conditions on n-type InxGa1-xN (χ=0.06-0.135) alloys was done for a series of five samples. The structural,electrical and optical properties were characterized by high resolution x-ray diffraction (HRXRD),Hall effect and photoluminescence (PL). Experimental results showed that different growth conditions,namely substrate rotation (SR) and change of total H2 flow (THF),strongly affect the properties of InGaN layers. This case can he clearly observed from the analytical results. When the SR speed decreased,the HRXRD scan peak of the samples shifted along a higher angle. Therefore,increasing the SR speed changed important structural properties of InGaN alloys such as peak broadening,values of strain,lattice parameters and defects including tilt,twist and dislocation density. From PL results it is observed that the growth conditions can be changed to control the emission wavelength and it is possible to shift the emission wavelength towards the green. Hall effect measurement has shown that the resistivity of the samples changes dramatically when THF changes.

  4. Construction and Calibration of Optically Efficient LCD-based Multi-Layer Light Field Displays

    Science.gov (United States)

    Hirsch, Matthew; Lanman, Douglas; Wetzstein, Gordon; Raskar, Ramesh

    2013-02-01

    Near-term commercial multi-view displays currently employ ray-based 3D or 4D light field techniques. Conventional approaches to ray-based display typically include lens arrays or heuristic barrier patterns combined with integral interlaced views on a display screen such as an LCD panel. Recent work has placed an emphasis on the co-design of optics and image formation algorithms to achieve increased frame rates, brighter images, and wider fields-of-view using optimization-in-the-loop and novel arrangements of commodity LCD panels. In this paper we examine the construction and calibration methods of computational, multi-layer LCD light field displays. We present several experimental configurations that are simple to build and can be tuned to sufficient precision to achieve a research quality light field display. We also present an analysis of moiré interference in these displays, and guidelines for diffuser placement and display alignment to reduce the effects of moiré. We describe a technique using the moiré magnifier to fine-tune the alignment of the LCD layers.

  5. Magnetic nanoparticles as a seed layer for growing ZnO nanowires for optical applications

    Science.gov (United States)

    AlSalhi, M. S.; Atif, M.; Ansari, Anees A.; Khun, K.; Ibupoto, Z. H.; Willander, M.

    2013-02-01

    In the present work, cerium oxide CeO2 nanoparticles were synthesised by sol-gel method and used for the growth of ZnO nanorods. The synthesised nanoparticles were studied by x-ray diffraction technique [XRD]. Furthermore, these nanoparticles were used as seed layer for the growth of ZnO nanorods by following the hydrothermal growth method. The structural study of ZnO nanorods was carried out by using field emission scanning electron microscopy [FESEM], and x-ray diffraction [XRD] techniques. This study demonstrated that the grown ZnO nanorods are well align, uniform, good in crystal quality and possess diameter of less than 200 nm. Energy dispersive x-rays [EDX] revealed that the ZnO nanorods are only composed of zinc, cerium as seed atom and oxygen atoms and no any other impurity in the grown nanorods. Moreover, photoluminescence [PL] approach was applied for the optical characterisation and it was observed that the near-band-edge emission [NBE] was same to that of zinc acetate seed layer, however the green emission and orange/red emission peaks were slightly raised due to possible higher level of defects in the cerium oxide seeded ZnO nanorods. This study provides an alternative approach for the synthesis of controlled ZnO nanorods using cerium oxide nanoparticles as seed nucleation layer which in reverse describe the application of these nanoparticles as well as due to controlled morphology of ZnO nanorods the performance of nanodevices based on ZnO can be increased using these particles as seed.

  6. A low-power all-optical bistable device based on a liquid crystal layer embedded in thin gold films

    Science.gov (United States)

    Takase, Yuki; Tien Thanh, Pham; Fujimura, Ryushi; Kajikawa, Kotaro

    2014-04-01

    An all-optical bistable (AOB) resonator device composed of a 430-nm-thick liquid crystal (LC) layer embedded in two thin gold films (MLM) is reported in this paper. This device allows the use of the incident illumination at normal incidence, whereas the previous AOB devices based on twisted nematic (TN)-LC function only for illumination at oblique incidence. The fastest switching time was measured to be 1.8 ms, which is significantly faster than that of TN-LC. Because the MLM device operates free from electronic circuits, it is promising for two-dimensional optical data processing, random access optical memories, and spatial light modulators.

  7. Separator-spacer for electrochemical systems

    Science.gov (United States)

    Grimes, Patrick G.; Einstein, Harry; Newby, Kenneth R.; Bellows, Richard J.

    1983-08-02

    An electrochemical cell construction features a novel co-extruded plastic electrode in an interleaved construction with a novel integral separator-spacer. Also featured is a leak and impact resistant construction for preventing the spill of corrosive materials in the event of rupture.

  8. Theoretical comparison of optical and electronic properties of uniformly and randomly arranged nano-porous ultra-thin layers.

    Science.gov (United States)

    Hubarevich, Aliaksandr; Marus, Mikita; Fan, Weijun; Smirnov, Aliaksandr; Sun, Xiao Wei; Wang, Hong

    2015-07-13

    The theoretical comparison of optical and electronic properties of aluminum and silver nano-porous ultra-thin layers in terms of the arrangement and size of the pores was presented. The uniform nano-porous layers exhibit a slightly higher average transmittance (up to 10%) in the wavelength range of the plasmonic response in comparison to the randomly arranged ones. Compared to uniform nano-porous layers, a much larger sheet resistance (up to 12 times) for random nano-porous layers is observed. The uniform and random Ag nano-porous layers possessing the strong plasmonic response over whole visible range can reach an average transmittance of 90 and 80% at the sheet resistance of 10 and 20 Ohm/sq, respectively, which is comparable to widely used ITO electrodes.

  9. Characterization of Choroidal Layers in Normal Aging Eyes Using Enface Swept-Source Optical Coherence Tomography

    Science.gov (United States)

    Mullins, Robert F.; Baumal, Caroline R.; Mohler, Kathrin J.; Kraus, Martin F.; Liu, Jonathan; Badaro, Emmerson; Alasil, Tarek; Hornegger, Joachim; Fujimoto, James G.; Duker, Jay S.; Waheed, Nadia K.

    2015-01-01

    Purpose To characterize qualitative and quantitative features of the choroid in normal eyes using enface swept-source optical coherence tomography (SS-OCT). Methods Fifty-two eyes of 26 consecutive normal subjects were prospectively recruited to obtain multiple three-dimensional 12x12mm volumetric scans using a long-wavelength high-speed SS-OCT prototype. A motion-correction algorithm merged multiple SS-OCT volumes to improve signal. Retinal pigment epithelium (RPE) was segmented as the reference and enface images were extracted at varying depths every 4.13μm intervals. Systematic analysis of the choroid at different depths was performed to qualitatively assess the morphology of the choroid and quantify the absolute thicknesses as well as the relative thicknesses of the choroidal vascular layers including the choroidal microvasculature (choriocapillaris, terminal arterioles and venules; CC) and choroidal vessels (CV) with respect to the subfoveal total choroidal thickness (TC). Subjects were divided into two age groups: younger (choroidal-scleral interface were used to assess specific qualitative features. In the younger age group, the mean absolute thicknesses were: TC 379.4μm (SD±75.7μm), CC 81.3μm (SD±21.2μm) and CV 298.1μm (SD±63.7μm). In the older group, the mean absolute thicknesses were: TC 305.0μm (SD±50.9μm), CC 56.4μm (SD±12.1μm) and CV 248.6μm (SD±49.7μm). In the younger group, the relative thicknesses of the individual choroidal layers were: CC 21.5% (SD±4.0%) and CV 78.4% (SD±4.0%). In the older group, the relative thicknesses were: CC 18.9% (SD±4.5%) and CV 81.1% (SD±4.5%). The absolute thicknesses were smaller in the older age group for all choroidal layers (TC p=0.006, CC p=0.0003, CV p=0.03) while the relative thickness was smaller only for the CC (p=0.04). Conclusions Enface SS-OCT at 1050nm enables a precise qualitative and quantitative characterization of the individual choroidal layers in normal eyes. Only the CC is

  10. Schottky barrier modulation of metal/4H-SiC junction with thin interface spacer driven by surface polarization charge on 4H-SiC substrate

    Science.gov (United States)

    Choi, Gahyun; Yoon, Hoon Hahn; Jung, Sungchul; Jeon, Youngeun; Lee, Jung Yong; Bahng, Wook; Park, Kibog

    2015-12-01

    The Au/Ni/Al2O3/4H-SiC junction with the Al2O3 film as a thin spacer layer was found to show the electrical characteristics of a typical rectifying Schottky contact, which is considered to be due to the leakiness of the spacer layer. The Schottky barrier of the junction was measured to be higher than an Au/Ni/4H-SiC junction with no spacer layer. It is believed that the negative surface bound charge originating from the spontaneous polarization of 4H-SiC causes the Schottky barrier increase. The use of a thin spacer layer can be an efficient experimental method to modulate Schottky barriers of metal/4H-SiC junctions.

  11. Retinal nerve fiber layer thickness in subgroups of multiple sclerosis, measured by optical coherence tomography and scanning laser polarimetry

    NARCIS (Netherlands)

    T.A.M. Siepman (Theodora); M. Wefers Bettink-Remeijer (Marijke); R.Q. Hintzen (Rogier)

    2010-01-01

    textabstractOptical coherence tomography (OCT) and scanning laser polarimetry (GDx ECC) are non-invasive methods used to assess retinal nerve fiber layer (RNFL) thickness, which may be a reliable tool used to monitor axonal loss in multiple sclerosis (MS). The objectives of this study are (1) to com

  12. Normative data of outer photoreceptor layer thickness obtained by software image enhancing based on Stratus optical coherence tomography images

    DEFF Research Database (Denmark)

    Christensen, U.C.; Kroyer, K.; Thomadsen, J.

    2008-01-01

    Aim: To present normative data of outer photoreceptor layer thickness obtained by a new semiautomatic image analysis algorithm operating on contrast-enhanced optical coherence tomography (OCT) images. Methods: Eight Stratus OCT3 scans from identical retinal locations from 25 normal eyes were regi...

  13. A surface-enhanced Raman scattering (SERS-active optical fiber sensor based on a three-dimensional sensing layer

    Directory of Open Access Journals (Sweden)

    Chunyu Liu

    2014-08-01

    Full Text Available To fabricate a new surface-enhanced Raman scattering (SERS-active optical fiber sensor, the design and preparation of SERS-active sensing layer is one of important topics. In this study, we fabricated a highly sensitive three-dimensional (3D SERS-active sensing layer on the optical fiber terminal via in situ polymerizing a porous polymer material on a flat optical fiber terminal through thermal-induced process, following with the photochemical silver nanoparticles growth. The polymerized polymer formed a 3D porous structure with the pore size of 0.29–0.81 μm, which were afterward decorated with abundant silver nanoparticles with the size of about 100 nm, allowing for higher SERS enhancement. This SERS-active optical fiber sensor was applied for the determination of 4-mercaptopyridine, crystal violet and maleic acid The enhancement factor of this SERS sensing layer can be reached as about 108. The optical fiber sensor with high sensitive SERS-active porous polymer is expected for online analysis and environment detection.

  14. The effects of doping layer location on the electronic and optical properties of GaN step quantum well

    Science.gov (United States)

    Dakhlaoui, Hassen

    2016-09-01

    In the present work, the intersubband transition and the optical absorption coefficient between the ground and the first excited states in the Si-δ-doped step AlGaN/GaN quantum well were theoretically studied by solving Schrödinger-Poisson equations self-consistently within the framework of effective mass approximation. The delta-doped layer was inserted in three different locations (middle of the quantum well, middle of the step quantum well and middle of the left barrier). The obtained results show that the energy difference between the ground and the first excited state and the optical absorption depend not only on the doping layer concentration but also on its location. The shape of the confining potential and the wavefunctions were also changed depending on the doped layer location. It was found that doping in the middle quantum well is advantageous to obtain an optical absorption with a higher energy separation; however, doping in the left barrier gives us an optical absorption with a lower energy separation. The obtained results in optical absorption give us a new degree of freedom in optoelectronic devices based on intersubband transitions.

  15. Accurate optical simulation of nano-particle based internal scattering layers for light outcoupling from organic light emitting diodes

    Science.gov (United States)

    Egel, Amos; Gomard, Guillaume; Kettlitz, Siegfried W.; Lemmer, Uli

    2017-02-01

    We present a numerical strategy for the accurate simulation of light extraction from organic light emitting diodes (OLEDs) comprising an internal nano-particle based scattering layer. On the one hand, the light emission and propagation through the OLED thin film system (including the scattering layer) is treated by means of rigorous wave optics calculations using the T-matrix formalism. On the other hand, the propagation through the substrate is modeled in a ray optics approach. The results from the wave optics calculations enter in terms of the initial substrate radiation pattern and the bidirectional reflectivity distribution of the OLED stack with scattering layer. In order to correct for the truncation error due to a finite number of particles in the simulations, we extrapolate the results to infinitely extended scattering layers. As an application example, we estimate the optimal particle filling fraction for an internal scattering layer in a realistic OLED geometry. The presented treatment is designed to emerge from electromagnetic theory with as few additional assumptions as possible. It could thus serve as a baseline to validate faster but approximate simulation approaches.

  16. Optical properties of a one-dimensional photonic crystal containing a graphene-based hyperbolic metamaterial defect layer.

    Science.gov (United States)

    Saleki, Ziba; Entezar, Samad Roshan; Madani, Amir

    2017-01-10

    The transmission properties of a one-dimensional defective photonic crystal have been investigated using the transfer matrix method. A layer of graphene-based hyperbolic metamaterial whose optical axis is tilted with respect to the interface is taken as a defect. It is shown that two kinds of the defect modes can be found in the band gaps of the structure for TM-polarized waves. One kind is created at the frequency range in which the principle elements of the effective permittivity tensor of the defect layer have the same signs. The frequency of this kind of defect mode is independent from the orientation of the optical axis of the defect layer. The other one is created at the hyperbolic dispersion frequency range. Such a defect mode appears due to the anisotropic behavior of the defect layer and its frequency strongly depends on the orientation of the optical axis. Unlike the conventional defect modes, the magnetic field of this defect mode is localized around the defect layer.

  17. Measurement of a multi-layered tear film phantom using optical coherence tomography and statistical decision theory.

    Science.gov (United States)

    Huang, Jinxin; Yuan, Qun; Zhang, Buyun; Xu, Ke; Tankam, Patrice; Clarkson, Eric; Kupinski, Matthew A; Hindman, Holly B; Aquavella, James V; Suleski, Thomas J; Rolland, Jannick P

    2014-12-01

    To extend our understanding of tear film dynamics for the management of dry eye disease, we propose a method to optically sense the tear film and estimate simultaneously the thicknesses of the lipid and aqueous layers. The proposed method, SDT-OCT, combines ultra-high axial resolution optical coherence tomography (OCT) and a robust estimator based on statistical decision theory (SDT) to achieve thickness measurements at the nanometer scale. Unlike conventional Fourier-domain OCT where peak detection of layers occurs in Fourier space, in SDT-OCT thickness is estimated using statistical decision theory directly on the raw spectra acquired with the OCT system. In this paper, we demonstrate in simulation that a customized OCT system tailored to ~1 µm axial point spread function (FWHM) in the corneal tissue, combined with the maximum-likelihood estimator, can estimate thicknesses of the nanometer-scale lipid and micron-scale aqueous layers of the tear film, simultaneously, with nanometer precision. This capability was validated in experiments using a physical phantom that consists of two layers of optical coatings that mimic the lipid and aqueous layers of the tear film.

  18. Evaluation of retinal nerve fiber layer thickness measurements using optical coherence tomography in patients with tobacco-alcohol-induced toxic optic neuropathy

    Directory of Open Access Journals (Sweden)

    Moura Frederico

    2010-01-01

    Full Text Available Three patients with progressive visual loss, chronic alcoholism and tabagism were submitted to a complete neuro-ophthalmic examination and to retinal nerve fiber layer (RNFL measurements using optical coherence tomography (OCT scanning. Two patients showed marked RNFL loss in the temporal sector of the optic disc. However, a third patient presented RNFL measurements within or above normal limits, based on the Stratus-OCT normative database. Such findings may be due to possible RNFL edema similar to the one that may occur in the acute phase of toxic optic neuropathies. Stratus-OCT was able to detect RNFL loss in the papillomacular bundle of patients with tobacco-alcohol-induced toxic optic neuropathy. However, interpretation must be careful when OCT does not show abnormality in order to prevent diagnostic confusion, since overestimation of RNFL thickness measurements is possible in such cases.

  19. Effects of Controlling the AZO Thin Film's Optical Band Gap on AZO/MEH-PPV Devices with Buffer Layer

    Directory of Open Access Journals (Sweden)

    Jaehyoung Park

    2012-01-01

    Full Text Available Organic/inorganic hybrid solar cells were fabricated incorporating aluminum-doped zinc oxide (AZO thin films of varying optical band gap in AZO/poly(2-methoxy-5-(2′-ethyl-hexyloxy-p-phenylene vinylene structures. The band gaps were controlled by varying the flow rates of Ar and O2 used to deposit the AZO. Devices with CdS buffer layer were also fabricated for improved efficiency. The effects of AZO optical band gap were assessed by testing the I–V characteristics of devices with structures of glass/ITO/AZO/MEH-PPV/Ag under AM1.5 illumination (100 mW/cm2. Efficiency was improved about 30 times by decreasing the AZO optical band gap, except in devices deposited without oxygen. A power conversion efficiency of 0.102% was obtained with the incorporation of a CdS buffer layer.

  20. Research and Design of Ge0.6Si0.4/Si Strained-layer Superlattice Planar Optical Waveguide

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Calculation shows that the refraction index of Ge0.6Si0.4/Si strained-layer superlattice n≈3.64, when Lw=9nm and Lb=24nm. An algorithm of numerical iteration for effective refraction index is employed to obtain different effective refraction indexes at different thickness (L). As a result, the thickness of Ge0.6Si0.4/Si strained-layer superlattice optical waveguide, L≤363nm, can be determined, which is very important for designing waveguide devices. An optical waveguide can be made into a nanometer device by using Ge0.6Si0.4/Si strained-layer superlattice.

  1. Magnetic nanoparticles-doped silica layer reported on ion-exchanged glass waveguide: towards integrated magneto-optical devices

    Science.gov (United States)

    Amata, Hadi; Royer, François; Choueikani, Fadi; Jamon, Damien; Broquin, Jean-Emmanuel; Plenet, Jean Claude; Rousseau, Jean Jaques

    2010-05-01

    In the framework of optical telecommunication systems, many functions are integrated on the same substrate. Nevertheless, one of the most important, such as isolation, is achieved using discrete components. It is based on magnetic materials which are always difficult to integrate with classical technologies. This is due to the annealing temperature of magnetic materials. In this paper we present another way for the realisation of such components. We use a dip coating process to report a magnetic nanoparticles doped silica layer on ion-exchanged glass waveguide. The advantages of this method is discussed and we demonstrate its compatibility with ion-exchanged technology. By varying the refractive index of the layer, we can adjust the interaction between the waveguide and the magneto-optical layer.

  2. Spacer Thickness-Dependent Electron Transport Performance of Titanium Dioxide Thick Film for Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Reda E. El-Shater

    2015-01-01

    Full Text Available A titanium dioxide (P25 film was deposited by cast coating as conductive photoelectrode and subsequently immersed in dye solution (N719 to fabricate the photoanode of dye-sensitized solar cells (DSSCs. A plastic spacer was used as a separation and sealant layer between the photoanode and the counter electrode. The effect of the thickness of this spacer on the transfer of electrons in the liquid electrolyte of the DSSCs was studied by means of both IV curves and electrochemical impedance. Using a spacer thickness range of 20 μm to 50 μm, efficiency ranges from 3.73% to 7.22%. The highest efficiency of 7.22% was obtained with an optimal spacer thickness of 40 μm.

  3. Retinal nerve fiber layer thickness in normal Indian pediatric population measured with optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Neelam Pawar

    2014-01-01

    Full Text Available Purpose: To measure the peripapillary retinal nerve fiber layer (RNFL thickness in normal Indian pediatric population. Subjects and Methods: 120 normal Indian children ages 5-17 years presenting to the Pediatric Clinic were included in this observational cross-sectional study. RNFL thickness was measured with stratus optical coherence tomography (OCT. Children with strabismus or amblyopia, with neurological, metabolic, vascular, or other disorders and those with abnormal optic discs were excluded. One eye of each subject was randomly selected for statistical analysis. The effect of age, refraction and gender on RNFL thickness was investigated statistically. Result: OCT measurements were obtained in 120 of 130 (92.3% subjects. Mean age was 10.8 ± 3.24 years (range 5-17. Average RNFL thickness was (± SD 106.11 ± 9.5 μm (range 82.26-146.25. The RNFL was thickest inferiorly (134.10 ± 16.16 μm and superiorly (133.44 ± 15.50 μm, thinner nasally (84.26 ± 16.43 μm, and thinnest temporally (70.72 ± 14.80 μm. In univariate regression analysis, age had no statistical significant effect on RNFL thickness (P = 0.7249 and refraction had a significant effect on RNFL thickness (P = 0.0008. Conclusion: OCT can be used to measure RNFL thickness in children. Refraction had an effect on RNFL thickness. In normal children, variation in RNFL thickness is large. The normative data provided by this study may assist in identifying changes in RNFL thickness in Indian children.

  4. Structures and optical properties of \\text{H}_{2}^{+} -implanted GaN epi-layers

    Science.gov (United States)

    Li, B. S.; Wang, Z. G.

    2015-06-01

    The implantation damage build-up and optical properties of GaN epitaxial films under \\text{H}2+ ion implantation have been investigated by a combination of Rutherford backscattering in channeling geometry, Raman spectroscopy, UV-visible spectroscopy and transmission electron microscopy. GaN epitaxial films were implanted with 134 keV \\text{H}2+ ions to doses ranging from 3.75   ×   1016 to 1.75   ×   1017 \\text{H}2+  cm-2 at room temperature or the same dose of 1.5   ×   1017 \\text{H}2+  cm-2 at room temperature, 573 and 723 K. The dependence of lattice disorder induced by \\text{H}2+ -implantation on the ion dose can be divided into a three-step damage process. A strong influence of the H concentration on the defect accumulation is discussed. The decrease in relative Ga disorder induced by \\text{H}2+ -implantation is linear with increasing implantation temperature. The absorption coefficient of GaN epitaxial films increases with increasing ion dose, leading to the decrease in Raman scattering spectra of Ga-N vibration. With increasing implantation doses up to 5   ×   1016 \\text{H}2+  cm-2, nanoscale hydrogen bubbles are observed in the H deposition peak region. Interstitial-type dislocation loops are observed in the damaged layer located near the damage peak region, and the geometry of the dislocation loops produced by H implantation is analyzed. The surface layer is almost free of lattice disorder induced by \\text{H}2+ -implantation.

  5. The intriguing electronic and optical properties modulation of hydrogen and fluorine codecorated silicene layers

    Science.gov (United States)

    Yang, Qun; Tan, Chunjian; Meng, Ruishen; Jiang, Junke; Liang, Qiuhua; Sun, Xiang; Yang, Daoguo; Chen, Xianping

    2017-03-01

    First-principles calculations based on density-functional theory reveal some superior physical properties of hydrogen and fluorine co-decorated silicene (HSiF) monolayer and bilayer. Our simulated results reveal that the HSiF monolayer is a large direct band gap semiconductor greatly differing from the gapless semi-metallic silicene. There exists strong interlayer coupling in HSiF bilayer, leading to the good stabilities of HSiF bilayer even beyond bilayer graphene. The proposed HSiF bilayer exhibits a moderate direct band gap of 0.296 eV which is much lower than that of HSiF monolayer. Encouragingly, HSiF layers all have a direct band gap nature, irrespective of stacking pattern, thickness and external electric fields, which is an advantage over MoS2 layers. Furthermore, an out-of-plane electric field has an evident impact on the band structures of the HSiF monolayer and bilayer. Especially, the band gap of HSiF bilayer can be effectively tuned by external electric field, even a semiconductor-metal transition occurs. More importantly, the HSiF bilayer exhibits a significant improved visible light adsorption peak with respect to that of HSiF monolayer, and the superior optical properties is robust, independent of stacking pattern. The complete electron-hole separation also enhances the photocatalytic efficiency of HSiF bilayer. In a word, the moderate band gap, effective band gap modification by external electric field, robust direct band gap nature, suitable band edge positions, electron-hole separation, and fascinating visible light adsorption, which enable HSiF bilayer to have great potential applications in the field of solar energy conversion, high performance photocatalysis and nanoelectronic devices, and we call for more concern over this kind of 2D Janus materials which possesses excellent properties.

  6. The mesospheric sodium layer as a remotely, optically pumped magnetometer for investigation of Birkeland currents

    Science.gov (United States)

    Johnsen, Magnar G.; Matzka, Jürgen; Hoppe, Ulf-Peter

    2016-04-01

    By means of optical pumping, it is possible to use the naturally occurring sodium layer in the mesosphere to measure Earth's scalar magnetic field at ~90 km above ground. This is an altitude not accessible by other means than rockets, which only will provide point measurements of very short time scales. We are planning to modify the sodium lidar at ALOMAR in Northern Norway to be able, for the first time, to measure and monitor the magnetic field in situ in the high latitude mesosphere over longer time scales. The planned modifications to the lidar instrument will allow alternating between the new magnetometer mode and its present mode for atmospheric temperatures and winds. The technique, which has been proposed earlier for measurements at low or mid-latitudes for studies of Earth's internal magnetic field, will in our project be applied to high latitudes in the auroral zone. This opens for a completely new domain of measurements of externally generated geomagnetic variations related to currents in the magnetosphere-ionosphere system. In particular, we aim to measure the magnetic field variations in close vicinity to Birkeland currents associated with particle precipitation events penetrating to altitudes below 90 km and small-scale, discrete auroral arcs. It is, furthermore, anticipated that it will be possible to detect horizontal current structures in the E-layer on much smaller length scales than it is presently possible from ground observations alone. During the project we plan take advantage of the rich space science infrastructure located in northern Norway, including ALOMAR, EISCAT and the Tromsø Geophysical Observatory magnetometer network. If possible, we also aim to make measurements in conjunction with overpasses of the SWARM satellites.

  7. Non-destructive testing of layer-to-layer fusion of a 3D print using ultrahigh resolution optical coherence tomography

    Science.gov (United States)

    Israelsen, Niels M.; Maria, Michael; Feuchter, Thomas; Podoleanu, Adrian; Bang, Ole

    2017-06-01

    Within the last decade, 3D printing has moved from a costly approach of building mechanical items to the present state-of-the-art phase where access to 3D printers is now common, both in industry and in private places. The plastic printers are the most common type of 3D printers providing prints that are light, robust and of lower cost. The robustness of the structure printed is only maintained if each layer printed is properly fused to its previously printed layers. In situations where the printed component has to accomplish a key mechanical role there is a need to characterize its mechanical strength. This may only be revealed by in-depth testing in order to discover unwanted air-gaps in the structure. Optical coherence tomography (OCT) is an in-depth imaging method, that is sensitive to variations in the refractive index and therefore can resolve with high resolution translucid samples. We report on volume imaging of a 3D printed block made with 100% PLA fill. By employing ultrahigh resolution OCT (UHR-OCT) we show that some parts of the PLA volume reveal highly scattering interfaces which likely correspond to transitions from one layer to another. In doing so, we document that UHR-OCT can act as a powerful tool that can be used in detecting fractures between layers stemming from insufficient fusion between printed structure layers. UHR-OCT can therefore serve as an useful assessment method of quality of 3D prints.

  8. Controlling Structure from the Bottom-Up: Structural and Optical Properties of Layer-by-Layer Assembled Palladium Coordination-Based Multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Altman,M.; Shukla, A.; Zubkov, T.; Evmenenko, G.; Dutta, P.; van der Boom, M.

    2006-01-01

    Layer-by-layer assembly of two palladium coordination-based multilayers on silicon and glass substrates is presented. The new assemblies consist of rigid-rod chromophores connected by terminal pyridine moieties to palladium centers. Both colloidal palladium and PdCl{sub 2}(PhCN){sub 2} were used in order to determine the effect of the metal complex precursor on multilayer structure and optical properties. The multilayers were formed by an iterative wet-chemical deposition process at room temperature in air on a siloxane-based template layer. Twelve consecutive deposition steps have been demonstrated resulting in structurally regular assemblies with an equal amount of chromophore and palladium added in each molecular bilayer. The optical intensity characteristics of the metal-organic films are clearly a function of the palladium precursor employed. The colloid-based system has a UV-vis absorption maximum an order of magnitude stronger than that of the PdCl{sub 2}-based multilayer. The absorption maximum of the PdCl{sub 2}-based film exhibits a significant red shift of 23 nm with the addition of 12 layers. Remarkably, the structure and physiochemical properties of the submicron scale PdCl{sub 2}-based structures are determined by the configuration of the {approx}15 Angstrom thick template layer. The refractive index of the PdCl2-based film was determined by spectroscopic ellipsometry. Well-defined three-dimensional structures, with a dimension of 5 m, were obtained using photopatterned template monolayers. The properties and microstructure of the films were studied by UV-vis spectroscopy, spectroscopic ellipsometry, atomic force microscopy (AFM), X-ray reflectivity (XRR), scanning electron microscopy (SEM), and aqueous contact angle measurements (CA).

  9. Optical topography guided semi-three-dimensional diffuse optical tomography for a multi-layer model of occipital cortex: a pilot methodological study

    Science.gov (United States)

    Ding, Hao; Zhang, Yao; He, Jie; Zhao, Huijuan; Gao, Feng

    2016-03-01

    In this paper, an optical topography (OT) guided diffuse optical tomography (DOT) scheme is developed for functional imaging of the occipital cortex. The method extends the previously proposed semi-three-dimensional DOT methodology to reconstruction of two-dimensional extracerebral and cerebral images using a visual cortex oriented five-layered slab geometry, and incorporate the OT localization regularization in the cerebral reconstruction to achieve enhanced quantitative accuracy and spatial resolution. We validate the methodology using simulated data and demonstrate its merits in comparison to the standalone OT and DOT.

  10. Influence of bias voltage on the optical and structural properties of nc-Si:H films grown by layer-by-layer (LBL) deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Tong, Goh Boon, E-mail: boontong77@yahoo.co [Solid State Research Laboratory, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Gani, Siti Meriam Ab.; Muhamad, Muhamad Rasat; Rahman, Saadah Abdul [Solid State Research Laboratory, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2009-07-01

    The effects of applying a positive bias of 25 to 100 V on the optical, structural and photoluminescence (PL) properties of hydrogenated nanocrystalline silicon (nc-Si:H) films produced by layer-by-layer (LBL) deposition technique has been studied. Optical characterization of the films has been obtained from UV-VIS-NIR spectroscopy measurements. Structural characterization has been performed using X-ray diffraction, micro-Raman spectroscopy and field emission scanning electron microscope (FESEM). PL spectroscopy technique has been used to investigate the PL properties of the films. In general, the films formed shows a mixed phase of silicon (Si) nanocrystallites embedded within an amorphous phase of the Si matrix. The crystalline volume fraction and grain size of the Si nanocrystallites have been shown to be strongly dependent on the applied bias voltage. High applied bias voltage enhances the growth rate of the films but reduces the refractive index and the optical energy gap of the films. Higher crystalline volume fraction of the films prepared at low bias voltages exhibits room temperature PL at around 1.8 eV (700 nm).

  11. Microstructures of NiFe/nonmagnetic metal spacer/FeMn films and their influences on exchange coupling

    Institute of Scientific and Technical Information of China (English)

    LI; Minghua(李明华); YU; Guanghua(于广华); ZHU; Fengwu(朱逢吾); HE; Ke(何珂); LAI; Wuyan(赖武彦)

    2003-01-01

    Ta/NiFe/nonmagnetic metal spacer/FeMn films were prepared by magnetron sputtering. The dependences of the exchange coupling field (Hex) between an antiferromagnetic FeMn layer and a ferromagnetic NiFe layer on the thickness of nonmagnetic metal spacer layers were systematically studied. The results show that the Hex dramatically decreases with the increase in the thicknesses of Bi and Ag spacer layers. However, it gradually decreases with the increase in the thickness of a Cu spacer layer. For a Cu space layer, its crystalline structure is the same as that of NiFe and the lattice parameters of them are close to each other. The Cu layer and FeMn layer will epitaxially grow on the NiFe layer in succession, so the (111) texture of the FeMn layer will not be damaged. As a result, the Hex gradually decreases with the deposition thickness of a Cu layer. For an Ag space layer, its crystalline structure is the same as that of NiFe, but its lattice parameter is very different from that of NiFe. Thus, neither an Ag nor an FeMn layer will epitaxially grow on the NiFe layer and the (111) texture of the FeMn layer will be damaged. The Hex rapidly decreases with the increase in the deposition thickness of an Ag layer. For a Bi spacer layer, not only its crystalline structure but also its lattice parameter is greatly different from that of NiFe. For the same reason, the Bi and FeMn layer cannot epitaxially grow on the NiFe layer. The texture of the FeMn layer will also be damaged. Therefore, the Hex rapidly decreases with the increase in the deposition thickness of a Bi layer as well. However, the research result of X-ray photoelectron spectroscopy indicates that a very small amount of surfactant Bi atoms will migrate to the FeMn layer surface when they are deposited on the NiFe/FeMn interface. Thus, the Hex will hardly decrease.

  12. BICM-ID with Physical Layer Network Coding in TWR Free Space Optical Communication Links

    Directory of Open Access Journals (Sweden)

    Alaa A. Saeed Al-Rubaie

    2017-07-01

    Full Text Available Physical layer network coding (PNC is a promising technique to improve the network throughput in a two-way relay (TWR channel for two users to exchange messages across a wireless network. The PNC technique incorporating a TWR channel is embraced by a free space optical (FSO communication link for full utilization of network resources, namely TWR-FSO PNC. In this paper, bit interleaved coded modulation with iterative decoding (BICM-ID is adopted to combat the deleterious effect of the turbulence channel by saving the message being transmitted to increase the reliability of the system. Moreover, based on this technique, comparative studies between end-to-end BICM-ID code, non-iterative convolutional coded and uncoded systems are carried out. Furthermore, this paper presents the extrinsic information transfer (ExIT charts to evaluate the performance of BICM-ID code combined with the TWR-FSO PNC system. The simulation results show that the proposed scheme can achieve a significant bit error rate (BER performance improvement through the introduction of an iterative process between a soft demapper and decoder. Similarly, Monte Carlo simulation results are provided to support the findings. Subsequently, the ExIT functions of the two receiver components are thoroughly analysed for a variety of parameters under the influence of a turbulence-induced channel fading, demonstrating the convergence behaviour of BICM-ID to enable the TWR-FSO PNC system, effectively mitigating the impact of the fading turbulence channel.

  13. Optical Effects in the Active Layer of Organic Solar Cells with Embedded Noble Metal Nanoparticles

    Directory of Open Access Journals (Sweden)

    Supachai Sompech

    2016-03-01

    Full Text Available The optical properties of organic solar cells with noble metal nanoparticles such as Ag and Au embedded in the active layer were investigated. The Discrete Dipole Approximation theory was used to analyze the light scattering and absorption efficiencies. The results show that the size, refractive index of medium and amount of the metal nanoparticles are key factors that directly influence the plasmonic enhancements in the devices. These parameters were adjusted for the light scattering and absorption efficiency calculations, which first reveal that as the imaginary part increases more (strongly absorbing medium both efficiencies decrease slightly and becomes spectrally more broadened. Ag nanoparticle size increases both efficiency peak shifts to the longer wavelength. In addition, the increasing of the nanoparticle size results to the broaden efficiency spectra. When a large amount of particles the scattering and absorption spectral peak of the particles increase, the arrangement in linear chain aligned on the axis which perpendicular to the propagation direction and parallel to the linear polarized light shifts to shorter wavelength. And the higher resonance peak for more particles number is obtained.

  14. Low-loss silicon slot waveguides and couplers fabricated with optical lithography and atomic layer deposition.

    Science.gov (United States)

    Säynätjoki, A; Karvonen, L; Alasaarela, T; Tu, X; Liow, T Y; Hiltunen, M; Tervonen, A; Lo, G Q; Honkanen, S

    2011-12-19

    We demonstrate low-loss silicon slot waveguides patterned with 248 nm deep-UV lithography and filled with atomic layer deposited aluminum oxide. Propagation losses less than 5 dB/cm are achieved with the waveguides. The devices are fabricated using low-temperature CMOS compatible processes. We also demonstrate simple, compact and efficient strip-to-slot waveguide couplers. With a coupler as short as 10 µm, coupling loss is less than 0.15 dB. The low-index and low-nonlinearity filling material allows nonlinearities nearly two orders of magnitude smaller than in silicon waveguides. Therefore, these waveguides are a good candidate for linear photonic devices on the silicon platform, and for distortion-free signal transmission channels between different parts of a silicon all-optical chip. The low-nonlinearity slot waveguides and robust couplers also facilitate a 50-fold local change of the waveguide nonlinearity within the chip by a simple mask design.

  15. Effects of ultraviolet nanosecond laser irradiation on structural modification and optical transmission of single layer graphene

    Science.gov (United States)

    Li, Chunhong; Kang, Xiaoli; Zhu, Qihua; Zheng, Wanguo

    2017-03-01

    Structural modifications and optical transmission change of single layer graphene (SLG) on transparent SiO2 substrate induced by nanosecond 355 nm laser irradiation were systematically studied by scanning electron microscopy (SEM), laser-excited Raman, X-ray photon spectroscopy (XPS) and UV-vis transmission spectra. In this study, to avoid damage to graphene, the selected irradiation fluence was set to be smaller than the laser damage threshold of SLG. Laser-driven formation of nano-dots, carbon clusters and spherical carbon morphologies were clearly presented using SEM magnification images, and the formation mechanism of such structures were discussed. Raman spectra revealed formation of D' peak and the continuously increasing of ID/IG intensity ratio with the concurrent increase of laser fluence, indicating the increase in amount of structural defects and disordering in SLG. XPS results disclosed that the oxygen content in SLG increases with laser fluence. The formation and relative content increase of Cdbnd O, Csbnd Osbnd C and Osbnd Cdbnd O bonds in SLG induced by laser irradiation were also revealed by XPS. Laser-driven micro-structure modifications of crystalline graphene to nano-crystalline graphene and photo-chemical reactions between graphene and O2 and H2O in air environment were suggested to be responsible for the Raman and XPS revealed modifications in SLG. It is worthy to point out that the above mentioned structural modifications only caused a slight decrease (graphene aiming at modifying its structure and thus taiorling its properties.

