WorldWideScience

Sample records for bandgap fiber devices

  1. Liquid Crystal Photonic bandgap Fibers: Modeling and Devices

    DEFF Research Database (Denmark)

    Weirich, Johannes

    In this PhD thesis an experimental and numerical investigation of liquid crystal infiltrated photonic bandgap fibers (LCPBGs) is presented. A simulation scheme for modeling LCPBG devices including electrical tunability is presented. New experimental techniques, boundary coating and the applications...... of monomer added LCs, are investigated. Waveplates based on LCPBGs and a tunable polarization maintaining filter are developed. An on-chip tunable notch filter based on long period gratings is presented. Furthermore, the application of a LCPBG device for the electrical control of a fiber laser is...

  2. Tunable photonic bandgap fiber based devices for optical networks

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Scolari, Lara; Rottwitt, Karsten;

    2005-01-01

    In future all optical networks one of the enabling technologies is tunable elements including reconfigurable routers, switches etc. Thus, the development of a technology platform that allows construction of tuning components is critical. Lately, microstructured optical fibers, filled with liquid...... crystals, have proven to be a candidate for such a platform. Microstructured optical fibers offer unique wave-guiding properties that are strongly related to the design of the air holes in the cladding of the fiber. These wave-guiding properties may be altered by filling the air holes with a material, for...... example a liquid crystal that changes optical properties when subjected to, for example, an optical or an electrical field. The utilization of these two basic properties allows design of tunable optical devices for optical networks. In this work, we focus on applications of such devices and discuss recent...

  3. Compact optically-fed microwave true-time delay using liquid crystal photonic bandgap fiber device

    DEFF Research Database (Denmark)

    Wei, Lei; Xue, Weiqi; Chen, Yaohui;

    2009-01-01

    Electrically tunable liquid crystal photonic bandgap fiber device based optically-fed microwave true-time delay is demonstrated. A maximum ~60° phase shift and an averaged ~7.2ps true time delay are obtained over the modulation frequency range 1GHz-19GHz.......Electrically tunable liquid crystal photonic bandgap fiber device based optically-fed microwave true-time delay is demonstrated. A maximum ~60° phase shift and an averaged ~7.2ps true time delay are obtained over the modulation frequency range 1GHz-19GHz....

  4. Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Barkou, Stig Eigil; Broeng, Jes; Bjarklev, Anders Overgaard

    1999-01-01

    Photonic bandgap fibers are describes using a new Kagomé cladding structure. These fibers may potentially guide light in low-index regions. Such fibers offer new dispersion properties, and large design flexibility.......Photonic bandgap fibers are describes using a new Kagomé cladding structure. These fibers may potentially guide light in low-index regions. Such fibers offer new dispersion properties, and large design flexibility....

  5. Gaussian Filtering with Tapered Liquid Crystal Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Scolari, Lara; Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard

    2006-01-01

    We present a device based on a tapered Liquid Crystal Photonic Bandgap Fiber that allows active all-in-fiber filtering. The resulting Photonic Bandgap Fiber device provides a Gaussian filter covering the wavelength range 1200-1600 nm......We present a device based on a tapered Liquid Crystal Photonic Bandgap Fiber that allows active all-in-fiber filtering. The resulting Photonic Bandgap Fiber device provides a Gaussian filter covering the wavelength range 1200-1600 nm...

  6. Continuously tunable devices based on electrical control of dual-frequency liquid crystal filled photonic bandgap fibers

    DEFF Research Database (Denmark)

    Scolari, Lara; Alkeskjold, Thomas Tanggaard; Riishede, Jesper;

    2005-01-01

    We present an electrically controlled photonic bandgap fiber device obtained by infiltrating the air holes of a photonic crystal fiber (PCF) with a dual-frequency liquid crystal (LC) with pre-tilted molecules. Compared to previously demonstrated devices of this kind, the main new feature of this...... one is its continuous tunability due to the fact that the used LC does not exhibit reverse tilt domain defects and threshold effects. Furthermore, the dual-frequency features of the LC enables electrical control of the spectral position of the bandgaps towards both shorter and longer wavelengths in...

  7. Optically fed microwave true-time delay based on a compact liquid-crystal hotonic-bandgap-fiber device

    DEFF Research Database (Denmark)

    Wei, Lei; Xue, Weiqi; Chen, Yaohui; Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard

    2009-01-01

    An electrically tunable liquid-crystal, photonic-bandgap-fiber-device-based, optically fed microwave true-time delay is demonstrated with the response time in the millisecond range. A maximum electrically controlled phase shift of around 70° at 15GHz and an averaged 12.9ps true time delay over the...

  8. Photonic bandgap fiber bundle spectrometer

    CERN Document Server

    Hang, Qu; Syed, Imran; Guo, Ning; Skorobogatiy, Maksim

    2010-01-01

    We experimentally demonstrate an all-fiber spectrometer consisting of a photonic bandgap fiber bundle and a black and white CCD camera. Photonic crystal fibers used in this work are the large solid core all-plastic Bragg fibers designed for operation in the visible spectral range and featuring bandgaps of 60nm - 180nm-wide. 100 Bragg fibers were chosen to have complimentary and partially overlapping bandgaps covering a 400nm-840nm spectral range. The fiber bundle used in our work is equivalent in its function to a set of 100 optical filters densely packed in the area of ~1cm2. Black and white CCD camera is then used to capture spectrally "binned" image of the incoming light at the output facet of a fiber bundle. To reconstruct the test spectrum from a single CCD image we developed an algorithm based on pseudo-inversion of the spectrometer transmission matrix. We then study resolution limit of this spectroscopic system by testing its performance using spectrally narrow test peaks (FWHM 5nm-25nm) centered at va...

  9. Polarization properties of photonic bandgap fibers

    DEFF Research Database (Denmark)

    Broeng, Jes; Libori, Stig E. Barkou; Bjarklev, Anders Overgaard

    2000-01-01

    We present the first analysis of polarization properties of photonic bandgap fibers. Strong birefringence may be obtained for modest non-uniformities in and around the core region, suggesting the use of photonic bandgap fibers as polarization maintaining components.......We present the first analysis of polarization properties of photonic bandgap fibers. Strong birefringence may be obtained for modest non-uniformities in and around the core region, suggesting the use of photonic bandgap fibers as polarization maintaining components....