  16. The effect of metal nano particle on optical absorption coefficient of multi-layer spherical quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Zamani, N., E-mail: n.zamani@sutech.ac.ir [Department of Physics, College of Science, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Keshavarz, A., E-mail: keshavarz@sutech.ac.ir [Department of Physics, Shiraz University of Technology, Shiraz 71555-313 (Iran, Islamic Republic of); Nadgaran, H., E-mail: nadgaran@susc.ac.ir [Department of Physics, College of Science, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)

    2016-06-01

    In this paper, we investigate the optical absorption coefficient of hybrid structure consisting of metal nano particle (MNP) coupled to multi-layer spherical quantum dot (MSQD). Energy eigenvalues and eigenfunctions of Schrödinger equation in this structure are obtained by using numerical solution (by the fourth-order Runge–Kutta method). The effect of MNP in the vicinity of MSQD is calculated by considering local field theory. Then the variation of optical absorption coefficient hybrid structure is calculated. The results show that the presence of MNP near MSQD enhances the optical absorption coefficient. Also, by changing the distance between MNP and MSQD and radius of MNP, variation of optical absorption coefficient and refractive index changes are introduced.

  17. The effect of metal nano particle on optical absorption coefficient of multi-layer spherical quantum dot

    Science.gov (United States)

    Zamani, N.; Keshavarz, A.; Nadgaran, H.

    2016-06-01

    In this paper, we investigate the optical absorption coefficient of hybrid structure consisting of metal nano particle (MNP) coupled to multi-layer spherical quantum dot (MSQD). Energy eigenvalues and eigenfunctions of Schrödinger equation in this structure are obtained by using numerical solution (by the fourth-order Runge-Kutta method). The effect of MNP in the vicinity of MSQD is calculated by considering local field theory. Then the variation of optical absorption coefficient hybrid structure is calculated. The results show that the presence of MNP near MSQD enhances the optical absorption coefficient. Also, by changing the distance between MNP and MSQD and radius of MNP, variation of optical absorption coefficient and refractive index changes are introduced.

  18. Heterogeneous diversity of spacers within CRISPR

    Science.gov (United States)

    Deem, Michael; He, Jiankui

    2011-03-01

    Clustered regularly interspaced short palindromic repeats (CRISPR) in bacterial and archaeal DNA have recently been shown to be a new type of anti-viral immune system in these organisms. We here study the diversity of spacers in CRISPR under selective pressure. We propose a population dynamics model that explains the biological observation that the leader-proximal end of CRISPR is more diversified and the leader-distal end of CRISPR is more conserved. This result is shown to be in agreement with recent experiments. Our results show that the CRISPR spacer structure is influenced by and provides a record of the viral challenges that bacteria face. 1) J. He and M. W. Deem, Phys. Rev. Lett. 105 (2010) 128102

  19. Acousto-optic effect in a nematic liquid-crystal layer under the binary effect of sound and viscous waves

    Energy Technology Data Exchange (ETDEWEB)

    Kozhevnikov, E. N., E-mail: kozhev@ssu.samara.ru [Samara State University (Russian Federation)

    2010-03-15

    The optical effect in a liquid crystal cell containing a homeotropic layer of nematic liquid crystal (NLC) is analyzed. An NLC layer, located between crossed polaroids and opaque in the absence of external effect, is cleared after irradiation by an ultrasonic beam with a sharp spatial boundary. This enlightenment is suggested to be caused by the reorientation of crystal molecules in the acoustic flows that arise under the binary effect of the layer compression in the irradiated region and the viscous waves propagating from the layer boundaries. The flows were calculated taking into account the stress caused by the velocity convection and crystal structure relaxation. An expression is derived for the cell transparency, and the relative role of the convection and relaxation processes in the effect is determined.

  20. Normative data of outer photoreceptor layer thickness obtained by software image enhancing based on Stratus optical coherence tomography images

    DEFF Research Database (Denmark)

    Christensen, U.C.; Krøyer, K.; Thomadsen, Jakob

    2008-01-01

    Aim: To present normative data of outer photoreceptor layer thickness obtained by a new semiautomatic image analysis algorithm operating on contrast-enhanced optical coherence tomography (OCT) images. Methods: Eight Stratus OCT3 scans from identical retinal locations from 25 normal eyes were...... registered and combined to form a contrast-enhanced average image. Utilising the vertical intensity gradients of the enhanced OCT images to demarcate retinal layers, thickness measurements of the outer photoreceptor- and retinal pigment epithelium layer (RPE-OScomplex) were obtained. Additionally...... in the superior macula 0.5-3 mm of the centre was significantly increased as compared with the corresponding inferior retina. In healthy subjects, the I-ratio-ONL was 1.06. Conclusions: Contrast-enhanced OCT images enable quantification of outer photoreceptor layer thickness, and normative values may help...

  1. Dependency of Tunneling-Magnetoresistance Ratio on Nanoscale Spacer Thickness and Material for Double MgO Based Perpendicular-Magnetic-Tunneling-Junction.

    Science.gov (United States)

    Lee, Du-Yeong; Hong, Song-Hwa; Lee, Seung-Eun; Park, Jea-Gun

    2016-12-08

    It was found that in double MgO based perpendicular magnetic tunneling junction spin-valves ex-situ annealed at 400 °C, the tunneling magnetoresistance ratio was extremely sensitive to the material and thickness of the nanoscale spacer: it peaked at a specific thickness (0.40~0.53 nm), and the TMR ratio for W spacers (~134%) was higher than that for Ta spacers (~98%). This dependency on the spacer material and thickness was associated with the (100) body-centered-cubic crystallinity of the MgO layers: the strain enhanced diffusion length in the MgO layers of W atoms (~1.40 nm) was much shorter than that of Ta atoms (~2.85 nm) and the shorter diffusion length led to the MgO layers having better (100) body-centered-cubic crystallinity.

  2. Comparison of a stoichiometric analysis of Fe3-delta O4 layers by magneto-optical Kerr spectroscopy with Mossbauer results

    NARCIS (Netherlands)

    Fontijn, WFJ; vanderHeijden, PAA; Voogt, FC; Hibma, T; vanderZaag, PJ

    1997-01-01

    The stoichiometry of a series of 300 Angstrom thick Fe3-deltaO4 layers grown by means of molecular beam epitaxy on MgO(100) has been investigated both by magneto-optical Ken spectroscopy and by Mossbauer spectroscopy, The layers consisted of a 200 Angstrom thick Fe3-deltaO4 layer grown with the Fe-5

  3. Study of carrier blocking property of poly-linalyl acetate thin layer by electric-field-induced optical second-harmonic generation measurement

    Science.gov (United States)

    Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa; Anderson, Liam J.; Jacob, Mohan V.

    2014-02-01

    By using electric-field-induced optical second-harmonic generation (EFISHG) measurement, we studied the carrier-blocking property of poly-linalyl acetate (PLA) thin layers sandwiched in indium-zinc-oxide (IZO)/PLA/C60/Al double-layer diodes. Results showed that the PLA layer totally blocks electrons crossing the C60 layer, and also blocks holes entering from the IZO layer. The EFISHG measurement effectively substantiates the hole-blocking electron-blocking property of the PLA layer sandwiched in double layer diodes.

  4. Characterization of Choroidal Layers in Normal Aging Eyes Using Enface Swept-Source Optical Coherence Tomography.

    Directory of Open Access Journals (Sweden)

    Mehreen Adhi

    Full Text Available To characterize qualitative and quantitative features of the choroid in normal eyes using enface swept-source optical coherence tomography (SS-OCT.Fifty-two eyes of 26 consecutive normal subjects were prospectively recruited to obtain multiple three-dimensional 12 x 12 mm volumetric scans using a long-wavelength high-speed SS-OCT prototype. A motion-correction algorithm merged multiple SS-OCT volumes to improve signal. Retinal pigment epithelium (RPE was segmented as the reference and enface images were extracted at varying depths every 4.13 μm intervals. Systematic analysis of the choroid at different depths was performed to qualitatively assess the morphology of the choroid and quantify the absolute thicknesses as well as the relative thicknesses of the choroidal vascular layers including the choroidal microvasculature (choriocapillaris, terminal arterioles and venules; CC and choroidal vessels (CV with respect to the subfoveal total choroidal thickness (TC. Subjects were divided into two age groups: younger (<40 years and older (≥ 40 years.Mean age of subjects was 41.92 (24-66 years. Enface images at the level of the RPE, CC, CV, and choroidal-scleral interface were used to assess specific qualitative features. In the younger age group, the mean absolute thicknesses were: TC 379.4 μm (SD ± 75.7 μm, CC 81.3 μm (SD ± 21.2 μm and CV 298.1 μm (SD ± 63.7 μm. In the older group, the mean absolute thicknesses were: TC 305.0 μm (SD ± 50.9 μm, CC 56.4μm (SD ± 12.1 μm and CV 248.6μm (SD ± 49.7 μm. In the younger group, the relative thicknesses of the individual choroidal layers were: CC 21.5% (SD ± 4.0% and CV 78.4% (SD ± 4.0%. In the older group, the relative thicknesses were: CC 18.9% (SD ± 4.5% and CV 81.1% (SD ± 4.5%. The absolute thicknesses were smaller in the older age group for all choroidal layers (TC p=0.006, CC p=0.0003, CV p=0.03 while the relative thickness was smaller only for the CC (p=0.04.Enface SS-OCT at 1050

  5. Optical coherence tomography angiography vessel density mapping at various retinal layers in healthy and normal tension glaucoma eyes.

    Science.gov (United States)

    Shin, Joong Won; Sung, Kyung Rim; Lee, Ji Yun; Kwon, Junki; Seong, Mincheol

    2017-06-01

    To investigate peripapillary vessel density at various spatial locations and layers in healthy and normal tension glaucoma eyes using optical coherence tomography angiography (OCTA). A commercial OCTA device (AngioPlex; Carl Zeiss Meditec) was used to image microvasculature in a 6 × 6-mm optic disc region. Vessel densities of superficial and deep retinal layers were calculated using an automatic thresholding algorithm. Vessel density maps were plotted by averaging individual angiogram images. The spatial characteristics of vessel densities were analyzed at clock-hour sectors and in five 0.7-mm-thick concentric circles from a diameter of 2.0 to 5.5 mm. Areas under the receiver operating characteristics curves (AUCs) assessed the glaucoma diagnostic ability. Vessel density maps of superficial and deep retinal layers were significantly reduced at the 7 and 11 o'clock positions in glaucomatous eyes. In superficial layer, vessel density significantly decreased as the distance from the optic disc margin increased, except in the innermost circle (2.0-2.7-mm). There were significant differences in AUCs of superficial vessel density between innermost circle and the other outer circles. In the deep layer, the innermost circle showed significantly higher vessel density than the outer circles. Vessel density at 7 o'clock showed the best diagnostic performance (AUCs, 0.898 and 0.789) both in the superficial and deep layers. The innermost circle showed eccentric feature compared to the outer circles in terms of spatial characteristics and diagnostic ability. Understanding of the spatial characteristics of peripapillary vasculature may be helpful in clinical practice and determining the optimal measurement area of vessel density.

  6. Retinal vessel diameters decrease with macular ganglion cell layer thickness in autosomal dominant optic atrophy and in healthy subjects

    DEFF Research Database (Denmark)

    Rönnbäck, Cecilia; Grønskov, Karen; Larsen, Michael

    2014-01-01

    PURPOSE: To investigate retinal trunk vessel diameters in subjects with autosomal dominant optic atrophy (ADOA) and mutation-free healthy relatives. METHODS: This cross-sectional study included 52 ADOA patients with the optic atrophy 1 (OPA1) exon 28 (c.2826_2836delinsGGATGCTCCA) mutation (age 8...... ganglion cell-inner plexiform layer (GC-IPL) thickness (p = 0.0017 and p = 0.0057, respectively). CONCLUSION: Narrow retinal arteries and veins were associated not only with the severity of ADOA but with ganglion cell volume in patients with ADOA and in healthy subjects. This suggests that narrow vessels...

  7. Optical emission of strained direct-band-gap Ge quantum well embedded inside InGaAs alloy layers

    OpenAIRE

    Pavarelli, Nicola; Ochalski, Tomasz J.; Murphy-Armando, Felipe; Huo, Y; Schmidt, Michael; Huyet, Guillaume; Harris, J. S.

    2013-01-01

    We studied the optical properties of a strain-induced direct-band-gap Ge quantum well embedded in InGaAs. We showed that the band offsets depend on the electronegativity of the layer in contact with Ge, leading to different types of optical transitions in the heterostructure. When group-V atoms compose the interfaces, only electrons are confined in Ge, whereas both carriers are confined when the interface consists of group-III atoms. The different carrier confinement results in different emis...

  8. Effect of Silver Addition on the Ethanol-Sensing Properties of Indium Oxide Nanoparticle Layers: Optical Absorption Study

    Directory of Open Access Journals (Sweden)

    Vidya Nand Singh

    2007-01-01

    Full Text Available In2O3 and In2O3:Ag nanoparticle layers have been deposited using a two-step method consisting of chemical capping and dip coating techniques. The result of optical absorption analysis of In2O3:Ag samples shows the presence of Ag2O and Ag in air-annealed and vacuum-annealed samples, respectively. These results have been correlated with the gas sensing properties of these layers towards ethanol and support the proposed mechanism that increase in sensor response on Ag addition is due to the conversion of Ag2O to Ag in the presence of ethanol.

  9. Partitioning aerosol optical depth between the boundary layer and the free troposphere

    Science.gov (United States)

    Bourgeois, Quentin; Ekman, Annica; Krejci, Radovan; Devasthale, Abhay; Renard, Jean-Baptiste

    2017-04-01

    Aerosols are short-lived (about a week) compounds in the atmosphere due to the efficient removal by dry and wet deposition in the boundary layer (BL) where a majority of the emission sources are located. As a consequence, most of the aerosol mass should be found in the BL and the aerosol optical depth (AOD) integrated over the atmospheric column should be dominated by the BL contribution. As a consequence, BL aerosols would most likely have the largest climate effect. However, aerosols advected to the free troposphere (FT) have a much longer residence time (typically a few weeks) than those in the BL, potentially inducing a more long-term effect on climate. Light-absorbing aerosols may in addition have an enhanced absorption, and thereby climate warming effect, if they are located above low-level reflective clouds. Light-absorbing aerosols above clouds may also modify below cloud formation and transformation. In this study, the global AOD has been retrieved using satellite observations from CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) over a nine-year period (2007-2015) and partitioned between the BL and FT using BL heights obtained from the ERA-Interim re-analysis data. The results show that the vertical distribution of AOD does not follow the diurnal cycle of the BL but remains similar between day and night highlighting the role of a residual layer during night. The BL and FT contribute 71% and 29%, respectively, to the global AOD during daytime. The FT AOD contribution is larger in the tropics than at mid-latitudes which indicates that convective transport largely controls the vertical profile of aerosols, and the FT AOD contribution over oceans is governed by neighboring continents. According to the CALIOP aerosol classification, dust and smoke particles are the main aerosol types transported into the FT. Overall, the study shows that the fraction of AOD in the FT - and thus potentially located above low-level clouds - is substantial and should

  10. Impact of an AlAs window layer upon the optical properties of Al x Ga1-x As photodiodes

    Science.gov (United States)

    Kang, T.; Chen, X. J.; Johnson, E. B.; Christian, J. F.; Lee, K.; Hammig, M. D.

    2016-05-01

    Recently developed advanced scintillators, which have the ability to distinguish gamma-ray interaction events from those that accompany neutron impact, require improved quantum efficiency in the blue to near UV region of the spectrum. We utilize GaAs/Al0.8Ga0.2As photodiode elements as components in a wide band-gap solid-state photomultiplier as a lower-cost, lower logistical burden, and higher quantum efficiency replacement for the photomultiplier tube. An AlAs window layer is employed as a means to increase the diode’s optical performance. Relative to structures absent the window layer, simulations and measurements demonstrate that the AlAs layer produces a spatial coincidence between regions of large drift fields with regions of high photon absorption. In addition to the AlAs layer, secondary ion mass spectrometry measurements show that an unexpected high degree of inter-diffusion of GaAs and AlAs quenches the photon-detection efficiency, a decrease that can be avoided by its post-growth removal. With the AlAs layer, the peak external quantum efficiency of 49% is achieved at 450 nm with 10 V reverse bias, which does not fully deplete the device. Simulations show that full depletion can result in efficiencies exceeding 90%. In order to enhance the optical response, a simple anti-reflective coating layer is designed using the existing passivation layer components that successfully minimizes the reflection at the wavelength range of interest (300 nm-500 nm).

  11. Optical and photoelectrochemical studies on Ag{sub 2}O/TiO{sub 2} double-layer thin films

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chuan, E-mail: cli10@yahoo.com [Department of Biomedical Engineering, National Yang Ming University, Taipei, Taiwan 11221 (China); Department of Mechanical Engineering, National Central University, Jhongli, Taoyuan, Taiwan 32001 (China); Hsieh, J.H. [Department of Materials Engineering, Ming Chi University of Technology, Taishan, Taipei, Taiwan 24301 (China); Cheng, J.C. [Department of Electronic Engineering, National Taipei University of Technology, Taipei, Taiwan 10608 (China); Huang, C.C. [Department of Biomedical Engineering, National Yang Ming University, Taipei, Taiwan 11221 (China)

    2014-11-03

    When two different oxides films stacked together, if the absorption (upper) layer has both its conduction and valence bands more negatively lower than that of the layer underneath, then the photo-excited electrons can be forwarded to the underneath layer to become an effect of energy storage. Recent studies discovered that the double-layers of Cu{sub 2}O/TiO{sub 2} films possess such capacity. In order to investigate this specific phenomenon, we use a DC magnetron reactive sputtering to deposit a double-layer of Ag{sub 2}O/TiO{sub 2} films on glass substrate. The film thicknesses of the double-layer are 300 nm and 200 nm respectively. X-Ray diffraction (XRD), scanning electron microscope (SEM) and UV–VIS–NIR photospectrometer and photoluminance tests were used to study the structure, morphology, optical absorption and band gaps of the stacked films. From XRD and SEM, we can confirm the microstructures of each layer. The UV–VIS–NIR spectrum revealed that the optical absorption of Ag{sub 2}O/TiO{sub 2} fell in between the single film of Ag{sub 2}O and TiO{sub 2}. Further, two band gaps were estimated for Ag{sub 2}O/TiO{sub 2} films based on the Beer-Lambert law and Tauc plot. Photoluminance and photoelectrochemical tests indicated that delayed emission by electron-hole recombination and photoelectrical current was effectively support the mechanism of electrons transfer from Ag{sub 2}O to TiO{sub 2} at Ag{sub 2}O/TiO{sub 2} interface in the double-layer films. - Highlights: • A double-layer of Ag{sub 2}O/TiO{sub 2} films was deposited on glass substrate by sputtering. • XRD confirms the nanocrystalline structures of the stack deposited films. • UV–VIS–NIR spectroscopy shows the enhanced of optical absorption in Ag{sub 2}O/TiO{sub 2}. • Photoluminance and photoelectrochemical tests show electron-hole separation effect.

  12. Scanning Laser Polarimetry and Optical Coherence Tomography for Detection of Retinal Nerve Fiber Layer Defects

    Science.gov (United States)

    Oh, Jong-Hyun

    2009-01-01

    Purpose To compare the ability of scanning laser polarimetry with variable corneal compensation (GDx-VCC) and Stratus optical coherence tomography (OCT) to detect photographic retinal nerve fiber layer (RNFL) defects. Methods This retrospective cross-sectional study included 45 eyes of 45 consecutive glaucoma patients with RNFL defects in red-free fundus photographs. The superior and inferior temporal quadrants in each eye were included for data analysis separately. The location and presence of RNFL defects seen in red-free fundus photographs were compared with those seen in GDx-VCC deviation maps and OCT RNFL analysis maps for each quadrant. Results Of the 90 quadrants (45 eyes), 31 (34%) had no apparent RNFL defects, 29 (32%) had focal RNFL defects, and 30 (33%) had diffuse RNFL defects in red-free fundus photographs. The highest agreement between GDx-VCC and red-free photography was 73% when we defined GDx-VCC RNFL defects as a cluster of three or more color-coded squares (p<5%) along the traveling line of the retinal nerve fiber in the GDx-VCC deviation map (kappa value, 0.388; 95% confidence interval (CI), 0.195 to 0.582). The highest agreement between OCT and red-free photography was 85% (kappa value, 0.666; 95% CI, 0.506 to 0.825) when a value of 5% outside the normal limit for the OCT analysis map was used as a cut-off value for OCT RNFL defects. Conclusions According to the kappa values, the agreement between GDx-VCC deviation maps and red-free photography was poor, whereas the agreement between OCT analysis maps and red-free photography was good. PMID:19794943

  13. Reproducibility of retinal nerve fiber layer measurements across the glaucoma spectrum using optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Jayesh Vazirani

    2015-01-01

    Full Text Available Purpose: The purpose was to determine intra-session and inter-session reproducibility of retinal nerve fiber layer (RNFL thickness measurements with the spectral-domain Cirrus optical coherence tomography (OCT ® (SD-OCT in normal and glaucomatous eyes, including a subset of advanced glaucoma. Materials and Methods: RNFL measurements of 40 eyes of 40 normal subjects and 40 eyes of 40 glaucomatous patients including 14 with advanced glaucoma were obtained on the Cirrus OCT ® (Carl Zeiss Meditec, Dublin, CA, USA five times on 1-day (intra-session and on five separate days (inter-session. Intraclass correlation coefficient (ICC, coefficient of variation (COV, and test-retest variability (TRT values were calculated for mean and quadrant RNFL in each group separately. Reproducibility values were correlated with age and stage of glaucoma. Results: For intra-session reproducibility, the ICC, COV, and TRT values for mean RNFL thickness in normal eyes were 0.993, 1.96%, and 4.02 µm, respectively, 0.996, 2.39%, and 3.84 µm in glaucomatous eyes, and 0.996, 2.41%, and 3.70 µm in advanced glaucoma. The corresponding inter-session values in normal eyes were 0.992, 2.16%, and 4.09 µm, 0.995, 2.62%, and 3.98 µm in glaucoma and 0.990, 2.70%, and 4.16 µm in advanced glaucoma. The mean RNFL thickness measurements were the most reproducible while the temporal quadrant had the lowest reproducibility values in all groups. There was no correlation between reproducibility and age or mean deviation on visual fields. Conclusions: Peripapillary RNFL thickness measurements using Cirrus OCT ® demonstrated excellent reproducibility in normal and glaucomatous eyes, including eyes with advanced glaucoma. Mean RNFL thickness measurements appear to be the most reproducible and probably represent the best parameter to use for longitudinal follow-up.

  14. Additive diagnostic role of imaging in glaucoma: optical coherence tomography and retinal nerve fiber layer photography.

    Science.gov (United States)

    Kim, Ko Eun; Kim, Seok Hwan; Oh, Sohee; Jeoung, Jin Wook; Suh, Min Hee; Seo, Je Hyun; Kim, Martha; Park, Ki Ho; Kim, Dong Myung

    2014-11-20

    To investigate the additive diagnostic role of spectral-domain optical coherence tomography (SD-OCT) and red-free retinal nerve fiber layer photography (RNFLP) in making clinical glaucoma diagnosis. Four diagnostic combination sets, including the most recent image from each measurement of 196 glaucoma eyes (including the 44 preperimetric glaucoma eyes) and 101 healthy eyes, were prepared: (1) stereo disc photography and Humphrey visual field (SH), (2) SH and SD-OCT (SHO), (3) SH and RNFLP (SHR), and (4) SHR and SD-OCT (SHRO). Each randomly sorted set was serially presented at 1-month intervals to five glaucoma specialists who were asked to evaluate them in a subjective and independent manner. The specialists' glaucoma-diagnostic performances based on the sets were then compared. For each specialist, adding SD-OCT to SH or SHR increased the glaucoma-diagnostic sensitivity but not to a level of statistical significance. For one specialist, adding RNFLP to SH significantly increased the sensitivity. Each specialist showed a high level of specificity regardless of the diagnostic set. The overall sensitivity of all specialists' assessments was significantly increased by adding RNFLP or the combination of SD-OCT and RNFLP to SH (P < 0.001); however, adding SD-OCT to SH or SHR did not significantly increase the sensitivity. A similar relationship was noted also for the preperimetric glaucoma subgroup. In contrast to RNFLP, SD-OCT did not significantly enhance the diagnostic accuracy of detecting glaucoma or even of preperimetric glaucoma. Our results suggest that, at least for glaucoma specialists, the additive diagnostic role of OCT is limited. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  15. Scanning laser polarimetry and optical coherence tomography for detection of retinal nerve fiber layer defects.

    Science.gov (United States)

    Oh, Jong-Hyun; Kim, Yong Yeon

    2009-09-01

    To compare the ability of scanning laser polarimetry with variable corneal compensation (GDx-VCC) and Stratus optical coherence tomography (OCT) to detect photographic retinal nerve fiber layer (RNFL) defects. This retrospective cross-sectional study included 45 eyes of 45 consecutive glaucoma patients with RNFL defects in red-free fundus photographs. The superior and inferior temporal quadrants in each eye were included for data analysis separately. The location and presence of RNFL defects seen in red-free fundus photographs were compared with those seen in GDx-VCC deviation maps and OCT RNFL analysis maps for each quadrant. Of the 90 quadrants (45 eyes), 31 (34%) had no apparent RNFL defects, 29 (32%) had focal RNFL defects, and 30 (33%) had diffuse RNFL defects in red-free fundus photographs. The highest agreement between GDx-VCC and red-free photography was 73% when we defined GDx-VCC RNFL defects as a cluster of three or more color-coded squares (p<5%) along the traveling line of the retinal nerve fiber in the GDx-VCC deviation map (kappa value, 0.388; 95% confidence interval (CI), 0.195 to 0.582). The highest agreement between OCT and red-free photography was 85% (kappa value, 0.666; 95% CI, 0.506 to 0.825) when a value of 5% outside the normal limit for the OCT analysis map was used as a cut-off value for OCT RNFL defects. According to the kappa values, the agreement between GDx-VCC deviation maps and red-free photography was poor, whereas the agreement between OCT analysis maps and red-free photography was good.

  16. Extending resolution of scanning optical microscopy beyond the Abbe limit through the assistance of InSb thin layers.

    Science.gov (United States)

    Ding, Chenliang; Wei, Jingsong; Li, Qisong; Liang, Xin; Wei, Tao

    2016-04-01

    The resolution of light imaging is required to extend beyond the Abbe limit to the subdiffraction, or even nanoscale. In this Letter, we propose to extend the resolution of scanning optical microscopy (SOM) beyond the Abbe limit as a kind of subdiffraction imaging technology through the assistance of InSb thin layers due to obvious nonlinear saturation absorption and reversible formation of an optical pinhole channel. The results show that the imaging resolution is greatly improved compared with the SOM itself. This work provides a way to improve the resolution of SOM without changing the SOM itself, but through the assistance of InSb thin layers. This is also a simple and practical way to extend the resolution of SOM beyond the Abbe limit.

  17. Nonlinear optical characterization of GaN layers grown by MOCVD on sapphire[Metal Organic Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Tiginyanu, I.M.; Kravetsky, I.V.; Pavlidis, D.; Eisenbach, A.; Hildebrandt, R.; Marowsky, G.; Hartnagel, H.L.

    2000-07-01

    Optical second and third harmonic generation measurements were carried out on GaN layers grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. The measured d{sub 33} is 33 times the d{sub 11} of quartz. The angular dependence of second-harmonic intensity as well as the measured ratios d{sub 33}/d{sub 15} = {minus}2.02 and d{sub 33}/d{sub 31} = {minus}2.03 confirm the wurzite structure of the studied GaN layers with the optical c-axis oriented perpendicular to the sample surface. Fine oscillations were observed in the measured second and third harmonic angular dependencies. A simple model based on the interference of the fundamental beam in the sample was used to explain these oscillations.

  18. Effects of an InGaAs Cap Layer on the Optical Properties of InAs Quantum Dot Molecules

    Institute of Scientific and Technical Information of China (English)

    TIAN Peng; HUANG Li-Rong; YUAN Xiu-Hua; HUANG De-Xiu

    2011-01-01

    @@ Self-assembled InAs quantum dot molecules are grown on GaAs substrates without following any special protocols by using metal-organic chemical vapor deposition.The effects of indium composition and the thickness of the InGaAs cap layer on the optical properties of InAs quantum dot molecules are investigated by photoluminescence.With increasing indium composition and thickness of the InGaAs cap layer, the ground-state wavelength of the emission spectrum redshifts and the peak intensity decreases.In addition, the structural and optical properties of quantum dots and quantum dot molecules are comparatively studied, and the results show that when quantum dots turn into quantum dot molecules, the emission wavelength red shifts.

  19. Intercalation assembly of optical hybrid materials based on layered terbium hydroxide hosts and organic sensitizer anions guests

    Institute of Scientific and Technical Information of China (English)

    Liang-Liang Liu; Qin Wang; Dan Xia; Ting-Ting Shen; Ming-Hui Yu; Wei-Sheng Liu; Yu Tang

    2013-01-01

    Optical hybrid materials based on inorganic hosts and organic sensitizer guests hold promise for a virtually unlimited number of applications.In particular,the interaction and the combination of the properties of a defined inorganic matrix and a specific sensitizer could lead to synergistic effects in luminescence enhancing and tuning.The current article focuses on the intercalation assembly of optical hybrid materials based on the layered terbium hydroxide (LTbH) hosts and organic divalent carboxylic sensitizer anion guests by a hydrothermal process.The studies on the interactions between hosts and guests indicate that the type and arrangement of organic guests in the layer spacing of the LTbH hosts can make a difference in the luminescence of the hybrid inorganic-organic materials.

  20. Two-layer optical model of skin for early, non-invasive detection of wound development on the diabetic foot

    Science.gov (United States)

    Yudovsky, Dmitry; Nouvong, Aksone; Schomacker, Kevin; Pilon, Laurent

    2010-02-01

    Foot ulceration is a debilitating comorbidity of diabetes that may result in loss of mobility and amputation. Optical detection of cutaneous tissue changes due to inflammation and necrosis at the preulcer site could constitute a preventative strategy. A commercial hyperspectral oximetry system was used to measure tissue oxygenation on the feet of diabetic patients. A previously developed predictive index was used to differentiate preulcer tissue from surrounding healthy tissue with a sensitivity of 92% and specificity of 80%. To improve prediction accuracy, an optical skin model was developed treating skin as a two-layer medium and explicitly accounting for (i) melanin content and thickness of the epidermis, (ii) blood content and hemoglobin saturation of the dermis, and (iii) tissue scattering in both layers. Using this forward model, an iterative inverse method was used to determine the skin properties from hyperspectral images of preulcerative areas. The use of this information in lowering the false positive rate was discussed.

  1. Energy-efficient optical line terminal for WDM-OFDM-PON based on two-dimensional subcarrier and layer allocation.

    Science.gov (United States)

    Hu, Xiaofeng; Cao, Pan; Zhuang, Zhiming; Zhang, Liang; Yang, Qi; Su, Yikai

    2012-11-05

    We propose and experimentally demonstrate a scheme to reduce the energy consumption of optical line terminal (OLT) in wavelength division multiplexing - orthogonal frequency division multiplexing - passive optical networks (WDM-OFDM-PONs). In our scheme, a wireless communication technique, termed layered modulation, is introduced to maximize the transmission capacity of OFDM modulation module in the OLT by multiplexing data from different ONU groups with signal-to-noise ratio (SNR) margins onto the same subcarriers. With adaptive and dynamic subcarrier and layer allocation, several ONU groups with low traffic demands can share one OFDM modulation module to deliver their data during non-peak hours of a day, thus greatly reducing the number of running devices and minimizing the energy consumption of the OLT. Numerical calculation shows that an energy efficiency improvement of 28.3% in the OLT can be achieved by using proposed scheme compared to the conventional WDM-OFDM-PON.

  2. Electronic and Optical Properties of Few Layer Black Phosphorus and Black Phosphorus Nanoribbons from First Principles Calculations

    Science.gov (United States)

    Tran, Vy

    Recently, a new semiconducting 2D material, black phosphorus, has piqued the interest of research groups in the field. In its bulk form, black phosphorus was synthesized over a century ago and in 2014 devices based on thin flakes of black phosphorus were successfully realized. This was a crucial step towards the exploration and characterization of this material. However, because this material was virtually ignored until this point, many open questions needed to be quickly addressed. Fundamental properties such as the band gap, carrier mobility, optical spectrum, and thermal transport had not been established. Furthermore, the effect of extrinsic factors such as the number of layers, external electric fields, and applied strain had not been explored. How these extrinsic factors affect the tunability of the aforementioned physical properties is of utmost importance for device engineers. Using first principle computations based on density functional theory and the GW approximation including many-electron effects, we calculate the fundamental electronic and optical properties of few-layer black phosphorus. Beyond basic calculations, such as the band structure, quasiparticle band gap, and optical absorption spectrum, we dig deeper to explore the origin and nature of some of black phosphorus' unusual and surprising properties. These properties include the existence of relativistic Dirac fermions as charge carriers, a highly anisotropic band structure, an anisotropic optical absorption spectrum, quasi-1D excitonic features, and an ultra-high sensitivity to a gate electric field. In the first chapter, we discuss the properties of few-layer black phosphorus. We calculate the quasiparticle band gap, and excitonic optical spectra for 1-4 layers. We provide an empirical formula in the form of a power law to fit the calculated results and predict the values for larger layer numbers. We also propose an effective mass hydrogenic model to describe the excitonic spectra calculated

  3. Optical coherence tomography (OCT) in hereditary retinal degenerations: Layer-by-layer analyses in normal and diseased retinas

    Science.gov (United States)

    Huang, Yijun

    OCT is a new technique for non-invasive, non-contact, cross-sectional imaging of biological tissues with micrometer longitudinal resolution. As it applies to the field of ophthalmology, OCT can delineate retinal sublayers based on their backscattering characteristics, and permit quantitative measurement of the structure of retina in vivo. This dissertation intended to clarify the basis of the OCT signals and whether this procedure has potential for diagnosis and monitoring of human retinal degenerative diseases. Key to this goal are quantitation of OCT signal features and accurate, layer-by-layer correlation of these features with underlying retinal microanatomy. In normal and degenerate avian and swine retinas, OCT signal features were quantified using custom computer programs, and were correlated with cryosections of unfixed retinas obtained at the same retinal location. The results suggested a definable and quantifiable relationship between OCT signal components and retinal microanatomy. The correlation in the outer retina indicated that the OCT posterior highly reflective band, or the outer- retina-choroid complex (ORCC), is attributable to the photoreceptor layer, RPE, and anterior choroid. Further evidence of OCT signal origin was provided by the rd chicken and the rhodopsin P347L mutant transgenic swine. In these animals where photoreceptors had degenerated, OCT abnormalities were observed at the level of and vitreal to the ORCC, consistent with the hypothesis that photoreceptors contribute to the ORCC. Studies of quantitative OCT analysis in man were also performed. In selected hereditary retinal degenerative diseases in which there was regional difference in retinal function, frequently observed OCT abnormalities that were associated with visual dysfunction were reduced OCT thickness, reduced ORCC thickness, increased reflectivity posterior to ORCC, and abnormal OCT signal lamination. These preliminary results suggested that OCT abnormalities at the level

  4. Bistability of optical response of an ultra thin layer consisting of two-level atoms: account of the local field

    Science.gov (United States)

    Shuval-Sergeeva, E. V.; Zaitsev, A. I.

    2008-03-01

    When describing the phenomenon of bistability of optical response of an ultra thin layer consisting of two-level atoms it is important to take into account the local field correction. The account of the correction results in the improvement of existence conditions of bistability. One more bistable region is formed starting with certain value of local field parameter. Both effects are induced by the dynamical frequency shift.

  5. Optic neuritis is associated with inner nuclear layer thickening and microcystic macular edema independently of multiple sclerosis.

    Directory of Open Access Journals (Sweden)

    Falko Kaufhold

    Full Text Available BACKGROUND: Microcystic macular edema (MME and inner nuclear layer thickening (INL were described in multiple sclerosis (MS and neuromyelitis optica (NMO patients using optical coherence tomography (OCT. The cause of these findings is currently unknown and a relation to inflammatory or degenerative processes in the optic nerve is discussed. OBJECTIVE: The aim of our study was to investigate whether INL thickening and MME are related to optic neuritis (ON in various neuro-inflammatory disorders causingON: MS, NMO and chronic inflammatory optic neuropathy. METHODS: We retrospectively analyzed data from 216 MS patients, 39 patients with a clinically isolated syndrome, 20 NMO spectrum disorder patients, 9 patients with chronic inflammatory optic neuropathy and 121 healthy subjects. Intra-retinal layer segmentation was performed for the eyes of patients with unilateral ON. Scanning laser ophthalmoscopy (SLO images were reviewed for characteristic ocular fundus changes. RESULTS: Intra-retinal layer segmentation showed that eyes with a history of ON displayed MME independent INL thickening compared to contralateral eyes without previous ON. MME was detected in 22 eyes from 15 patients (5.3% of all screened patients, including 7 patients with bilateral edema. Of these, 21 had a prior history of ON (95%. The SLO images of all 22 MME-affected eyes showed crescent-shaped texture changes which were visible in the perifoveal region. A second grader who was blinded to the results of the OCT classified all SLO images for the presence of these characteristic fundus changes. All MME eyes were correctly classified (sensitivity = 100% with high specificity (95.2%. CONCLUSION: This study shows that both MME and INL thickening occur in various neuro-inflammatory disorders associated with ON. We also demonstrate that detection and analysis of MME by OCT is not limited to B-scans, but also possible using SLO images.

  6. Pathfinder first light: alignment, calibration, and commissioning of the LINC-NIRVANA ground-layer adaptive optics subsystem

    Science.gov (United States)

    Kopon, Derek; Conrad, Al; Arcidiacono, Carmelo; Herbst, Tom; Viotto, Valentina; Farinato, Jacopo; Bergomi, Maria; Ragazzoni, Roberto; Marafatto, Luca; Baumeister, Harald; Bertram, Thomas; Berwein, Jürgen; Briegel, Florian; Hofferbert, Ralph; Kittmann, Frank; Kürster, Martin; Mohr, Lars; Radhakrishnan, Kalyan

    2014-08-01

    We present descriptions of the alignment and calibration tests of the Pathfinder, which achieved first light during our 2013 commissioning campaign at the LBT. The full LINC-NIRVANA instrument is a Fizeau interferometric imager with fringe tracking and 2-layer natural guide star multi-conjugate adaptive optics (MCAO) systems on each eye of the LBT. The MCAO correction for each side is achieved using a ground layer wavefront sensor that drives the LBT adaptive secondary mirror and a mid-high layer wavefront sensor that drives a Xinetics 349 actuator DM conjugated to an altitude of 7.1 km. When the LINC-NIRVANA MCAO system is commissioned, it will be one of only two such systems on an 8-meter telescope and the only such system in the northern hemisphere. In order to mitigate risk, we take a modular approach to commissioning by decoupling and testing the LINC-NIRVANA subsystems individually. The Pathfinder is the ground-layer wavefront sensor for the DX eye of the LBT. It uses 12 pyramid wavefront sensors to optically co-add light from natural guide stars in order to make four pupil images that sense ground layer turbulence. Pathfinder is now the first LINC-NIRVANA subsystem to be fully integrated with the telescope and commissioned on sky. Our 2013 commissioning campaign consisted of 7 runs at the LBT with the tasks of assembly, integration and communication with the LBT telescope control system, alignment to the telescope optical axis, off-sky closed loop AO calibration, and finally closed loop on-sky AO. We present the programmatics of this campaign, along with the novel designs of our alignment scheme and our off-sky calibration test, which lead to the Pathfinder's first on-sky closed loop images.

  7. Prevalence of Split Nerve Fiber Layer Bundles in Healthy People Imaged with Spectral Domain Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Sirel Gür Güngör

    2016-12-01

    Full Text Available Objectives: The presence of retinal nerve fiber layer (RNFL split bundles was recently described in normal eyes scanned using scanning laser polarimetry and by histologic studies. Split bundles may resemble RNFL loss in healthy eyes. The aim of our study was to determine the prevalence of nerve fiber layer split bundles in healthy people. Materials and Methods: We imaged 718 eyes of 359 healthy persons with the spectral domain optical coherence tomography in this cross-sectional study. All eyes had intraocular pressure of 21 mmHg or less, normal appearance of the optic nerve head, and normal visual fields (Humphrey Field Analyzer 24-2 full threshold program. In our study, a bundle was defined as ‘split’ when there is localized defect not resembling a wedge defect in the RNFL deviation map with a symmetrically divided RNFL appearance on the RNFL thickness map. The classification was performed by two independent observers who used an identical set of reference examples to standardize the classification. Results: Inter-observer consensus was reached in all cases. Bilateral superior split bundles were seen in 19 cases (5.29% and unilateral superior split was observed in 15 cases (4.16%. In 325 cases (90.52% there was no split bundle. Conclusion: Split nerve fiber layer bundles, in contrast to single nerve fiber layer bundles, are not common findings in healthy eyes. In eyes with normal optic disc appearance, especially when a superior RNFL defect is observed in RNFL deviation map, the RNLF thickness map and graphs should also be examined for split nerve fiber layer bundles.

  8. Adaptive optics microscopy enhances image quality in deep layers of CLARITY processed brains of YFP-H mice

    Science.gov (United States)

    Reinig, Marc R.; Novack, Samuel W.; Tao, Xiaodong; Ermini, Florian; Bentolila, Laurent A.; Roberts, Dustin G.; MacKenzie-Graham, Allan; Godshalk, S. E.; Raven, M. A.; Kubby, Joel

    2016-03-01

    Optical sectioning of biological tissues has become the method of choice for three-dimensional histological analyses. This is particularly important in the brain were neurons can extend processes over large distances and often whole brain tracing of neuronal processes is desirable. To allow deeper optical penetration, which in fixed tissue is limited by scattering and refractive index mismatching, tissue-clearing procedures such as CLARITY have been developed. CLARITY processed brains have a nearly uniform refractive index and three-dimensional reconstructions at cellular resolution have been published. However, when imaging in deep layers at submicron resolution some limitations caused by residual refractive index mismatching become apparent, as the resulting wavefront aberrations distort the microscopic image. The wavefront can be corrected with adaptive optics. Here, we investigate the wavefront aberrations at different depths in CLARITY processed mouse brains and demonstrate the potential of adaptive optics to enable higher resolution and a better signal-to-noise ratio. Our adaptive optics system achieves high-speed measurement and correction of the wavefront with an open-loop control using a wave front sensor and a deformable mirror. Using adaptive optics enhanced microscopy, we demonstrate improved image quality wavefront, point spread function, and signal to noise in the cortex of YFP-H mice.

  9. Enhancement of magneto-optical Faraday effects and extraordinary optical transmission in a tri-layer structure with rectangular annular arrays.

    Science.gov (United States)

    Lei, Chengxin; Chen, Leyi; Tang, Zhixiong; Li, Daoyong; Cheng, Zhenzhi; Tang, Shaolong; Du, Youwei

    2016-02-15

    The properties of optics and magneto-optical Faraday effects in a metal-dielectric tri-layer structure with subwavelength rectangular annular arrays are investigated. It is noteworthy that we obtained the strongly enhanced Faraday rotation of the desired sign along with high transmittance by optimizing the parameters of the nanostructure in the visible spectral ranges. In this system, we obtained two extraordinary optical transmission (EOT) resonant peaks with enhanced Faraday rotations, whose signs are opposite, which may provide the possibility of designing multi-channel magneto-optical devices. Study results show that the maximum of the figure of merit (FOM) of the structure can be obtained between two EOT resonant peaks accompanied by an enhanced Faraday rotation. The positions of the maximum value of the FOM and resonant peaks of transmission along with a large Faraday rotation can be tailored by simply adjusting the geometric parameters of our models. These research findings are of great importance for future applications of magneto-optical devices.

  10. Optical properties of pure and Ce{sup 3+} doped gadolinium gallium garnet crystals and epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Syvorotka, I.I. [Scientific Research Company “Carat”, 202 Stryjska Street, Lviv 79031 (Ukraine); Sugak, D. [Scientific Research Company “Carat”, 202 Stryjska Street, Lviv 79031 (Ukraine); Lviv Polytechnic National University, 12, S. Bandera Street, Lviv, 79013 (Ukraine); Wierzbicka, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Wittlin, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Cardinal Stefan Wyszyński University in Warsaw, ul. Dewajtis 5, 01-815 Warsaw (Poland); Przybylińska, H. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Barzowska, J. [Institute of Experimental Physics, Gdańsk University, ul. Wita Stwosza 57, Gdańsk (Poland); Barcz, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warsaw (Poland); Berkowski, M.; Domagała, J. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Mahlik, S.; Grinberg, M. [Institute of Experimental Physics, Gdańsk University, ul. Wita Stwosza 57, Gdańsk (Poland); Ma, Chong-Geng [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); and others

    2015-08-15

    Results of X-ray diffraction and low temperature optical absorption measurements of cerium doped gadolinium gallium garnet single crystals and epitaxial layers are reported. In the region of intra-configurational 4f–4f transitions the spectra of the bulk crystals exhibit the signatures of several different Ce{sup 3+} related centers. Apart from the dominant center, associated with Ce substituting gadolinium, at least three other centers are found, some of them attributed to the so-called antisite locations of rare-earth ions in the garnet host, i.e., in the Ga positions. X-ray diffraction data prove lattice expansion of bulk GGG crystals due to the presence of rare-earth antisites. The concentration of the additional Ce-related centers in epitaxial layers is much lower than in the bulk crystals. However, the Ce-doped layers incorporate a large amount of Pb from flux, which is the most probable source of nonradiative quenching of Ce luminescence, not observed in crystals grown by the Czochralski method. - Highlights: • Ce{sup 3+} multicenters found in Gadolinium Gallium Garnet crystals and epitaxial layers. • High quality epitaxial layers of pure and Ce-doped GGG were grown. • Luminescence quenching of Ce{sup 3+} by Pb ions from flux detected in GGG epitaxial layers. • X-ray diffraction allows measuring the amount of the rare-earth antisites in GGG.

  11. Study of interface layer effect in organic solar cells by electric-field-induced optical second-harmonic generation measurement

    Energy Technology Data Exchange (ETDEWEB)

    Taguchi, Dai; Sumiyoshi, Ryota; Chen, Xiangyu; Manaka, Takaaki; Iwamoto, Mitsumasa, E-mail: iwamoto@pe.titech.ac.jp

    2014-03-03

    By using electric-field-induced optical second-harmonic generation (EFISHG) measurement, we studied the effect of the use of bathocuproine (BCP) interface layer. The EFISHG measurements of indium–zinc–oxide (IZO)/C{sub 60}/Al diodes showed that the BCP layer inserted between C{sub 60} and Al formed an electrostatic field |E{sub i}| = 2.5 × 10{sup 4} V/cm in the C{sub 60} layer, pointing in a direction from the Al to the IZO. Accordingly, in the IZO/pentacene/C{sub 60}/BCP/Al organic solar cells (OSCs), holes (electrons) move to the IZO (Al) electrode, enhancing the short-circuit current. The EFISHG measurement is capable of directly probing internal fields in the layers used for OSCs, and is helpful for studying the contribution of the interface layer in OSCs. - Highlights: • Internal field in organic solar cells (OSCs) were directly probed. • Interface layer formed internal electric field, enhancing the OSC performance. • Maxwell–Wagner effect accounts for the internal electric field formation.

  12. Graph search: active appearance model based automated segmentation of retinal layers for optic nerve head centered OCT images

    Science.gov (United States)

    Gao, Enting; Shi, Fei; Zhu, Weifang; Jin, Chao; Sun, Min; Chen, Haoyu; Chen, Xinjian

    2017-02-01

    In this paper, a novel approach combining the active appearance model (AAM) and graph search is proposed to segment retinal layers for optic nerve head(ONH) centered optical coherence tomography(OCT) images. The method includes two parts: preprocessing and layer segmentation. During the preprocessing phase, images is first filtered for denoising, then the B-scans are flattened. During layer segmentation, the AAM is first used to obtain the coarse segmentation results. Then a multi-resolution GS-AAM algorithm is applied to further refine the results, in which AAM is efficiently integrated into the graph search segmentation process. The proposed method was tested on a dataset which contained113-D SD-OCT images, and compared to the manual tracings of two observers on all the volumetric scans. The overall mean border positioning error for layer segmentation was found to be 7.09 +/- 6.18μm for normal subjects. It was comparable to the results of traditional graph search method (8.03+/-10.47μm) and mean inter-observer variability (6.35+/-6.93μm).The preliminary results demonstrated the feasibility and efficiency of the proposed method.

  13. Optical properties of three-layer metal-organic nanoparticles with a molecular J-aggregate shell

    Energy Technology Data Exchange (ETDEWEB)

    Lebedev, V S [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Medvedev, A S [Moscow Institute of Physics and Technology (State University), Dolgoprudnyi, Moscow Region (Russian Federation)

    2013-11-30

    This paper examines the optical properties of two types of spherical three-component nanoparticles: (1) particles comprising a metallic core, outer organic dye J-aggregate shell and passive intermediate layer and (2) metallic nanoshells having an insulator or semiconductor core and coated with a molecular J-aggregate layer. The two types of nanoparticles are shown to differ significantly in the behaviour of electromagnetic fields and photoabsorption spectra. As a result of additional possibilities to control the magnitude and nature of the coupling between Frenkel excitons and localised surface plasmons in these systems, the spectral properties of the three-layer particles have radically new inherent features in comparison with earlier studied metal/J-aggregate bilayer particles. In the case of J-aggregate-coated metallic nanoshells, particular attention is paid to the strong plasmon – exciton coupling regime, which takes place when the plasmon resonance frequency of the nanoshell approaches the centre frequency of the J-band of the dye forming the outer layer of the particle. (optics of nanoparticles)

  14. Optical properties and defect levels in a surface layer found on CuInSe{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Abulfotuh, F.; Wangensteen, T.; Ahrenkiel, R.; Kazmerski, L.L. [National Renewable Energy Lab., Golden, CO (United States)

    1996-09-01

    In this paper the authors have used photoluminescence (PL) and wavelength scanning ellipsometry (WSE) to clarify the relationship among the electro-optical properties of copper indium diselenide (CIS) thin films, the type and origin of dominant defect states, and device performance. The PL study has revealed several shallow acceptor and donor levels dominating the semiconductor. PL emission from points at different depths from the surface of the CIS sample has been obtained by changing the angle of incidence of the excitation laser beam. The resulting data were used to determine the dominant defect states as a function of composition gradient at the surface of the chalcopyrite compound. The significance of this type of measurement is that it allowed the detection of a very thin layer with a larger bandgap (1.15--1.26 eV) than the CIS present on the surface of the CIS thin films. The presence of this layer has been correlated by several groups to improve the CIS cell performance. An important need that results from detecting this layer on the surface of the CIS semiconductor is the determination of its thickness and optical constants (n, k) as a function of wavelength. The thickness of this surface layer is about 500 {angstrom}.

  15. Optical properties and defect levels in a surface layer found on CuInSe{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Abulfotuh, F.; Wangensteen, T.; Ahrenkiel, R.; Kazmerski, L.L. [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    In this paper the authors have used photoluminescence (PL) and wavelength scanning ellipsometry (WSE) to clarify the relationship among the electro-optical properties of copper indium diselenide (CIS) thin films, the type and origin of dominant defect states, and device performance. The PL study has revealed several shallow acceptor and donor levels dominating the semiconductor. PL emission from points at different depths from the surface of the CIS sample has been obtained by changing the angle of incidence of the excitation laser beam. The resulting data were used to determine the dominant defect states as a function of composition gradient at the surface of the chalcopyrite compound. The significance of this type of measurement is that it allowed the detection of a very thin layer with a larger bandgap (1.15-1.26 eV) than the CIS present on the surface of the CIS thin films. The presence of this layer has been correlated by several groups to improvement of the CIS cell performance. An important need that results from detecting this layer on the surface of the CIS semiconductor is the determination of its thickness and optical constants (n, k) as a function of wavelength. The thickness of this surface layer is about 500 {Angstrom}.

  16. Room-Temperature Optical Tunability and Inhomogeneous Broadening in 2D-Layered Organic-Inorganic Perovskite Pseudobinary Alloys.

    Science.gov (United States)

    Lanty, Gaëtan; Jemli, Khaoula; Wei, Yi; Leymarie, Joël; Even, Jacky; Lauret, Jean-Sébastien; Deleporte, Emmanuelle

    2014-11-20

    We focus here our attention on a particular family of 2D-layered and 3D hybrid perovskite molecular crystals, the mixed perovskites (C6H5-C2H4-NH3)2PbZ4(1-x)Y4x and (CH3-NH3)PbZ3(1-x)Y3x, where Z and Y are halogen ions such as I, Br, and Cl. Studying experimentally the disorder-induced effects on the optical properties of the 2D mixed layered materials, we demonstrate that they can be considered as pseudobinary alloys, exactly like Ga1-xAlxAs, Cd1-xHgxTe inorganic semiconductors, or previously reported 3D mixed hybrid perovskite compounds. 2D-layered and 3D hybrid perovskites afford similar continuous optical tunability at room temperature. Our theoretical analysis allows one to describe the influence of alloying on the excitonic properties of 2D-layered perovskite molecular crystals. This model is further refined by considering different Bohr radii for pure compounds. This study confirms that despite a large binding energy of several 100 meV, the 2D excitons present a Wannier character rather than a Frenkel character. The small inhomogeneous broadening previously reported in 3D hybrid compounds at low temperature is similarly consistent with the Wannier character of free excitons.

  17. A Method for Quantification of Penetration of Nanoparticles through Skin Layers Using Near-Infrared Optical Imaging

    Directory of Open Access Journals (Sweden)

    Melinda Stees

    2015-07-01

    Full Text Available Our study presents a new method for tracking nanoparticle penetration through different layers of the skin using near-infrared dye-loaded nanoparticles (hydrodynamic diameter = 156 nm and optical imaging. The dye-loaded nanoparticles were mixed in a topical skin cream, applied to human cadaver skin and incubated either for three or 24 h post-application, skin tissue was clipped between glass slides prior to imaging for signal intensity across the skin thickness using an optical imaging system. The data show that nanoparticles penetrate through all the layers of the skin but there is almost an exponential decay in the signal intensity from epidermis to dermis. Depending upon the incubation time, about 55%–59% of the total signal was seen in the epidermis and the remaining through dermis and hypodermis. The advantage of the method is that it allows quantitative analysis of the extent of penetration of nanoparticles through different layers of the skin without interference of any background signal from skin tissue, and without requiring extensive tissue processing. Our method could potentially be used to study the effect of nanoparticle properties and/or the use of different formulation additives on penetration of nanoparticles through different skin layers.

  18. Modified Kubelka's layer model for calculation of infrared properties of low emissivity coatings with optically-rough surface

    Science.gov (United States)

    Jian, Shuai; Xie, Jianliang; Liu, Yunfeng; Liu, Wenle; Deng, Longjiang

    2017-06-01

    A Modified Kubelka's layer model is developed to accurately predict the infrared emissivity of low infrared emissivity coatings. The coatings are formed by mixing aluminum flakes with polymeric binders. According to distribution of the flake pigment, the Modified Kubelka's layer model is constructed with two sub-models: rough-surface and Kubelka's layer models. The facts of root-mean-square roughness (δ), root-mean-square surface slope (δ/a), thickness and volume concentration of flake pigment are systematically discussed. The results show that the flat distribution and high volume concentration of thin flake pigment result in low infrared emissivity. Our works offer the possibility of predicting the infrared optical properties of coatings.

  19. Measurement of retinal nerve fiber layer thickness in eyes with optic disc swelling by using scanning laser polarimetry and optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Hata M

    2013-12-01

    Full Text Available Masayuki Hata, Kazuaki Miyamoto, Akio Oishi, Yugo Kimura, Satoko Nakagawa, Takahiro Horii, Nagahisa Yoshimura Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan Background: The retinal nerve fiber layer thickness (RNFLT in patients with optic disc swelling of different etiologies was compared using scanning laser polarimetry (SLP and spectral-domain optical coherence tomography (OCT. Methods: Forty-seven patients with optic disc swelling participated in the cross-sectional study. Both GDx SLP (enhanced corneal compensation and Spectralis spectral-domain OCT measurements of RNFLT were made in 19 eyes with papilledema (PE, ten eyes with optic neuritis (ON, and 18 eyes with nonarteritic anterior ischemic optic neuropathy (NAION at the neuro-ophthalmology clinic at Kyoto University Hospital. Differences in SLP (SLP-RNFLT and OCT (OCT-RNFLT measurements among different etiologies were investigated. Results: No statistical differences in average OCT-RNFLT among PE, ON, and NAION patients were noted. Average SLP-RNFLT in NAION patients was smaller than in PE (P<0.01 or ON (P=0.02 patients. When RNFLT in each retinal quadrant was compared, no difference among etiologies was noted on OCT, but on SLP, the superior quadrant was thinner in NAION than in PE (P<0.001 or ON (P=0.001 patients. Compared with age-adjusted normative data of SLP-RNFLT, average SLP-RNFLT in PE (P<0.01 and ON (P<0.01 patients was greater. Superior SLP-RNFLT in NAION patients was smaller (P=0.026. The ratio of average SLP-RNFLT to average OCT-RNFLT was smaller in NAION than in PE (P=0.001 patients. Conclusion: In the setting of RNFL thickening, despite increased light retardance in PE and ON eyes, SLP revealed that NAION eyes have less retardance, possibly associated with ischemic axonal loss. Keywords: optic disc swelling, scanning laser polarimetry, optical coherence tomography

  20. Bending of the Flexible Spacer Chain of Gemini Surfactant Induced by Hydrophobic Interaction

    Institute of Scientific and Technical Information of China (English)

    YOU,Yi; JIANG,Rong; LING,Tingting; ZHAO,Jianxi

    2009-01-01

    In order to understand the special role of the flexible alkylene spacer of gemini surfactant in the self-assembly,three gemini surfactants,alkylene-α,ω-bis(didodecylmethylammonium bromide)that is designated as 2C12-s-2C12·2Br (s=3,6,8),were synthesized.When the spread films of 2C12-s-2C12·2Br on the surface of water were con-structed,they form the dense layer of the alkyl tails owing to four dodecyl chains per molecule.This induced the bending of the spacer chain toward the air-side at the s smaller than that of C12-s-C12·2Br adsorbed on the air/water interface owing to the enhanced hydrophobic interaction between the alkyl tails and the spacer chain, where C12-s-C12·2Br has only two alkyl tails per molecule. Conclusively.,the enhanced hydrophobic interaction between the alkyl tails and the spacer chain can effectively induce the bending of the latter toward the air-side.

  1. Mechanical Properties Of 3D-Structure Composites Based On Warp-Knitted Spacer Fabrics

    Directory of Open Access Journals (Sweden)

    Chen Si

    2015-06-01

    Full Text Available In this paper, the mechanical properties (compression and impact behaviours of three-dimension structure (3D-structure composites based on warp-knitted spacer fabrics have been thoroughly investigated. In order to discuss the effect of fabric structural parameters on the mechanical performance of composites, six different types of warp-knitted spacer fabrics having different structural parameters (such as outer layer structure, diameter of spacer yarn, spacer yarn inclination angle and thickness were involved for comparison study. The 3D-structure composites were fabricated based on a flexible polyurethane foam. The produced composites were characterised for compression and impact properties. The findings obtained indicate that the fabric structural parameters have strong influence on the compression and impact responses of 3D-structure composites. Additionally, the impact test carried out on the 3D-structure composites shows that the impact loads do not affect the integrity of composite structure. All the results reveal that the product exhibits promising mechanical performance and its service life can be sustained.

  2. Study of Electrical Conduction Mechanism of Organic Double-Layer Diode Using Electric Field Induced Optical Second Harmonic Generation Measurement.

    Science.gov (United States)

    Nishi, Shohei; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

    2016-04-01

    By using electric field induced optical second harmonic generation (EFISHG) and current voltage (I-V) measurements, we studied the electrical transport mechanism of organic double-layer diodes with a structure of Au/N, N'-di-[(1-naphthyl)-N, N'-diphenyl]-(1,1'-biphenyl)-4,4'-diamine (a-NPD)/poly(methyl methacrylate) (PMMA)/indium zinc oxide (IZO). Here the α-NPD is a carrier transport layer and the PMMA is an electrical insulating layer. The current level was very low, but the I-V characteristics showed a rectifying behavior. The EFISHG measurement selectively and directly probed the electric field across the α-NPD layer, and showed that the electric field across the a-NPD layer is completely relaxed owing to the charge accumulation at the a-NPD/PMMA interface in the region V > 0, whereas the carrier accumulation was not significant in the region V < 0. On the basis of these experimental results, we proposed a model of the rectification. Further, by coupling the I-V characteristics with the EFISHG measurement, the I-V characteristics of the diodes were well converted into the current-electric field (I-E) characteristics of the α-NPD layer and the PMMA layer. The I-E characteristics suggested the Schottky-type conduction governs the carrier transport. We conclude that the I-V measurement coupled with the EFISHG measurement is very useful to study carrier transport mechanism of the organic double-layer diodes.

  3. Analysis of macular and nerve fiber layer thickness in multiple sclerosis patients according to severity level and optic neuritis episodes.

    Science.gov (United States)

    Soler García, A; Padilla Parrado, F; Figueroa-Ortiz, L C; González Gómez, A; García-Ben, A; García-Ben, E; García-Campos, J M

    2016-01-01

    Quantitative assessment of macular and nerve fibre layer thickness in multiple sclerosis patients with regard to expanded disability status scale (EDSS) and presence or absence of previous optic neuritis episodes. We recruited 62 patients with multiple sclerosis (53 relapsing-remitting and 9 secondary progressive) and 12 disease-free controls. All patients underwent an ophthalmological examination, including quantitative analysis of the nerve fibre layer and macular thickness using optical coherence tomography. Patients were classified according to EDSS as A (lower than 1.5), B (between 1.5 and 3.5), and C (above 3.5). Mean nerve fibre layer thickness in control, A, B, and C groups was 103.35±12.62, 99.04±14.35, 93.59±15.41, and 87.36±18.75μm respectively, with statistically significant differences (P<.05). In patients with no history of optic neuritis, history of episodes in the last 3 to 6 months, or history longer than 6 months, mean nerve fibre layer thickness was 99.25±13.71, 93.92±13.30 and 80.07±15.91μm respectively; differences were significant (P<.05). Mean macular thickness in control, A, B, and C groups was 220.01±12.07, 217.78±20.02, 217.68±20.77, and 219.04±24.26μm respectively. Differences were not statistically significant. The mean retinal nerve fibre layer thickness in multiple sclerosis patients is related to the EDSS level. Patients with previous optic neuritis episodes have a thinner retinal nerve fibre layer than patients with no history of these episodes. Mean macular thickness is not correlated to EDSS level. Copyright © 2014 Sociedad Española de Neurología. Publicado por Elsevier España, S.L.U. All rights reserved.

  4. Effect of Spacer and the Enzyme-Linked Immunosorbent Assay

    Directory of Open Access Journals (Sweden)

    Manisha Sathe

    2016-09-01

    Full Text Available The effect of spacers and the enzyme-linked immunosorbent assay (ELISA formats on the functional parameters of assays such as lower detection limit, inhibitory concentration at 50 per cent (IC50, and specificity were studied. Enzyme conjugates having hydrophobic and hydrophilic spacers were prepared using O-isopropyl methylphosphonic acid (IMPA and horseradish peroxidase (HRP as an enzyme label. Comparison was made with reference to enzyme conjugate without any spacer. The present investigation revealed that the presence of a hydrophilic spacer in the enzyme conjugate significantly improves the sensitivity of assays. An enhanced IC50 value achieved was 0.01 μg mL−1 for free antigen detection by direct immunoassay using hydrophilic spacers and precoating of ELISA plates by secondary antibody. The use of a hydrophilic spacer might have helped in projecting the hapten in the aqueous phase, leading to enhanced antibody binding signal and improved sensitivity of the assay.

  5. Exchange coupling and magnetoresistance in CoFe/NiCu/CoFe spin valves near the Curie point of the spacer

    Science.gov (United States)

    Andersson, S.; Korenivski, V.

    2010-05-01

    Thermal control of exchange coupling between two strongly ferromagnetic layers through a weakly ferromagnetic Ni-Cu spacer and the associated magnetoresistance is investigated. The spacer, having a Curie point slightly above room temperature, can be cycled between its paramagnetic and ferromagnetic states by varying the temperature externally or using joule heating. It is shown that the giant magnetoresistance vanishes due to a strong reduction in the mean free path in the spacer at above ˜30% Ni concentration—before the onset of ferromagnetism. Finally, a device is proposed which combines thermally controlled exchange coupling and large magnetoresistance by separating the switching and the readout elements.

  6. Optical Properties of Hybrid Inorganic/Organic Thin Film Encapsulation Layers for Flexible Top-Emission Organic Light-Emitting Diodes.

    Science.gov (United States)

    An, Jae Seok; Jang, Ha Jun; Park, Cheol Young; Youn, Hongseok; Lee, Jong Ho; Heo, Gi-Seok; Choi, Bum Ho; Lee, Choong Hun

    2015-10-01

    Inorganic/organic hybrid thin film encapsulation layers consist of a thin Al2O3 layer together with polymer material. We have investigated optical properties of thin film encapsulation layers for top-emission flexible organic light-emitting diodes. The transmittance of hybrid thin film encapsulation layers and the electroluminescent spectrum of organic light-emitting diodes that were passivated by hybrid organic/inorganic thin film encapsulation layers were also examined as a function of the thickness of inorganic Al203 and monomer layers. The number of interference peaks, their intensity, and their positions in the visible range can be controlled by varying the thickness of inorganic Al2O3 layer. On the other hand, changing the thickness of monomer layer had a negligible effect on the optical properties. We also verified that there is a trade-off between transparency in the visible range and the permeation of water vapor in hybrid thin film encapsulation layers. As the number of dyads decreased, optical transparency improved while the water vapor permeation barrier was degraded. Our study suggests that, in top-emission organic light-emitting diodes, the thickness of each thin film encapsulation layer, in particular that of the inorganic layer, and the number of dyads should be controlled for highly efficient top-emission flexible organic light-emitting diodes.

  7. ϒ-secretase and LARG mediate distinct RGMa activities to control appropriate layer targeting within the optic tectum.

    Science.gov (United States)

    Banerjee, P; Harada, H; Tassew, N G; Charish, J; Goldschneider, D; Wallace, V A; Sugita, S; Mehlen, P; Monnier, P P

    2016-03-01

    While a great deal of progress has been made in understanding the molecular mechanisms that regulate retino-tectal mapping, the determinants that target retinal projections to specific layers of the optic tectum remain elusive. Here we show that two independent RGMa-peptides, C- and N-RGMa, activate two distinct intracellular pathways to regulate axonal growth. C-RGMa utilizes a Leukemia-associated RhoGEF (LARG)/Rho/Rock pathway to inhibit axonal growth. N-RGMa on the other hand relies on ϒ-secretase cleavage of the intracellular portion of Neogenin to generate an intracellular domain (NeICD) that uses LIM-only protein 4 (LMO4) to block growth. In the developing tectum (E18), overexpression of C-RGMa and dominant-negative LARG (LARG-PDZ) induced overshoots in the superficial tectal layer but not in deeper tectal layers. In younger embryos (E12), C-RGMa and LARG-PDZ prevented ectopic projections toward deeper tectal layers, indicating that C-RGMa may act as a barrier to descending axons. In contrast both N-RGMa and NeICD overexpression resulted in aberrant axonal-paths, all of which suggests that it is a repulsive guidance molecule. Thus, two RGMa fragments activate distinct pathways resulting in different axonal responses. These data reveal how retinal projections are targeted to the appropriate layer in their target tissue.

  8. Modulation of porphyrin photoluminescence by nanoscale spacers on silicon substrates

    Science.gov (United States)

    Fang, Y. C.; Zhang, Y.; Gao, H. Y.; Chen, L. G.; Gao, B.; He, W. Z.; Meng, Q. S.; Zhang, C.; Dong, Z. C.

    2013-11-01

    We investigate photoluminescence (PL) properties of quasi-monolayered tetraphenyl porphyrin (TPP) molecules on silicon substrates modulated by three different nanoscale spacers: native oxide layer (NOL), hydrogen (H)-passivated layer, and Ag nanoparticle (AgNP) thin film, respectively. In comparison with the PL intensity from the TPP molecules on the NOL-covered silicon, the fluorescence intensity from the molecules on the AgNP-covered surface was greatly enhanced while that for the H-passivated surface was found dramatically suppressed. Time-resolved fluorescence spectra indicated shortened lifetimes for TPP molecules in both cases, but the decay kinetics is believed to be different. The suppressed emission for the H-passivated sample was attributed to the weaker decoupling effect of the monolayer of hydrogen atoms as compared to the NOL, leading to increased nonradiative decay rate; whereas the enhanced fluorescence with shortened lifetime for the AgNP-covered sample is attributed not only to the resonant excitation by local surface plasmons, but also to the increased radiative decay rate originating from the emission enhancement in plasmonic "hot-spots".

  9. Material and optical properties of low-temperature NH3-free PECVD SiN x layers for photonic applications

    Science.gov (United States)

    Domínguez Bucio, Thalía; Khokhar, Ali Z.; Lacava, Cosimo; Stankovic, Stevan; Mashanovich, Goran Z.; Petropoulos, Periklis; Gardes, Frederic Y.

    2017-01-01

    SiN x layers intended for photonic applications are typically fabricated using LPCVD and PECVD. These techniques rely on high-temperature processing (>400 °C) to obtain low propagation losses. An alternative version of PECVD SiN x layers deposited at temperatures below 400 °C with a recipe that does not use ammonia (NH3-free PECVD) was previously demonstrated to be a good option to fabricate strip waveguides with propagation losses   <3 dB cm-1. We have conducted a systematic investigation of the influence of the deposition parameters on the material and optical properties of NH3-free PECVD SiN x layers fabricated at 350 °C using a design of experiments methodology. In particular, this paper discusses the effect of the SiH4 flow, RF power, chamber pressure and substrate on the structure, uniformity, roughness, deposition rate, refractive index, chemical composition, bond structure and H content of NH3-free PECVD SiN x layers. The results show that the properties and the propagation losses of the studied SiN x layers depend entirely on their compositional N/Si ratio, which is in fact the only parameter that can be directly tuned using the deposition parameters along with the film uniformity and deposition rate. These observations provide the means to optimise the propagation losses of the layers for photonic applications through the deposition parameters. In fact, we have been able to fabricate SiN x waveguides with H content  <20%, good uniformity and propagation losses of 1.5 dB cm-1 at 1550 nm and   <1 dB cm-1 at 1310 nm. As a result, this study can potentially help optimise the properties of the studied SiN x layers for different applications.

  10. Findings of Optical Coherence Tomography of Retinal Nerve Fiber Layer in Two Common Types of Multiple Sclerosis.

    Science.gov (United States)

    Yousefipour, Gholamali; Hashemzahi, Zabihollah; Yasemi, Masood; Jahani, Pegah

    2016-06-01

    Multiple sclerosis (MS) is the most prevalent disease caused by the inflammatory demyelinating process that causes progressive nervous system degeneration over the time. Optical Coherence Tomography (OCT) is a non-invasive optical imaging technology, which can measure the thickness of retinal nerve fiber layer as well as the diameter of the macula. The purpose of the study is evaluation OCT findings in two common types of multiple sclerosis. For doing the cross-sectional study, 63 patients with two prevalent types of multiple sclerosis (35 patients with Relapse Remitting Multiple Sclerosis (RRMS) and 28 patients with Secondary Progressive Multiple Sclerosis (SPMS) were evaluated for 6 months. Exclusion criteria of the study were a history of optic neuritis, suffering from diabetes mellitus, hypertension, ocular disease, and the presence of other neurologic degenerative diseases. Then, the thickness of retinal nerve fiber layer (RNFL), as well as thickness and volume of the macula, were measured in the patients using OCT technology. The disability rate of patients was evaluated according to Expanded Disability Status Scale (EDSS). Finally, data was analyzed by means of SPSS software. Overall, 35 patients with RRMS (with mean age of 32.37+10.01, average disease period of 3.81+3.42 and mean EDSS of 1.84+0.45) and 28 patients with SPMS (with mean age of 39.21+9.33, average disease period of 11.32+5.87 and mean EDSS of 5.12+1.46) were assessed and compared in terms of retinal nerve fiber layer and size and thickness of macula. In all of these sections, the thicknesses were smaller in SPMS patients than patients with RRMS. But, there was a significant difference in total thickness (81.82µm versus 96.03µm with P=0.04) and thickness of temporal sector (54.5 µm versus 69.34 µm with P=0.04) of retinal nerve fiber layer and macular size at the superior sector of external ring (1.48 mm³ versus 1.58 mm³ with P=0.03), and nasal sector of external ring surrounding macula (1

  11. Findings of Optical Coherence Tomography of Retinal Nerve Fiber Layer in Two Common Types of Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    Gholamali Yousefipour

    2016-06-01

    Full Text Available Multiple sclerosis (MS is the most prevalent disease caused by the inflammatory demyelinating process that causes progressive nervous system degeneration over the time. Optical Coherence Tomography (OCT is a non-invasive optical imaging technology, which can measure the thickness of retinal nerve fiber layer as well as the diameter of the macula. The purpose of the study is evaluation OCT findings in two common types of multiple sclerosis. For doing the cross-sectional study, 63 patients with two prevalent types of multiple sclerosis (35 patients with Relapse Remitting Multiple Sclerosis (RRMS and 28 patients with Secondary Progressive Multiple Sclerosis (SPMS were evaluated for 6 months. Exclusion criteria of the study were a history of optic neuritis, suffering from diabetes mellitus, hypertension, ocular disease, and the presence of other neurologic degenerative diseases. Then, the thickness of retinal nerve fiber layer (RNFL, as well as thickness and volume of the macula, were measured in the patients using OCT technology. The disability rate of patients was evaluated according to Expanded Disability Status Scale (EDSS. Finally, data was analyzed by means of SPSS software. Overall, 35 patients with RRMS (with mean age of 32.37+10.01, average disease period of 3.81+3.42 and mean EDSS of 1.84+0.45 and 28 patients with SPMS (with mean age of 39.21+9.33, average disease period of 11.32+5.87 and mean EDSS of 5.12+1.46 were assessed and compared in terms of retinal nerve fiber layer and size and thickness of macula. In all of these sections, the thicknesses were smaller in SPMS patients than patients with RRMS. But, there was a significant difference in total thickness (81.82µm versus 96.03µm with P=0.04 and thickness of temporal sector (54.5 µm versus 69.34 µm with P=0.04 of retinal nerve fiber layer and macular size at the superior sector of external ring (1.48 mm³ versus 1.58 mm³ with P=0.03, and nasal sector of external ring surrounding

  12. Optical characterization of non-annealed CdS:O films for window layers in solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Kitano, Atsushi; Shim, YongGu [Graduate School of Engineering, Osaka Prefecture University, Sakai 599-8531 (Japan); Wakita, Kazuki [Faculty of Engineering, Chiba Institute of Technology, Narashino, Chiba 275-0016 (Japan); Khalilova, Khuraman; Mamedov, Nazim; Bayramov, Ayaz; Huseynov, Emil; Hasanov, Ilham [Institute of Physics, Azerbaijan National Academy of Sciences, Baku 1143 (Azerbaijan)

    2013-08-15

    Optical constants of CdS:O window layers for solar cells were studied as a function of the oxygen content. The CdS:O thin films were deposited on glass substrates in the presence of oxygen at 0, 2, 3 and 5% values of O/Ar ratio by rf magnetron sputtering. Ellipsometric measurements on CdS:O thin films were carried out over 0.75-6.0 eV photon energies at room temperature. Optical constants were determined by using a the best-fit dispersion model. Broadening of spectral features of the obtained optical constants is found to increase with increasing O/Ar ratio. Besides, the CdS:O films grown at 100 C as compared to those grown at 200 C exhibit increased spectral broadening. In fact, almost complete smearing of band gap spectral feature is observed for CdS:O films deposited at 5% value of O/Ar ratio, resulting in appreciable transparency of the films in a spectral range above the energy gap of CdS. This, in turn, leads to an increased carrier collection in the UV spectral range and allows to considering CdS:O film as a candidate for improved window-layer material for solar cell application. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. CHIRAL CONJUGATED OLIGOMER BASED ON 1,1'-BINOL WITH 3,3'-ACETYLENE-PHENYLENE-ACETYLENE SPACER

    Institute of Scientific and Technical Information of China (English)

    Tian-jun Liu; Ke-shen Zhang; Yong-jun Chen; Dong Wang; Chao-jun Li

    2001-01-01

    The 1,1'-binaphthol based oligomers 3 and 7 with 3,3'-acetylene-phenylene-acetylene spacer were prepared from BINOL 1. The high optical rotation value and CD spectra demonstrated the main chain chirality of the oligomer molecule. The UV-VIS and fluorescent spectra evidence the characteristics of conjugated structure. In comparison with oligomer 2 bearing 3,3'-acetylene spacer, the oligomers 3 and 7 have longer efficient conjugation segment, and their fluorescent quantum yields (φ) increased (0.60-0.65 versus 0.14). Extending the effective conjugation segment would improve the photophysical properties of chiral conjugated polymers.``

  14. Influence of Drying Temperature on the Structural, Optical, and Electrical Properties of Layer-by-Layer ZnO Nanoparticles Seeded Catalyst

    Directory of Open Access Journals (Sweden)

    S. S. Shariffudin

    2012-01-01

    Full Text Available Layer-by-layer zinc oxide (ZnO nanoparticles have been prepared using sol-gel spin coating technique. The films were dried at different temperature from 100°C to 300°C to study its effect to the surface morphology, optical and electrical properties of the films. Film dried at 200°C shows the highest (0 0 2 peak of X-ray diffraction pattern which is due to complete decomposition of zinc acetate and complete vaporization of the stabilizer and solvent. It was found that the grain size increased with the increased of drying temperature from 100 to 200°C, but for films dried at above 200°C, the grain size decreased. Photoluminescence measurements show a sharp ultraviolet emission centred at 380 nm and a very low intensity visible emission. Blue visible emission was detected for sample dried at temperature below 200°C, while for films dried above 250°C, the visible emission is red shifted. The films were transparent in the visible range from 400 to 800 nm with average transmittance of above 85%. Linear I-V characteristics were shown confirming the ohmic behaviour of the gold contacts to the films. A minimum resistivity was given by 5.08 Ω · cm for the film dried at 300°C.