  10. Electrically tunable liquid crystal photonic bandgap fiber laser

    DEFF Research Database (Denmark)

    Olausson, Christina Bjarnal Thulin; Scolari, Lara; Wei, Lei;

    2010-01-01

    We demonstrate electrical tunability of a fiber laser by using a liquid crystal photonic bandgap fiber. Tuning of the laser is achieved by combining the wavelength filtering effect of a liquid crystal photonic bandgap fiber device with an ytterbium-doped photonic crystal fiber. We fabricate an all......-spliced laser cavity based on a liquid crystal photonic bandgap fiber mounted on a silicon assembly, a pump/signal combiner with single-mode signal feed-through and an ytterbium-doped photonic crystal fiber. The laser cavity produces a single-mode output and is tuned in the range 1040-1065nm by applying...

  11. Continuously tunable all-in-fiber devices based on thermal and electrical control of negative dielectric anisotropy liquid crystal photonic bandgap fibers

    DEFF Research Database (Denmark)

    Wei, Lei; Eskildsen, Lars; Weirich, Johannes;

    2009-01-01

    We infiltrate photonic crystal fibers with a negative dielectric anisotropy liquid crystal. 396nm bandgap shift is obtained in the temperature range 22°C-80°C, and 67 nm shift of long-wavelength bandgap edge is achieved by applying a voltage of 200Vrms. The polarization sensitivity and correspond......We infiltrate photonic crystal fibers with a negative dielectric anisotropy liquid crystal. 396nm bandgap shift is obtained in the temperature range 22°C-80°C, and 67 nm shift of long-wavelength bandgap edge is achieved by applying a voltage of 200Vrms. The polarization sensitivity and...

  12. Actively doped solid core Photonic Bandgap Fiber

    DEFF Research Database (Denmark)

    Broeng, Jes; Olausson, Christina Bjarnal Thulin; Lyngsøe, Jens Kristian;

    2010-01-01

    Solid photonic bandgap fibers offer distributed spectral filtering with extraordinary high suppression. This opens new possibilities of artificially tailoring the gain spectrum of fibers. We present record-performance of such fibers and outline their future applications....

  13. Liquid Crystals and Photonic Bandgap Fiber Components

    DEFF Research Database (Denmark)

    Weirich, Johannes; Wei, Lei; Scolari, Lara;

    Liquid Crystal(LC)filled Photonic Crystal Fibers(PCFs) represent a promising platform for the design and the fabrication of tunable all-in fiber devices. Tunability is achieved by varying the refractive index of the LC thermally, optically or electrically. In this contribution we present important...... parts of the LC theory as well as an application of a LC infiltrated PCF subject to an external electrostatic field. The fiber is placed between two electrodes and the voltage is increased step by step leading to the reorientation of the LC in the fiber capillaries. This mechanism can be used to produce...... a swichable polarizer, and an on chip LC photonic bandgap fiber polarimeter is presented, which admits strong attenuation of one polarization direction while the other one is nearly unaffected....

  14. Novel device concepts for optical WDM communications based on silicon etalons, fiber resonators and photonic bandgap fibers

    OpenAIRE

    Tuominen, Jesse

    2008-01-01

    Since the invention of the Erbium-doped fiber amplifier in 1987 and the preceding advances in low-loss single-mode fiber technology, fiber optic wavelength-division-multiplexing (WDM) has been the dominant technology of long-haul data transmission in the 1.55-mm region. Modern dense WDM (DWDM) systems can utilize more than 60 transmission channels in the C-band (1530-1570 nm) with a channel spacing of only 25 GHz. The combination of high modulation frequencies and small channel spacing place ...

  15. Low-bandgap, monolithic, multi-bandgap, optoelectronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Wanlass, Mark W.; Carapella, Jeffrey J.

    2016-01-05

    Low bandgap, monolithic, multi-bandgap, optoelectronic devices (10), including PV converters, photodetectors, and LED's, have lattice-matched (LM), double-heterostructure (DH), low-bandgap GaInAs(P) subcells (22, 24) including those that are lattice-mismatched (LMM) to InP, grown on an InP substrate (26) by use of at least one graded lattice constant transition layer (20) of InAsP positioned somewhere between the InP substrate (26) and the LMM subcell(s) (22, 24). These devices are monofacial (10) or bifacial (80) and include monolithic, integrated, modules (MIMs) (190) with a plurality of voltage-matched subcell circuits (262, 264, 266, 270, 272) as well as other variations and embodiments.

  16. Low-bandgap, monolithic, multi-bandgap, optoelectronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Wanlass, Mark W.; Carapella, Jeffrey J.

    2016-03-22

    Low bandgap, monolithic, multi-bandgap, optoelectronic devices (10), including PV converters, photodetectors, and LED's, have lattice-matched (LM), double-heterostructure (DH), low-bandgap GaInAs(P) subcells (22, 24) including those that are lattice-mismatched (LMM) to InP, grown on an InP substrate (26) by use of at least one graded lattice constant transition layer (20) of InAsP positioned somewhere between the InP substrate (26) and the LMM subcell(s) (22, 24). These devices are monofacial (10) or bifacial (80) and include monolithic, integrated, modules (MIMs) (190) with a plurality of voltage-matched subcell circuits (262, 264, 266, 270, 272) as well as other variations and embodiments.

  17. Advances in photonic bandgap fiber functionality

    DEFF Research Database (Denmark)

    Lyngsøe, Jens Kristian

    In order to take advantage of the many intriguing optical properties of photonic bandgap fibers, there are some technological challenges that have to be addressed. Among other things this includes transmission loss and the fibers ability to maintain field polarization. The work presented in this ...

  18. Electrically controllable liquid crystal photonic bandgap fiber with dual-frequency control

    DEFF Research Database (Denmark)

    Scolari, Lara; Alkeskjold, Thomas Tanggaard; Riishede, Jesper;

    2005-01-01

    We present an electrically tunable liquid crystal photonic bandgap fiber device based on a dual frequency liquid crystal with pre-tilted molecules that allows the bandgaps to be continuously tuned. The frequency dependent behavior of the liquid crystal enables active shifting of the bandgaps toward...