  15. Measurement of retinal nerve fiber layer thickness in eyes with optic disc swelling by using scanning laser polarimetry and optical coherence tomography.

    Science.gov (United States)

    Hata, Masayuki; Miyamoto, Kazuaki; Oishi, Akio; Kimura, Yugo; Nakagawa, Satoko; Horii, Takahiro; Yoshimura, Nagahisa

    2014-01-01

    The retinal nerve fiber layer thickness (RNFLT) in patients with optic disc swelling of different etiologies was compared using scanning laser polarimetry (SLP) and spectral-domain optical coherence tomography (OCT). Forty-seven patients with optic disc swelling participated in the cross-sectional study. Both GDx SLP (enhanced corneal compensation) and Spectralis spectral-domain OCT measurements of RNFLT were made in 19 eyes with papilledema (PE), ten eyes with optic neuritis (ON), and 18 eyes with nonarteritic anterior ischemic optic neuropathy (NAION) at the neuro-ophthalmology clinic at Kyoto University Hospital. Differences in SLP (SLP-RNFLT) and OCT (OCT-RNFLT) measurements among different etiologies were investigated. No statistical differences in average OCT-RNFLT among PE, ON, and NAION patients were noted. Average SLP-RNFLT in NAION patients was smaller than in PE (P<0.01) or ON (P=0.02) patients. When RNFLT in each retinal quadrant was compared, no difference among etiologies was noted on OCT, but on SLP, the superior quadrant was thinner in NAION than in PE (P<0.001) or ON (P=0.001) patients. Compared with age-adjusted normative data of SLP-RNFLT, average SLP-RNFLT in PE (P<0.01) and ON (P<0.01) patients was greater. Superior SLP-RNFLT in NAION patients was smaller (P=0.026). The ratio of average SLP-RNFLT to average OCT-RNFLT was smaller in NAION than in PE (P=0.001) patients. In the setting of RNFL thickening, despite increased light retardance in PE and ON eyes, SLP revealed that NAION eyes have less retardance, possibly associated with ischemic axonal loss.

  16. Comparative study of the retinal nerve fibre layer thickness performed with optical coherence tomography and GDx scanning laser polarimetry in patients with primary open-angle glaucoma.

    Science.gov (United States)

    Wasyluk, Jaromir T; Jankowska-Lech, Irmina; Terelak-Borys, Barbara; Grabska-Liberek, Iwona

    2012-03-01

    We compared the parameters of retinal nerve fibre layer in patients with advanced glaucoma with the use of different OCT (Optical Coherence Tomograph) devices in relation to analogical measurements performed with GDx VCC (Nerve Fiber Analyzer with Variable Corneal Compensation) scanning laser polarimetry. Study subjects had advanced primary open-angle glaucoma, previously treated conservatively, diagnosed and confirmed by additional examinations (visual field, ophthalmoscopy of optic nerve, gonioscopy), A total of 10 patients were enrolled (9 women and 1 man), aged 18-70 years of age. Nineteen eyes with advanced glaucomatous neuropathy were examined. 1) Performing a threshold perimetry Octopus, G2 strategy and ophthalmoscopy of optic nerve to confirm the presence of advanced primary open-angle glaucoma; 2) performing a GDx VCC scanning laser polarimetry of retinal nerve fibre layer; 3) measuring the retinal nerve fibre layer thickness with 3 different optical coherence tomographs. The parameters of the retinal nerve fibre layer thickness are highly correlated between the GDx and OCT Stratus and 3D OCT-1000 devices in mean retinal nerve fibre layer thickness, retinal nerve fibre layer thickness in the upper sector, and correlation of NFI (GDx) with mean retinal nerve fibre layer thickness in OCT examinations. Absolute values of the retinal nerve fibre layer thickness (measured in µm) differ significantly between GDx and all OCT devices. Examination with OCT devices is a sensitive diagnostic method of glaucoma, with good correlation with the results of GDx scanning laser polarimetry of the patients.

  17. Split ring resonators: the effect of titanium adhesion layers on the optical response

    Science.gov (United States)

    Lahiri, Basudev; Dylewicz, Rafal; McMeekin, Scott G.; Khokhar, Ali Z.; De La Rue, Richard M.; Johnson, Nigel P.

    2010-04-01

    The response of metallic split ring resonators (SRRs) scales linearly with their dimensions. At higher frequencies, metals do not behave like perfect conductors but display properties characterized by the Drude model. In this paper we compare the responses of nano-sized gold-based SRRs at near infra-red wavelengths. Deposition of gold SRRs onto dielectric substrates typically involves the use of an additional adhesion layer. We have employed the commonly used metal titanium (Ti) to provide an adhesive layer for sticking gold SRRs to silicon substrates - and have investigated the effect of this adhesion layer on the overall response of these gold SRRs. Both experimental and theoretical results show that even a two nm thick titanium adhesion layer can shift the overall SRR response by 20 nm.

  18. Optically sensitive devices based on Pt nano particles fabricated by atomic layer deposition and embedded in a dielectric stack

    Energy Technology Data Exchange (ETDEWEB)

    Mikhelashvili, V.; Padmanabhan, R.; Eisenstein, G. [Electrical Engineering Department, Technion, Haifa 3200 (Israel); Russell Berrie Nanotechnology Institute, Technion, Haifa 3200 (Israel); Meyler, B.; Yofis, S.; Weindling, S.; Salzman, J. [Electrical Engineering Department, Technion, Haifa 3200 (Israel); Atiya, G.; Cohen-Hyams, Z.; Kaplan, W. D. [Department of Material Science and Engineering, Technion, Haifa 3200 (Israel); Russell Berrie Nanotechnology Institute, Technion, Haifa 3200 (Israel); Ankonina, G. [Russell Berrie Nanotechnology Institute, Technion, Haifa 3200 (Israel); Photovoltaic Laboratory, Technion, Haifa 3200 (Israel)

    2015-10-07

    We report a series of metal insulator semiconductor devices with embedded Pt nano particles (NPs) fabricated using a low temperature atomic layer deposition process. Optically sensitive nonvolatile memory cells as well as optical sensors: (i) varactors, whose capacitance-voltage characteristics, nonlinearity, and peak capacitance are strongly dependent on illumination intensity; (ii) highly linear photo detectors whose responsivity is enhanced due to the Pt NPs. Both single devices and back to back pairs of diodes were used. The different configurations enable a variety of functionalities with many potential applications in biomedical sensing, environmental surveying, simple imagers for consumer electronics and military uses. The simplicity and planar configuration of the proposed devices makes them suitable for standard CMOS fabrication technology.

  19. 无源光网络(PON)光层监测技术%PON optical layer monitoring techniques

    Institute of Scientific and Technical Information of China (English)

    傅珂; 钱渊; 张锐

    2012-01-01

    This paper discussed PON networks optical layer test using OTDR-based methods, analyse their shortcomings, unavailable characters and modified OTDR-based techniques. For above concerns, reseached the Non-OTDR based monitor approaches, focus on Brillouin frequency shifted and optical coded reflectome-tre methods, reviewed their technical chracters and application prospectives.%讨论了基于OTDR的PON网络测试,分析其局限和改进技术.针对OTDR-based技术的缺陷,研究了非OTDR监测技术,重点是布里渊频率移位和基于光编码的反射测试等,讨论了相关技术的特点和应用前景.

  20. Optically sensitive devices based on Pt nano particles fabricated by atomic layer deposition and embedded in a dielectric stack

    Science.gov (United States)

    Mikhelashvili, V.; Padmanabhan, R.; Meyler, B.; Yofis, S.; Atiya, G.; Cohen-Hyams, Z.; Weindling, S.; Ankonina, G.; Salzman, J.; Kaplan, W. D.; Eisenstein, G.

    2015-10-01

    We report a series of metal insulator semiconductor devices with embedded Pt nano particles (NPs) fabricated using a low temperature atomic layer deposition process. Optically sensitive nonvolatile memory cells as well as optical sensors: (i) varactors, whose capacitance-voltage characteristics, nonlinearity, and peak capacitance are strongly dependent on illumination intensity; (ii) highly linear photo detectors whose responsivity is enhanced due to the Pt NPs. Both single devices and back to back pairs of diodes were used. The different configurations enable a variety of functionalities with many potential applications in biomedical sensing, environmental surveying, simple imagers for consumer electronics and military uses. The simplicity and planar configuration of the proposed devices makes them suitable for standard CMOS fabrication technology.

  1. Molecular recordings by directed CRISPR spacer acquisition.

    Science.gov (United States)

    Shipman, Seth L; Nivala, Jeff; Macklis, Jeffrey D; Church, George M

    2016-07-29

    The ability to write a stable record of identified molecular events into a specific genomic locus would enable the examination of long cellular histories and have many applications, ranging from developmental biology to synthetic devices. We show that the type I-E CRISPR (clustered regularly interspaced short palindromic repeats)-Cas system of Escherichia coli can mediate acquisition of defined pieces of synthetic DNA. We harnessed this feature to generate records of specific DNA sequences into a population of bacterial genomes. We then applied directed evolution so as to alter the recognition of a protospacer adjacent motif by the Cas1-Cas2 complex, which enabled recording in two modes simultaneously. We used this system to reveal aspects of spacer acquisition, fundamental to the CRISPR-Cas adaptation process. These results lay the foundations of a multimodal intracellular recording device.

  2. Damage of multilayer optics with varying capping layers induced by focused extreme ultraviolet beam

    Energy Technology Data Exchange (ETDEWEB)

    Jody Corso, Alain; Nicolosi, Piergiorgio; Nardello, Marco; Guglielmina Pelizzo, Maria [National Research Council of Italy, Institute for Photonics and Nanotechnology, via Trasea 7, 35131 Padova (Italy); Department of Information Engineering, University of Padova, via Gradenigo 6/B, 35131 Padova (Italy); Zuppella, Paola [National Research Council of Italy, Institute for Photonics and Nanotechnology, via Trasea 7, 35131 Padova (Italy); Barkusky, Frank [Laser-Laboratorium Goettingen e.V, Goettingen (Germany); KLA-Tencor, 5 Technology Dr., Milpitas, California 95035 (United States); Mann, Klaus; Mueller, Matthias [Laser-Laboratorium Goettingen e.V, Goettingen (Germany)

    2013-05-28

    Extreme ultraviolet Mo/Si multilayers protected by capping layers of different materials were exposed to 13.5 nm plasma source radiation generated with a table-top laser to study the irradiation damage mechanism. Morphology of single-shot damaged areas has been analyzed by means of atomic force microscopy. Threshold fluences were evaluated for each type of sample in order to determine the capability of the capping layer to protect the structure underneath.

  3. Retinal nerve fibre layer thinning in patients with clinically isolated optic neuritis and early treatment with interferon-beta.

    Directory of Open Access Journals (Sweden)

    Kurt-Wolfram Sühs

    Full Text Available BACKGROUND: Optic neuritis is associated with neurodegeneration leading to chronic impairment of visual functions. OBJECTIVE: This study investigated whether early treatment with interferon beta (IFN-β slows retinal nerve fibre layer (RNFL thinning in clinically isolated optic neuritis. METHODS: Twenty patients with optic neuritis and visual acuity decreased to ≤0.5 (decimal system were included into this prospective, open-label, parallel group 4-month observation. After methylprednisolone pulse therapy, 10 patients received IFN-β from week 2 onwards. This group was compared to 10 patients free of any disease modifying treatment (DMT. The parameter of interest was change in RNFL thickness assessed at baseline and at weeks 4, 8, and 16. Changes in visual acuity, visual field, and visual evoked potentials (VEPs served as additional outcome parameters. RESULTS: RNFL thinning did not differ between the groups with a mean reduction of 9.80±2.80 µm in IFN-β-treated patients (±SD vs. 12.44±5.79 µm in patients who did not receive DMT (baseline non-affected eye minus affected eye at week 16; p = 0.67, t-test, 95% confidence interval: -15.77 to 10.48. Parameters of visual function did not show any differences between the groups either. CONCLUSIONS: In isolated optic neuritis, early IFN-β treatment did not influence RNFL thinning nor had it any effect on recovery of visual functions.

  4. Improving depth resolution of diffuse optical tomography with an exponential adjustment method based on maximum singular value of layered sensitivity

    Institute of Scientific and Technical Information of China (English)

    Haijing Niu; Ping Guo; Xiaodong Song; Tianzi Jiang

    2008-01-01

    The sensitivity of diffuse optical tomography (DOT) imaging exponentially decreases with the increase of photon penetration depth, which leads to a poor depth resolution for DOT. In this letter, an exponential adjustment method (EAM) based on maximum singular value of layered sensitivity is proposed. Optimal depth resolution can be achieved by compensating the reduced sensitivity in the deep medium. Simulations are performed using a semi-infinite model and the simulation results show that the EAM method can substantially improve the depth resolution of deeply embedded objects in the medium. Consequently, the image quality and the reconstruction accuracy for these objects have been largely improved.

  5. Vector soliton fiber laser passively mode locked by few layer black phosphorus-based optical saturable absorber.

    Science.gov (United States)

    Song, Yufeng; Chen, Si; Zhang, Qian; Li, Lei; Zhao, Luming; Zhang, Han; Tang, Dingyuan

    2016-11-14

    We report on the optical saturable absorption of few-layer black phosphorus nanoflakes and demonstrate its application for the generation of vector solitons in an erbium-doped fiber laser. By incorporating the black phosphorus nanoflakes-based saturable absorber (SA) into an all-fiber erbium-doped fiber laser cavity, we are able to obtain passive mode-locking operation with soliton pulses down to ~670 fs. The properties and dynamics of the as-generated vector solitons are experimentally investigated. Our results show that BP nanoflakes could be developed as an effective SA for ultrashort pulse fiber lasers, particularly for the generation of vector soliton pulses in fiber lasers.

  6. Optical properties of three-layer metal-organic nanoparticles with a molecular J-aggregate shell

    Science.gov (United States)

    Lebedev, V. S.; Medvedev, A. S.

    2013-11-01

    This paper examines the optical properties of two types of spherical three-component nanoparticles: (1) particles comprising a metallic core, outer organic dye J-aggregate shell and passive intermediate layer and (2) metallic nanoshells having an insulator or semiconductor core and coated with a molecular J-aggregate layer. The two types of nanoparticles are shown to differ significantly in the behaviour of electromagnetic fields and photoabsorption spectra. As a result of additional possibilities to control the magnitude and nature of the coupling between Frenkel excitons and localised surface plasmons in these systems, the spectral properties of the three-layer particles have radically new inherent features in comparison with earlier studied metal/J-aggregate bilayer particles. In the case of J-aggregate-coated metallic nanoshells, particular attention is paid to the strong plasmon - exciton coupling regime, which takes place when the plasmon resonance frequency of the nanoshell approaches the centre frequency of the J-band of the dye forming the outer layer of the particle.

  7. Pathfinder first light: alignment, calibration, and commissioning of the LINC-NIRVANA ground-layer adaptive optics subsystem

    CERN Document Server

    Kopon, Derek; Arcidiacono, Carmelo; Herbst, Tom; Viotto, Valentina; Farinato, Jacopo; Bergomi, Maria; Ragazzoni, Roberto; Marafatto, Luca; Baumeister, Harald; Bertram, Thomas; Berwein, Jürgen; Briegel, Florian; Hofferbert, Ralph; Kittmann, Frank; Kürster, Martin; Mohr, Lars; Radhakrishnan, Kalyan

    2014-01-01

    We present descriptions of the alignment and calibration tests of the Pathfinder, which achieved first light during our 2013 commissioning campaign at the LBT. The full LINC-NIRVANA instrument is a Fizeau interferometric imager with fringe tracking and 2-layer natural guide star multi-conjugate adaptive optics (MCAO) systems on each eye of the LBT. The MCAO correction for each side is achieved using a ground layer wavefront sensor that drives the LBT adaptive secondary mirror and a mid-high layer wavefront sensor that drives a Xinetics 349 actuator DM conjugated to an altitude of 7.1 km. When the LINC-NIRVANA MCAO system is commissioned, it will be one of only two such systems on an 8-meter telescope and the only such system in the northern hemisphere. In order to mitigate risk, we take a modular approach to commissioning by decoupling and testing the LINC-NIRVANA subsystems individually. The Pathfinder is the ground-layer wavefront sensor for the DX eye of the LBT. It uses 12 pyramid wavefront sensors to opt...

  8. Investigation the optical and radiative properties of aerosol vertical profile of boundary layer by lidar and ground based measurements

    Science.gov (United States)

    Chen, W.; Chou, C.; Lin, P.; Wang, S.

    2011-12-01

    The planetary boundary layer is the air layer near the ground directly affected by diurnal heat, moisture, aerosol, and cloud transfer to or from the surface. In the daytime solar radiation heats the surface, initiating thermal instability or convection. Whereas, the scattering and absorption of aerosols or clouds might decrease the surface radiation or heat atmosphere which induce feedbacks such as the enhanced stratification and change in relative humidity in the boundary layer. This study is aimed to understand the possible radiative effect of aerosols basing on ground based aerosol measurements and lidar installed in National Taiwan University in Taipei. The optical and radiative properties of aerosols are dominated by aerosol composition, particle size, hygroscopicity property, and shape. In this study, aerosol instruments including integrating nephelometer, open air nephelometer, aethalometer are applied to investigate the relationship between aerosol hygroscopicity properties and aerosol types. The aerosol hygroscopicity properties are further applied to investigate the effect of relative humidity on aerosol vertical profiles measured by a dual-wavelength and depolarization lidar. The possible radiative effect of aerosols are approached by vertical atmospheric extinction profiles measured by lidar. Calculated atmospheric and aerosol heating effects was compared with vertical meteorological parameters measured by radiosonde. The result shows light-absorbing aerosol has the potential to affect the stability of planetary boundary layer.

  9. Structural, optical and electrical study of undoped GaN layers obtained by metalorganic chemical vapor deposition on sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Rangel-Kuoppa, Victor-Tapio, E-mail: tapio.rangel@gmail.co [Institute of Semiconductor and Solid State Physics, Johannes Kepler Universitaet, A-4040 Linz (Austria); Aguilar, Cesia Guarneros [Seccion de Electronica del Estado Solido, Departamento de Ingenieria Electrica, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, A.P. 14740, C.P. 07360, Mexico, Distrito Federal (Mexico); Sanchez-Resendiz, Victor, E-mail: victors@sees.cinvestav.m [Seccion de Electronica del Estado Solido, Departamento de Ingenieria Electrica, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, A.P. 14740, C.P. 07360, Mexico, Distrito Federal (Mexico)

    2011-01-31

    We investigate optical, structural and electrical properties of undoped GaN grown on sapphire. The layers were prepared in a horizontal reactor by low pressure metal organic chemical vapor deposition at temperatures of 900 {sup o}C and 950 {sup o}C on a low temperature grown (520 {sup o}C) GaN buffer layer on (0001) sapphire substrate. The growth pressure was kept at 10,132 Pa. The photoluminescence study of such layers revealed a band-to-band emission around 366 nm and a yellow band around 550 nm. The yellow band intensity decreases with increasing deposition temperature. X-ray diffraction, atomic force microscopy and scanning electron microscopy studies show the formation of hexagonal GaN layers with a thickness of around 1 {mu}m. The electrical study was performed using temperature dependent Hall measurements between 35 and 373 K. Two activation energies are obtained from the temperature dependent conductivity, one smaller than 1 meV and the other one around 20 meV. For the samples grown at 900 {sup o}C the mobilities are constant around 10 and 20 cm{sup 2} V{sup -1} s{sup -1}, while for the sample grown at 950 {sup o}C the mobility shows a thermally activated behavior with an activation energy of 2.15 meV.

  10. Stress Analysis of Single Spacer Grid Support considering Fuel Rod

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Y. G.; Jung, D. H.; Kim, J. H. [Chungnam National University, Daejeon (Korea, Republic of); Park, J. K.; Jeon, K. L. [Korea Nuclear Fuel, Daejeon (Korea, Republic of)

    2010-10-15

    Pressurized water reactor (PWR) nuclear fuel assembly is mainly composed of a top-end piece, a bottom-end piece, lots of fuel rods, and several spacer grids. Among them, the main function of spacer grid is protecting fuel rods from Fluid Induced Vibration (FIV). The cross section of spacer grid assembled by laser welding in upper and lower point. When the fuel rod inserted in spacer gird, spring and dimple and around of welded area got a stresses. The main hypothesis of this analysis is the boundary area of HAZ and base metal can get a lot of damage than other area by FIV. So, design factors of spacer grid mainly considered to preventing the fatigue failure in HAZ and spring and dimple of spacer grid. From previous researching, the environment in reactor verified. Pressure and temperature of light water observed 15MPa and 320 .deg. C, and vibration of the fuel rod observed within 0 {approx} 50Hz. In this study, mechanical properties of zirconium alloy that extracted from the test and the spacer grid model which used in the PWR were applied in stress analyzing. General-purpose finite element analysis program was used ANSYS Workbench 12.0.1 version. 3-D CAD program CATIA was used to create spacer grid model

  11. Orthognathic model surgery with LEGO key-spacer.

    Science.gov (United States)

    Tsang, Alfred Chee-Ching; Lee, Alfred Siu Hong; Li, Wai Keung

    2013-12-01

    A new technique of model surgery using LEGO plates as key-spacers is described. This technique requires less time to set up compared with the conventional plaster model method. It also retains the preoperative setup with the same set of models. Movement of the segments can be measured and examined in detail with LEGO key-spacers.

  12. SYNTHESIS OF NOVEL LIQUID CRYSTALLINE POLY(METH)ACRYLATES CONTAINING SILOXANE SPACER AND TERPHENYLENE MESOGENIC UNIT

    Institute of Scientific and Technical Information of China (English)

    Zhi-qian Zang; Yu-fei Luo; Dong Zhang; Xin-hua Wan; Qi-feng Zhou

    2000-01-01

    Novel side-chain liquid-crystalline poly(meth)acrylates were synthesized using 1-(3-hydroxyl-propyl)-3-[(4"cyano-p-terphenyloxycarbonyl)alkyl]-1, 1,3,3-tetramethyldisiloxane as the key intermediate. The polymers used a disiloxane moiety as decoupling spacer with cyano-p-terphenyl as mesogenic unit. The products were characterized by NMR, GPC,DSC and polarizing optical microscopy. All the polymers with cyano-p-terphenyl mesogens formed a stable mesophase.However, if the mesogenic unit is replaced by cyano-p-biphenyl, the liquid crystalline character will be lost. The results also showed that the decoupling is incomplete even if a complex and very flexible decoupling spacer is deliberately incorporated to obtain the highest possible decoupling effect.

  13. Analysis of sound absorption of tuck spacer fabrics to reduce automotive noise

    Science.gov (United States)

    Dias, Tilak; Monaragala, Ravindra; Needham, Peter; Lay, Edward

    2007-08-01

    Textiles are widely used in the automotive industry to provide both comfort to the passengers and an aesthetic appearance to the automotive interior. They can also be used to reduce automotive interior noise, which can make automotive travel safer and more comfortable. Knitted fabrics are used widely in automotive upholstery; however, the sound absorbency of a single layer of a knitted fabric is inadequate for the reduction of automotive interior noise. This paper investigates the sound absorbency of a novel knitted spacer fabric, which can be used in automotive upholstery and has the potential for greater sound absorbency than a conventional plain knitted fabric and its derivatives. The spacer fabric is modelled as a porous sound absorber and its sound absorbency is studied with regard to its structural parameters.

  14. Enhanced spin-torque in double tunnel junctions using a nonmagnetic-metal spacer

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C. H.; Cheng, Y. H.; Ko, C. W.; Hsueh, W. J., E-mail: hsuehwj@ntu.edu.tw [Nanomagnetism Group, Department of Engineering Science and Ocean Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei 10660, Taiwan (China)

    2015-10-12

    This study proposes an enhancement in the spin-transfer torque of a magnetic tunnel junction (MTJ) designed with double-barrier layer structure using a nonmagnetic metal spacer, as a replacement for the ferromagnetic material, which is traditionally used in these double-barrier stacks. Our calculation results show that the spin-transfer torque and charge current density of the proposed double-barrier MTJ can be as much as two orders of magnitude larger than the traditional double-barrier one. In other words, the proposed double-barrier MTJ has a spin-transfer torque that is three orders larger than that of the single-barrier stack. This improvement may be attributed to the quantum-well states that are formed in the nonmagnetic metal spacer and the resonant tunneling mechanism that exists throughout the system.

  15. Invariance of the magnetic behavior and AMI in ferromagnetic biphase films with distinct non-magnetic metallic spacers

    Energy Technology Data Exchange (ETDEWEB)

    Silva, E.F. [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59078-900 Natal, RN (Brazil); Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Gamino, M. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Instituto de Física, Universidade Federal do Rio Grande de Sul, 91501-970 Porto Alegre, RS (Brazil); Andrade, A.M.H. de [Instituto de Física, Universidade Federal do Rio Grande de Sul, 91501-970 Porto Alegre, RS (Brazil); Vázquez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, 28049 Madrid (Spain); Correa, M.A. [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59078-900 Natal, RN (Brazil); Bohn, F., E-mail: felipebohn@fisica.ufrn.br [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59078-900 Natal, RN (Brazil)

    2017-02-01

    We investigate the quasi-static magnetic, magnetotransport, and dynamic magnetic properties in ferromagnetic biphase films with distinct non-magnetic metallic spacer layers. We observe that the nature of the non-magnetic metallic spacer material does not have significant influence on the overall biphase magnetic behavior, and, consequently, on the magnetotransport and dynamic magnetic responses. We focus on the magnetoimpedance effect and verify that the films present asymmetric magnetoimpedance effect. Moreover, we explore the possibility of tuning the linear region of the magnetoimpedance curves around zero magnetic field by varying the probe current frequency in order to achieve higher sensitivity values. The invariance of the magnetic behavior and the asymmetric magnetoimpedance effect in ferromagnetic biphase films with distinct non-magnetic metallic spacers place them as promising candidates for probe element and open possibilities to the development of lower-cost high sensitivity linear magnetic field sensor devices.

  16. Invariance of the magnetic behavior and AMI in ferromagnetic biphase films with distinct non-magnetic metallic spacers

    Science.gov (United States)

    Silva, E. F.; Gamino, M.; Andrade, A. M. H. de; Vázquez, M.; Correa, M. A.; Bohn, F.

    2017-02-01

    We investigate the quasi-static magnetic, magnetotransport, and dynamic magnetic properties in ferromagnetic biphase films with distinct non-magnetic metallic spacer layers. We observe that the nature of the non-magnetic metallic spacer material does not have significant influence on the overall biphase magnetic behavior, and, consequently, on the magnetotransport and dynamic magnetic responses. We focus on the magnetoimpedance effect and verify that the films present asymmetric magnetoimpedance effect. Moreover, we explore the possibility of tuning the linear region of the magnetoimpedance curves around zero magnetic field by varying the probe current frequency in order to achieve higher sensitivity values. The invariance of the magnetic behavior and the asymmetric magnetoimpedance effect in ferromagnetic biphase films with distinct non-magnetic metallic spacers place them as promising candidates for probe element and open possibilities to the development of lower-cost high sensitivity linear magnetic field sensor devices.

  17. Parylene C-on-photoresist (POP): a low temperature spacer scheme for polymer/metal nanowire fabrication

    Science.gov (United States)

    Li, Yuanhui; Xie, Quan; Wang, Wei; Zheng, Mingxin; Zhang, Hao; Lei, Yinhua; Zhang, Haixia Alice; Wu, Wengang; Li, Zhihong

    2011-06-01

    This work introduced a novel spacer scheme for polymer/metal nanowire preparation by combining Parylene C and photoresist (Parylene C on photoresist, POP, process), both of which possess a low temperature fabrication essence. Adhesion between the Parylene C and the substrate with photoresist onside was improved by introducing a modified silanization pretreatment. Parylene C filled in an undercut generated by regular lithography on a dual-layered photoresist was left as nanometer-sized residues after an isotropic oxygen plasma etching. Parylene C nanowires with the minimal width down to 200 nm were successfully obtained by this POP-based spacer technique, and were then utilized as the etching mask for ion milling of the metal films beneath to realize corresponding chromium/gold nanowires. The present POP scheme will expand the application of the spacer technique in polymer/metal nanowire fabrication for integrated micro/nanoelectromechanical systems.

  18. Generation of unipolar half-cycle pulses via unusual reflection of a single-cycle pulse from an optically thin metallic or dielectric layer.

    Science.gov (United States)

    Arkhipov, M V; Arkhipov, R M; Pakhomov, A V; Babushkin, I V; Demircan, A; Morgner, U; Rosanov, N N

    2017-06-01

    We propose a strikingly simple method to form approximately unipolar half-cycle optical pulses via reflection of a single-cycle optical pulse from a thin flat metallic or dielectric layer. Unipolar pulses in reflection arise due to specifics of one-dimensional pulse propagation. Namely, we show that the field emitted by the layer is proportional to the velocity of the oscillating charges in the medium, instead of their acceleration. Besides, the oscillation velocity of the charges can be forced to keep a constant sign throughout the pulse duration. That is, reflection of ultrashort pulses from broad-area layers with nanometer-scale thickness can be very different from the common reflection in the case of longer pulses and thicker layers. This suggests a possibility of unusual transformations of few-cycle light pulses in completely linear optical systems.

  19. UAS and DTS: Using Drones and Fiber Optics to Measure High Resolution Temperature of the Atmospheric Boundary Layer

    Science.gov (United States)

    Predosa, R. A.; Darricau, B.; Higgins, C. W.

    2015-12-01

    The atmospheric boundary layer (ABL) is the lowest part of the atmosphere that directly interacts with the planet's surface. The development of the ABL plays a vital role, as it affects the transport of atmospheric constituents such as air pollutants, water vapor, and greenhouse gases. Measurements of the processes in the ABL have been difficult due to the limitations in the spatial and temporal resolutions of the equipment as well as the height of the traditional flux tower. Recent advances in the unmanned aerial vehicle (UAV) and distributed temperature sensing (DTS) technologies have provided us with new tools to study the complex processes in ABL. We conducted a series of pioneering experiments in Eastern Oregon using a platform that combines UAV and DTS to collect data during morning and evening transitions in the ABL. The major components of this platform consists of a quad-copter, a DTS computer unit, and a set of customized fiber optic cables. A total of 75 flights were completed to investigate: (1) the capability of a duplexed fiber optic cable to reduce noise in the high spatial and temporal temperature measurements taken during the morning transition; (2) the possibility of using fiber optic cable as "wet bulb" thermometer to calculate relative humidity in the ABL at high spatial and temporal resolution. The preliminary results showed that using a fiber optic cable in a duplexed configuration with the UAV-DTS platform can effectively reduce noise level during the morning transition data collection. The customized "wet bulb" fiber optic cable is capable of providing information for the calculation of relative humidity in the ABL at unprecedented spatial and temporal resolutions. From this study, the UAV-DTS platform demonstrated great potential in collecting temperature data in the ABL and with the development of atmospheric sensor technologies, it will have more applications in the future.

  20. Vertical profiles, optical and microphysical properties of Saharan dust layers determined by a ship-borne lidar

    Directory of Open Access Journals (Sweden)

    F. Immler

    2003-05-01

    Full Text Available A unique data set of ship-borne lidar measurements of Saharan dust layers above the Atlantic ocean has been collected aboard the research vessel Polarstern with a mobile Aerosol Raman Lidar (MARL during the LIMPIDO-campaign in June 2000. Extended Saharan dust layers have been observed in the region between 8.5° N and 34° N in an altitude range between 2 and 6 km. The continental, North African origin of the probed air masses is confirmed by 8-day backward trajectories. The Saharan dust is characterized by an optical depth in the range of 0.1 and 0.3, a depolarization around 10\\% and high lidar ratios of 45 sr at 532 nm and 75 sr at 355 nm. The backscattering by the dust particles at the UV-wavelength is relatively weak, resulting in a negative color index. From the measured optical properties the effective radius and the refractive index of the dust particles are derived using a new approach based on Mie Theory and non-spherical scattering calculations. The low backscatter coefficient observed at 355 nm is due to significant absorption which increases with decreasing wavelength. This finding agrees very well with results from satellite and sun photometer measurements. The effective radii decrease from about 3 mm base to 0.6 mm at the top of the dust plumes. The non-spherical shapes of the dust particles are responsible for the high values of the lidar ratios.

  1. Vertical profiles, optical and microphysical properties of Saharan dust layers determined by a ship-borne lidar

    Directory of Open Access Journals (Sweden)

    F. Immler

    2003-01-01

    Full Text Available A unique data set of ship-borne lidar measurements of Saharan dust layers above the Atlantic ocean has been collected aboard the research vessel Polarstern with a mobile Aerosol Raman Lidar (MARL during the LIMPIDO-campaign in June 2000. Extended Saharan dust layers have been observed in the region between 8.5º N and 34º N in an altitude range between 2 and 6 km. The continental, North African origin of the probed air masses is confirmed by 8-day backward trajectories. The Saharan dust is characterized by an optical depth in the range of 0.1 and 0.3, a depolarization around 10% and high lidar ratios of 45 sr at 532 nm and 75 sr at 355 nm. The backscattering by the dust particles at the UV-wavelength is relatively weak, resulting in a negative color index. From the measured optical properties the effective radius and the refractive index of the dust particles are derived using a new approach based on Mie Theory and non-spherical scattering calculations. The low backscatter coefficient observed at 355 nm is due to significant absorption which increases with decreasing wavelength. This finding agrees very well with results from satellite and sun photometer measurements. The effective radii decrease from about 3 mm at the base to 0.6 mm at the top of the dust plumes. The non-spherical shapes of the dust particles are responsible for the high values of the lidar ratios.

  2. Spacer effect on nanostructures and self-assembly in organogels via some bolaform cholesteryl imide derivatives with different spacers

    Science.gov (United States)

    Jiao, Tifeng; Gao, Fengqing; Zhang, Qingrui; Zhou, Jingxin; Gao, Faming

    2013-10-01

    In this paper, new bolaform cholesteryl imide derivatives with different spacers were designed and synthesized. Their gelation behaviors in 23 solvents were investigated, and some of them were found to be low molecular mass organic gelators. The experimental results indicated that these as-formed organogels can be regulated by changing the flexible/rigid segments in spacers and organic solvents. Suitable combination of flexible/rigid segments in molecular spacers in the present cholesteryl gelators is favorable for the gelation of organic solvents. Scanning electron microscopy and atomic force microscopy observations revealed that the gelator molecules self-assemble into different aggregates, from wrinkle and belt to fiber with the change of spacers and solvents. Spectral studies indicated that there existed different H-bond formations between imide groups and assembly modes, depending on the substituent spacers in molecular skeletons. The present work may give some insight into the design and character of new organogelators and soft materials with special molecular structures.

  3. Analysis of morphological features and vascular layers of choroid in diabetic retinopathy using spectral-domain optical coherence tomography.

    Science.gov (United States)

    Adhi, Mehreen; Brewer, Erika; Waheed, Nadia K; Duker, Jay S

    2013-10-01

    Diabetic retinopathy (DR) is characterized by microaneurysms, capillary nonperfusion, and ischemia within the retina, ultimately leading to neovascularization and/or macular edema. Evidence suggests that choroidal angiopathy may coexist with retinal vascular damage. Recent advances in spectral-domain optical coherence tomography (SD-OCT) permit an efficient visualization of the choroid. To analyze the morphological features and vascular layers of the choroid in patients with DR using SD-OCT. A cross-sectional retrospective review identified patients with DR and healthy (control) subjects who underwent 1-line raster scanning from February 1, 2010, through June 30, 2012. Patients were classified into the following 3 groups: nonproliferative DR without macular edema (9 eyes), proliferative DR without macular edema (PDR) (10 eyes), and diabetic macular edema (DME) (14 eyes). Two independent raters experienced in analyzing OCT images evaluated the morphological features and vasculature of the choroid. New England Eye Center. Thirty-three eyes of 33 patients with DR and 24 eyes of 24 controls. Diabetic retinopathy. Choroidal morphological features and vasculature analysis. The choroidoscleral interface had an irregular contour in 8 of 9 eyes with nonproliferative DR (89%), 9 of 10 eyes with PDR (90%), and 13 of 14 eyes with DME (93%) compared with 0 of 24 controls. The thickest point of the choroid was displaced from under the fovea, and focal choroidal thinning was observed in eyes with DR. Mean subfoveal choroidal thickness and mean subfoveal medium choroidal vessel layer and choriocapillaris layer thickness were significantly reduced in eyes with PDR (P Choroidal morphological features are altered in patients with moderate to severe DR. The subfoveal choroidal thickness and the subfoveal medium choroidal vessel layer and choriocapillaris layer thicknesses are significantly reduced in patients with PDR and DME. To our knowledge, this is the first study to analyze the

  4. Optical properties of a metal island film close to a smooth metal surface.

    Science.gov (United States)

    Leitner, A; Zhao, Z; Brunner, H; Aussenegg, F R; Wokaun, A

    1993-01-01

    Bright colors have been observed when a metal island film is deposited on top of a silver mirror with a separating quartz layer. For spacer layer thicknesses that are varied from 0 to 140 nm, the visual appearance changes from blue/black to a series of brilliant spectrumlike colors. The sequence is repeated similarly for higher interlayer thicknesses. The phenomenon is analyzed in terms of a stratified medium theory by using TEM data and an electromagnetic model for the optical constants of the metal island film. For island films with a sufficiently high absorbance (> 0.35), the spectra are characterized by two sharp minima where the reflectivity drops to values below l0(-3). The observed thickness dependence is analyzed in terms of a complex combination of the phase shifts caused by the island film, the spacer, and the relevant interfaces.

  5. Methods and means of Stokes-polarimetry microscopy of optically anisotropic biological layers

    Science.gov (United States)

    Ushenko, A. G.; Dubolazov, A. V.; Ushenko, V. A.; Ushenko, Yu. A.; Sakhnovskiy, M. Yu.; Sidor, M.; Prydiy, O. G.; Olar, O. I.; Lakusta, I. I.

    2016-12-01

    The results of optical modeling of biological tissues polycrystalline multilayer networks have been presented. Algorithms of reconstruction of parameter distributions were determined that describe the linear and circular birefringence. For the separation of the manifestations of these mechanisms we propose a method of space-frequency filtering. Criteria for differentiation of benign and malignant tissues of the women reproductive sphere were found.

  6. Cross layer optimization for cloud-based radio over optical fiber networks

    Science.gov (United States)

    Shao, Sujie; Guo, Shaoyong; Qiu, Xuesong; Yang, Hui; Meng, Luoming

    2016-07-01

    To adapt the 5G communication, the cloud radio access network is a paradigm introduced by operators which aggregates all base stations computational resources into a cloud BBU pool. The interaction between RRH and BBU or resource schedule among BBUs in cloud have become more frequent and complex with the development of system scale and user requirement. It can promote the networking demand among RRHs and BBUs, and force to form elastic optical fiber switching and networking. In such network, multiple stratum resources of radio, optical and BBU processing unit have interweaved with each other. In this paper, we propose a novel multiple stratum optimization (MSO) architecture for cloud-based radio over optical fiber networks (C-RoFN) with software defined networking. Additionally, a global evaluation strategy (GES) is introduced in the proposed architecture. MSO can enhance the responsiveness to end-to-end user demands and globally optimize radio frequency, optical spectrum and BBU processing resources effectively to maximize radio coverage. The feasibility and efficiency of the proposed architecture with GES strategy are experimentally verified on OpenFlow-enabled testbed in terms of resource occupation and path provisioning latency.

  7. Bi-layer cross chiral structure with strong optical activity and negative refractive index.

    Science.gov (United States)

    Dong, Jianfeng; Zhou, Jiangfeng; Koschny, Thomas; Soukoulis, Costas

    2009-08-03

    The properties of periodic pairs of mutually twisted metallic (silver) crosses separated by dielectric layer have been investigated by numerical simulation. The results show that the exceptionally strong polarization rotation and circular dichroism, negative permeability and negative refractive index are found at the infrared communication wavelength (1.55 microm).

  8. Optimization of optical absorption in thin layers of amorphous silicon enhanced by silver nanospheres

    CERN Document Server

    Omelyanovich, Mikhail; Simovski, Constantin

    2015-01-01

    We study a highly controllable perfect plasmonic absorber -- a thin metamaterial layer which possess balanced electric and magnetic responses in some frequency range. We show that this regime is compatible with both metal-backed variant of the structure or its semitransparent variant. This regime can be implemented in a prospective thin-film photovoltaic cell with negligible parasitic losses.

  9. Mapping the Spatial Dynamics in Optically Significant Bottom Nepheloid Layers Using Autonomous Underwater Gliders

    Science.gov (United States)

    2016-06-07

    attenuation using the Zaneveld and Pegau (2001) algorithm: 4.8/(cpg650*1.18+0.081). Visibility was always lowest, from ~1 to 6 m, in the ubiquitous ...Visibility was always lowest, from ~1 to 6 m, in the ubiquitous bottom boundary layer. During the full water column mixing events, the entire water

  10. A Comparative Study on Structural and Optical Properties of ZnO Micro-Nanorod Arrays Grown on Seed Layers Using Chemical Bath Deposition and Spin Coating Methods

    Directory of Open Access Journals (Sweden)

    Sibel MORKOÇ KARADENİZ

    2016-11-01

    Full Text Available In this study, Zinc Oxide (ZnO seed layers were prepared on Indium Tin Oxide (ITO substrates by using Chemical Bath Deposition (CBD method and Sol-gel Spin Coating (SC method. ZnO micro-nanorod arrays were grown on ZnO seed layers by using Hydrothermal Synthesis method. Seed layer effects of structural and optical properties of ZnO arrays were characterized. X-ray diffractometer (XRD, Scanning Electron Microscopy (SEM and Ultraviolet Visible (UV-Vis Spectrometer were used for analyses. ZnO micro-nanorod arrays consisted of a single crystalline wurtzite ZnO structure for each seed layer. Besides, ZnO rod arrays were grown smoothly and vertically on SC seed layer, while ZnO rod arrays were grown randomly and flower like structures on CBD seed layer. The optical absorbance peaks found at 422 nm wavelength in the visible region for both ZnO arrays. Optical bandgap values were determined by using UV-Vis measurements at 3.12 and 3.15 eV for ZnO micro-nanorod arrays on CBD seed layer and for ZnO micro-nanorod arrays on SC-seed layer respectively.DOI: http://dx.doi.org/10.5755/j01.ms.22.4.13443

  11. Retinal nerve fibre layer thickness measured by Spectralis spectral-domain optical coherence tomography: The Beijing Eye Study.

    Science.gov (United States)

    Zhao, Liang; Wang, Yaxing; Chen, Chang X; Xu, Liang; Jonas, Jost B

    2014-02-01

    The aim of this study was to measure retinal nerve fibre layer thickness (RNFLT) and its associated factors in a population-based setting. The population-based Beijing Eye Study 2011 included 3468 individuals. The study participants underwent spectral-domain optical coherence tomography (Spectralis(®) ; Spectralis OCT)-assisted measurement of the RNFLT. For this study, exclusion criteria were glaucoma, pseudoexfoliation, best-corrected visual acuity of >0.5 logMAR, macular diseases, previous ocular surgery and known neurological diseases. The only inclusion criterion was an age of 50+ years. The inclusion criteria were fulfilled by 2548 participants. Mean RNFLT was 102 ± 11 μm. RNFLT was significantly (p region (p = 0.003), larger optic disc size (p measured by Spectralis(®) OCT; 102 ± 11 μm) was associated with younger age, female gender, urban region of habitation, larger optic disc, larger rim, hyperopic refractive error, larger parapapillary beta zone and thicker subfoveal choroidal thickness. Independent of age and refractive error, the RNFL was thickest temporal inferiorly and thinnest temporally and nasally. © 2013 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  12. Advanced hole patterning technology using soft spacer materials (Conference Presentation)

    Science.gov (United States)

    Park, Jong Keun; Hustad, Phillip D.; Aqad, Emad; Valeri, David; Wagner, Mike D.; Li, Mingqi

    2017-03-01

    A continuing goal in integrated circuit industry is to increase density of features within patterned masks. One pathway being used by the device manufacturers for patterning beyond the 80nm pitch limitation of 193 immersion lithography is the self-aligned spacer double patterning (SADP). Two orthogonal line space patterns with subsequent SADP can be used for contact holes multiplication. However, a combination of two immersion exposures, two spacer deposition processes, and two etch processes to reach the desired dimensions makes this process expensive and complicated. One alternative technique for contact hole multiplication is the use of an array of pillar patterns. Pillars, imaged with 193 immersion photolithography, can be uniformly deposited with spacer materials until a hole is formed in the center of 4 pillars. Selective removal of the pillar core gives a reversal of phases, a contact hole where there was once a pillar. However, the highly conformal nature of conventional spacer materials causes a problem with this application. The new holes, formed between 4 pillars, by this method have a tendency to be imperfect and not circular. To improve the contact hole circularity, this paper presents the use of both conventional spacer material and soft spacer materials. Application of soft spacer materials can be achieved by an existing coating track without additional cost burden to the device manufacturers.

  13. Bidirectional Reflectance of Flat, Optically Thick Particulate Layers: An Efficient Radiative Transfer Solution and Applications to Snow and Soil Surfaces

    Science.gov (United States)

    Mishchenko, Michael I.; Dlugach, Janna M.; Yanovitsku, Edgard G.; Zakharova, Nadia T.

    1999-01-01

    We describe a simple and highly efficient and accurate radiative transfer technique for computing bidirectional reflectance of a macroscopically flat scattering layer composed of nonabsorbing or weakly absorbing, arbitrarily shaped, randomly oriented and randomly distributed particles. The layer is assumed to be homogeneous and optically semi-infinite, and the bidirectional reflection function (BRF) is found by a simple iterative solution of the Ambartsumian's nonlinear integral equation. As an exact Solution of the radiative transfer equation, the reflection function thus obtained fully obeys the fundamental physical laws of energy conservation and reciprocity. Since this technique bypasses the computation of the internal radiation field, it is by far the fastest numerical approach available and can be used as an ideal input for Monte Carlo procedures calculating BRFs of scattering layers with macroscopically rough surfaces. Although the effects of packing density and coherent backscattering are currently neglected, they can also be incorporated. The FORTRAN implementation of the technique is available on the World Wide Web at http://ww,,v.giss.nasa.gov/-crmim/brf.html and can be applied to a wide range of remote sensing, engineering, and biophysical problems. We also examine the potential effect of ice crystal shape on the bidirectional reflectance of flat snow surfaces and the applicability of the Henyey-Greenstein phase function and the 6-Eddington approximation in calculations for soil surfaces.

  14. Perpendicular magnetic anisotropy and magneto-optical Kerr effect of vapor-deposited Co/Pt-layered structures

    Science.gov (United States)

    Zeper, W. B.; Greidanus, F. J. A. M.; Carcia, P. F.; Fincher, C. R.

    1989-06-01

    We prepared by vapor deposition at room temperature thin (500 Å) Co/Pt multilayers or layered structures directly onto glass or Si substrates. They show a preferential magnetization perpendicular to the film plane for Co thicknesses below 12 Å and a 100% perpendicular remanence for Co thicknesses below 4.5 Å. The magnetic anisotropy can be explained by an interface contribution to the anisotropy. We also investigated the magneto-optical (MO) polar Kerr effect of these multilayers. Because of their excellent magnetic properties and their potentially high oxidation and corrosion resistance, these Co/Pt-layered structures are very promising candidates for MO recording. The Kerr rotation θk at λ=820 nm for a 35×(4.0 Å Co+12.7 Å Pt)-layered structure, which has 100% magnetic remanence, is modest (-0.12°), but the reflectivity R is high (70%), which results in a respectable figure of merit Rθ2k. Furthermore, the Kerr effect increases towards shorter wavelengths and thus favors future higher-density recording.

  15. Infiltrating a thin or single layer opal with an atomic vapour: sub-doppler signals and crystal optics

    CERN Document Server

    Moufarej, Elias; Zabkov, Ilya; Laliotis, Athanasios; Ballin, Philippe; Klimov, Vasily; Bloch, Daniel

    2014-01-01

    Artificial thin glass opals can be infiltrated with a resonant alkali-metal vapour, providing novel types of hybrid systems. The reflection at the interface between the substrate and the opal yields a resonant signal, which exhibits sub-Doppler structures in linear spectroscopy for a range of oblique incidences. This result is suspected to originate in an effect of the three-dimensional confinement of the vapour in the opal interstices. It is here extended to a situation where the opal is limited to a few or even a single layer opal film, which is a kind of bidimensional grating. We have developed a flexible one-dimensional layered optical model, well suited for a Langmuir-Blodgett opal. Once extended to the case of a resonant infiltration, the model reproduces quick variations of the lineshape with incidence angle or polarization. Alternately, for an opal limited to a single layer of identical spheres, a three-dimensional numerical calculation was developed. It predicts crystalline anisotropy, which is demon...

  16. Organic double layer element driven by triboelectric nanogenerator: Study of carrier behavior by non-contact optical method

    Science.gov (United States)

    Chen, Xiangyu; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

    2016-02-01

    By using optical electric-field-induced second-harmonic generation (EFISHG) technique, we studied carrier behavior caused by contact electrification (CE) in an organic double-layer element. This double-layer sample was half suspended in the open air, where one electrode (anode or cathode) was connected with a Cu foil for electrification while the other electrode was floated. Results showed two distinct carrier behaviors, depending on the (anode or cathode) connections to the Cu foil, and these carrier behaviors were analyzed based on the Maxwell-Wagner model. The double-layer sample works as a simple solar cell device. The photovoltaic effect and CE process have been proved to be two paralleled effects without strong interaction with each other, while photoconductivity changing in the sample can enhance the relaxation of CE induced charges. By probing the carrier behavior in this half-suspended device, the EFISHG technique has been demonstrated to be an effective non-contact method for clarifying the CE effect on related energy harvesting devices and electronics devices. Meanwhile, the related physical analysis in this letter is also useful for elucidating the fundamental characteristic of hybrid energy system based on solar cell and triboelectric nanogenerator.

  17. Morphology and Vascular Layers of the Choroid in Stargardt Disease Analyzed Using Spectral-Domain Optical Coherence Tomography.

    Science.gov (United States)

    Adhi, Mehreen; Read, Sarah P; Ferrara, Daniela; Weber, Marissa; Duker, Jay S; Waheed, Nadia K

    2015-12-01

    To analyze total thickness, morphology and individual vascular layers of the choroid in eyes with Stargardt disease using spectral-domain optical coherence tomography (SD OCT). Cross-sectional retrospective review. Twenty-eight patients with Stargardt disease (53 eyes) with a mean age of 46 (15-79) years and 30 healthy subjects (30 eyes) with a mean age of 49 (22-79) years who underwent 1-line raster scanning with SD OCT were identified. Diagnosis of Stargardt disease was based on ophthalmic history and complete ophthalmic evaluation. The healthy subjects had best-corrected visual acuity of 20/20 or better with no chorioretinal pathology. Two independent raters assessed the total thickness, morphology, and the individual vascular layers of the choroid. The choroid was irregularly shaped in 26 of 41 eyes (64%) with Stargardt disease when compared to 0 of 30 healthy eyes (0%). Mean subfoveal total choroidal thickness and mean subfoveal large choroidal vessel layer thickness were significantly reduced in eyes with Stargardt disease when compared to healthy eyes (272.8 ± 32.8 μm vs 225.4 ± 69.9 μm; P = .03 and 219.5 ± 30.6 vs169.2 ± 70.1; P = .04, respectively). The maximal choroidal thickness was subfoveal in 9 of 41 eyes (22%), focal choroidal thinning was observed in 21 of 41 eyes (51%), and attenuation of large choroidal vessel layer was observed in 8 of 41 eyes (20%) with Stargardt disease. There was no association of the best-corrected visual acuity with any choroidal morphologic feature, except that it was better by a mean of 0.61 ± 0.21 in eyes that had preservation of large choroidal vessel layer (33 of 41, 80%) when compared to those that had attenuation of large choroidal vessel layer (P = .007). This study shows alterations in the total thickness, morphology, and the individual vascular layers of the choroid in eyes with Stargardt disease on SD OCT. These findings may potentially contribute to the clinical staging and monitoring of Stargardt

  18. Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

    Energy Technology Data Exchange (ETDEWEB)

    Ngah Demon, Siti Zulaikha [School of Materials Science, Japan Advanced Institute of Science and Technology, 923-1292 Ishikawa (Japan); Department of Physics, Centre of Defence Foundation Studies, National Defence University of Malaysia, 53 000 Kuala Lumpur (Malaysia); Miyauchi, Yoshihiro [Department of Applied Physics, School of Applied Sciences, National Defense Academy of Japan, 239-8686 Kanagawa (Japan); Mizutani, Goro, E-mail: mizutani@jaist.ac.jp [School of Materials Science, Japan Advanced Institute of Science and Technology, 923-1292 Ishikawa (Japan); Matsushima, Toshinori; Murata, Hideyuki [School of Materials Science, Japan Advanced Institute of Science and Technology, 923-1292 Ishikawa (Japan)

    2014-08-30

    Highlights: • SHG phase from the interfaces of ITO/CuPc and ITO/pentacene was observed. • Optical dispersion of the organic thin film was taken into account. • Phase shift from bare ITO was 140° for ITO/CuPc and 160° for ITO/pentacene. - Abstract: We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕ{sub interface} with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°.

  19. Ellipsometric study of optical properties of GaSxSe1-x layered mixed crystals

    Science.gov (United States)

    Isik, Mehmet; Gasanly, Nizami

    2016-04-01

    Spectroscopic ellipsometry measurements were performed on GaSxSe1-x mixed crystals (0 ⩽ x ⩽ 1) in the 1.2-6.2 eV range. Spectral dependence of optical parameters; real and imaginary components of pseudodielectric function, pseudorefractive index and pseudoextinction coefficient were reported in the present work. Critical point (CP) analyses on second-energy derivative spectra of the pseudodielectric function were accomplished to find the interband transition energies. The revealed energy values were associated with each other taking into account the fact that band gap energy of mixed crystals rises with increase in sulfur content. The variation of CP energies with composition (x) was also plotted. Peaks in the spectra of studied optical parameters and CP energy values were observed to be shifted to higher energy values as sulfur concentration is increased in the mixed crystals.

  20. Optical and electrical properties of composites based on functional components of an electroluminescent layer

    Science.gov (United States)

    Avanesyan, V. T.; Rakina, A. V.; Sychov, M. M.; Vasina, E. S.

    2016-07-01

    Optical and electrical properties of cyanoethyl ether of polyvinyl alcohol with filling of barium titanate BaTiO3 modified by shungite carbon nanoparticles are studied. It is found that the modification affects the diffuse reflectance spectra and dispersion characteristics of the impedance components due to a change in the nature of interfacial interactions in the system. The values of the forbidden band width for various modifier and filler concentrations are determined.

  1. Multianalyte electrochemical biosensor on a monolith electrode by optically scanning the electrical double layer.

    Science.gov (United States)

    Lee, Seung-Woo; Saraf, Ravi F

    2014-07-15

    Redox on an electrode is an interfacial phenomenon that modulates the charge in the electrical double layer (EDL). A novel instrument, the Scanning Electrometer for Electrical Double-layer (SEED) has been developed to measure multiple enzyme reactions on a monolith electrode due to immunospecific binding with a mixture of respective analytes. SEED quantitatively maps the local redox reaction by scanning a laser on the array of enzyme monolayer spots immobilized on the monolith electrode. SEED measures the change in local charge state of the EDL that abruptly changes due to the redox reaction. The measurement spot size defined by the size of the laser beam is ~10 µm. The SEED signal is linearly proportional to the local redox current density and analyte concentration. The specificity is close to 100%. The SEED readout is compatible with microfluidics platform where the signal degrades less than 2% due to the poly(dimethyl siloxane) (PDMS) body.

  2. The influence on biotissue laser resection of a strongly absorbing layer at the optical fiber tip

    Directory of Open Access Journals (Sweden)

    Daria Kuznetsova

    2016-09-01

    Full Text Available In this paper, we consider a method of laser resection using the silica glass core from which the cladding layer has been removed as the cutting part of a laser scalpel. An absorbing layer coating the silica fiber tip markedly alters its biotissue cutting characteristics. The results of histological studies of skin after exposure to a laser scalpel with and without a strongly absorbing coating (SAC at a wavelength of 0.97μm show that resection using a coated scalpel is more sparing. When an uncoated scalpel was used, skin injury was more apparent in both its surface spread and the depth of structural damage, resulting in poorer tissue regeneration.

  3. Applicability of the Aero-Optic Linking Equation to a Highly Coherent, Transitional Shear Layer

    Science.gov (United States)

    Hugo, Ronald J.; Jumper, Eric J.

    2000-08-01

    We investigate the validity of applying a simplified (under the assumptions of isotropic and homogeneous turbulence) aero-optic linking equation to a flow field that is known to consist of anisotropic and nonhomogeneous turbulence. The investigation is performed in the near-nozzle region of a heated two-dimensional jet, and the study makes use of a conditional-sampling experiment to acquire a spatiotemporal temperature field database for the heated-jet flow field. After compensating for the bandwidth limitations of constant-current wire temperature measurements, the temperature field database is applied to the computation of optical degradation through both direct and indirect methods, relying on the aero-optic linking equation. The simplified version of the linking equation was found to provide good agreement with direct calculations, provided that the length scale of the density fluctuations was interpreted as being the integral scale, with the limits of integration being the first two zero crossings of the covariance coefficient function.

  4. PHYSICAL BASIS OF ISOTOPE-ENRICHED LAYERS FORMATION IN FIBER OPTICS

    Directory of Open Access Journals (Sweden)

    Myshkin V. F.

    2015-06-01

    Full Text Available It is known that transmission coefficient of quartz glass containing the same amount of 28Si and 30Si in the silicon optical fiber is lesser than in commercial LEDs for telecommunications. Therefore it is topical to develop the method of optical glass formation with specified isotope composition in the core and in the shell. The article provides an analysis of physical and chemical processes occurring at the formation of quartz optical fiber blanks by vapor deposition from the gas phase. It is shown that the part of the silicon tetrachloride oxidation stages passes through the radical processes. Therefore for quartz glass formation with specified isotope composition it is possible to use the paramagnetic phenomena caused by the external magnetic field in a high-temperature flow at the quartz glass chemical deposition from the vapor phase. In this case alloy additive using is not necessary. Alloy additives can form density inhomogeneities in the glass. Simultaneous silicon glass formation and silicon isotope separation process bring to significant reduction of the fiber cost in comparison with isotope-enriched materials using. The permanent magnets can be used for magnetic field formation at existing process units

  5. Preclinical Evaluation of Bioabsorbable Polyglycolic Acid Spacer for Particle Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Akasaka, Hiroaki [Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan (Japan); Sasaki, Ryohei, E-mail: rsasaki@med.kobe-u.ac.jp [Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan (Japan); Miyawaki, Daisuke; Mukumoto, Naritoshi; Sulaiman, Nor Shazrina Binti [Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan (Japan); Nagata, Masaaki [Division of Gastroenterology, Kobe University Graduate School of Medicine, Hyogo Japan (Japan); Yamada, Shigeru [Research Center Hospital, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba (Japan); Murakami, Masao [Radiation Oncology Center, Dokkyo Medical University, Tochigi (Japan); Demizu, Yusuke [Department of Radiology, Hyogo Ion Beam Medical Center, Hyogo (Japan); Fukumoto, Takumi [Division of Hepato-Biliary-Pancreatic Surgery, Kobe University Graduate School of Medicine, Hyogo Japan (Japan)

    2014-12-01

    Purpose: To evaluate the efficacy and safety of a polyglycolic acid (PGA) spacer through physical and animal experiments. Methods and Materials: The spacer was produced with surgical suture material made of PGA, forming a 3-dimensional nonwoven fabric. For evaluation or physical experiments, 150-MeV proton or 320-MeV carbon-ion beams were used to generate 60-mm width of spread-out Bragg peak. For animal experiments, the abdomens of C57BL/6 mice, with or without the inserted PGA spacers, were irradiated with 20 Gy of carbon-ion beam (290 MeV) using the spread-out Bragg peak. Body weight changes over time were scored, and radiation damage to the intestine was investigated using hematoxylin and eosin stain. Blood samples were also evaluated 24 days after the irradiation. Long-term thickness retention and safety were evaluated using crab-eating macaques. Results: No chemical or structural changes after 100 Gy of proton or carbon-ion irradiation were observed in the PGA spacer. Water equivalency of the PGA spacer was equal to the water thickness under wet condition. During 24 days' observation after 20 Gy of carbon-ion irradiation, the body weights of mice with the PGA spacer were relatively unchanged, whereas significant weight loss was observed in those mice without the PGA spacer (P<.05). In mice with the PGA spacer, villus and crypt structure were preserved after irradiation. No inflammatory reactions or liver or renal dysfunctions due to placement of the PGA spacer were observed. In the abdomen of crab-eating macaques, thickness of the PGA spacer was maintained 8 weeks after placement. Conclusions: The absorbable PGA spacer had water-equivalent, bio-compatible, and thickness-retaining properties. Although further evaluation is warranted in a clinical setting, the PGA spacer may be effective to stop proton or carbon-ion beams and to separate normal tissues from the radiation field.

  6. Surface plasmon resonance investigation of optical detection in plasma-modified phospholipid layers

    Energy Technology Data Exchange (ETDEWEB)

    Park, Byoungchoo; Cho, Chanyoun; Choi, Kyoungho; Jeon, Honggoo [Kwangwoon University, Seoul (Korea, Republic of)

    2012-03-15

    We herein report on a study of surface plasmon resonance (SPR) in thin gold (Au) films coated with thin layers of phospholipid material, which had been exposed to an atmospheric pressure (AP) plasma containing both pure Ar and Ar mixed with O{sub 2} (Ar/O{sub 2}, 0.8%). The phospholipid material that we used for the SPR experiments was lecithin, and the AP plasma system was applied in air by means of a radio-frequency (RF) plasma generator. A thin (∼60 nm) film of Au and a thin (∼15 nm) layer of lecithin were deposited and attached to the face of a prism, and surface plasmon modes were excited along the interfaces of the prism-Au-lecithin-air system by means of prism coupling using a He-Ne Laser (632.8 nm). The experimental SPR reflectance curves of the Au-lecithin-air modes were found to be shifted towards those of the Au-air mode with increasing applications of AP RF plasma treatment. From the shifts in the SPR curves, we found that the estimated thickness of the lecithin layer treated with a pure Ar plasma showed a linear decrease with etching rate of about 3 nm per treatment while the thickness of the lecithin layer treated with a mixed Ar/O{sub 2} plasma showed a tendency to saturate following a large initial decrease (ca. 14 nm). All these results demonstrate that the use of SPR sensing could facilitate the detection of extremely small variations in plasma-treated films of biomaterials.

  7. Analysis of the Band-Structure in (Ga, Mn)As Epitaxial Layers by Optical Methods

    OpenAIRE

    Yastrubchak, O.

    2012-01-01

    The ternary III-V semiconductor (Ga, Mn)As has recently drawn a lot of attention as the model diluted ferromagnetic semiconductor, combining semiconducting properties with magnetism. (Ga, Mn)As layers are usually gown by the low-temperature molecular-beam epitaxy (LT-MBE) technique. Below a magnetic transition temperature, TC, substitutional Mn2+ ions are ferromagnetically ordered owing to interaction with spin-polarized holes. However, the character of electronic states near the Fermi energy...

  8. Evaluation of a multi-layer diffuse reflectance spectroscopy system using optical phantoms

    Science.gov (United States)

    Fredriksson, Ingemar; Saager, Rolf B.; Durkin, Anthony J.; Strömberg, Tomas

    2017-03-01

    A fiber probe-based device for assessing microcirculatory parameters, especially red blood cell (RBC) tissue fraction, their oxygen saturation and speed resolved perfusion, has been evaluated using state-of-the-art multi-layer tissue simulating phantoms. The device comprises both diffuse reflectance spectroscopy (DRS) at two source-detector separations (0.4 and 1.2 mm) and laser Doppler flowmetry (LDF) and use an inverse Monte Carlo method for identifying the parameters of a multi-layered tissue model. First, model parameters affecting scattering, absorption and geometrical parameters are fitted to measured DRS spectra, then speed parameters are fitted to LDF spectra. In this paper, the accuracy of the spectral parameters is evaluated. The measured spectral shapes at the two source-detector separations were in good agreement with forward calculated spectral shapes. In conclusion, the multi-layer skin model based on spectral features of the included chromophores, can reliably estimate the tissue fraction of RBC, its oxygen saturation and the reduced scattering coefficient spectrum of the tissue. Furthermore, it was concluded that some freedom in the relative intensity difference between the two DRS channels is necessary in order to compensate for non-modeled surface structure effects.

  9. Analysis of the Band-Structure in (Ga, MnAs Epitaxial Layers by Optical Methods

    Directory of Open Access Journals (Sweden)

    O. Yastrubchak

    2012-03-01

    Full Text Available The ternary III-V semiconductor (Ga, MnAs has recently drawn a lot of attention as the model diluted ferromagnetic semiconductor, combining semiconducting properties with magnetism. (Ga, MnAs layers are usually gown by the low-temperature molecular-beam epitaxy (LT-MBE technique. Below a magnetic transition temperature, TC, substitutional Mn2+ ions are ferromagnetically ordered owing to interaction with spin-polarized holes. However, the character of electronic states near the Fermi energy and the electronic structure in ferromagnetic (Ga, MnAs are still a matter of controversy. The photoreflectance (PR spectroscopy was applied to study the band-structure evolution in (Ga, MnAs layers with increasing Mn content. We have investigated thick (800-700 nm and 230-300 nm (Ga, MnAs layers with Mn content in the wide range from 0.001 % to 6 % and, as a reference, undoped GaAs layer, grown by LT-MBE on semi-insulating (001 GaAs substrates. Our findings were interpreted in terms of the model, which assumes that the mobile holes residing in the valence band of ferromagnetic (Ga, MnAs and the Fermi level position determined by the concentration of valence-band holes. The ternary III-V semiconductor (Ga, MnAs has recently drawn a lot of attention as the model diluted ferromagnetic semiconductor, combining semiconducting properties with magnetism. (Ga, MnAs layers are usually gown by the low-temperature molecular-beam epitaxy (LT-MBE technique. Below a magnetic transition temperature, TC, substitutional Mn2+ ions are ferromagnetically ordered owing to interaction with spin-polarized holes. However, the character of electronic states near the Fermi energy and the electronic structure in ferromagnetic (Ga, MnAs are still a matter of controversy. The photoreflectance (PR spectroscopy was applied to study the band-structure evolution in (Ga, MnAs layers with increasing Mn content. We have investigated thick (800-700 nm and 230-300 nm (Ga

  10. The Two-Column Aerosol Project: Phase I - Overview and Impact of Elevated Aerosol Layers on Aerosol Optical Depth

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Larry K.; Fast, Jerome D.; Barnard, James C.; Burton, Sharon; Cairns, Brian; Chand, Duli; Comstock, Jennifer M.; Dunagan, Stephen; Ferrare, Richard A.; Flynn, Connor J.; Hair, John; Hostetler, Chris A.; Hubbe, John M.; Jefferson, Anne; Johnson, Roy; Kassianov, Evgueni I.; Kluzek, Celine D.; Kollias, Pavlos; Lamer, Katia; Lantz, K.; Mei, Fan; Miller, Mark A.; Michalsky, Joseph; Ortega, Ivan; Pekour, Mikhail S.; Rogers, Ray; Russell, P.; Redemann, Jens; Sedlacek, Art; Segal Rozenhaimer, Michal; Schmid, Beat; Shilling, John E.; Shinozuka, Yohei; Springston, Stephen R.; Tomlinson, Jason M.; Tyrrell, Megan; Wilson, Jacqueline; Volkamer, Rainer M.; Zelenyuk, Alla; Berkowitz, Carl M.

    2016-01-08

    The Two-Column Aerosol Project (TCAP), which was conducted from June 2012 through June 2013, was a unique field study that was designed to provide a comprehensive data set that can be used to investigate a number of important climate science questions, including those related to aerosol mixing state and aerosol radiative forcing. The study was designed to sample the atmosphere at a number of altitudes, from near the surface to as high as 8 km, within two atmospheric columns; one located near the coast of North America (over Cape Cod, MA) and a second over the Atlantic Ocean several hundred kilometers from the coast. TCAP included the yearlong deployment of the U.S. Department of Energy’s (DOE) Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) that was located at the base of the Cape Cod column, as well as summer and winter aircraft intensive observation periods of the ARM Aerial Facility. One important finding from TCAP is the relatively common occurrence (on four of six nearly cloud-free flights) of elevated aerosol layers in both the Cape Cod and maritime columns that were detected using the nadir pointing second-generation NASA high-spectral resolution lidar (HSRL-2). These layers contributed up to 60% of the total aerosol optical depth (AOD) observed in the column. Many of these layers were also intercepted by the aircraft configured for in situ sampling, and the aerosol in the layers was found to have increased amounts of biomass burning aerosol and nitrate compared to the aerosol found near the surface.

  11. Structural and optical properties of silicon nanocrystals embedded in silicon carbide: Comparison of single layers and multilayer structures

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, Charlotte, E-mail: charlotte.weiss@ise.fraunhofer.de; Schnabel, Manuel; Reichert, Andreas; Löper, Philipp; Janz, Stefan

    2015-10-01

    Highlights: • Si nanocrystal size control in a SiC matrix achieved by Si content variation. • We proved sublayer intermixing in Si{sub x}C{sub 1−x}/SiC multilayer during annealing. • Excess Si in SiC hinders SiC crystallization. • We performed a comparison between Si{sub x}C{sub 1−x}/SiC multilayers and Si{sub x}C{sub 1−x} single layers. • Si nanocrystal size correlates with the E{sub 04} bandgap. - Abstract: The outstanding demonstration of quantum confinement in Si nanocrystals (Si NC) in a SiC matrix requires the fabrication of Si NC with a narrow size distribution. It is understood without controversy that this fabrication is a difficult exercise and that a multilayer (ML) structure is suitable for such fabrication only in a narrow parameter range. This parameter range is sought by varying both the stoichiometric SiC barrier thickness and the Si-rich SiC well thickness between 3 and 9 nm and comparing them to single layers (SL). The samples processed for this investigation were deposited by plasma-enhanced chemical vapor deposition (PECVD) and subsequently subjected to thermal annealing at 1000–1100 °C for crystal formation. Bulk information about the entire sample area and depth were obtained by structural and optical characterization methods: information about the mean Si NC size was determined from grazing incidence X-ray diffraction (GIXRD) measurements. Fourier-transform infrared spectroscopy (FTIR) was applied to gain insight into the structure of the Si–C network, and spectrophotometry measurements were performed to investigate the absorption coefficient and to estimate the bandgap E{sub 04}. All measurements showed that the influence of the ML structure on the Si NC size, on the Si–C network and on the absorption properties is subordinate to the influence of the overall Si content in the samples, which we identified as the key parameter for the structural and optical properties. We attribute this behavior to interdiffusion of the

  12. Development of dual-layer GSO depth-of-interaction block detector using angled optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Okumura, Satoshi, E-mail: okumura.satoshi@c.mbox.nagoya-u.ac.jp [Nagoya University Graduate School of Medicine (Japan); Yamamoto, Seiichi [Nagoya University Graduate School of Medicine (Japan); Watabe, Hiroshi [Cyclotron and Radioisotope Center (CYRIC), Tohoku University (Japan); Kato, Natsuki; Hamamura, Huka [Nagoya University Graduate School of Medicine (Japan)

    2015-05-01

    A PET system for small animals requires a small detector ring to obtain high-spatial resolution images. However, when we use a relatively large size of photodetector such as a position-sensitive photomultiplier tube (PSPMT), the detector ring is arranged in a hexagonal- or octagonal-shape, and the PET system has large gaps between the block detectors. The large gaps produce image distortion, and the reconstruction algorithm is difficult. To solve these problems, we proposed to arrange two scintillator blocks on one PSPMT using two angled optical fiber-based image guides. We could set two scintillator blocks angled at 22.5° on a PSPMT so that these scintillator blocks are arranged in a nearly circular (hexadecagonal) shape with eight developed block detectors. We used Gd{sub 2}SiO{sub 5} (GSO) scintillators with Ce concentrations of 1.5 mol% (decay time: 39 ns) and 0.4 mol% (decay time: 63 ns). Sizes of these GSO cells were 1.6×2.4×7.0 mm{sup 3} and 1.6×2.4×8.0 mm{sup 3} for 1.5 mol% Ce and 0.4 mol% Ce, respectively. These two types of GSO were arranged in an 11×15 matrix and optically coupled in the depth direction to form a depth-of-interaction (DOI) detector. Two GSO blocks and two optical fiber-based image guides were optically coupled to a 2-in. PSPMT (Hamamatsu Photonics H8500: 8×8 anodes). We measured the performances of the block detector with Cs-137 gamma photons (662-keV). We could resolve almost all pixels clearly in a two-dimensional position histogram. The average peak-to-valley ratios (P/Vs) of the two-dimensional position histogram along profiles were 2.6 and 4.8 in horizontal and vertical directions, respectively. The energy resolution was 28.4% full-width at half-maximum (FWHM). The pulse shape spectra showed good separation with a P/V of 5.2. The developed block detector performed well and shows promise for the development of high-sensitivity and high-spatial resolution PET systems.

  13. In vivo sweat film layer thickness measured with Fourier-domain optical coherence tomography

    CSIR Research Space (South Africa)

    Jonathan, E

    2008-01-01

    Full Text Available and pore can be located. In addition, other measure- ments of interest, for example, thickness of the SCL, diameter of an open sweat pore or depth position of DEJ can be performed. References [1] Weller AS. Body temperature and its regulation. Physiol... of tissue microstructure is achieved from operating in the optical low-coherence interferometry domain. 1. Introduction Sweat secretion in humans is accepted as a mechanism by which the body cools off [1,2]. Interest in sweat secretion in humans’ dates...

  14. Optically readout write once read many memory with single active organic layer

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Viet Cuong; Lee, Pooi See, E-mail: pslee@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, Singapore 639798 (Singapore)

    2016-01-18

    An optically readable write once read many memory (WORM) in Ag/Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH PPV)/ITO is demonstrated in this work. Utilising characteristics of the organic light emitting diode structure of Ag/MEH PPV/ITO and electrochemical metallization of Ag, a WORM with light emitting capability can be realised. The simple fabrication process and multifunction capability of the device can be useful for future wearable optoelectronics and photomemory applications, where fast and parallel readout can be achieved by photons.

  15. Optical constants and dynamic conductivities of single layer MoS{sub 2}, MoSe{sub 2}, and WSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Morozov, Yurii V. [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Department of Physics, Taras Shevchenko National University, Kiev (Ukraine); Kuno, Masaru [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

    2015-08-24

    The complex optical constants of single layer MoS{sub 2}, MoSe{sub 2}, and WSe{sub 2} transition metal dichalcogenides (TMDCs) have been measured using concerted frequency-dependent transmittance and reflectance measurements. Absolute absorptivities as well as complex refractive indices and dielectric permittivities have been extracted. Comparisons to associated bulk responses reveal differences due to increased electron-hole interactions in single layer TMDCs. In parallel, corresponding complex optical conductivities (σ) have been determined. For MoS{sub 2}, extracted σ-values qualitatively agree with recent theoretical estimates. Significant differences exist, though, between experiment and theory regarding the imaginary part of σ. In all cases, the current approach distinguishes itself to other measurements of single layer TMDC optical constants in which it does not rely on Kramers-Kronig transformations of reflectance data.

  16. Preparation of Layered Double Hydroxide-Immobilized Lipase for High Yield and Optically Active (-)-Menthyl butyrate

    Institute of Scientific and Technical Information of China (English)

    Siti; Salhah; Othman; Mahiran; Basri; Mohd.Zobir; Hussein; Mohd; Basyaruddin; Abdul; Rahman; Raja; Noor; Zaliha; Raja; Abdul; Rahman; Abu; Bakar; Salleh; Salina; Mat; Radzi; Azwani; Sofia; Ahmad; Khiar

    2007-01-01

    1 Results Layered Double Hydroxide (LDH) finds extensive usage in the areas of pharmaceutical sciences and catalysis. In this study, a member of the LDH family, Mg/Al-hydrotalcite (HT), or the so-called anionic clay, was prepared at ratio 4 (HT) by co-precipitating through continuous agitation. X-ray diffraction pattern and thermogravimetric analysis of the material indicated that a pure HT had been successfully synthesized. This matrix was then used as support in the immobilization of lipase from Cand...