  19. Thermal tunability of photonic bandgaps in liquid crystal filled polymer photonic crystal fiber

    Science.gov (United States)

    Wang, Doudou; Chen, Guoxiang; Wang, Lili

    2016-05-01

    A highly tunable bandgap-guiding polymer photonic crystal fiber is designed by infiltrating the cladding air holes with liquid crystal 5CB. Structural parameter dependence and thermal tunability of the photonic bandgaps, mode properties and confinement losses of the designed fiber are investigated. Bandgaps red shift as the temperature goes up. Average thermal tuning sensitivity of 30.9 nm/°C and 20.6 nm/°C is achieved around room temperature for the first and second photonic bandgap, respectively. Our results provide theoretical references for applications of polymer photonic crystal fiber in sensing and tunable fiber-optic devices.

  20. Air-guiding Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Hansen, Theis Peter

    2005-01-01

    Photonic bandgap fibers that guide light in an air core have attracted much interest since their first demonstration in 1999. The prospect of low-loss guiding of light in air has importance for a multitude of applications, such as data transmission, gas sensors, dispersion compensation and guiding...

  1. Jacquard-woven photonic bandgap fiber displays

    CERN Document Server

    Sayed, Imran; Skorobogatiy, Maksim

    2010-01-01

    We present an overview of photonic textile displays woven on a Jacquard loom, using newly discovered polymer photonic bandgap fibers that have the ability to change color and appearance when illuminated with ambient or transmitted light. The photonic fiber can be thin (smaller than 300 microns in diameter) and highly flexible, which makes it possible to weave in the weft on a computerized Jacquard loom and develop intricate double weave structures together with a secondary weft yarn. We demonstrate how photonic crystal fibers enable a variety of color and structural patterns on the textile, and how dynamic imagery can be created by balancing the ambient and emitted radiation. Finally, a possible application in security ware for low visibility conditions is described as an example.

  2. Advances in Solid Core Photonic Bandgap Fiber Amplifiers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Laurila, Marko; Petersen, Sidsel Rübner;

    2012-01-01

    We present recent development of photonic crystal fiber amplifiers containing photonic bandgap structures for enhanced spectral and modal filtering functionality.......We present recent development of photonic crystal fiber amplifiers containing photonic bandgap structures for enhanced spectral and modal filtering functionality....

  3. Modeling of realistic cladding structures for photonic bandgap fibers

    DEFF Research Database (Denmark)

    Mortensen, Niels Asger; Nielsen, Martin Dybendal

    2004-01-01

    Cladding structures of photonic bandgap fibers often have airholes of noncircular shape, and, typically, close-to-hexagonal airholes with curved corners are observed. We study photonic bandgaps in such structures by aid of a two-parameter representation of the size and curvature. For the fundamen......Cladding structures of photonic bandgap fibers often have airholes of noncircular shape, and, typically, close-to-hexagonal airholes with curved corners are observed. We study photonic bandgaps in such structures by aid of a two-parameter representation of the size and curvature. For the...... fundamental bandgap we find that the bandgap edges (the intersections with the air line) shift toward shorter wavelengths when the air-filling fraction f is increased. The bandgap also broadens, and the relative bandwidth increases exponentially with f2. Compared with recent experiments [Nature 424, 657 (2003...

  4. Photonic bandgap fiber lasers and multicore fiber lasers for next generation high power lasers

    DEFF Research Database (Denmark)

    Shirakawa, A.; Chen, M.; Suzuki, Y.;

    2014-01-01

    Photonic bandgap fiber lasers are realizing new laser spectra and nonlinearity mitigation that a conventional fiber laser cannot. Multicore fiber lasers are a promising tool for power scaling by coherent beam combination. © 2014 OSA....

  5. Gas sensing using air-guiding photonic bandgap fibers

    DEFF Research Database (Denmark)

    Ritar, Tuomo; Tuominen, J.; Ludvigsen, Hanne;

    2004-01-01

    We demonstrate the high sensitivity of gas sensing using a novel air-guiding photonic bandgap fiber. The bandgap fiber is spliced to a standard single-mode fiber at the input end for easy coupling and filled with gas through the other end placed in a vacuum chamber. The technique is applied to...... characterize absorption lines of acetylene and hydrogen cyanide employing a tunable laser as light source. Measurements with a LED are also performed for comparison. Detection of weakly absorbing gases such as methane and ammonia is explored....

  6. Mode Division Multiplexing Exploring Hollow-Core Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Xu, Jing; Lyngso, Jens Kristian; Leick, Lasse; Carpenter, Joel; Wilkinson, Timothy D.; Peucheret, Christophe

    2013-01-01

    We review our recent exploratory investigations on mode division multiplexing using hollow-core photonic bandgap fibers (HC-PBGFs). Compared with traditional multimode fibers, HC-PBGFs have several attractive features such as ultra-low nonlinearities, low-loss transmission window around 2 µm etc....

  7. All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Lægsgaard, Jesper; Bjarklev, Anders Overgaard;

    2004-01-01

    Photonic crystal fibers (PCFs) have attracted significant attention during the last years and much research has been devoted to develop fiber designs for various applications, hereunder tunable fiber devices. Recently, thermally and electrically tunable PCF devices based on liquid crystals (LCs......) have been demonstrated. However, optical tuning of the LC PCF has until now not been demonstrated. Here we demonstrate an all-optical modulator, which utilizes a pulsed 532nm laser to modulate the spectral position of the bandgaps in a photonic crystal fiber infiltrated with a dye-doped nematic liquid...

  8. Noise filtering in a multi-channel system using a tunable liquid crystal photonic bandgap fiber

    DEFF Research Database (Denmark)

    Petersen, Martin Nordal; Scolari, Lara; Tokle, Torger; Alkeskjold, Thomas Tanggaard; Gauza, S.; Wu, Shin-Ton; Bjarklev, Anders Overgaard

    2008-01-01

    This paper reports on the first application of a liquid crystal infiltrated photonic bandgap fiber used as a tunable filter in an optical transmission system. The device allows low-cost amplified spontaneous emission (ASE) noise filtering and gain equalization with low insertion loss and broad...