  17. Non-linear optical functions of crystalline-Si resulting from nanoscale layered systems

    Energy Technology Data Exchange (ETDEWEB)

    Kuznicki, Z.T. [Laboratoire PHASE, CNRS UPR 292, 23 rue du Loess, F-67037 Strasbourg cedex 2 (France)]. E-mail: kuznicki@phase.c-strasbourg.fr; Ley, M. [Laboratoire PHASE, CNRS UPR 292, 23 rue du Loess, F-67037 Strasbourg cedex 2 (France); Lezec, H.J. [ISIS, ULP, 8 allee Gaspard Monge, F-67083 Strasbourg cedex (France); Sarrabayrouse, G. [LAAS-CNRS, 7 av. du colonel Roche, 31077 Toulouse cedex 4 (France); Rousset, B. [LAAS-CNRS, 7 av. du colonel Roche, 31077 Toulouse cedex 4 (France); Rossel, F. [LAAS-CNRS, 7 av. du colonel Roche, 31077 Toulouse cedex 4 (France); Migeon, H. [LAM, Centre de Recherche Public - Gabriel Lippmann, 162a, av. de la Faiaencerie, L-1511 Luxembourg (Luxembourg); Wirtz, T. [LAM, Centre de Recherche Public - Gabriel Lippmann, 162a, av. de la Faiaencerie, L-1511 Luxembourg (Luxembourg)

    2006-07-15

    New non-linear optoelectronic and photovoltaic behavior of crystalline silicon (c-Si) has been obtained with a strained nanoscale Si-layered system. We have found c-Si absorptances that even exceed values of amorphous silicon (a-Si) thin films. The present investigation exploits charge carrier and photon flux transformations at the so-called carrier collection limit. A correlation between free carrier density and the absorption coefficient could be established by combining reflectivity and transmissivity measurements on samples having different surface free carrier reservoirs. In summary, Si modifications implemented on the nanoscale lead to new effects that can widen applications of conventional Si devices.

  18. Evaluation of epoxy for use on NuSTAR optics

    DEFF Research Database (Denmark)

    An, H.; Christensen, Finn Erland; Doll, M.

    2009-01-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer (SMEX) mission which employs two focusing optics. The optics are composed of stacks of thin mirror shells and spacers. Epoxy is used to bond the mirror shells to the spacers and is a crucial component in determining...... the structural and optical performance of the telescopes. We describe the epoxy selection for NuSTAR optics, emphasizing those epoxy characteristics essential to obtaining good optical performance....

  19. Technique for adapting a spacer for a custom impression tray.

    Science.gov (United States)

    Kaur, Harsimran; Nanda, Aditi; Verma, Mahesh; Koli, Dheeraj

    2016-12-01

    A method of adapting a spacer for the custom trays used to make a definite impression for complete dentures is presented. The technique can be used under a variety of conditions and offers several advantages.

  20. Response of an electrostatic probe for a right cylindrical spacer

    DEFF Research Database (Denmark)

    Rerup, T; Crichton, George C; McAllister, Iain Wilson

    1994-01-01

    During the last decade many experimental studies of surface charge phenomena have been undertaken employing right cylindrical spacers. Measurement of the surface charge was performed using small electrostatic field probes to scan across the dielectric surface. Charges are electrostatically induced...

  1. Bottom-Up Abstract Modelling of Optical Networks-on-Chip: From Physical to Architectural Layer

    Directory of Open Access Journals (Sweden)

    Alberto Parini

    2012-01-01

    Full Text Available This work presents a bottom-up abstraction procedure based on the design-flow FDTD + SystemC suitable for the modelling of optical Networks-on-Chip. In this procedure, a complex network is decomposed into elementary switching elements whose input-output behavior is described by means of scattering parameters models. The parameters of each elementary block are then determined through 2D-FDTD simulation, and the resulting analytical models are exported within functional blocks in SystemC environment. The inherent modularity and scalability of the S-matrix formalism are preserved inside SystemC, thus allowing the incremental composition and successive characterization of complex topologies typically out of reach for full-vectorial electromagnetic simulators. The consistency of the outlined approach is verified, in the first instance, by performing a SystemC analysis of a four-input, four-output ports switch and making a comparison with the results of 2D-FDTD simulations of the same device. Finally, a further complex network encompassing 160 microrings is investigated, the losses over each routing path are calculated, and the minimum amount of power needed to guarantee an assigned BER is determined. This work is a basic step in the direction of an automatic technology-aware network-level simulation framework capable of assembling complex optical switching fabrics, while at the same time assessing the practical feasibility and effectiveness at the physical/technological level.

  2. Thin-layer Spectroelectrochemistry of 3, 3',5, 5' -Tetramethyl- benzidine on Pt Minigrid Optically Transparent Electrode

    Institute of Scientific and Technical Information of China (English)

    Kui JIAO; Tao YANG; Zeng Jian WANG

    2005-01-01

    The electrooxidation behavior of 3, 3' 5, 5'-tetramethylbenzidine(TMB) was investigated using a platinum minigrid optically transparent thin-layer spectroelectrochemical cell. TMB underwent one two-electron electrooxidation process to yield quinonediimine in the pH range from2.0 to < 4.0, and two consecutive one-electron electrooxidation processes, gave the mediate product free radical of TMB first, then gave the oxidation product quinonediimine in the pH range from 4.0 to < 7.0. In the pH range from 7.0 to 10.0, the electrooxidation of TMB was also one two-electron electrooxidation process to yield an azo compound. The formal potential E0' and the electron transfer number of the electrooxidation of TMB at pH 2.0 and pH 8.4 were determined by spectroelectrochemical techniques.

  3. { P }{ T }-symmetric transport in non-{ P }{ T }-symmetric bi-layer optical arrays

    Science.gov (United States)

    Ramirez-Hernandez, J.; Izrailev, F. M.; Makarov, N. M.; Christodoulides, D. N.

    2016-09-01

    We study transport properties of an array created by alternating (a, b) layers with balanced loss/gain characterized by the key parameter γ. It is shown that for non-equal widths of (a, b) layers, i.e., when the corresponding Hamiltonian is non-{ P }{ T }-symmetric, the system exhibits the scattering properties similar to those of truly { P }{ T }-symmetric models provided that without loss/gain the structure presents the matched quarter stack. The inclusion of the loss/gain terms leads to an emergence of a finite number of spectral bands characterized by real values of the Bloch index. Each spectral band consists of a central region where the transmission coefficient {T}N≥slant 1, and two side regions with {T}N≤slant 1. At the borders between these regions the unidirectional reflectivity occurs. Also, the set of Fabry-Perot resonances with T N = 1 are found in spite of the presence of loss/gain.

  4. Double-layer optical fiber coating analysis in MHD flow of an elastico-viscous fluid using wet-on-wet coating process

    Science.gov (United States)

    Khan, Zeeshan; Islam, Saeed; Shah, Rehan Ali; Khan, Muhammad Altaf; Bonyah, Ebenezer; Jan, Bilal; Khan, Aurangzeb

    Modern optical fibers require a double-layer coating on the glass fiber in order to provide protection from signal attenuation and mechanical damage. The most important plastic resins used in wires and optical fibers are plastic polyvinyl chloride (PVC) and low and high density polyethylene (LDPE/HDPE), nylon and Polysulfone. One of the most important things which affect the final product after processing is the design of the coating die. In the present study, double-layer optical fiber coating is performed using melt polymer satisfying Oldroyd 8-constant fluid model in a pressure type die with the effect of magneto-hydrodynamic (MHD). Wet-on-wet coating process is applied for double-layer optical fiber coating. The coating process in the coating die is modeled as a simple two-layer Couette flow of two immiscible fluids in an annulus with an assigned pressure gradient. Based on the assumptions of fully developed laminar and MHD flow, the Oldroyd 8-constant model of non-Newtonian fluid of two immiscible resin layers is modeled. The governing nonlinear equations are solved analytically by the new technique of Optimal Homotopy Asymptotic Method (OHAM). The convergence of the series solution is established. The results are also verified by the Adomian Decomposition Method (ADM). The effect of important parameters such as magnetic parameter Mi , the dilatant constant α , the Pseodoplastic constant β , the radii ratio δ , the pressure gradient Ω , the speed of fiber optics V , and the viscosity ratio κ on the velocity profiles, thickness of coated fiber optics, volume flow rate, and shear stress on the fiber optics are investigated. At the end the result of the present work is also compared with the experimental results already available in the literature by taking non-Newtonian parameters tends to zero.

  5. Bioinformatics analyses of Shigella CRISPR structure and spacer classification.

    Science.gov (United States)

    Wang, Pengfei; Zhang, Bing; Duan, Guangcai; Wang, Yingfang; Hong, Lijuan; Wang, Linlin; Guo, Xiangjiao; Xi, Yuanlin; Yang, Haiyan

    2016-03-01

    Clustered regularly interspaced short palindromic repeats (CRISPR) are inheritable genetic elements of a variety of archaea and bacteria and indicative of the bacterial ecological adaptation, conferring acquired immunity against invading foreign nucleic acids. Shigella is an important pathogen for anthroponosis. This study aimed to analyze the features of Shigella CRISPR structure and classify the spacers through bioinformatics approach. Among 107 Shigella, 434 CRISPR structure loci were identified with two to seven loci in different strains. CRISPR-Q1, CRISPR-Q4 and CRISPR-Q5 were widely distributed in Shigella strains. Comparison of the first and last repeats of CRISPR1, CRISPR2 and CRISPR3 revealed several base variants and different stem-loop structures. A total of 259 cas genes were found among these 107 Shigella strains. The cas gene deletions were discovered in 88 strains. However, there is one strain that does not contain cas gene. Intact clusters of cas genes were found in 19 strains. From comprehensive analysis of sequence signature and BLAST and CRISPRTarget score, the 708 spacers were classified into three subtypes: Type I, Type II and Type III. Of them, Type I spacer referred to those linked with one gene segment, Type II spacer linked with two or more different gene segments, and Type III spacer undefined. This study examined the diversity of CRISPR/cas system in Shigella strains, demonstrated the main features of CRISPR structure and spacer classification, which provided critical information for elucidation of the mechanisms of spacer formation and exploration of the role the spacers play in the function of the CRISPR/cas system.

  6. The exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses

    Institute of Scientific and Technical Information of China (English)

    Hu Xiao-Long; Zhang Jiang-Yong; Shang Jing-Zhi; Liu Wen-Jie; Zhang Bao-Ping

    2010-01-01

    This paper studies the exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses by low temperature photoluminescence (PL) measurements. With increasing cap layer thickness, the PL peak energy shifts to lower energy and the coupling strength between the exciton and longitudinal-optical (LO) phonon, described by Huang-Rhys factor, increases remarkably due to an enhancement of the internal electric field. With increasing excitation intensity, the zero-phonon peak shows a blueshift and the Huang-Rhys factor decreases. These results reveal that there is a large built-in electric field in the well layer and the exciton-LO-phonon coupling is strongly affected by the thickness of the cap layer.

  7. Sidewall spacer optimization for steep switching junctionless transistors

    Science.gov (United States)

    Gupta, Manish; Kranti, Abhinav

    2016-06-01

    In this work, we analyze the impact of a high permittivity (high-κ) sidewall spacer and gate dielectric on the occurrence of sub-60 mV/decade subthreshold swing (S-swing) in symmetrical junctionless (JL) double gate (DG) transistors. It is shown that steep S-swing values (≤10 mV/decade) can be achieved in JL devices with a combination of a high permittivity (high-κ) gate dielectric and a narrow low permittivity (low-κ) sidewall spacer. Implementation of a wider high-κ spacer will diminish the degree of impact ionization by the influence of the fringing component of the gate electric field, and will not be useful for steep off-to-on current transition. A wider spacer with low-κ and a narrow spacer with high-κ permittivity will be useful to limit the latching effect that can occur at lower temperatures (250 K). For high temperature operation, the decrease in the impact ionization rate can be compensated by designing a JL transistor with a thicker silicon film. The work demonstrates opportunities to enhance impact ionization at sub bandgap voltages, and proposes optimal guidelines for selecting a sidewall spacer to facilitate steep switching in JL transistors.

  8. Experimental and statistical models of impact determination of the electron beam parameters on surface layers properties of optical elements in precision instruments building

    Directory of Open Access Journals (Sweden)

    I.V. Yatsenko

    2016-05-01

    Full Text Available Modern devices with optical elements for measurement and thermal control of different physical nature objects subjected to intense external thermal actions. To prevent destruction of optical elements the electron beam methods of work surfaces finishing at the stage of manufacture has practical significance. These methods can improve the properties of the element surface layers and thus make them more resistant to external thermal and mechanical action. Aim: The aim is to determine the optimal ranges of parameters of the electron beam and the development of experimental and statistical models that will automatically generate database with improved properties of the surface layers of optical elements in real time mode after previous electron beam treatment. Materials and Methods: To study the influence of parameters of the electron beam on the properties of the surface layers of the optical elements used plates of optical glass (K8, K108, etc. and ceramics (KO1, KO2, etc.. The strip electron beam has the following characteristics: density of heat flow Fn = 5∙10^6…9∙10^8 W/m2 and rate of displacement V = 0…0.1 m/s. Determination of the surface layers properties of the optical elements before and after electron beam treatment was carried out by known methods of physical and chemical analysis. Results: It was established that under the influence of the electron beam on the surface of the optical element there is visible clearing of various impurities take place, various micro-defects that remain on it after standard processing methods (mechanical, chemical, etc. remove and also its smoothness significantly increases, i.e. height of residual asperities on the surface is reduced. It was also found that the processing of optical glass elements by electron beam their surface layers change their structure, which is close to the quartz. It is shown that the surface of the preprocessed electron beam elements able to withstand the critical value of

  9. Raman Studies Of Laser Damaged Single- And Multi-Layer Optical Coatings

    Science.gov (United States)

    Exarhos, G. J.; Morse, P. L.

    1985-11-01

    Structural changes in dielectric optical coatings induced thermally or by high energy pulsed laser irradiation have been studied by the non-destructive technique of Raman Spectroscopy. A two laser (damage, probe) arrangement was used to characterize the damage process in crystalline and amorphous TiO2 and Zr02 coatings on silica during irradiation and at longer times following the onset of damage. Raman measurements were also undertaken to assess the effects of coating phase and microcrystalline grain orientation on laser induced damage in Ti02. Results suggest that certain phases have higher damage thresholds for comparable coating thicknesses and that thermal and electronic excitation effects are important considerations for modeling the damage process.

  10. Forest fire smoke layers observed in the free troposphere over Portugal with a multiwavelength Raman lidar: optical and microphysical properties.

    Science.gov (United States)

    Nepomuceno Pereira, Sérgio; Preißler, Jana; Guerrero-Rascado, Juan Luis; Silva, Ana Maria; Wagner, Frank

    2014-01-01

    Vertically resolved optical and microphysical properties of biomass burning aerosols, measured in 2011 with a multiwavelength Raman lidar, are presented. The transportation time, within 1-2 days (or less), pointed towards the presence of relatively fresh smoke particles over the site. Some strong layers aloft were observed with particle backscatter and extinction coefficients (at 355 nm) greater than 5 Mm(-1)sr(-1) and close to 300 Mm(-1), respectively. The particle intensive optical properties showed features different from the ones reported for aged smoke, but rather consistent with fresh smoke. The Ångström exponents were generally high, mainly above 1.4, indicating a dominating accumulation mode. Weak depolarization values, as shown by the small depolarization ratio of 5% or lower, were measured. Furthermore, the lidar ratio presented no clear wavelength dependency. The inversion of the lidar signals provided a set of microphysical properties including particle effective radius below 0.2 μm, which is less than values previously observed for aged smoke particles. Real and imaginary parts of refractive index of about 1.5-1.6 and 0.02i, respectively, were derived. The single scattering albedo was in the range between 0.85 and 0.93; these last two quantities indicate the nonnegligible absorbing characteristics of the observed particles.

  11. Polar interface and surface optical vibration spectra in multi-layer wurtzite quantum wires:transfer matrix method

    Institute of Scientific and Technical Information of China (English)

    Zhang Li

    2006-01-01

    The polar interface optical (IO) and surface optical (SO) phonon modes and the corresponding Frohlich electronphonon-interaction Hamiltonian in a freestanding multi-layer wurtzite cylindrical quantum wire (QWR) are derived and studied by employing the transfer matrix method in the dielectric continuum approximation and Loudon's uniaxial crystal model. A numerical calculation of a freestanding wurtzite GaN/AlN QWR is performed. The results reveal that for a relatively large azimuthal quantum number m or wave-number kz in the free z-direction, there exist two branches of IO phonon modes localized at the interface, and only one branch of SO mode localized at the surface in the system.The degenerating behaviours of the IO and SO phonon modes in the wurtzite QWR have also been clearly observed for a smallkz or m. The limiting frequency properties of the IO and SO modes for large kz and m have been explained reasonably from the mathematical and physical viewpoints. The calculations of electron-phonon coupling functions show that the high-frequency IO phonon branch and SO mode play a more important role in the electron-phonon interaction.

  12. Forest Fire Smoke Layers Observed in the Free Troposphere over Portugal with a Multiwavelength Raman Lidar: Optical and Microphysical Properties

    Directory of Open Access Journals (Sweden)

    Sérgio Nepomuceno Pereira

    2014-01-01

    Full Text Available Vertically resolved optical and microphysical properties of biomass burning aerosols, measured in 2011 with a multiwavelength Raman lidar, are presented. The transportation time, within 1-2 days (or less, pointed towards the presence of relatively fresh smoke particles over the site. Some strong layers aloft were observed with particle backscatter and extinction coefficients (at 355 nm greater than 5 Mm−1 sr−1 and close to 300 Mm−1, respectively. The particle intensive optical properties showed features different from the ones reported for aged smoke, but rather consistent with fresh smoke. The Ångström exponents were generally high, mainly above 1.4, indicating a dominating accumulation mode. Weak depolarization values, as shown by the small depolarization ratio of 5% or lower, were measured. Furthermore, the lidar ratio presented no clear wavelength dependency. The inversion of the lidar signals provided a set of microphysical properties including particle effective radius below 0.2 μm, which is less than values previously observed for aged smoke particles. Real and imaginary parts of refractive index of about 1.5-1.6 and 0.02i, respectively, were derived. The single scattering albedo was in the range between 0.85 and 0.93; these last two quantities indicate the nonnegligible absorbing characteristics of the observed particles.

  13. Variation in optical coherence tomography signal quality as an indicator of retinal nerve fibre layer segmentation error.

    Science.gov (United States)

    Folio, Lindsey S; Wollstein, Gadi; Ishikawa, Hiroshi; Bilonick, Richard A; Ling, Yun; Kagemann, Larry; Noecker, Robert J; Fujimoto, James G; Schuman, Joel S

    2012-04-01

    Commercial optical coherence tomography (OCT) systems use global signal quality indices to quantify scan quality. Signal quality can vary throughout a scan, contributing to local retinal nerve fibre layer segmentation errors (SegE). The purpose of this study was to develop an automated method, using local scan quality, to predict SegE. Good-quality (global signal strength (SS) ≥ 6; manufacturer specification) peripapillary circular OCT scans (fast retinal nerve fibre layer scan protocol; Stratus OCT; Carl Zeiss Meditec, Dublin, California, USA) were obtained from 6 healthy, 19 glaucoma-suspect and 43 glaucoma subjects. Scans were grouped based on SegE. Quality index (QI) values were computed for each A-scan using software of our own design. Logistic mixed-effects regression modelling was applied to evaluate SS, global mean and SD of QI, and the probability of SegE. The difference between local mean QI in SegE regions and No-SegE regions was -5.06 (95% CI -6.38 to 3.734) (psignal quality parameter, the variation of signal quality between A-scans provides significant information about the quality of an OCT scan and can be used as a predictor of segmentation error.

  14. Optical properties of ion-doped ZnO(Se) layers in the context of band anticrossing theory

    Energy Technology Data Exchange (ETDEWEB)

    Morozova, N. K., E-mail: MorozovaNK@mail.ru [National Research University “Moscow Power Engineering Institute” (Russian Federation); Galstyan, V. G. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Volkov, A. O. [National Research University “Moscow Power Engineering Institute” (Russian Federation); Mashchenko, V. E. [Russian Academy of Sciences, Frumkin Institute of Physical Chemistry and Electrochemistry (Russian Federation)

    2015-09-15

    The study of the optical properties of ZnO(Se) is a continuation of previous studies of ZnS(O), ZnSe(O), and CdS(O) systems in the context of band anticrossing theory. Selenium ions are implanted into high-purity zinc oxide crystals to a concentration of 10{sup 20} cm{sup –3}. The microcathodoluminescence spectra recorded with a scanning electron microscope at a temperature of 100 K provide information from the bulk of the implanted layer. The origin of the orange-red luminescence of ZnO(Se)–Zn layers is clarified. Orangered luminescence is thought to be a result of the formation of a highly mismatched alloy system, in which ZnSe(O) is formed during implantation and radiation annealing. Data suggesting that the green luminescence of pure self-activated ZnO–Zn is the self-activated (SA) emission studied in detail for other II–VI compounds (ZnS(O), ZnSe(O)) and defined by intrinsic defect complexes (A centers) are reported.

  15. Effect of Refractive Correction Error on Retinal Nerve Fiber Layer Thickness: A Spectralis Optical Coherence Tomography Study

    Science.gov (United States)

    Ma, Xiaoli; Chen, Yutong; Liu, Xianjie; Ning, Hong

    2016-01-01

    Background Identifying and assessing retinal nerve fiber layer defects are important for diagnosing and managing glaucoma. We aimed to investigate the effect of refractive correction error on retinal nerve fiber layer (RNFL) thickness measured with Spectralis spectral-domain optical coherence tomography (SD-OCT). Material/Methods We included 68 participants: 32 healthy (normal) and 36 glaucoma patients. RNFL thickness was measured using Spectralis SD-OCT circular scan. Measurements were made with a refractive correction of the spherical equivalent (SE), the SE+2.00D and the SE–2.00D. Results Average RNFL thickness was significantly higher in the normal group (105.88±10.47 μm) than in the glaucoma group (67.67±17.27 μm, Prefractive correction error significantly affected measurements of average (Prefractive correction error significantly increased average (Prefractive correction. However, −2.00D of refractive correction error did not significantly affect RNFL thickness measurements in either group. Conclusions Positive defocus error significantly affects RNFL thickness measurements made by the Spectralis SD-OCT. Negative defocus error did not affect RNFL measurement examined. Careful correction of refractive error is necessary to obtain accurate baseline and follow-up RNFL thickness measurements in healthy and glaucomatous eyes. PMID:28030536

  16. Structural and optical investigations on seed layer assisted hydrothermally grown ZnO nanorods on flat and textured substrates

    Science.gov (United States)

    Rayerfrancis, Arokiyadoss; Balaji Bhargav, P.; Ahmed, Nafis; Balaji, C.; Dhara, Sandip

    2016-12-01

    In this article we report the synthesis of vertically aligned ZnO nanorods on plain as well as textured fluorine doped tin oxide (FTO) coated glass substrate using hydrothermal method. Prior to hydrothermal method, AZO seed layer of thickness 5, 10 and 15 nm were deposited on the chosen substrates by DC magnetron sputtering. The as-grown nanorods were annealed at 450 °C for 3 h to improve the crystallinity. Morphology and structure of the nanorods was observed by field emission scanning electron microscopy. The formation of wurtzite structure was confirmed through x-ray diffraction studies. The optical mode of ZnO, E2 (high) at 434 cm-1 present in the samples was confirmed by Raman spectroscopy. The seed layer assisted growth of ZnO nanorods were defect free, which is confirmed from the photoluminescence spectra, and the intensity of band to band emission is much greater than the emission from the defects at the deep level.

  17. Effect of Hydroxychloroquine on the Retinal Layers: A Quantitative Evaluation with Spectral-Domain Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Hasim Uslu

    2016-01-01

    Full Text Available Purpose. To evaluate the effect of hydroxychloroquine on retinal pigment epithelium- (RPE- Bruch’s membrane complex, photoreceptor outer segment, and macular ganglion cell-inner plexiform layer (GCIPL thicknesses using spectral-domain optical coherence tomography (SD-OCT. Methods. In this prospective case-control study, 51 eyes of 51 hydroxychloroquine patients and 30 eyes of 30 healthy subjects were included. High-quality images were obtained using a Cirrus HD-OCT with 5-line raster mode; the photoreceptor inner segment (IS and outer segment (OS, sum of the segments (IS + OS, and RPE-Bruch’s membrane complex were analyzed. Results. The thicknesses of the IS + OS and OS layers were significantly lower in the hydroxychloroquine subjects compared to the control subjects (P<0.05. RPE-Bruch’s membrane complex thicknesses were significantly higher in the hydroxychloroquine subjects than for those of the control subjects (P<0.05. The minimum and temporal-inferior macular GCIPL thicknesses were significantly different between the patients with hydroxychloroquine use and the control subjects (P=0.04 and P=0.03, resp.. Conclusions. The foveal photoreceptor OS thinning, loss of GCIPL, and RPE-Bruch’s membrane thickening were detected in patients with hydroxychloroquine therapy. This quantitative approach using SD-OCT images may have important implications to use as an early indicator of retinal toxicity without any visible signs of hydroxychloroquine retinopathy.

  18. Structural Alterations of Segmented Macular Inner Layers in Aquaporin4-Antibody-Positive Optic Neuritis Patients in a Chinese Population.

    Directory of Open Access Journals (Sweden)

    Chunxia Peng

    Full Text Available This study aimed to analyse the structural injury of the peripapillary retinal nerve fibre layer (pRNFL and segmented macular layers in optic neuritis (ON in aquaporin4-antibody (AQP4-Ab seropositivity(AQP4-Ab-positiveON patients and in AQP4-Ab seronegativity (AQP4-Ab-negative ON patients in order to evaluate their correlations with the best-corrected visual acuity (BCVA and the value of the early diagnosis of neuromyelitis optica (NMO.This is a retrospective, cross-sectional and control observational study.In total, 213 ON patients (291 eyes and 50 healthy controls (HC (100 eyes were recruited in this study. According to a serum AQP4-Ab assay, 98 ON patients (132 eyes were grouped as AQP4-Ab-positive ON and 115 ON patients (159 eyes were grouped as AQP4-Ab-negative ON cohorts. All subjects underwent scanning with spectralis optical coherence tomography (OCT and BCVA tests. pRNFL and segmented macular layer measurements were analysed.The pRNFL thickness in AQP4-Ab-positive ON eyes showed a more serious loss during 0-2 months (-27.61μm versus -14.47 μm and ≥6 months (-57.91μm versus -47.19μm when compared with AQP4-Ab-negative ON eyes. AQP4-Ab-positive ON preferentially damaged the nasal lateral pRNFL. The alterations in the macular ganglion cell layer plus the inner plexiform layer (GCIP in AQP4-Ab-positive ON eyes were similar to those in AQP4-Ab-negative ON eyes. AQP4-Ab-positive ON eyes had entirely different injury patterns in the inner nuclear layer (INL compared with AQP4-Ab-negative ON eyes during the first 6 months after the initial ON attack. These differences were as follows: the INL volume of AQP4-Ab-positive ON eyes had a gradual growing trend compared with AQP4-Ab-negative ON eyes, and it increased rapidly during 0-2 months, reached its peak during 2-4 months, and then decreased gradually. The pRNFL and GCIP in AQP4-Ab-positive ON eyes had positive correlations with BCVA. When the pRNFL thickness decreased to 95%CI (50.77

  19. Structural Alterations of Segmented Macular Inner Layers in Aquaporin4-Antibody-Positive Optic Neuritis Patients in a Chinese Population

    Science.gov (United States)

    Peng, Chunxia; Wang, Wei; Xu, Quangang; Zhao, Shuo; Li, Hongyang; Yang, Mo; Cao, Shanshan; Zhou, Huanfen; Wei, Shihui

    2016-01-01

    Objectives This study aimed to analyse the structural injury of the peripapillary retinal nerve fibre layer (pRNFL) and segmented macular layers in optic neuritis (ON) in aquaporin4-antibody (AQP4-Ab) seropositivity(AQP4-Ab-positiveON) patients and in AQP4-Ab seronegativity (AQP4-Ab-negative ON) patients in order to evaluate their correlations with the best-corrected visual acuity (BCVA) and the value of the early diagnosis of neuromyelitis optica (NMO). Design This is a retrospective, cross-sectional and control observational study. Methods In total, 213 ON patients (291 eyes) and 50 healthy controls (HC) (100 eyes) were recruited in this study. According to a serum AQP4-Ab assay, 98 ON patients (132 eyes) were grouped as AQP4-Ab-positive ON and 115 ON patients (159 eyes) were grouped as AQP4-Ab-negative ON cohorts. All subjects underwent scanning with spectralis optical coherence tomography (OCT) and BCVA tests. pRNFL and segmented macular layer measurements were analysed. Results The pRNFL thickness in AQP4-Ab-positive ON eyes showed a more serious loss during 0–2 months (-27.61μm versus -14.47 μm) and ≥6 months (-57.91μm versus -47.19μm) when compared with AQP4-Ab-negative ON eyes. AQP4-Ab-positive ON preferentially damaged the nasal lateral pRNFL. The alterations in the macular ganglion cell layer plus the inner plexiform layer (GCIP) in AQP4-Ab-positive ON eyes were similar to those in AQP4-Ab-negative ON eyes. AQP4-Ab-positive ON eyes had entirely different injury patterns in the inner nuclear layer (INL) compared with AQP4-Ab-negative ON eyes during the first 6 months after the initial ON attack. These differences were as follows: the INL volume of AQP4-Ab-positive ON eyes had a gradual growing trend compared with AQP4-Ab-negative ON eyes, and it increased rapidly during 0–2 months, reached its peak during 2–4 months, and then decreased gradually. The pRNFL and GCIP in AQP4-Ab-positive ON eyes had positive correlations with BCVA. When the p

  20. Optical Addressing Electronic Tongue Based on Low Selective Photovoltaic Transducer with Nanoporous Silicon Layer

    Science.gov (United States)

    Litvinenko, S. V.; Bielobrov, D. O.; Lysenko, V.; Skryshevsky, V. A.

    2016-08-01

    The electronic tongue based on the array of low selective photovoltaic (PV) sensors and principal component analysis is proposed for detection of various alcohol solutions. A sensor array is created at the forming of p-n junction on silicon wafer with porous silicon layer on the opposite side. A dynamical set of sensors is formed due to the inhomogeneous distribution of the surface recombination rate at this porous silicon side. The sensitive to molecular adsorption photocurrent is induced at the scanning of this side by laser beam. Water, ethanol, iso-propanol, and their mixtures were selected for testing. It is shown that the use of the random dispersion of surface recombination rates on different spots of the rear side of p-n junction and principal component analysis of PV signals allows identifying mentioned liquid substances and their mixtures.

  1. Optical nonlinear response of a single nonlinear dielectric layer sandwiched between two linear dielectric structures

    Energy Technology Data Exchange (ETDEWEB)

    Lidorikis, E. [Ames Laboratory--USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States); Busch, K. [Ames Laboratory--USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)]|[Instituet fuer Theorie der Kondensierten Materie, Universitaet Karlsruhe, D-76128, Karlsruhe (Germany); Li, Q. [Ames Laboratory--USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States); Chan, C.T. [Ames Laboratory--USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)]|[Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Soukoulis, C.M. [Ames Laboratory--USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

    1997-12-01

    We consider the general problem of electromagnetic wave propagation through a one-dimensional system consisting of a nonlinear medium sandwiched between two linear structures. Special emphasis is given to systems where the latter comprise Bragg reflectors. We obtain an exact expression for the nonlinear response of such dielectric superlattices when the nonlinear impurity is very thin, or in the {delta}-function limit. We find that both the switching-up and switching-down intensities of the bistable response can be made very low, when the frequency of the incident wave matches that of the impurity mode of the structure. Numerical results for a nonlinear layer of finite width display qualitatively similar behavior, thus confirming the usefulness of the simpler {delta}-function model. In addition, an analytical solution for the resonance states of an infinitely extended finite-width superlattice with a finite-width nonlinear impurity is presented. {copyright} {ital 1997} {ital The American Physical Society}

  2. Fabrication and optical property of silicon oxide layer coated semiconductor gallium nitride nanowires.

    Science.gov (United States)

    Zhang, Jun; Zhang, Lide; Jiang, Feihong; Yang, Yongdong; Li, Jianping

    2005-01-13

    Quasi one-dimensional GaN-SiO(2) nanostructures, with a silicon oxide layer coated on semiconductor GaN nanowires, were successfully synthesized through as-synthesized SiO(2) nanoparticles-assisted reaction. The experimental results indicate that the nanostructure consists of single-crystalline wurtzite GaN nanowire core, an amorphous SiO(2) outer shell separated in the radial direction. These quasi one-dimensional nanowires have the diameters of a few tens of nanometers and lengths up to several hundreds of micrometers. The photoluminescence spectrum of the GaN-SiO(2) nanostructures consists of one broad blue-light emission peak at 480 nm and another weak UV emission peak at 345 nm. The novel method, which may results in high yield and high reproducibility, is demonstrated to be a unique technique for producing nanostructures with controlled morphology.

  3. Optical Addressing Electronic Tongue Based on Low Selective Photovoltaic Transducer with Nanoporous Silicon Layer.

    Science.gov (United States)

    Litvinenko, S V; Bielobrov, D O; Lysenko, V; Skryshevsky, V A

    2016-12-01

    The electronic tongue based on the array of low selective photovoltaic (PV) sensors and principal component analysis is proposed for detection of various alcohol solutions. A sensor array is created at the forming of p-n junction on silicon wafer with porous silicon layer on the opposite side. A dynamical set of sensors is formed due to the inhomogeneous distribution of the surface recombination rate at this porous silicon side. The sensitive to molecular adsorption photocurrent is induced at the scanning of this side by laser beam. Water, ethanol, iso-propanol, and their mixtures were selected for testing. It is shown that the use of the random dispersion of surface recombination rates on different spots of the rear side of p-n junction and principal component analysis of PV signals allows identifying mentioned liquid substances and their mixtures.

  4. Free-space optical communication links and evaporation layer study near sea surface at 1.55 μm

    Science.gov (United States)

    Zeller, John; Manzur, Tariq

    2011-06-01

    In many situations where it is necessary to set up a communication link such as emergencies or in remote locations, running fiber between two sites is not practical. Free-space optics (FSO) holds the potential for high bandwidth communication in such situations with relatively low cost, low maintenance, quick installation times, and average 70- 80% connectivity. Since atmospheric conditions can significantly affect the capability of this type of communication system to transfer information consistently and operate effectively, the effects of atmosphere on FSO communication and consequent optimal wavelength range for transmission are investigated through MODTRAN-based modeling of 1.55 μm transmission. Simulations were performed for multiple elevation angles in atmospheric weather conditions including clear maritime, desert extinction, and various levels of rain and fog to simulate surface-to-surface and surfaceto- air FSO communication networks. Atmospheric, free-space, and scintillation losses are analyzed for optical path lengths of up to 2 km or greater to determine minimum transmit power required for successful data reception. In addition, the effects of atmospheric turbulence on beam propagation in the evaporation layer are investigated, where wavefront sensing with adaptive optics as well as a software Kalman filter are seen as a means to compensate for wavefront distortion. Using advanced laser sources to provide illumination at infrared wavelengths, particularly around the eye-safe 1.55 μm wavelength, it should be possible to overcome many transmission limitations associated with atmospheric conditions such as adverse weather and turbulence to enable high data rate communication links where the use of fiber is not practical or prohibited.

  5. The potential of standard and modified feed spacers for biofouling control

    KAUST Repository

    Araújo, Paula A.

    2012-06-01

    The impact of feed spacers on initial feed channel pressure (FCP) drop, FCP increase and biomass accumulation has been studied in membrane fouling simulators using feed spacers applied in commercially available nanofiltration and reverse osmosis spiral wound membrane modules. All spacers had a similar geometry.Our studies showed that biofouling was not prevented by (i) variation of spacer thickness, (ii) feed spacer orientation, (iii) feed spacer coating with silver, copper or gold and (iv) using a biostatic feed spacer. At constant feed flow, a lower FCP and FCP increase were observed for a thicker feed spacer. At constant linear flow velocity, roughly the same FCP development and biomass accumulation were found irrespective of the feed spacer thickness: hydrodynamics and substrate load were more important for development and impact of biofouling than the thickness of currently applied spacers. Use of biostatic and metal coated spacers were not effective for biofouling control. The same small reduction of biofouling rate was observed with copper and silver coated spacers as well as uncoated 45° rotated spacers.The studied modified spacers were not effective for biofouling prevention and control. The impact of biofouling on FCP increase was reduced significantly by a lower linear flow velocity, while spacer orientation and spacer thickness in membrane modules had a smaller but still significant effect. © 2012 Elsevier B.V.

  6. Optical coherence tomography, scanning laser polarimetry and confocal scanning laser ophthalmoscopy in retinal nerve fiber layer measurements of glaucoma patients.