  9. Broadband optically controlled switching effect in a microfluid-filled photonic bandgap fiber

    Science.gov (United States)

    Guo, Junqi; Liu, Yan-ge; Wang, Zhi; Luo, Mingming; Huang, Wei; Han, Tingting; Liu, Xiaoqi

    2016-05-01

    Broadband optically controlled switching in a microfluid-filled photonic bandgap fiber (MF-PBGF) was observed and investigated. The MF-PBGF was formed by infusing a temperature-sensitive high-index fluid into all of the cladding holes of a microstructured optical fiber (MOF). The fiber was then side pumped with a 532 nm continuous wave laser. An extinction ratio of greater than 20 dB at most of the bandgap wavelengths (more than 200 nm) was obtained with a switching power of ∼147 mW. Theoretical and experimental investigations revealed that the effect originated from changes in the temperature gradient induced by heat absorption of the fiber coating with laser illumination. These investigations offer a new and simple approach to achieve wideband and flexible all-optical fiber switching devices without using any photosensitive materials.

  10. Polarization Maintaining Hybrid TIR/Bandgap All-Solid Photonic Crystal Fiber

    DEFF Research Database (Denmark)

    Lyngsøe, Jens Kristian; Mangan, Brian J.; Roberts, John

    2008-01-01

    We report on fabricated all-solid fibers which guide by a combination of bandgap and TIR mechanisms. The fibers show high birefringence and possess a dispersion characteristic similar to the pure bandgap guiding form....

  11. A plasma photonic crystal bandgap device

    Science.gov (United States)

    Wang, B.; Cappelli, M. A.

    2016-04-01

    A fully tunable plasma photonic crystal is used to control the propagation of free space electromagnetic waves in the S to X bands of the microwave spectrum. An array of discharge plasma tubes forms a simple square crystal structure with the individual plasma dielectric constant tuned through variation in the plasma density. We show, through simulations and experiments, that transverse electric mode bandgaps exist, arising from the positive and negative dielectric constant regimes of the plasma, and that the respective bandgap frequencies can be shifted through changing the dielectric constant by varying discharge current density.

  12. Gap solitons in inhomogeneous high-index photonic bandgap fibers

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2011-01-01

    Microstructured optical fibers based on As2Se3 glass may be designed to have an in-plane photonic bandgap, and thereby support modes with zero propagation constant and zero group velocity [1]. It has been shown that such structures will support gap solitons which by way of Raman scattering will be...

  13. Photonic bandgap fibers: theory and experiments

    DEFF Research Database (Denmark)

    Bjarklev, Anders Overgaard; Broeng, Jes; Libori, Stig E. Barkou

    2000-01-01

    We will in this presentation address, show how the fiber cladding structure influences the resulting waveguiding properties. The core may be introduced by breaking the periodicity of the air holes at the center of the fiber. It has been demonstrated experimentally that this makes it possible to...

  14. Biased liquid crystal photonic bandgap fiber

    DEFF Research Database (Denmark)

    Weirich, Johannes; Lægsgaard, Jesper; Alkeskjold, Thomas Tanggaard;

    2008-01-01

    We simulate the director structure of all capillaries in a biased photonic crystal fiber infiltrated with liquid crystals. Various mode simulations for different capillaries show the necessity to consider the entire structure.......We simulate the director structure of all capillaries in a biased photonic crystal fiber infiltrated with liquid crystals. Various mode simulations for different capillaries show the necessity to consider the entire structure....

  15. Mode Division Multiplexing Exploring Hollow-Core Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Xu, Jing; Lyngso, Jens Kristian; Leick, Lasse;

    2013-01-01

    . After having discussed the potential and challenges of using HC-PBGFs as transmission fibers for mode multiplexing applications, we will report a number of recent proof-of-concept results obtained in our group using direct detection receivers. The first one is the transmission of two 10.7 Gbit/s non......We review our recent exploratory investigations on mode division multiplexing using hollow-core photonic bandgap fibers (HC-PBGFs). Compared with traditional multimode fibers, HC-PBGFs have several attractive features such as ultra-low nonlinearities, low-loss transmission window around 2 µm etc...

  16. Photonic bandgap confinement in an all-solid tellurite glass photonic crystal fiber

    OpenAIRE

    Lousteau, Joris; Mura, Emanuele; Milanese, Daniel; Boetti, Nadia Giovanna; Scarpignato, Gerardo Cristian

    2012-01-01

    We report on the fabrication and optical assessment of an all-solid tellurite-glass photonic bandgap fiber. The manufacturing process via a preform drawing approach and the fiber characterization procedures are described and discussed. The fiber exhibits some minor morphological deformations that do not prevent the observation of optical confinement within the fiber by bandgap effects. The experimental fiber attenuation spectrum displays clear bandgap confinement regions whose positions are c...

  17. Biased liquid crystal infiltrated photonic bandgap fiber

    DEFF Research Database (Denmark)

    Weirich, Johannes; Lægsgaard, Jesper; Scolari, Lara;

    2009-01-01

    A simulation scheme for the transmission spectrum of a photonic crystal fiber infiltrated with a nematic liquid crystal and subject to an external bias is presented. The alignment of the biased liquid crystal is simulated using the finite element method to solve the relevant system of coupled...... partial differential equations. From the liquid crystal alignment the full tensorial dielectric permittivity in the capillaries is derived. The transmission spectrum for the photonic crystal fiber is obtained by solving the generalized eigenvalue problem deriving from Maxwell’s equations using a vector...... element based finite element method. We demonstrate results for a splay aligned liquid crystal infiltrated into the capillaries of a four-ring photonic crystal fiber and compare them to corresponding experiments....

  18. Compact Design of an Electrically Tunable and Rotatable Polarizer Based on a Liquid Crystal Photonic Bandgap Fiber

    DEFF Research Database (Denmark)

    Wei, Lei; Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard

    2009-01-01

    In this letter, a compact electrically controlled broadband liquid crystal (LC) photonic bandgap fiber polarizer is designed and fabricated. A good fiber coupling quality between two single-mode fibers and one 10-mm-long LC-filled photonic crystal fiber is obtained and protected by using SU-8 fiber...... fixing structures during the device assembly. The total insertion loss of this all-in-fiber device is 2.7 dB. An electrically tunable polarization extinction ratio of 21.3 dB is achieved with 45$^{circ}$ rotatable transmission axis as well as switched on and off in the wavelength range of 1300–1600 nm....

  19. Advances and limitations in the modelling of fabricated photonic bandgap fibers

    OpenAIRE

    Poletti, F.; Petrovich, M.N.; Amezcua-Correa, R.; Broderick, N.G.; Monro, T.M.; Richardson, D. J.

    2006-01-01

    We model fabricated silica photonic bandgap fibers and achieve good agreement between simulated and measured properties. We identify the size of the SEM bitmap image as the ultimate limit to the accurate calculation of surfaces modes within the bandgap.

  20. Tunable All-in-Fiber Waveplates Based on Negative Dielectric Liquid Crystal Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Wei, Lei; Eskildsen, Lars; Weirich, Johannes;

    2008-01-01

    Tunable all-in-fiber waveplates based on negative dielectric liquid crystal photonic bandgap fibers are presented. The birefringence can be tuned electrically and thermally to work as a quarter-wave or a half-wave plate in the range 1520 nm-1580 nm.......Tunable all-in-fiber waveplates based on negative dielectric liquid crystal photonic bandgap fibers are presented. The birefringence can be tuned electrically and thermally to work as a quarter-wave or a half-wave plate in the range 1520 nm-1580 nm....

  1. Fiber optic monitoring device

    Science.gov (United States)

    Samborsky, James K.

    1993-01-01

    A device for the purpose of monitoring light transmissions in optical fibers comprises a fiber optic tap that optically diverts a fraction of a transmitted optical signal without disrupting the integrity of the signal. The diverted signal is carried, preferably by the fiber optic tap, to a lens or lens system that disperses the light over a solid angle that facilitates viewing. The dispersed light indicates whether or not the monitored optical fiber or system of optical fibers is currently transmitting optical information.

  2. Wide band-gap nanostructure based devices

    OpenAIRE

    Chen, Xinyi; 陈辛夷

    2012-01-01

    Wide band gap based nanostructures have being attracting much research interest because of their promise for application in optoelectronic devices. Among those wide band gap semiconductors, gallium nitride (GaN) and zinc oxide (ZnO) are the most commonly studied and optoelectronic devices based on GaN and ZnO have been widely investigated. This thesis concentrates on the growth, optical and electrical properties of GaN and ZnO nanostructures, plus their application in solar cells and light e...

  3. Design of photonic bandgap fibers by topology optimization

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard; Sigmund, Ole; Feurer, Thomas

    2010-01-01

    A method based on topology optimization is presented to design the cross section of hollow-core photonic bandgap fibers for minimizing energy loss by material absorption. The optical problem is modeled by the timeharmonic wave equation and solved with the finite element program Comsol Multiphysics....... The optimization is based on continuous material interpolation functions between the refractive indices and is carried out by the method of moving asymptotes. An example illustrates the performance of the method where air and silica are redistributed around the core so that the overlap between the...

  4. Investigation on single taper-based all-solid photonic bandgap fiber modal interferometers.

    Science.gov (United States)

    Li, Jie; Geng, Mengmei; Sun, Li-Peng; Fan, Pengcheng; Liu, Bo; Guan, Bai-Ou

    2016-04-18

    We demonstrate a single taper-based all-solid photonic bandgap (AS-PBG) fiber modal interferometer that consists of a central tapered fiber region connected to the untapered via two abrupt transitions. Modal interference is given by superimposing the bandgap-guided fundamental core mode with a lower effective index and a specific index-guided cladding supermode with a higher effective index. A series of interferometers with taper diameter of 50μm ~60μm and device length of ~3mm are fabricated and studied in contrast to the conventional counterparts. The temperature coefficient of the interferometer is closely determined by the fraction of the cladding supermode energy localized within the index-raised regions of the fiber. The refractive index (RI) responsivities associated to fiber taper sizes are investigated. The measured maximal RI sensitivity is ~3512.36nm/RIU at the taper diameter of 50μm around RI = 1.423. This research gives a deep understanding to the modal-interferometric AS-PBG structure, which we believe to be valuable for the future application of the related device. PMID:27137292

  5. Polarization-maintaining fiber pulse compressor by birefringent hollow-core photonic bandgap fiber.

    Science.gov (United States)

    Shirakawa, Akira; Tanisho, Motoyuki; Ueda, Ken-Ichi

    2006-12-11

    Structural birefringent properties of a hollow-core photonic-bandgap fiber were carefully investigated and applied to all-fiber chirped-pulse amplification as a compressor. The group birefringence of as high as 6.9x10(-4) and the dispersion splitting by as large as 149 ps/nm/km between the two principal polarization modes were observed at 1557 nm. By launching the amplifier output to one of the polarization modes a 17-dB polarization extinction ratio was obtained without any pulse degradation originating from polarization-mode dispersion. A hybrid fiber stretcher effectively compensates the peculiar dispersion of the photonic-bandgap fiber and pedestal-free 440-fs pulses with a 1-W average power and 21-nJ pulse energy were obtained. Polarization-maintaining fiber-pigtail output of high-power femtosecond pulses is useful for various applications. PMID:19529631

  6. Liquid Crystal photonic Bandgap Fiber Devices

    DEFF Research Database (Denmark)

    Wei, Lei

    polarizer with electrically tunable polarization extinction ratio is obtained. An on-chip tunable notch filter based on long-period gratings is presented, exhibiting high polarization sensitivity. A tunable polarization controller using negative dielectric LCs is developed, which can be thermally and...... electrically controlled to work both as a quarter-wave plate or half-wave plate. An electrically tunable bandpass filter based on two solid-core PCFs filled with different LCs is fabricated, and the tunability of the bandwidth is achieved by individually or simultaneously controlling the driving voltage of...