    Science.gov (United States)

    Fanihagh, Farsad; Kremmer, Stephan; Anastassiou, Gerasimos; Schallenberg, Maurice

    2015-01-01

    To determine the correlations and strength of association between different imaging systems in analyzing the retinal nerve fiber layer (RNFL) of glaucoma patients: optical coherence tomography (OCT), scanning laser polarimetry (SLP) and confocal scanning laser ophthalmoscopy (CSLO). 114 eyes of patients with moderate open angle glaucoma underwent spectral domain OCT (Topcon SD-OCT 2000 and Zeiss Cirrus HD-OCT), SLP (GDx VCC and GDx Pro) and CSLO (Heidelberg Retina Tomograph, HRT 3). Correlation coefficients were calculated between the structural parameters yielded by these examinations. The quantitative relationship between the measured RNFL thickness globally and for the four regions (superior, inferior, nasal, temporal) were evaluated with different regression models for all used imaging systems. The strongest correlation of RNFL measurements was found between devices using the same technology like GDx VCC and GDx Pro as well as Topcon OCT and Cirrus OCT. In glaucoma patients, the strongest associations (R²) were found between RNFL measurements of the two optical coherence tomography devices Topcon OCT and Cirrus OCT (R² = 0.513) and between GDx VCC and GDx Pro (R² = 0.451). The results of the OCTs and GDX Pro also had a strong quantitative relationship (Topcon OCT R² = 0.339 and Cirrus OCT R² = 0.347). GDx VCC and the OCTs showed a mild to moderate association (Topcon OCT R² = 0.207 and Cirrus OCT R² = 0.258). The confocal scanning laser ophthalmoscopy (HRT 3) had the lowest association to all other devices (Topcon OCT R² = 0.254, Cirrus OCT R² = 0.158, GDx Pro R² = 0.086 and GDx VCC R² = 0.1). The measurements of the RNFL in glaucoma patients reveal a high correlation of OCT and GDx devices because OCTs can measure all major retinal layers and SLP can detect nerve fibers allowing a comparison between the results of this devices. However, CSLO by means of HRT topography can only measure height values of the retinal surface but it cannot distinguish

  7. Optic Nerve Head and Retinal Nerve Fiber Layer Analysis in Ocular Hypertension and Early-Stage Glucoma Using Spectral-Domain Optical Coherence Tomography Copernicus

    Directory of Open Access Journals (Sweden)

    Nilgün Solmaz

    2014-01-01

    Full Text Available Objectives: Evaluation of structural alterations of the optic nerve head (ONH and the retinal nerve fiber layer (RNFL in patients with ocular hypertension (OHT and early-stage glaucoma and assessment of the discriminatory diagnostic performance of spectral-domain optical coherence tomography (SD-OCT Copernicus (Optopol Technology S.A.. Materials and Methods: This study included 59 eyes of a total of 59 patients, 29 of whom were diagnosed with OHT (Group 1 and 30 with early-stage glaucoma (Group 2. The differentiation of early-stage glaucoma and OHT was carried out on the basis of standard achromatic visual field test results. Analysis of the ONH and RNFL thickness of all cases was made using SD-OCT. Group 1 and Group 2 were compared with respect to the ONH parameters and RNFL thickness. The diagnostic sensitivity of the OCT parameters was evaluated by the area under the receiver operating characteristics curves (AUC. Results: The average, superior, inferior, and nasal RNFL thicknesses in early-stage glaucoma cases were approximately 10% (12-14 µm less compared to the OHT eyes, with differences being highly significant (p≤0.001. However, there was no statistically significant difference in the temporal RNFL thicknesses. The most sensitive parameter in the early diagnosis of glaucoma was average RNFL thickness corresponding to AUC: 0.852, followed by AUC: 0.816 and AUC: 0.773 values in superior and inferior RNFL thickness, respectively. In localized RNFL defects, the highest sensitivity corresponded to superior and superonasal quadrants (ACU: 0.805 and ACU: 0.781, respectively. There were not any statistically significant differences between the ONH morphological parameters of the two groups. Conclusion: RNFL analysis obtained using SD-OCT Copernicus is able to discriminate early-stage glaucoma eyes from those with OHT. However, ONH morphological parameters do not have the same diagnostic sensitivity. Turk J Ophthalmol 2014; 44: 35-41

  8. Spectral domain optical coherence tomography in glaucoma: qualitative and quantitative analysis of the optic nerve head and retinal nerve fiber layer (an AOS thesis).

    Science.gov (United States)

    Chen, Teresa C

    2009-12-01

    To demonstrate that video-rate spectral domain optical coherence tomography (SDOCT) can qualitatively and quantitatively evaluate optic nerve head (ONH) and retinal nerve fiber layer (RNFL) glaucomatous structural changes. To correlate quantitative SDOCT parameters with disc photography and visual fields. SDOCT images from 4 glaucoma eyes (4 patients) with varying stages of open-angle glaucoma (ie, early, moderate, late) were qualitatively contrasted with 2 age-matched normal eyes (2 patients). Of 61 other consecutive patients recruited in an institutional setting, 53 eyes (33 patients) met inclusion/exclusion criteria for quantitative studies. Images were obtained using two experimental SDOCT systems, one utilizing a superluminescent diode and the other a titanium:sapphire laser source, with axial resolutions of about 6 microm and 3 microm, respectively. Classic glaucomatous ONH and RNFL structural changes were seen in SDOCT images. An SDOCT reference plane 139 microm above the retinal pigment epithelium yielded cup-disc ratios that best correlated with masked physician disc photography cup-disc ratio assessments. The minimum distance band, a novel SDOCT neuroretinal rim parameter, showed good correlation with physician cup-disc ratio assessments, visual field mean deviation, and pattern standard deviation (P values range, .0003-.024). RNFL and retinal thickness maps correlated well with disc photography and visual field testing. To our knowledge, this thesis presents the first comprehensive qualitative and quantitative evaluation of SDOCT images of the ONH and RNFL in glaucoma. This pilot study provides basis for developing more automated quantitative SDOCT-specific glaucoma algorithms needed for future prospective multicenter national trials.

  9. Spectral Domain Optical Coherence Tomography in Glaucoma: Qualitative and Quantitative Analysis of the Optic Nerve Head and Retinal Nerve Fiber Layer (An AOS Thesis)

    Science.gov (United States)

    Chen, Teresa C.

    2009-01-01

    Purpose: To demonstrate that video-rate spectral domain optical coherence tomography (SDOCT) can qualitatively and quantitatively evaluate optic nerve head (ONH) and retinal nerve fiber layer (RNFL) glaucomatous structural changes. To correlate quantitative SDOCT parameters with disc photography and visual fields. Methods: SDOCT images from 4 glaucoma eyes (4 patients) with varying stages of open-angle glaucoma (ie, early, moderate, late) were qualitatively contrasted with 2 age-matched normal eyes (2 patients). Of 61 other consecutive patients recruited in an institutional setting, 53 eyes (33 patients) met inclusion/exclusion criteria for quantitative studies. Images were obtained using two experimental SDOCT systems, one utilizing a superluminescent diode and the other a titanium:sapphire laser source, with axial resolutions of about 6 μm and 3 μm, respectively. Results: Classic glaucomatous ONH and RNFL structural changes were seen in SDOCT images. An SDOCT reference plane 139 μm above the retinal pigment epithelium yielded cup-disc ratios that best correlated with masked physician disc photography cup-disc ratio assessments. The minimum distance band, a novel SDOCT neuroretinal rim parameter, showed good correlation with physician cup-disc ratio assessments, visual field mean deviation, and pattern standard deviation (P values range, .0003–.024). RNFL and retinal thickness maps correlated well with disc photography and visual field testing. Conclusions: To our knowledge, this thesis presents the first comprehensive qualitative and quantitative evaluation of SDOCT images of the ONH and RNFL in glaucoma. This pilot study provides basis for developing more automated quantitative SDOCT-specific glaucoma algorithms needed for future prospective multicenter national trials. PMID:20126502

  10. Optical characterization of free electron concentration in heteroepitaxial InN layers using Fourier transform infrared spectroscopy and a 2 Multiplication-Sign 2 transfer-matrix algebra

    Energy Technology Data Exchange (ETDEWEB)

    Katsidis, C. C. [Department of Materials Science and Technology, University of Crete, P.O. Box 2208, 71003 Heraklion-Crete (Greece); Ajagunna, A. O.; Georgakilas, A. [Microelectronics Research Group, IESL, FORTH, P.O. Box 1385, 71110 Heraklion-Crete (Greece); Physics Department, University of Crete, P.O. Box 2208, 71003 Heraklion-Crete (Greece)

    2013-02-21

    Fourier Transform Infrared (FTIR) reflectance spectroscopy has been implemented as a non-destructive, non-invasive, tool for the optical characterization of a set of c-plane InN single heteroepitaxial layers spanning a wide range of thicknesses (30-2000 nm). The c-plane (0001) InN epilayers were grown by plasma-assisted molecular beam epitaxy (PAMBE) on GaN(0001) buffer layers which had been grown on Al{sub 2}O{sub 3}(0001) substrates. It is shown that for arbitrary multilayers with homogeneous anisotropic layers having their principal axes coincident with the laboratory coordinates, a 2 Multiplication-Sign 2 matrix algebra based on a general transfer-matrix method (GTMM) is adequate to interpret their optical response. Analysis of optical reflectance in the far and mid infrared spectral range has been found capable to discriminate between the bulk, the surface and interface contributions of free carriers in the InN epilayers revealing the existence of electron accumulation layers with carrier concentrations in mid 10{sup 19} cm{sup -3} at both the InN surface and the InN/GaN interface. The spectra could be fitted with a three-layer model, determining the different electron concentration and mobility values of the bulk and of the surface and the interface electron accumulation layers in the InN films. The variation of these values with increasing InN thickness could be also sensitively detected by the optical measurements. The comparison between the optically determined drift mobility and the Hall mobility of the thickest sample reveals a value of r{sub H} = 1.49 for the Hall factor of InN at a carrier concentration of 1.11 Multiplication-Sign 10{sup 19} cm{sup -3} at 300 Degree-Sign {Kappa}.

  11. Determination of the types and densities of dislocations in GaN epitaxial layers of different thicknesses by optical and atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kravchuk, K. S. [Moscow State Institute of Steel and Alloys (Russian Federation); Mezhennyi, M. V. [Institute of Chemical Problems for Microelectronics (Russian Federation); Yugova, T. G., E-mail: p_Yugov@mail.ru [Institute of Rare Metals (Russian Federation)

    2012-03-15

    The change in the dislocation density on the surface of GaN epitaxial layers, which were grown by hydride vapor-phase epitaxy on sapphire substrates with c and r orientations, has been investigated by optical and atomic force microscopy (AFM). It is shown that the observed decrease in the density of threading dislocations with an increase in the layer thickness is related to the annihilation of mixed dislocations. The experimental and theoretical data on the change in the density of mixed dislocations with an increase in the epitaxial-layer thickness are in good correspondence.

  12. Validation of ASH Optical Depth and Layer Height from IASI using Earlinet Lidar Data

    Science.gov (United States)

    Balis, D.; Siomos, N.; Koukouli, M.; Clarisse, L.; Carboni, E.; Ventress, L.; Grainger, R.; Mona, L.; Pappalardo, G.

    2016-06-01

    The 2010 eruptions of the Icelandic volcano Eyjafjallajökull attracted the attention of the public and the scientific community to the vulnerability of the European airspace to volcanic eruptions. The European Space Agency project "Satellite Monitoring of Ash and Sulphur Dioxide for the mitigation of Aviation Hazards", called for the creation of an optimal End-to-End System for Volcanic Ash Plume Monitoring and Prediction. This system is based on improved and dedicated satellite-derived ash plume and sulphur dioxide level assessments, as well as an extensive validation, using among others ground-based measurements (Koukouli et al., 2014). The validation of volcanic ash levels and height extracted from IASI/MetopA is presented in this work with emphasis on the ash plume height and ash optical depth levels. European Aerosol Research Lidar Network [EARLINET] lidar measurements are compared to different satellite estimates for two eruptive episodes. The validation results are extremely promising within the estimated uncertainties of each of the comparative datasets.

  13. Optical properties of spray coated layers with carbon nanotubes and graphene nanoplatelets

    Science.gov (United States)

    Lorenc, Zofia; Krzeminski, Jakub; Wroblewski, Grzegorz; Salbut, Leszek

    2016-04-01

    Carbon nanotubes as well as graphene are allotropic forms of carbon. Graphene is a two dimensional (2D) form of atomic-scale, hexagonal lattice, while carbon nanotube is a cylindrical nanostructure composed of a rolled sheet of graphene lattice at specific and discrete angles. Both of discussed materials have a high potential for modern engineering, especially in organic and printed electronics. High transparency in the visible part of the electromagnetic spectrum and low electrical resistance are desirable features in various applications and may be fulfilled with studied carbon nanomaterials. They have chances to become an important technological improvement in customers electronic devices by applying them to electrodes production in flexible screens and light sources. Graphene end carbon nanotubes are conceptually similar. However, characteristic properties of these two substances are different. In the article authors present the results of the transmission in visible electromagnetic spectrum characteristics of different samples. This parameter and the resistance of electrodes are tested, analysed and compared. Characteristics of optical transmittance against resistance with the optimal point of that relationship are presented in paper. Moreover, dependency of graphene nanoplatelets agglomerates arrangement against type of nano-fillers is shown. Two groups of tested inks contain graphene nanoplatelets with different fillers diameters. The third group contains carbon nanotubes. Described parameters are important for production process and results of analysis can be used by technologists working with elastic electronics.

  14. Negative refractive index and higher-order harmonics in layered metallodielectric optical metamaterials

    CERN Document Server

    Maas, Ruben; Parsons, James; Polman, Albert

    2014-01-01

    We study the propagation of light in a three-dimensional double-periodic Ag/TiO2 multilayer metamaterial composed of coupled plasmonic waveguides operating in the visible and UV spectral range. For these frequencies, light propagation in the plane of the waveguides is described by a negative phase velocity, while for the orthogonal direction light propagation is described by a Bloch wave composed of a large number of harmonics. As a result, the material cannot generally be described by a single phase index: decomposing the Bloch wave into different harmonics we show that for the wavelength range of interest the positive index m=1 harmonic dominates the propagation of light in the orthogonal direction. These results are corroborated by numerical simulations and optical refraction experiments on a double-periodic Ag/TiO2 multilayer metamaterial prism in the 380-600 nm spectral range, which show that positive refraction associated with right-handed harmonics dominates. Studying the isofrequency contours we find ...

  15. Noninvasive Quantitative Evaluation of the Dentin Layer during Dental Procedures Using Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Cosmin Sinescu

    2015-01-01

    Full Text Available A routine cavity preparation of a tooth may lead to opening the pulp chamber. The present study evaluates quantitatively, in real time, for the first time to the best of our knowledge, the drilled cavities during dental procedures. An established noninvasive imaging technique, Optical Coherence Tomography (OCT, is used. The main scope is to prevent accidental openings of the dental pulp chamber. Six teeth with dental cavities have been used in this ex vivo study. The real time assessment of the distances between the bottom of the drilled cavities and the top of the pulp chamber was performed using an own assembled OCT system. The evaluation of the remaining dentin thickness (RDT allowed for the positioning of the drilling tools in the cavities in relation to the pulp horns. Estimations of the safe and of the critical RDT were made; for the latter, the opening of the pulp chamber becomes unavoidable. Also, by following the fractures that can occur when the extent of the decay is too large, the dentist can decide upon the right therapy to follow, endodontic or conventional filling. The study demonstrates the usefulness of OCT imaging in guiding such evaluations during dental procedures.

  16. Improving optical performance of concentrator cells by means of a deposited nanopattern layer

    Energy Technology Data Exchange (ETDEWEB)

    García-Linares, Pablo, E-mail: pablo.garcia-linares@cea.fr; Besson, Pierre; Weick, Clément; Baudrit, Mathieu [CEA-LITEN, Laboratoire de Photovoltaïque à Concentration, INES, Le Bourget du Lac (France); Dominguez, César [CEA-LITEN, Laboratoire de Photovoltaïque à Concentration, INES, Le Bourget du Lac (France); Instituto de Energía Solar - Universidad Politécnica de Madrid, Madrid (Spain); Dellea, Olivier [CEA-LITEN, Laboratoire de Surfaces Nanostructurées, Grenoble (France); Kämpfe, Thomas; Jourlin, Yves [Laboratoire Hubert Curien UMR CNRS, Université de Lyon, St. Etienne (France)

    2015-09-28

    Multijunction solar cells (MJSC) use anti-reflective coatings (ARC) to minimize Fresnel reflection losses for a family of light incidence angles. These coatings adapt the refractive index of the cell to that of the surrounding medium. Patterns with sizes in the range of the light wavelength can be used to further reduce reflections through diffraction. Transparent nanopatterns with a gradual profile, called moth-eye nanostructures, can adapt the refractive index of the optical interfaces (often with n∼1.5) used to encapsulate concentrator solar cells to that of the air (n{sub air}∼1). Here we show the effect of a nanometric moth-eye ARC with a round motif deposited on commercial MJSC that achieves short-circuit current (I{sub SC}) gains greater than 2% at normal incidence and even higher in the case of tilted illumination. In this work, MJSC with different moth-eye ARC are characterized under quantum efficiency (QE) as well as under concentrated illumination I-V in order to assess their potential. Simulations based on coupled wave analysis (RCWA) are used to fit the experimental results with successful results.

  17. Speckle Noise Reduction for the Enhancement of Retinal Layers in Optical Coherence Tomography Images

    Directory of Open Access Journals (Sweden)

    Fereydoon Nowshiravan Rahatabad

    2015-09-01

    Full Text Available Introduction One of the most important pre-processing steps in optical coherence tomography (OCT is reducing speckle noise, resulting from multiple scattering of tissues, which degrades the quality of OCT images. Materials and Methods The present study focused on speckle noise reduction and edge detection techniques. Statistical filters with different masks and noise variances were applied on OCT and test images. Objective evaluation of both types of images was performed, using various image metrics such as peak signal-to-noise ratio (PSNR, root mean square error, correlation coefficient and elapsed time. For the purpose of recovery, Kuan filter was used as an input for edge enhancement. Also, a spatial filter was applied to improve image quality. Results The obtained results were presented as statistical tables and images. Based on statistical measures and visual quality of OCT images, Enhanced Lee filter (3×3 with a PSNR value of 43.6735 in low noise variance and Kuan filter (3×3 with a PSNR value of 37.2850 in high noise variance showed superior performance over other filters. Conclusion Based on the obtained results, by using speckle reduction filters such as Enhanced Lee and Kuan filters on OCT images, the number of compounded images, required to achieve a given image quality, could be reduced. Moreover, use of Kuan filters for promoting the edges allowed smoothing of speckle regions, while preserving image tissue texture.

  18. Vertically oriented few-layered HfS2 nanosheets: growth mechanism and optical properties

    Science.gov (United States)

    Zheng, Binjie; Chen, Yuanfu; Wang, Zegao; Qi, Fei; Huang, Zhishuo; Hao, Xin; Li, Pingjian; Zhang, Wanli; Li, Yanrong

    2016-09-01

    For the first time, large-area, vertically oriented few-layered hafnium disulfide (V-{{{HfS}}}2) nanosheets have been grown by chemical vapor deposition. The individual {{{HfS}}}2 nanosheets are well [001] oriented, with highly crystalline quality. Far different from conventional van der Waals epitaxial growth mechanism for two-dimensional transition metal dichalcogenides, a novel dangling-bond-assisted self-seeding growth mechanism is proposed to describe the growth of V-{{{HfS}}}2 nanosheets: difficult migration of {{{HfS}}}2 adatoms on substrate surface results in {{{HfS}}}2 seeds growing perpendicularly to the substrate; V-{{{HfS}}}2 nanosheets inherit the growth direction of {{{HfS}}}2 seeds; V-{{{HfS}}}2 nanosheets further expand in the in-plane direction with time evolution. Moreover, the V-{{{HfS}}}2 nanosheets show strong and broadened photons absorption from near infrared to ultraviolet; the V-{{{HfS}}}2-based photodetector exhibits an ultrafast photoresponse time of 24 ms, and a high photosensitivity ca. 103 for 405 nm laser.

  19. A high-sensitivity fiber-optic evanescent wave sensor with a three-layer structure composed of Canada balsam doped with GeO2.

    Science.gov (United States)

    Zhong, Nianbing; Zhao, Mingfu; Zhong, Lianchao; Liao, Qiang; Zhu, Xun; Luo, Binbin; Li, Yishan

    2016-11-15

    In this paper, we present a high-sensitivity polymer fiber-optic evanescent wave (FOEW) sensor with a three-layer structure that includes bottom, inter-, and surface layers in the sensing region. The bottom layer and inter-layer are POFs composed of standard cladding and the core of the plastic optical fiber, and the surface layer is made of dilute Canada balsam in xylene doped with GeO2. We examine the morphology of the doped GeO2, the refractive index and composition of the surface layer and the surface luminous properties of the sensing region. We investigate the effects of the content and morphology of the GeO2 particles on the sensitivity of the FOEW sensors by using glucose solutions. In addition, we examine the response of sensors incubated with staphylococcal protein A plus mouse IgG isotype to goat anti-mouse IgG solutions. Results indicate very good sensitivity of the three-layer FOEW sensor, which showed a 3.91-fold improvement in the detection of the target antibody relative to a conventional sensor with a core-cladding structure, and the novel sensor showed a lower limit of detection of 0.2ng/l and a response time around 320s. The application of this high-sensitivity FOEW sensor can be extended to biodefense, disease diagnosis, biomedical and biochemical analysis.

  20. Topography, complex refractive index, and conductivity of graphene layers measured by correlation of optical interference contrast, atomic force, and back scattered electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Vaupel, Matthias, E-mail: Matthias.vaupel@zeiss.com; Dutschke, Anke [Training Application Support Center, Carl Zeiss Microscopy GmbH, Königsallee 9-21, 37081 Göttingen (Germany); Wurstbauer, Ulrich; Pasupathy, Abhay [Department of Physics, Columbia University New York, 538 West 120th Street, New York, New York 10027 (United States); Hitzel, Frank [DME Nanotechnologie GmbH, Geysostr. 13, D-38106 Braunschweig (Germany)

    2013-11-14

    The optical phase shift by reflection on graphene is measured by interference contrast microscopy. The height profile across graphene layers on 300 nm thick SiO{sub 2} on silicon is derived from the phase profile. The complex refractive index and conductivity of graphene layers on silicon with 2 nm thin SiO{sub 2} are evaluated from a phase profile, while the height profile of the layers is measured by atomic force microscopy. It is observed that the conductivity measured on thin SiO{sub 2} is significantly greater than on thick SiO{sub 2}. Back scattered electron contrast of graphene layers is correlated to the height of graphene layers.

  1. Slow relaxation of the magnetization in non-linear optical active layered mixed metal oxalate chains.

    Science.gov (United States)

    Cariati, Elena; Ugo, Renato; Santoro, Giuseppe; Tordin, Elisa; Sorace, Lorenzo; Caneschi, Andrea; Sironi, Angelo; Macchi, Piero; Casati, Nicola

    2010-12-06

    New Co(II) members of the family of multifunctional materials of general formula [DAMS](4)[M(2)Co(C(2)O(4))(6)]·2DAMBA·2H(2)O (M(III) = Rh, Fe, Cr; DAMBA = para-dimethylaminobenzaldehyde and [DAMS(+)] = trans-4-(4-dimethylaminostyryl)-1-methylpyridinium) have been isolated and characterized. Such new hybrid mixed metal oxalates are isostructural with the previously investigated containing Zn(II), Mn(II), and Ni(II). This allows to preserve the exceptional second harmonic generation (SHG) activity, due to both the large molecular quadratic hyperpolarizability of [DAMS(+)] and the efficiency of the crystalline network which organizes [DAMS(+)] into head-to-tail arranged J-type aggregates, and to further tune the magnetic properties. In particular, the magnetic data of the Rh(III) derivative demonstrate that high spin octacoordinated Co(II) centers behave very similarly to the hexacoordinated Co(II) ones, being dominated by a large orbital contribution. The Cr(III) derivative is characterized by ferromagnetic Cr(III)-Co(II) interactions. Most relevantly, the Fe(III) compound is characterized by a moderate antiferromagnetic interaction between Fe(III) and Co(II), resulting in a ferrimagnetic like structure. Its low temperature dynamic magnetic properties were found to follow a thermally activated behavior (τ(0) = 8.6 × 10(-11) s and ΔE = 21.4 K) and make this a candidate for the second oxalate-based single chain magnet (SCM) reported up to date, a property which in this case is coupled to the second order non linear optical (NLO) ones.

  2. Direct charge carrier injection into Ga2O3 thin films using an In2O3 cathode buffer layer: their optical, electrical and surface state properties

    Science.gov (United States)

    Cui, W.; Zhao, X. L.; An, Y. H.; Guo, D. Y.; Qing, X. Y.; Wu, Z. P.; Li, P. G.; Li, L. H.; Cui, C.; Tang, W. H.

    2017-04-01

    Conductive Ga2O3 thin films with an In2O3 buffer layer have been prepared on c-plane sapphire substrates using a laser molecular beam epitaxy technique. The effects of the In2O3 buffer layer on the structure and optical, electrical and surface state properties of the Ga2O3 films have been studied. The change in conductivity of the thin films is attributed to different thicknesses of the In2O3 buffer layer, which determine the concentration of charge carriers injected into the upper Ga2O3 layer from the interface of the bilayer thin films. In addition, the increase in flat band voltage shift and capacitance values as the In2O3 buffer layer thickens are attributed to the increase in surface state density, which also contributes to the rapid shrinkage of the optical band gap of the Ga2O3. With transparency to visible light, high n-type conduction and the ability to tune the optical band gap and surface state density, we propose that Ga2O3/In2O3 bilayer thin film is an ideal n-type semiconductor for fabrication of transparent power devices, solar cell electrodes and gas sensors.

  3. Indium gallium zinc oxide layer used to decrease optical reflection loss at intermediate adhesive region for fabricating mechanical stacked multijunction solar cells

    Science.gov (United States)

    Sameshima, Toshiyuki; Nimura, Takeshi; Sugawara, Takashi; Ogawa, Yoshihiro; Yoshidomi, Shinya; Kimura, Shunsuke; Hasumi, Masahiko

    2017-01-01

    Reduction of optical reflection loss is discussed in three mechanical stacked samples: top crystalline silicon and bottom crystalline germanium substrates, top crystalline GaAs and bottom crystalline silicon substrates, and top crystalline GaP and bottom crystalline silicon substrates using an epoxy-type adhesive with a reflective index of 1.47. Transparent conductive Indium gallium zinc oxide (IGZO) layers with a refractive index of 1.85 were used as antireflection layers. IGZO layers were formed on the bottom surface of the top substrate and the top surface of the bottom substrate of the three stacked samples with thicknesses of 188, 130, and 102 nm. The insertion of IGZO layers decreased the optical reflectivity of the stacked samples. The IGZO layers provided high effective optical absorbency of bottom substrates of 0.925, 0.943, and 0.931, respectively, for light wavelength regions for light in which the top substrates were transparent and the bottom substrates were opaque.

  4. Continuous measurements of Arctic boundary layer aerosol physical and optical properties

    Science.gov (United States)

    Asmi, E.; Kondratyev, V.; Brus, D.; Lihavainen, H.; Laurila, T. J.; Aurela, M.; Hatakka, J.; Viisanen, Y.; Reshetnikov, A.; Ivakhov, V.; Uttal, T.; Makshtas, A. P.

    2013-12-01

    The Arctic and northern boreal regions of Eurasia are experiencing rapid environmental changes due to pressures by human activities. The largest anthropogenic climate forcings are due to aerosol particles and greenhouse gases (GHGs). The Arctic environment is highly sensitive to changes in aerosol concentrations or composition, largely due to the high surface reflectance for the most part of the year. Concentrations of aerosols in winter and spring Arctic are affected by 'Arctic Haze', a phenomenon suggested to arise from the transport of pollutants from lower latitudes and further strengthened by the strong stratification of the Arctic wintertime atmosphere. Sources and transport patterns of aerosols into the Arctic are, however, not fully understood. In order to monitor the changes within the Arctic region, as well as to understand the sources and feedback mechanisms, direct measurements of aerosols within the Arctic are needed. So far, direct year-round observations have been inadequate especially within the Russian side of the Arctic. This is the reason why a new climate observatory was founded on the shore of the Arctic Ocean, in Tiksi, Russia. Tiksi meteorological observatory in northern Siberia (71_360N; 128_530E) has been operating since 1930s. Recently, it was upgraded and joint in the network of the IASOA, in the framework of the International Polar Year Activity project. The project is run in collaboration between National Oceanic and Atmospheric Administration (NOAA) with the support of the National Science Foundation (NSF), Roshydromet (AARI and MGO units), government of the Republic of Sakha (Yakutia) and the Finnish Meteorological Institute (FMI). The research activities of FMI in Tiksi include e.g. continuous long-term measurements of aerosol particle physical and optical properties. Measurements were initiated in summer 2010 and further extended in summer 2013. Together with the FMI measurements in Pallas GAW station in northern Finland since 1999

  5. Comparison between the structural, morphological and optical properties of CdS layers prepared by Close Space Sublimation and RF magnetron sputtering for CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Feldmeier, E.M., E-mail: efeldmeier@surface.tu-darmstadt.de; Fuchs, A.; Schaffner, J.; Schimper, H.-J.; Klein, A.; Jaegermann, W.

    2011-08-31

    CdS layers deposited by radio frequency (RF) magnetron sputtering at different substrate temperatures and Close Space Sublimation (CSS) on SnO{sub 2}:F films have been investigated. Both types of films were prepared in the integrated ultra high-vacuum system known as DAISY-SOL and characterised with respect to crystal structure, texture, morphology, stoichiometry and optical properties. For this purpose, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction and optical transmittance measurements were used in this work. The results show that RF sputtering produces dense and pin-hole free CdS layers with a more pronounced crystallographic texture, a cadmium excess and a higher optical absorption than those prepared by CSS.

  6. Improvement of optical and electrical properties of indium tin oxide layer of GaN-based light-emitting diode by surface plasmon in silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Chu-Young [Applied Device and Material Department, Korea Advanced Nano fab Center, Suwon 443–270 (Korea, Republic of); Hong, Sang-Hyun [Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 500–712 (Korea, Republic of); Park, Seong-Ju, E-mail: esjpark@gist.ac.kr [Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 500–712 (Korea, Republic of)

    2015-09-01

    We report on the effect of silver (Ag) nanoparticles on the optical transmittance and electrical conductivity of indium tin oxide (ITO) transparent conducting layer deposited on p-GaN layer of light-emitting diodes (LEDs). The sheet resistance of ITO and the series resistance of LEDs were decreased due to the increased electrical conductivity of ITO by Ag nanoparticles, compared with those of the LEDs with a bare ITO only. The ITO transmittance was also improved by localized surface plasmon resonance between the incident light and the randomly distributed Ag nanoparticles on ITO. The optical output power of LEDs with Ag nanoparticles on ITO was increased by 16% at 20 mA of injection current. - Highlights: • We studied the effect of Ag nanoparticles deposited on ITO on the properties of LED. • The optical power of LED and transmittance of ITO were improved by Ag surface plasmon. • The electrical conductivity of ITO was increased by Ag nanoparticles.

  7. The Influences of Thickness on the Optical and Electrical Properties of Dual-Ion-Beam Sputtering-Deposited Molybdenum-Doped Zinc Oxide Layer

    Directory of Open Access Journals (Sweden)

    Chin-Chiuan Kuo

    2011-01-01

    Full Text Available The thickness of transparent conductive oxide (TCO layer significantly affects not only the optical and electrical properties, but also its mechanical durability. To evaluate these influences on the molybdenum-doped zinc oxide layer deposited on a flexible polyethersulfone (PES substrate by using a dual-ion-beam sputtering system, films with various thicknesses were prepared at a same condition and their optical and electrical performances have been compared. The results show that all the deposited films present a crystalline wurtzite structure, but the preferred orientation changes from (002 to (100 with increasing the film thickness. Thicker layer contains a relative higher carrier concentration, but the consequently accumulated higher internal stress might crack the film and retard the carrier mobility. The competition of these two opposite trends for carrier concentration and carrier mobility results in that the electrical resistivity of molybdenum-doped zinc oxide first decreases with the thickness but suddenly rises when a critical thickness is reached.

  8. Precise Measurement of the Thickness of a Dielectric Layer on a Metal Surface by Use of a Modified Otto Optical Configuration

    Science.gov (United States)

    Kaneoka, Yoshiki; Nishigaki, Kentaro; Mizutani, Yasuhiro; Iwata, Tetsuo

    2015-01-01

    We propose a modified method for thickness measurement of a dielectric coating layer on metal based on Otto optical configuration (O-configuration). This method enables us to estimate the coating thickness that typically ranges from several tens of nanometers to more than one micrometer with precision less than a few nanometers. The common method to measure the thickness of dielectric coating layer is to utilize the frustrated total-internal reflection. In order to measure the thickness of several tens of nanometers, one can apply the surface-plasmon-resonance (SPR) phenomenon generated by the p-polarized light. For thickness larger than one hundred nanometers, a metal-clad leaky-waveguide (MCLW) mode generated by the p- or the s-polarized light can be employed without significant changes to the optical setup. The numerical and experimental verifications of the modified O-configuration reveals its effectiveness for precise measurement of moderately-thick dielectric coating layer on the metal.

  9. SiO$_2$/TiO$_2$ multi-layered thin films with self-cleaning and enhanced optical properties

    Indian Academy of Sciences (India)

    CIPRIAN MIHOREANU; ALEXANDRU ENESCA; ANCA DUTA

    2017-06-01

    Self-cleaning, high transmittance glazing was obtained by cold spray deposition for glazings. The thin films contain TiO$_2$, SiO$_2$ and Au nanoparticles in different structures which allow for tailoring the optical, hydrophilic and photocatalytic properties. The crystallinity, morphology and surface energy were correlated with the optical transmittanceand reflectance; the transmittance increased from 89.45 (for the glass substrate) to 91.76% when Au nanoparticles were used in the tandem layered structures. The samples containing alternating multi-layered SiO$_2$ and TiO$_2$ thin films without gold nanoparticles show hydrophilic surface; for these layers, the photocatalytic efficiency reaches 40% under simulated solar radiation. A conditioning effect based on adsorption was observed to increase the photocatalytic efficiency. These highly transparent coatings are well suited for glazings and fenestration, showing the self-cleaning effect based on combinedsuperhydrophilicity and photocatalysis.

  10. Final design of a spacer grid using axiomatic design

    Energy Technology Data Exchange (ETDEWEB)

    Park, Gyung-Jin; Lee, Hyun-Ah; Kim, Chong-Ki [Hanyang Univ., Seoul (Korea, Republic of); Song, Gi-Nam [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2007-03-15

    The spacer grid set is a component in the nuclear fuel assembly. The set supports the fuel rod safely. The spacer grid set must have enough strength to sustain external loads such as earthquake. The fretting wear occurs between the spring of the fuel rod and the spacer grid due to the flow-induced vibration after the fuel rod is inserted to the spacer grid set. Design of the spring is carried out by using the independence axiom in axiomatic design to solve the two problems. The spacer grid is divided into two parts for sustaining the impact load and reducing fretting wear based on the function requirements. The design for the impact load is performed through non-linear analysis and the homology theory is adopted to reduce fretting wear achieved for shape optimization. The objective function to be minimized ids the maximum stress and constraints are defined to increase the contact area between the fuel rod and the spring using the homology theory. In the design results, the contact area becomes large and it is conformed by nonlinear static analysis. The final design shows that larger impact loads can be sustained compared to the current model.

  11. Impact of spacer thickness on biofouling in forward osmosis

    KAUST Repository

    Valladares Linares, Rodrigo

    2014-06-01

    Forward osmosis (FO) indirect desalination systems integrate wastewater recovery with seawater desalination. Niche applications for FO systems have been reported recently, due to the demonstrated advantages compared to conventional high-pressure membrane processes such as nanofiltration (NF) and reverse osmosis (RO). Among them, wastewater recovery has been identified to be particularly suitable for practical applications. However, biofouling in FO membranes has rarely been studied in applications involving wastewater effluents. Feed spacers separating the membrane sheets in cross-flow systems play an important role in biofilm formation. The objective of this study was to determine the influence of feed spacer thickness (28, 31 and 46mil) on biofouling development and membrane performance in a FO system, using identical cross-flow cells in parallel studies. Flux development, biomass accumulation, fouling localization and composition were determined and analyzed. For all spacer thicknesses, operated at the same feed flow and the same run time, the same amount of biomass was found, while the flux reduction decreased with thicker spacers. These observations are in good agreement with biofouling studies for RO systems, considering the key differences between FO and RO. Our findings contradict previous cross-flow studies on particulate/colloidal fouling, where higher cross-flow velocities improved system performance. Thicker spacers reduced the impact of biofouling on FO membrane flux. © 2014 Elsevier Ltd.

  12. Impact of spacer thickness on biofouling in forward osmosis.

    Science.gov (United States)

    Valladares Linares, R; Bucs, Sz S; Li, Z; AbuGhdeeb, M; Amy, G; Vrouwenvelder, J S

    2014-06-15

    Forward osmosis (FO) indirect desalination systems integrate wastewater recovery with seawater desalination. Niche applications for FO systems have been reported recently, due to the demonstrated advantages compared to conventional high-pressure membrane processes such as nanofiltration (NF) and reverse osmosis (RO). Among them, wastewater recovery has been identified to be particularly suitable for practical applications. However, biofouling in FO membranes has rarely been studied in applications involving wastewater effluents. Feed spacers separating the membrane sheets in cross-flow systems play an important role in biofilm formation. The objective of this study was to determine the influence of feed spacer thickness (28, 31 and 46 mil) on biofouling development and membrane performance in a FO system, using identical cross-flow cells in parallel studies. Flux development, biomass accumulation, fouling localization and composition were determined and analyzed. For all spacer thicknesses, operated at the same feed flow and the same run time, the same amount of biomass was found, while the flux reduction decreased with thicker spacers. These observations are in good agreement with biofouling studies for RO systems, considering the key differences between FO and RO. Our findings contradict previous cross-flow studies on particulate/colloidal fouling, where higher cross-flow velocities improved system performance. Thicker spacers reduced the impact of biofouling on FO membrane flux.

  13. CRISPR interference and priming varies with individual spacer sequences.

    Science.gov (United States)

    Xue, Chaoyou; Seetharam, Arun S; Musharova, Olga; Severinov, Konstantin; Brouns, Stan J J; Severin, Andrew J; Sashital, Dipali G

    2015-12-15

    CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR associated) systems allow bacteria to adapt to infection by acquiring 'spacer' sequences from invader DNA into genomic CRISPR loci. Cas proteins use RNAs derived from these loci to target cognate sequences for destruction through CRISPR interference. Mutations in the protospacer adjacent motif (PAM) and seed regions block interference but promote rapid 'primed' adaptation. Here, we use multiple spacer sequences to reexamine the PAM and seed sequence requirements for interference and priming in the Escherichia coli Type I-E CRISPR-Cas system. Surprisingly, CRISPR interference is far more tolerant of mutations in the seed and the PAM than previously reported, and this mutational tolerance, as well as priming activity, is highly dependent on spacer sequence. We identify a large number of functional PAMs that can promote interference, priming or both activities, depending on the associated spacer sequence. Functional PAMs are preferentially acquired during unprimed 'naïve' adaptation, leading to a rapid priming response following infection. Our results provide numerous insights into the importance of both spacer and target sequences for interference and priming, and reveal that priming is a major pathway for adaptation during initial infection.

  14. A non-electrostatic spacer for aerosol delivery

    DEFF Research Database (Denmark)

    Bisgaard, H; Anhøj, J; Klug, B;

    1995-01-01

    A pear shaped non-electrostatic spacer, composed of steel with a volume of 250 ml and equipped with a facemask containing integrated inlet and outlet valves for inspiration and expiration, was compared with three plastic spacers. The plastic spacers were primed with repeated puffs from a budesonide...... pressurised metered dose inhaler (p-MDI) to minimise the electrostatic charge on the plastic. The procedure prolonged the half life (t1/2) of the aerosol in the Nebuhaler from nine to 32 seconds. A normal cleaning procedure reduced the aerosol t1/2 back to baseline. The t1/2 of the aerosol in the metal spacer...... was 27 seconds and independent of the use of p-MDI. In vitro the maximum dose of budesonide from a p-MDI, expressed as a percentage of the nominal dose, was 56% from the non-electrostatic spacer, 61% from the Nebuhaler, 45% from the Babyhaler, and 30% from the AeroChamber. In 124 children, age 6 months...