  7. High Thermal and Electrical Tunability of Negative Dielectric Liquid Crystal Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Wei, Lei; Scolari, Lara; Weirich, Johannes;

    2008-01-01

    We infiltrate photonic crystal fibers with negative dielectric liquid crystals. 400nm bandgap shift is obtained in the range 22ºC-80ºC and 119nm shift of the long-wavelength bandgap edge is achieved by applying a voltage of 200V.......We infiltrate photonic crystal fibers with negative dielectric liquid crystals. 400nm bandgap shift is obtained in the range 22ºC-80ºC and 119nm shift of the long-wavelength bandgap edge is achieved by applying a voltage of 200V....

  8. Thermal tunability of photonic bandgaps in liquid crystal infiltrated microstructured polymer optical fibers

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Wei, Lei; Alkeskjold, Thomas Tanggaard;

    2009-01-01

    We demonstrate the photonic bandgap effect and the thermal tunability of bandgaps in microstructured polymer optical fibers infiltrated with liquid crystal. Two liquid crystals with opposite sign of the temperature gradient of the ordinary refractive index (E7 and MDA-00- 1444) are used to...

  9. Power-scalable long-wavelength Yb-doped photonic bandgap fiber sources

    DEFF Research Database (Denmark)

    Olausson, Christina Bjarnal Thulin; Shirakawa, Akira; Maurayama, Hiroki; Ken-ichi, Ueda; Lyngsøe, Jens Kristian; Broeng, Jes

    2010-01-01

    Ytterbium-doped photonic-bandgap fiber sources operationg at the long-wavelength edge of the ytterbium gain band are being investigated for high power amplification. Artificial shaping of the gain spectrum by the characteristic distributed filtering effect of the photonic bandgap enables spontane...

  10. Low loss liquid crystal photonic bandgap fiber in the near-infrared region

    DEFF Research Database (Denmark)

    Scolari, Lara; Wei, Lei; Gauza, S.;

    2010-01-01

    We infiltrate a photonic crystal fiber with a perdeuterated liquid crystal, which has a reduced infrared absorption. The lowest loss ever reported (about 1 dB) in the middle of the near-infrared bandgap is achieved.......We infiltrate a photonic crystal fiber with a perdeuterated liquid crystal, which has a reduced infrared absorption. The lowest loss ever reported (about 1 dB) in the middle of the near-infrared bandgap is achieved....

  11. Bandgaps of the Chalcogenide Glass Hollow-Core Photonic Crystal Fiber

    International Nuclear Information System (INIS)

    Bandgaps of chalcogenide glass hollow-core photonic crystal fibers (GLS HC-PCFs) are analyzed by using the plane-wave expansion method. A mid-infrared laser can propagate in these low confinement loss fibers when the wavelength falls into the bandgaps. For enlarging the bandgap width, an improved GLS HC-PCF is put forward, the normalized frequency kΛ of the improved fiber is from 7.2 to 8.5 in its first bandgap. The improved GLS HC-PCF with pitch of 4.2 μm can transmit the lights with wavelengths ranging from 3.1 μm to 3.7 μm. (fundamental areas of phenomenology(including applications))

  12. Mode areas and field energy distribution in honeycomb photonic bandgap fibers

    CERN Document Server

    Laegsgaard, J; Bjarklev, A; Laegsgaard, Jesper; Mortensen, Niels Asger; Bjarklev, Anders

    2003-01-01

    The field energy distributions and effective mode areas of silica-based photonic bandgap fibers with a honeycomb airhole structure in the cladding and an extra airhole defining the core are investigated. We present a generalization of the common effective area definition, suitable for the problem at hand, and compare the results for the photonic bandgap fibers with those of index-guiding microstructured fibers. While the majority of the field energy in the honeycomb photonic bandgap fibers is found to reside in the silica, a substantial fraction (up to ~30%) can be located in the airholes. This property may show such fibers particularly interesting for sensor applications, especially those based on nonlinear effects or interaction with other structures (e.g. Bragg gratings) in the glass.

  13. Air-guiding photonic bandgap fiber with improved triangular air-silica photonic crystal cladding

    OpenAIRE

    Yan, M; Shum, P

    2005-01-01

    We introduce a small-core air-guiding photonic crystal fiber whose cladding is made of improved air-silica photonic crystal with non-circular air holes placed in triangular lattice. The fiber achieves un-disturbed bandgap guidance over 350nm wavelength range.

  14. Highly tunable large core single-mode liquid crystal photonic bandgap fiber

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Lægsgaard, Jesper; Bjarklev, Anders Overgaard;

    2006-01-01

    We demonstrate a highly tunable photonic bandgap fiber, which has a large-core diameter of 25 mu m and an effective mode area of 440 mu m(2). The tunability is achieved by infiltrating the air holes of a photonic crystal fiber with an optimized liquid-crystal mixture having a large temperature...... Society of America....

  15. Low index-contrast photonic bandgap fiber for transmission of short pulsed light

    DEFF Research Database (Denmark)

    Riishede, Jesper; Lægsgaard, Jesper; Broeng, Jes;

    2004-01-01

    The use of low-index-contrast photonic bandgap (PBG) fiber for transmission of short pulsed light is discussed. PBG fibers have positive waveguide dispersion at long wavelengths at which conventional index-guiding fibers have negative waveguide dispersion. PBG fibers with low-index contrast can be...... used to obtain fibers with zero dispersion and a large mode area below 800 nm$+3$/. The results show that the PBG fiber is less sensitive to nonlinear effects and allows transmission of considerably larger intensities....

  16. Photonic band-gap fiber gas cell fabricated using femtosecond micromachining.

    Science.gov (United States)

    Hensley, Christopher; Broaddus, Daniel H; Schaffer, Chris B; Gaeta, Alexander L

    2007-05-28

    Femtosecond laser drilling is used to produce a variablepressure fiber gas cell. Tightly focused laser pulses are used to produce micrometer-diameter radial channels in a hollow-core photonic band-gap fiber (HC-PBGF), and through these microchannels the core of the fiber is filled with a gas. The fiber cell is formed by fusion splicing and sealing the ends of the HC-PBGF to standard step-index fiber. As a demonstration, acetylene is introduced into an evacuated fiber at multiple backing pressures and spectra are measured. PMID:19546979

  17. SU-8 process optimization for high fiber coupling efficiency of liquid crystal filled photonic bandgap fiber components

    DEFF Research Database (Denmark)

    Wei, Lei; Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard

    2009-01-01

    SU-8 structures are built up to increase the fiber coupling efficiency of liquid crystal photonic bandgap fiber components. The resolution reduction of UV exposure is minimized to 4%, and insertion loss is reduced to 2.7dB....

  18. Transmission Bandwidth Tunability of a Liquid-Filled Photonic Bandgap Fiber

    Institute of Scientific and Technical Information of China (English)

    ZOU Bing; LIU Yan-Ge; DU Jiang-Sing; WANG Zhi; HAN Ting-Ting; XU Jian-Bo; LI Yuan; LIU Bo

    2009-01-01

    @@ A temperature tunable photonic bandgap tiber (PBGF) is demonstrated by an index-guiding photonic crystal fiber filled with high-index liquid. The temperature tunable characteristics of the fiber axe experimentally and numerically investigated. Compression of transmission bandwidth of the PBGF is demonstrated by changing the temperature of part of the fiber. The tunable transmission bandwidth with a range of 250 nm is achieved by changing the temperature from 30℃ to 90℃.

  19. Study on the photonic bandgaps of hollow-core microstructured fibers

    Institute of Scientific and Technical Information of China (English)

    Zhaolun Liu; Guiyao Zhou; Lantian Hou

    2006-01-01

    A simple method is presented to measure the transmission spectrum of hollow-core microstructured fibers in the visible, near-infrared, and mid-infrared regions. The plane wave expansion method is applied to analyze the photonic bandgaps of hollow-core microstructured fibers. The experimental results indicate that there are several strong transmission bands in the near-infrared and mid-infrared region, but hardly any transmission phenomena in the visible region, which shows that there are some bandgaps in nearinfrared wavelength. The experimental results are consistent with the numerically simulative results using a plane wave expansion method.

  20. A 158 fs 5.3 nJ fiber-laser system at 1 mu m using photonic bandgap fibers for dispersion control and pulse compression

    DEFF Research Database (Denmark)

    Nielsen, C.K.; Jespersen, Kim Giessmann; Keiding, S.R.

    2006-01-01

    We demonstrate a 158 fs 5.3 nJ mode-locked laser system based on a fiber oscillator, fiber amplifier and fiber compressor. Dispersion compensation in the fiber oscillator was obtained with a solid-core photonic bandgap (SC-PBG) fiber spliced to standard fibers, and external compression is obtained...

  1. High-power narrow-linewidth large mode area photonic bandgap fiber amplifier

    Science.gov (United States)

    Pulford, Benjamin; Dajani, Iyad; Ehrenreich, Thomas; Holten, Roger; Vergien, Christopher; Naderi, Nader; Mart, Cody; Gu, Guancheng; Kong, Fanting; Hawkins, Thomas; Dong, Liang

    2015-03-01

    Ytterbium-doped large mode area all-solid photonic bandgap fiber amplifiers were used to demonstrate power at 1064 nm. In an initial set of experiments, a fiber with a core diameter of ~50 μm, and a calculated effective area of 1450 μm2 in a straight fiber, was used to generate approximately 600 W. In this case, the input seed was modulated using a sinusoidal format at a frequency of 400 MHz. The output, however, was multimode as the fiber design did not allow for single-mode operation at this wavelength. A second fiber was then fabricated to operate predominantly in single mode at 1064 nm by having the seed closer to the short wavelength edge of the bandgap. This fiber was used to demonstrate 400 W of single-frequency output with excellent beam quality. As the signal power exceeded 450 W, there was significant degradation in the beam quality due to the modal instability. Nevertheless, to the best of our knowledge, the power scaling results obtained in this work far exceed results from prior state of the art all-solid photonic bandgap fiber lasers.

  2. Generation of Low Divergent High Power Supercontinuum Through a Large Mode Area Photonic Bandgap Fiber

    CERN Document Server

    Ghosh, S; Varshney, R K; Pal, B P

    2012-01-01

    We report generation of broadband low divergent supercontinuum over the entire wavelength window of 1.5 to 3.5 {\\mu}m from a 2.25 meter long effective single moded photonic bandgap fiber with mode area of 1100 {\\mu}m2.

  3. Millijoule Pulse Energy Second Harmonic Generation With Single-Stage Photonic Bandgap Rod Fiber Laser

    DEFF Research Database (Denmark)

    Laurila, Marko; Saby, Julien; Alkeskjold, Thomas Tanggaard; Scolari, Lara; Cocquelin, Benjamin; Salin, Francois; Broeng, Jes; Lægsgaard, Jesper

    2011-01-01

    In this paper, we demonstrate, for the first time, a single-stage Q-switched single-mode (SM) ytterbium-doped rod fiber laser delivering record breaking pulse energies at visible and UV light. We use a photonic bandgap rod fiber with a mode field diameter of 59μm based on a new distributed......-mode-filtering (DMF) fiber design, where germanium-doped high-index inclusions are added in order to enable efficient suppression of higher order modes. The rod fiber design is illustrated....

  4. Air-Guiding Photonic Bandgap Fibers: Spectral Properties, Macrobending Loss, and Practical Handling

    DEFF Research Database (Denmark)

    Hansen, Theis Peter; Broeng, Jes; Jakobsen, Christian; Vienne, Guillaume; Simonsen, Harald R.; Nielsen, Martin Dybendal; Skovgaard, Peter M.W.; Folkenberg, Jacob Riis; Bjarklev, Anders Overgaard

    2004-01-01

    For development of hollow-core transmission fibers, the realizable fibers lengths, bandwidth, characterization, and compatibility with standard technology are important issues. We report record-length air-guiding fiber, spectral properties, splicing, and optical time domain reflectometer (OTDR) m......) measurements. Furthermore, spectral macrobending loss measurements for two different designs of air-core photonic bandgap fibers are presented. While bending loss is observed, it does not limit operation for all practical bending diameters (>tex/tex......For development of hollow-core transmission fibers, the realizable fibers lengths, bandwidth, characterization, and compatibility with standard technology are important issues. We report record-length air-guiding fiber, spectral properties, splicing, and optical time domain reflectometer (OTDR...