  15. An optical sensor based on H-acid/layered double hydroxide composite film for the selective detection of mercury ion.

    Science.gov (United States)

    Sun, Zhiyong; Jin, Lan; Zhang, Shitong; Shi, Wenying; Pu, Min; Wei, Min; Evans, David G; Duan, Xue

    2011-09-19

    A novel optical chemosensor was fabricated based on 1-amino-8-naphthol-3,6-disulfonic acid sodium (H-acid) intercalated layered double hydroxide (LDH) film via the electrophoretic deposition (EPD) method. The film of H-acid/LDH with the thickness of 1 μm possesses a well c-orientation of the LDH microcrystals confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The fluorescence detection for Hg(II) in aqueous solution was performed by using the H-acid/LDH film sensor at pH 7.0, with a linear response range in 1.0 × 10(-7) to 1.0 × 10(-5) mol L(-1) and a detection limit of 6.3 × 10(-8) mol L(-1). Furthermore, it exhibits excellent selectivity for Hg(II) over a large number of competitive cations including alkali, alkaline earth, heavy metal and transitional metals. The specific fluorescence response of the optical sensor is attributed to the coordination between Hg(II) and sulfonic group in the H-acid immobilized in the LDH matrix, which was verified by NMR spectroscopy and UV-vis spectra. In addition, density functional theory (DFT) calculation further confirms that the coordination occurs between one Hg(2+) and two O atoms in the sulfonic group, which is responsible for the significant fluorescence quenching of the H-acid/LDH film. The results indicate that the H-acid/LDH composite film can be potentially used as a chemosensor for the detection of Hg(2+) in the environmental and biomedical field.

  16. Evaluation of changes in retinal nerve fiber layer thickness and visual functions in cases of optic neuritis and multiple sclerosis

    Directory of Open Access Journals (Sweden)

    Rohit Saxena

    2013-01-01

    Full Text Available Context: Retinal nerve fiber layer (RNFL thinning has been demonstrated in cases of optic neuritis (ON and multiple sclerosis (MS in Caucasian eyes, but no definite RNFL loss pattern or association with visual functions is known in Indian eyes. Aim : To evaluate RNFL thickness in cases of ON and MS, and to correlate it with visual function changes in Indian patients. Settings and Design: Cross-sectional case-control study at a tertiary level institution . Materials and Methods: Cases consisted of patients of (i typical ON without a recent episode (n = 30:39 ON eyes and 21 fellow eyes, (ii MS without ON (n = 15;30 eyes while the controls were age-matched (n = 15; 30 eyes. RNFL thickness was measured using the Stratus 3 °CT. The visual functions tested included the best-corrected visual acuity (BCVA, contrast sensitivity, stereopsis, visual evoked responses, and visual fields. Statistical analysis used: Intergroup analysis was done using ANOVA and Pearson′s correlation coefficient used for associations. Results: RNFL thickness was reduced significantly in the ON and MS patients compared to the controls (P-0.001. Maximum loss is in the temporal quadrant. Lower visual function scores are associated with reduced average overall RNFL thickness. In ON group, RNFL thinning is associated with severe visual field defects while contrast sensitivity has strongest correlation with RNFL in the MS group. Conclusions:RNFL thickness is reduced in ON and MS cases in a pattern similar to Caucasians and is associated with the magnitude of impairment of other visual parameters. Contrast sensitivity and stereoacuity are useful tests to identify subclinical optic nerve involvement in multiple sclerosis.

  17. Peripapillary retinal nerve fiber layer assessment of spectral domain optical coherence tomography and scanning laser polarimetry to diagnose preperimetric glaucoma.

    Directory of Open Access Journals (Sweden)

    Harsha L Rao

    Full Text Available To compare the abilities of peripapillary retinal nerve fiber layer (RNFL parameters of spectral domain optical coherence tomograph (SDOCT and scanning laser polarimeter (GDx enhanced corneal compensation; ECC in detecting preperimetric glaucoma.In a cross-sectional study, 35 preperimetric glaucoma eyes (32 subjects and 94 control eyes (74 subjects underwent digital optic disc photography and RNFL imaging with SDOCT and GDx ECC. Ability of RNFL parameters of SDOCT and GDx ECC to discriminate preperimetric glaucoma eyes from control eyes was compared using area under receiver operating characteristic curves (AUC, sensitivities at fixed specificities and likelihood ratios (LR.AUC of the global average RNFL thickness of SDOCT (0.786 was significantly greater (p<0.001 than that of GDx ECC (0.627. Sensitivities at 95% specificity of the corresponding parameters were 20% and 8.6% respectively. AUCs of the inferior, superior and temporal quadrant RNFL thickness parameters of SDOCT were also significantly (p<0.05 greater than the respective RNFL parameters of GDx ECC. LRs of outside normal limits category of SDOCT parameters ranged between 3.3 and 4.0 while the same of GDx ECC parameters ranged between 1.2 and 2.1. LRs of within normal limits category of SDOCT parameters ranged between 0.4 and 0.7 while the same of GDx ECC parameters ranged between 0.7 and 1.0.Abilities of the RNFL parameters of SDOCT and GDx ECC to diagnose preperimetric glaucoma were only moderate. Diagnostic abilities of the RNFL parameters of SDOCT were significantly better than that of GDx ECC in preperimetric glaucoma.

  18. Retinal nerve fiber layer thickness of middle aged or elderly people measured by 3D optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Li Li

    2015-11-01

    Full Text Available AIM: To build the reference values of normal eye retinal nerve fiber layer(RNFLthickness on middle aged people between 40~69 years old, and infer the baseline data for early diagnosis of glaucoma. METHODS:A total of 180 eyes from 90 healthy subjects(age ranged from 40~69 years oldwere recruited for this study. Topcon 3D optical coherence tomography(OCT-2000(Ver 8.0was used to measure RNFL thickness. Each subject was performed circular scans around the optic nerve with a circle size of 3.4mm. Clock-hour, quadrant and total average RNFL thicknesses were recorded. The data was analyzed with SPSS statistical. The relationship between age, gender and laterality was analyzed, and the reference value for normal eye RNFL thickness parameters was obtained, RESULTS:Normal RNFL thickness distribution was bimodal curve type in 40~69 year-old middle aged or elderly people. RNFL thickness was decreased for temporal quadrant, followed by nasal, superior, inferior. RNFL thickness at 10 o'clock, 5 o'clock, 6 o'clock, superior got thinner with age prolong. Except 10 o'clock(PP>0.05. The RNFL thickness at 11 o'clock was associated with different gender. the RNFL thickness at 11 o'clock, 12 o'clock, 1 o'clock, 4 o'clock, superior, nasal was associated with different eyes, the differences was statistically significant between different eyes(PCONCLUSION: Topcon 3D OCT-2000 is effectively used to measure the RNFL thickness of 40~69 years people and provide diagnostic basis for early diagnosis of glaucoma.

  19. Heterogeneous pattern of retinal nerve fiber layer in multiple sclerosis. High resolution optical coherence tomography: potential and limitations.

    Directory of Open Access Journals (Sweden)

    Nermin Serbecic

    Full Text Available BACKGROUND: Recently the reduction of the retinal nerve fibre layer (RNFL was suggested to be associated with diffuse axonal damage in the whole CNS of multiple sclerosis (MS patients. However, several points are still under discussion. (1 Is high resolution optical coherence tomography (OCT required to detect the partly very subtle RNFL changes seen in MS patients? (2 Can a reduction of RNFL be detected in all MS patients, even in early disease courses and in all MS subtypes? (3 Does an optic neuritis (ON or focal lesions along the visual pathways, which are both very common in MS, limit the predication of diffuse axonal degeneration in the whole CNS? The purpose of our study was to determine the baseline characteristics of clinical definite relapsing-remitting (RRMS and secondary progressive (SPMS MS patients with high resolution OCT technique. METHODOLOGY: Forty-two RRMS and 17 SPMS patients with and without history of uni- or bilateral ON, and 59 age- and sex-matched healthy controls were analysed prospectively with the high resolution spectral-domain OCT device (SD-OCT using the Spectralis 3.5mm circle scan protocol with locked reference images and eye tracking mode. Furthermore we performed tests for visual and contrast acuity and sensitivity (ETDRS, Sloan and Pelli-Robson-charts, for color vision (Lanthony D-15, the Humphrey visual field and visual evoked potential testing (VEP. PRINCIPAL FINDINGS: All 4 groups (RRMS and SPMS with or without ON showed significantly reduced RNFL globally, or at least in one of the peripapillary sectors compared to age-/sex-matched healthy controls. In patients with previous ON additional RNFL reduction was found. However, in many RRMS patients the RNFL was found within normal range. We found no correlation between RNFL reduction and disease duration (range 9-540 months. CONCLUSIONS: RNFL baseline characteristics of RRMS and SPMS are heterogeneous (range from normal to markedly reduced levels.

  20. Peripapillary retinal nerve fiber layer assessment of spectral domain optical coherence tomography and scanning laser polarimetry to diagnose preperimetric glaucoma.

    Science.gov (United States)

    Rao, Harsha L; Yadav, Ravi K; Addepalli, Uday K; Chaudhary, Shashikant; Senthil, Sirisha; Choudhari, Nikhil S; Garudadri, Chandra S

    2014-01-01

    To compare the abilities of peripapillary retinal nerve fiber layer (RNFL) parameters of spectral domain optical coherence tomograph (SDOCT) and scanning laser polarimeter (GDx enhanced corneal compensation; ECC) in detecting preperimetric glaucoma. In a cross-sectional study, 35 preperimetric glaucoma eyes (32 subjects) and 94 control eyes (74 subjects) underwent digital optic disc photography and RNFL imaging with SDOCT and GDx ECC. Ability of RNFL parameters of SDOCT and GDx ECC to discriminate preperimetric glaucoma eyes from control eyes was compared using area under receiver operating characteristic curves (AUC), sensitivities at fixed specificities and likelihood ratios (LR). AUC of the global average RNFL thickness of SDOCT (0.786) was significantly greater (p<0.001) than that of GDx ECC (0.627). Sensitivities at 95% specificity of the corresponding parameters were 20% and 8.6% respectively. AUCs of the inferior, superior and temporal quadrant RNFL thickness parameters of SDOCT were also significantly (p<0.05) greater than the respective RNFL parameters of GDx ECC. LRs of outside normal limits category of SDOCT parameters ranged between 3.3 and 4.0 while the same of GDx ECC parameters ranged between 1.2 and 2.1. LRs of within normal limits category of SDOCT parameters ranged between 0.4 and 0.7 while the same of GDx ECC parameters ranged between 0.7 and 1.0. Abilities of the RNFL parameters of SDOCT and GDx ECC to diagnose preperimetric glaucoma were only moderate. Diagnostic abilities of the RNFL parameters of SDOCT were significantly better than that of GDx ECC in preperimetric glaucoma.

  1. Retinal nerve fiber layer thickness measured by optical coherence tomography in patients with schizophrenia: A short report

    Directory of Open Access Journals (Sweden)

    Francisco J. Ascaso

    2010-12-01

    Full Text Available Background and Objectives: Our study aims to assess retinal nerve fiber layer (RNFL thickness in patients affected by schizophrenia. Methods: Ten schizophrenic patients (mean age 39 +/- 13 years, best corrected visual acuity > 20/20, refractive error between +/-2 diopters, and intraocular pressure <18 mmHg were enrolled. They were compared with 10 age-matched controls. In all subjects, optic nerve head (ONH measurements, peripapillary RNFL thickness, macular thickness and volume were measured by optical coherence tomography (OCT. Results: Schizophrenic patients showed an statistically significant reduction of the overall RNFL thickness (95+/-13 µm, range: 53-110 compared with those values observed in control eyes (103+/-8 µm, range: 88-119 (p = 0.047, Mann-Whitney U test. We also observed reduced peripapillary RNFL thickness in nasal quadrant in schizophrenic patients (75+/-17 µm, range: 41-111 when compared with controls (84+/-10 µm, range: 67-105 (p = 0.048, Mann-Whitney U test. The remaining peripapillary RNFL quadrants, macular thickness and volume did not reveal differences between both groups. No statistically significant differences were observed between the control group and schizophrenia patients with regard to ONH measurements, macular thickness and volume. Conclusions: Schizophrenia patients had a reduction of peripapillary RNFL thickness evaluated by OCT. To our knowledge, neither reduced RNFL thickness nor macular thickness and volume have been previously documented in patients diagnosed with schizophrenia. These findings suggest that neuronal degeneration could be present in the retina of schizophrenic patients as previously observed in neurodegenerative disorders.

  2. Evaluation of the retinal nerve fibre layer and ganglion cell complex thickness in pituitary macroadenomas without optic chiasmal compression

    Science.gov (United States)

    Cennamo, G; Auriemma, R S; Cardone, D; Grasso, L F S; Velotti, N; Simeoli, C; Di Somma, C; Pivonello, R; Colao, A; de Crecchio, G

    2015-01-01

    Purpose The aim of this prospective study was to measure the thickness of the circumpapillary retinal nerve fibre layer (cpRNFL) and the ganglion cell complex (GCC) using spectral domain optical coherence tomography (SD-OCT) in a cohort of consecutive de novo patients with pituitary macroadenomas without chiasmal compression. Patients and methods Twenty-two consecutive patients with pituitary macroadenoma without chiasmal compression (16 men, 6 women, aged 45.2±14.6 years, 43 eyes) entered the study between September 2011 and June 2013. Among them, 31.8% harboured a growth hormone-secreting pituitary adenoma, 27.3% a prolactin-secreting pituitary adenoma, 27.3% a corticotrophin-secreting pituitary adenoma, and 13.6% a non-secreting pituitary tumour. Eighteen subjects (nine females, nine males, mean age 36.47±6.37 years; 33 eyes) without pituitary adenoma, with normal ophthalmic examination, served as controls. In both patients and controls, cpRNFL and GCC thicknesses were measured by SD-OCT. Results Patients were significantly older (P=0.02) than controls. Best corrected visual acuity, intraocular pressure, colour fundus photography, and automatic perimetry test were within the normal range in patients and controls. Conversely, cpRNFL (P=0.009) and GCC (P<0.0001) were significantly thinner in patients than in controls. The average GCC (r=0.306, P=0.046) significantly correlated with the presence of arterial hypertension. OCT parameters did not differ significantly between patients with a tumour volume above the median and those with a tumour volume below the median. Conclusion Pituitary macroadenomas, even in the absence of chiasmal compression, may induce GCC and retinal nerve fibre layer thinning. SD-OCT may have a role in the early diagnosis and management of patients with pituitary tumours. PMID:25853400

  3. Unexpected Temperature Behavior of Polyethylene Glycol Spacers in Copolymer Dendrimers in Chloroform

    Science.gov (United States)

    Markelov, Denis A.; Matveev, Vladimir V.; Ingman, Petri; Nikolaeva, Marianna N.; Penkova, Anastasia V.; Lahderanta, Erkki; Boiko, Natalia I.; Chizhik, Vladimir I.

    2016-04-01

    We have studied copolymer dendrimer structure: carbosilane dendrimers with terminal phenylbenzoate mesogenic groups attached by poly(ethylene) glycol (PEG) spacers. In this system PEG spacers are additional tuning to usual copolymer structure: dendrimer with terminal mesogenic groups. The dendrimer macromolecules were investigated in a dilute chloroform solution by 1H NMR methods (spectra and relaxations). It was found that the PEG layer in G = 5 generations dendrimer is “frozen” at high temperatures (above 260 K), but it unexpectedly becomes “unfrozen” at temperatures below 250 K (i.e., melting when cooling). The transition between these two states occurs within a small temperature range (~10 K). Such a behavior is not observed for smaller dendrimer generations (G = 1 and 3). This effect is likely related to the low critical solution temperature (LCST) of PEG and is caused by dendrimer conformations, in which the PEG group concentration in the layer increases with growing G. We suppose that the unusual behavior of PEG fragments in dendrimers will be interesting for practical applications such as nanocontainers or nanoreactors.

  4. Nonlinear optical rectification in a vertically coupled lens-shaped InAs/GaAs quantum dots with wetting layers under hydrostatic pressure and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ben Mahrsia, R.; Choubani, M., E-mail: mohsenchoubani3@yahoo.fr; Bouzaiene, L.; Maaref, H.

    2016-06-25

    In this paper we explore the structure parameters, hydrostatic pressure and temperature effects on Nonlinear optical rectification (NOR) in an asymmetric vertically coupled lens-shaped InAs/GaAs quantum dots. During epitaxial growth, lens-shaped quantum dots (QDs) are formed on the wetting layer (WL). Many theoretical works have neglected WL and its effect on nonlinear optical properties of QD-based systems for sake of simplicity. However, in this work the WL has been shown to be so influential in the intersubband energy and nonlinear optical rectification magnitude. Also, a detailed and comprehensive study of the nonlinear optical rectification is theoretical investigated within the framework of the compact density-matrix approach and finite difference method (FDM). It's found that nonlinear optical rectification coefficient is strongly affected not only by the WL, but also by the pressure, temperature and the coupled width between the QDs. Obtained results revealed that a red or a blue shift cane be observed. This behavior in the NOR gives a new degree of freedom in regions of interest for device applications. - Highlights: • Vertically coupled lens-shaped InAs/GaAs quantum dots is investigated. • Photon energy shifts towards the red with increasing pressure. • Photon energy shifts towards the blue with increasing temperature. • Intersubband energy decreases with increasing the wetting layer width. • Nonlinear optical rectification magnitude is controlled and adjusted.

  5. Poly(methyl methacrylate)/layered zinc sulfide nanocomposites: Preparation, characterization and the improvements in thermal stability, flame retardant and optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Biao; Zhou, Keqing; Jiang, Saihua [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Shi, Yongqian [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, 166 Ren’ai Road, Suzhou, Jiangsu 215123 (China); Wang, Bibo [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Gui, Zhou, E-mail: zgui@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Hu, Yuan, E-mail: yuanhu@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, 166 Ren’ai Road, Suzhou, Jiangsu 215123 (China)

    2014-08-15

    Highlights: • Layered zinc sulfide (LZnS) was synthesized successfully via hydrothermal method. • We prepare PMMA/LZnS nanocomposites by in situ bulk polymerization of MMA. • PMMA/LZnS nanocomposites were investigated by TGA, DSC, MCC, UV–vis and PL test. • The thermal stability, flame retardant and optical properties of PMMA are improved. - Abstract: Layered zinc sulfide (LZnS) was synthesized successfully via hydrothermal method and poly(methyl methacrylate) (PMMA)/layered zinc sulfide nanocomposites were obtained by in situ bulk polymerization of methyl methacrylate (MMA). X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the as-synthesized layered zinc sulfide and PMMA/layered zinc sulfide nanocomposites. Microscale combustion calorimeter (MCC), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) were used to test the thermal properties of the composites. Ultraviolet visible (UV–vis) transmittance spectra and photoluminence (PL) spectra were obtained to investigate the optical properties of the composites. From the results, the thermal degradation temperature is increased by 20–50 °C, the peak of heat release rate (pHRR) and total heat release (THR) are both decreased by above 30%, and the photoluminence intensity is enhanced with the increasing loading of layered zinc sulfide.

  6. EFFECTS OF GEOMETRICAL STRUCTURE ON MICROWAVE AND OPTICAL PROPERTIES OF TRAVELING WAVE ELECTROABSORPTION MODULATORS BASED ON ASYMMETRIC COUPLED STRAINED QUANTUM WELLS ACTIVE LAYER

    Directory of Open Access Journals (Sweden)

    KAMBIZ ABEDI

    2011-08-01

    Full Text Available This paper presents the effects of geometrical structure on microwave and optical properties of traveling wave electroabsorption modulators (TWEAMs based on asymmetric intra-step-barrier coupled double strained quantum wells (AICD-SQW active layer. The AICD-SQW active layer structure has advantages such as very low insertion loss, zero chirp, large Stark shift and high extinction ratio in comparison with the intra-step quantum well (IQW structure. Firstly, the influences of the intrinsic (active layer thickness and width on effective optical index and confinement factor are analyzed. Furthermore, the effect of the intrinsic layer thickness on their transmission line microwave properties such as microwave index, microwave loss, andcharacteristic impedance are evaluated. The thickness and width of active layer are changed from 0 μm to 1.4 μm and 1 μm to 3 μm, respectively. Finally, the frequency response of TWEAM based on AICD-SQW active layer is calculated using circuit model.

  7. Effect of a spacer moiety on radiometal labelled Neurotensin derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Mascarin, A.; Valverde, I.E.; Mindt, T.L. [Univ. of Basel Hospital (Switzerland). Div. of Radiopharmaceutical Chemistry

    2013-07-01

    The binding sequence of the regulatory peptide Neurotensin, NT(8-13), represents a promising tumour-specific vector for the development of radiopeptides useful in nuclear oncology for the diagnosis (imaging) and therapy of cancer. A number of radiometal-labelled NT(8-13) derivatives have been reported, however, the effect of the spacer which connects the vector with the radiometal complex has yet not been investigated systematically. Because a spacer moiety can influence potentially important biological characteristics of radiopeptides, we synthesized three [DOTA({sup 177}Lu)]-X-NT(8-13) derivatives and evaluated the effect of a spacer (X) on the physico-chemical properties of the conjugate including lipophilicity, stability, and in vitro receptor affinity and cell internalization. (orig.)

  8. Optical properties of double layer thin films zinc oxide doping aluminum (ZnO/Al) were deposited on glass substrates by sol gel method spray coating technique

    Science.gov (United States)

    Permatasari, Anes; Sutanto, Heri; Marito Siagian, Sinta

    2017-01-01

    Thin films of double layer of ZnO/Al has succeeded in deposition on a glass substrate using sol-gel method and spray coating techniques. Variations of doping Al as much as 2%, 4%, 6% and 8%. ZnO precursor synthesized using zinc acetate dehydrate (Zn(COOCH3)2.2H2O), isopropanol ((CH3)2CHOH) and monoethanolamine (MEA) were stirred using a magnetic stirrer for 45 minutes. ZnO precursor get homogeneous and then added of aluminum nitrate nonahydrate predetermined doping concentration and stirred again for 15 minutes. Deposition solution is done by the spray on a glass substrate and then heated at a temperature of 450°C. A layer of ZnO/Al deposited over the ZnO to produce a thin layer of a double layer. Optical properties layer of ZnO/Al characterized using UV-Vis spectrophotometer. Based on data from UV-Vis absorbance was determined the value of the energy band gap. Pure and dopped layers has different energy due the Al dopping. For pure ZnO layer has energy band gap of 3.347 eV and decreased to 3.09 eV for ZnO layer with Al dopant.

  9. Optical and structural properties of zinc oxide films with different thicknesses prepared by successive ionic layer adsorption and reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Taner, Ahmet, E-mail: ataner@anadolu.edu.tr [Institute of Science and Technology, Anadolu University, Eskisehir 26470 (Turkey); Kul, Metin; Turan, Evren; Aybek, A. Senol; Zor, Muhsin [Department of Physics, Anadolu University, Eskisehir 26470 (Turkey); Taskoeprue, Turan [Department of Physics, Anadolu University, Eskisehir 26470 (Turkey); Department of Physics, Cank Latin-Small-Letter-Dotless-I r Latin-Small-Letter-Dotless-I Karatekin University, Cank Latin-Small-Letter-Dotless-I r Latin-Small-Letter-Dotless-I 18100 (Turkey)

    2011-12-01

    In this work, zinc oxide semiconducting films belonging to the II-VI group have been produced by successive ionic layer adsorption and reaction (SILAR) method on glass substrates with 10, 15, 20 and 25 cycles at room temperature. Following the deposition, the samples were dried in air at 400 Degree-Sign C for 1 h. The films were characterized by X-ray diffraction, field emission scanning electron microscopy and optical absorption measurement techniques. The X-ray diffractions of the films showed that they are hexagonal in structure. The crystallite size of ZnO films varied between 34 and 38 nm accordingly with the number of SILAR cycles. The material has exhibited direct band gap transition with the band gap values lying in the range between 3.13 and 3.18 eV. The red shift is observed in the absorption edge as the cycles increased. Transmission of the films decreased from 65 to 40% with increasing the number of cycles.

  10. Surface plasmon resonance based fiber optic trichloroacetic acid sensor utilizing layer of silver nanoparticles and chitosan doped hydrogel

    Science.gov (United States)

    Semwal, Vivek; Shrivastav, Anand M.; Gupta, Banshi D.

    2017-02-01

    In this study, we report a silver nanoparticles/chitosan doped hydrogel-based fiber optic sensor for the detection of trichloroacetic acid (TCA). The sensor is based on the combined phenomenon of localized and propagating surface plasmons. The sensing relies on the interaction of TCA with silver nanoparticles (AgNP) which results in the electron transfer between the negative group of TCA and positive amino group of AgNP stabilizer (chitosan). This alters the mechanical properties/refractive index of the AgNP embedded hydrogel matrix as well as the refractive index of the AgNP. The change in refractive index of both in turn changes the effective refractive index of the nanocomposite hydrogel layer which can be determined using the Maxwell-Garnet Theory. Four stage optimization of the probe fabrication parameters is performed to obtain the best performance of the sensing probe. The sensor operates in the TCA concentration range 0-120 μm which is harmful for the humans and environment. The shift in peak extinction wavelength observed for the same TCA concentration range is 42 nm. The sensor has the linearity range for the TCA concentration range of 40-100 μm. The sensor possesses high sensitivity, selectivity and numerous other advantages such as ease of handling, quick response, modest cost and capability of online monitoring and remote sensing.

  11. Plasma-enhanced chemical vapor deposition of low- loss as-grown germanosilicate layers for optical waveguides

    Science.gov (United States)

    Ay, Feridun; Agan, Sedat; Aydinli, Atilla

    2004-08-01

    We report on systematic growth and characterization of low-loss germanosilicate layers for use in optical waveguides. Plasma enhanced chemical vapor deposition (PECVD) technique was used to grow the films using silane, germane and nitrous oxide as precursor gases. Chemical composition was monitored by Fourier transform infrared (FTIR) spectroscopy. N-H bond concentration of the films decreased from 0.43x1022 cm-3 down to below 0.06x1022 cm-3, by a factor of seven as the GeH4 flow rate increased from 0 to 70 sccm. A simultaneous decrease of O-H related bonds was also observed by a factor of 10 in the same germane flow range. The measured TE rate increased from 5 to 50 sccm, respectively. In contrast, the propagation loss values for TE polarization at λ=632.8 nm were found to increase from are 0.20 +/- 0.02 to 6.46 +/- 0.04 dB/cm as the germane flow rate increased from 5 to 50 sccm, respectively. In contrast, the propagation loss values for TE polarization at λ=1550 nm were found to decrease from 0.32 +/- 0.03 down to 0.14 +/- 0.06 dB/cm for the same samples leading to the lowest values reported so far in the literature, eliminating the need for high temperature annealing as is usually done for these materials to be used in waveguide devices.

  12. Ability of spectral domain optical coherence tomography peripapillary retinal nerve fiber layer thickness measurements to identify early glaucoma

    Directory of Open Access Journals (Sweden)

    Tarannum Mansoori

    2011-01-01

    Full Text Available Purpose : To evaluate the ability of spectral domain optical coherence tomography (OCT peripapillary retinal nerve fiber layer thickness (RNFLT parameters to distinguish normal eyes from those with early glaucoma in Asian Indian eyes. Design : Observational cross-sectional study. Materials and Methods : One hundred and seventy eight eyes (83 glaucoma patients and 95 age matched healthy subjects of subjects more than 40 years of age were included in the study. All subjects underwent RNFLT measurement with spectral OCT/ scanning laser ophthalmoscope (SLO after dilatation. Sensitivity, specificity and area under the receiving operating characteristic curve (AROC were calculated for various OCT peripapillary RNFL parameters. Results: The mean RNFLT in healthy subjects and patients with early glaucoma were 105.7 ± 5.1 μm and 90.7 ± 7.5 μm, respectively. The largest AROC was found for 12 o′clock- hour (0.98, average (0.96 and superior quadrant RNFLT (0.9. When target specificity was set at ≥ 90% and ≥ 80%, the parameters with highest sensitivity were 12 o′clock -hour (91.6%, average RNFLT (85.3% and 12 o′ clock- hour (96.8 %, average RNFLT (94.7% respectively. Conclusion : Our study showed good ability of spectral OCT/ SLO to differentiate normal eyes from patients with early glaucoma and hence it may serve as an useful adjunct for early diagnosis of glaucoma.

  13. Electro-optical switching at 1550 nm using a two-state GeSe phase-change layer.

    Science.gov (United States)

    Soref, Richard; Hendrickson, Joshua; Liang, Haibo; Majumdar, Arka; Mu, Jianwei; Li, Xun; Huang, Wei-Ping

    2015-01-26

    New designs for electro-optical free-space and waveguided 2 x 2 switches are presented and analyzed at the 1.55 μm telecoms wavelength. The proposed devices employ a ~10 nm film of GeSe that is electrically actuated to transition the layer forth-and-back from the amorphous to the crystal phase, yielding a switch with two self-sustaining states. This phase change material was selected for its very low absorption loss at the operation wavelength, along with its electro-refraction Δn ~0.6. All switches are cascadeable into N x M devices. The free-space prism-shaped structures use III-V prism material to match the GeSe crystal index. The Si/GeSe/Si "active waveguides" are quite suitable for directional-coupler switches as well as Mach-Zehnder devices-all of which have an active length 16x less than that in the free-carrier art.

  14. Hydrogenic impurity, external electric and magnetic fields effects on the nonlinear optical properties of a multi-layer spherical quantum dot

    Science.gov (United States)

    Tanhaei, M. H.; Rezaei, G.

    2016-10-01

    In this work, effects of an on-center hydrogenic impurity, external electric and magnetic fields on the optical rectification coefficient (ORC), second and third harmonic generations (SHG and THG) of a multi-layer spherical quantum dot (MLSQD) are studied. Energy eigenvalues and eigenvectors are calculated using the direct matrix diagonalization method and optical properties are obtained using the compact density matrix approach. Our results reveal that the hydrogenic impurity and external fields have a great influence on these optical quantities. Hydrogenic impurity reduces the magnitude of the resonant peaks and shifts them to the higher energies. An increase in the magnetic (electric) field, leads to increase (decrease) the interval energies and the dipole moment matrix elements. Therefore, resonant peaks of these optical quantities find an obvious blue (red) shift and their magnitudes enhance (diminish) with increasing the external magnetic (electric) field.

  15. Optics

    CERN Document Server

    Fincham, W H A

    2013-01-01

    Optics: Ninth Edition Optics: Ninth Edition covers the work necessary for the specialization in such subjects as ophthalmic optics, optical instruments and lens design. The text includes topics such as the propagation and behavior of light; reflection and refraction - their laws and how different media affect them; lenses - thick and thin, cylindrical and subcylindrical; photometry; dispersion and color; interference; and polarization. Also included are topics such as diffraction and holography; the limitation of beams in optical systems and its effects; and lens systems. The book is recommen

  16. Optical and photovoltaic properties of zinc sulfide quantum dots fabricated by spin-assisted successive ion layer adsorption and reaction technique

    Science.gov (United States)

    Mehrabian, Masood; Mirabbaszadeh, Kavoos; Afarideh, Hossein; Kim, Yoon Sang

    2014-01-01

    Zinc sulfide (ZnS) quantum dots were prepared by successive ion layer adsorption and reaction (SILAR) technique based on spin coating (spin-SILAR). The effect of the number of SILAR cycle (n) on optical and photovoltaic properties was studied. An optimized ZnS quantum dot sensitized solar cell demonstrated maximum power conversion efficiency of 3.58% with a short-circuit current of 10.53 mA/cm2 and an open-circuit voltage of 0.58 V under one sun illumination (AM1.5). The results showed that a ZnS QD layer with n=10 (thickness ˜80 nm) can be used as a highly efficient sensitizer for solar cells. The ZnS QD layer acts as a light absorber and a recombination blocking layer in the ITO/ZnO film/ZnS QD/P3HT/PCBM/Ag structure.

  17. Steady flow and heat transfer analysis of Phan-Thein-Tanner fluid in double-layer optical fiber coating analysis with Slip Conditions

    Science.gov (United States)

    Khan, Zeeshan; Shah, Rehan Ali; Islam, Saeed; Jan, Bilal; Imran, Muhammad; Tahir, Farisa

    2016-10-01

    Modern optical fibers require double-layer coating on the glass fiber to provide protection from signal attenuation and mechanical damage. The most important plastic resins used in wires and optical fibers are plastic polyvinyl chloride (PVC) and low-high density polyethylene (LDPE/HDPE), nylon and Polysulfone. In this paper, double-layer optical fiber coating is performed using melt polymer satisfying PTT fluid model in a pressure type die using wet-on-wet coating process. The assumption of fully developed flow of Phan-Thien-Tanner (PTT) fluid model, two-layer liquid flows of an immiscible fluid is modeled in an annular die, where the fiber is dragged at a higher speed. The equations characterizing the flow and heat transfer phenomena are solved exactly and the effects of emerging parameters (Deborah and slip parameters, characteristic velocity, radii ratio and Brinkman numbers on the axial velocity, flow rate, thickness of coated fiber optics, and temperature distribution) are reported in graphs. It is shown that an increase in the non-Newtonian parameters increase the velocity in the absence or presence of slip parameters which coincides with related work. The comparison is done with experimental work by taking λ → 0 (non-Newtonian parameter).

  18. Steady flow and heat transfer analysis of Phan-Thein-Tanner fluid in double-layer optical fiber coating analysis with Slip Conditions

    Science.gov (United States)

    Khan, Zeeshan; Shah, Rehan Ali; Islam, Saeed; Jan, Bilal; Imran, Muhammad; Tahir, Farisa

    2016-01-01

    Modern optical fibers require double-layer coating on the glass fiber to provide protection from signal attenuation and mechanical damage. The most important plastic resins used in wires and optical fibers are plastic polyvinyl chloride (PVC) and low-high density polyethylene (LDPE/HDPE), nylon and Polysulfone. In this paper, double-layer optical fiber coating is performed using melt polymer satisfying PTT fluid model in a pressure type die using wet-on-wet coating process. The assumption of fully developed flow of Phan-Thien-Tanner (PTT) fluid model, two-layer liquid flows of an immiscible fluid is modeled in an annular die, where the fiber is dragged at a higher speed. The equations characterizing the flow and heat transfer phenomena are solved exactly and the effects of emerging parameters (Deborah and slip parameters, characteristic velocity, radii ratio and Brinkman numbers on the axial velocity, flow rate, thickness of coated fiber optics, and temperature distribution) are reported in graphs. It is shown that an increase in the non-Newtonian parameters increase the velocity in the absence or presence of slip parameters which coincides with related work. The comparison is done with experimental work by taking λ → 0 (non-Newtonian parameter). PMID:27708412

  19. Thermo-Optical Properties of Thin-Film TiO2–Al2O3 Bilayers Fabricated by Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Rizwan Ali

    2015-05-01

    Full Text Available We investigate the optical and thermo-optical properties of amorphous TiO\\(_2\\–Al\\(_2\\O\\(_3\\ thin-film bilayers fabricated by atomic layer deposition (ALD. Seven samples of TiO\\(_2\\–Al\\(_2\\O\\(_3\\ bilayers are fabricated by growing Al\\(_2\\O\\(_3\\ films of different thicknesses on the surface of TiO\\(_2\\ films of constant thickness (100 nm. Temperature-induced changes in the optical refractive indices of these thin-film bilayers are measured by a variable angle spectroscopic ellipsometer VASE\\textsuperscript{\\textregistered}. The optical data and the thermo-optic coefficients of the films are retrieved and calculated by applying the Cauchy model and the linear fitting regression algorithm, in order to evaluate the surface porosity model of TiO\\(_2\\ films. The effects of TiO\\(_2\\ surface defects on the films' thermo-optic properties are reduced and modified by depositing ultra-thin ALD-Al\\(_2\\O\\(_3\\ diffusion barrier layers. Increasing the ALD-Al\\(_2\\O\\(_3\\ thickness from 20 nm to 30 nm results in a sign change of the thermo-optic coefficient of the ALD-TiO\\(_2\\. The thermo-optic coefficients of the 100 nm-thick ALD-TiO\\(_2\\ film and 30 nm-thick ALD-Al\\(_2\\O\\(_3\\ film in a bilayer are (0.048 \\(\\pm\\ 0.134 \\(\\times 10 ^{-4} {^\\circ}\\mathrm {C}^{-1}\\ and (0.680 \\(\\pm\\ 0.313 \\(\\times 10^{-4} {^\\circ} \\mathrm {C}^{-1}\\, respectively, at a temperature \\(T = 62 ^\\circ \\mathrm{C}\\.

  20. 层层自组装聚电解质膜光纤传感器的制备和应用%Preparation and Application of Fiber-Optic Sensors Based on Layer-by-Layer Self-Assembly Multilayers

    Institute of Scientific and Technical Information of China (English)

    殷明杰; 安全福; 钱锦文; 张阿平

    2011-01-01

    During last several decades,optical fiber has been applied in many disciplines and areas.Among its kinds of applications,optical fiber sensors have become an interesting research project due to the advantages of optical fiber,such as immunity to electromagnetic interferences,capability of remote measurements,multiplexed detection,small size and low weight and so on.Optical fiber has been applied in fiber-optic sensors based on polyelectrolyte layer-by-layer(LbL) self-assembly multilayers have become into a hot research field since it was reported in 2000.It has widely application in measuring trace substances.In this paper,layer-by-layer self-assembly polyelectrolytes on the surface of optical fibers as well as test of fiber-optic sensors are introduced.The fiber-optic structures,assembly materials,detection principle and performance of different fiber-optic sensors based on multilayers nanocoating are also summarized.Particularly,the preparation,test and application of fiber-optic pH sensors,fiber-optic humidity sensors,fiber-optic gas sensors and fiber-optic biosensors in last decade are reviewed.The outlook of fiber-optic sensors based on LbL polyelectrolyte self-assembly multilayers is suggested.%在过去几十年中,光纤的应用已经渗透到多个学科领域。光纤的抗电磁干扰、可远程监控、多重监测、体积小及质量轻等特点,使其在传感器研究领域备受关注。聚电解质层层自组装膜构建的光纤传感器自2000年诞生以来,已快速发展成为传感器领域新的研究热点。该类光纤传感器在微量物质的监测方面具有广泛的应用前景。本文从光纤和光纤传感器优点出发,总结了基于层层自组装多层膜的光纤传感器种类、性能、检测原理以及相应的光纤结构和自组装材料;进而结合作者已做的相关工作,论述了在光纤基底上的聚电解质层层自组装及基于自组装膜的光纤传感器的测试;重点综述了近十年