  5. Paving the way for third harmonic generation in hollow-core photonic bandgap fibers

    CERN Document Server

    Montz, Z

    2014-01-01

    We present two novel hybrid photonic structures made of silica that possess two well-separated frequency bandgaps. The addition of interstitial air holes in a precise location and size allows these bandgaps to open up with a ratio of ${\\sim3}$ between their central frequencies at the air line ${ck_z/w=1}$, thus fulfilling the basic guidance condition for third harmonic generation in hollow-core fibers. In addition, these designs may serve as high-power laser delivery of two well-separated wavelengths, such as visible and near infrared.

  6. Manipulating the Propagation of Solitons with Solid-Core Photonic Bandgap Fibers

    Directory of Open Access Journals (Sweden)

    O. Vanvincq

    2012-01-01

    Full Text Available We review the dynamics of soliton self-frequency shift induced by Raman gain in special solid-core photonic bandgap fibers and its consequences in terms of supercontinuum generation. These photonic bandgap fibers have been designed to allow nonlinear experiments in the first bandgap without suffering from significant loss even when working close to the photonic bandgap edge. We studied experimentally, numerically, and analytically the extreme deceleration of the soliton self-frequency shift at the long-wavelength edge of the first transmission window. This phenomenon is interpreted as being due to a large variation of the group-velocity dispersion in this spectral range and has been obtained with no significant power loss. Then, we investigated experimentally and numerically the generation of supercontinuum in this kind of fibers, in both spectral and temporal domains. In particular, we demonstrated an efficient tailoring of the supercontinuum spectral extension as well as a strong noise reduction at its long-wavelength edge.

  7. The Second Order Guided Modes Based on Photonic Bandgap Effects in Air/Glass Photonic Crystal Fibers

    International Nuclear Information System (INIS)

    We introduce a defect site in the periodic structure of a photonic bandgap fiber, to confine and guide the second order mode by photonic bandgap effects. Based on a high air-filling fraction photonic crystal cladding structure, a simplified model with an equivalent air cladding was proposed to explore and analyze the properties of this second order guided mode

  8. Gaussian Filtering with Tapered Oil-Filled Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Brunetti, Anna Chiara; Scolari, Lara; Weirich, Johannes;

    2008-01-01

    A tunable Gaussian filter based on a tapered oil-filled photonic crystal fiber is demonstrated. The filter is centered at X=1364nm with a bandwidth (FWHM) of 237nm. Tunability is achieved by changing the temperature of the filter. A shift of 210nm of the central wavelength has been observed by...

  9. THz Photonic Band-Gap Prisms Fabricated by Fiber Drawing

    DEFF Research Database (Denmark)

    Busch, Stefan F.; Xu, Lipeng; Stecher, Matthias;

    2012-01-01

    We suggest a novel form of polymeric based 3D photonic crystal prisms for THz frequencies which could be fabricated using a standard fiber drawing technique. The structures are modeled and designed using a finite element analyzing technique. Using this simulation software we theoretically study...... their performance....

  10. Microstructured and Photonic Bandgap Fibers for Applications in the Resonant Bio- and Chemical Sensors

    Directory of Open Access Journals (Sweden)

    Maksim Skorobogatiy

    2009-01-01

    Full Text Available We review application of microstructured and photonic bandgap fibers for designing resonant optical sensors of changes in the value of analyte refractive index. This research subject has recently invoked much attention due to development of novel fiber types, as well as due to development of techniques for the activation of fiber microstructure with functional materials. Particularly, we consider two sensors types. The first sensor type employs hollow core photonic bandgap fibers where core guided mode is confined in the analyte filled core through resonant effect in the surrounding periodic reflector. The second sensor type employs metalized microstructured or photonic bandgap waveguides and fibers, where core guided mode is phase matched with a plasmon propagating at the fiber/analyte interface. In resonant sensors one typically employs fibers with strongly nonuniform spectral transmission characteristics that are sensitive to changes in the real part of the analyte refractive index. Moreover, if narrow absorption lines are present in the analyte transmission spectrum, due to Kramers-Kronig relation this will also result in strong variation in the real part of the refractive index in the vicinity of an absorption line. Therefore, resonant sensors allow detection of minute changes both in the real part of the analyte refractive index (10−6–10−4 RIU, as well as in the imaginary part of the analyte refractive index in the vicinity of absorption lines. In the following we detail various resonant sensor implementations, modes of operation, as well as analysis of sensitivities for some of the common transduction mechanisms for bio- and chemical sensing applications. Sensor designs considered in this review span spectral operation regions from the visible to terahertz.

  11. Transmission and Propagation of an Accelerating Mode in a Photonic Bandgap Fiber

    Energy Technology Data Exchange (ETDEWEB)

    Ng, C.-K.; England, R.J.; Lee, L.-Q.; Noble, R.; Rawat, V.; Spencer, J.; /SLAC

    2010-08-26

    A hollow core photonic bandgap (PBG) lattice in a dielectric fiber can provide high gradient acceleration in the optical regime, where the accelerating mode resulting from a defect in the PBG fiber can be excited by high-power lasers. Efficient methods of coupling laser power into the PBG fiber are an area of active research. In this paper, we develop a simulation method using the parallel finite-element electromagnetic suite ACE3P to study the propagation of the accelerating mode in the PBG fiber and determine the radiation pattern into free space at the end of the PBG fiber. The far-field radiation will be calculated and the mechanism of coupling power from an experimental laser setup will be discussed.

  12. Photonic Bandgap Propagation in All-Solid Chalcogenide Microstructured Optical Fibers

    Directory of Open Access Journals (Sweden)

    Celine Caillaud

    2014-08-01

    Full Text Available An original way to obtain fibers with special chromatic dispersion and single-mode behavior is to consider microstructured optical fibers (MOFs. These fibers present unique optical properties thanks to the high degree of freedom in the design of their geometrical structure. In this study, the first all-solid all-chalcogenide MOFs exhibiting photonic bandgap transmission have been achieved and optically characterized. The fibers are made of an As38Se62 matrix, with inclusions of Te20As30Se50 glass that shows a higher refractive index (n = 2.9. In those fibers, several transmission bands have been observed in mid infrared depending on the geometry. In addition, for the first time, propagation by photonic bandgap effect in an all-chalcogenide MOF has been observed at 3.39 µm, 9.3 µm, and 10.6 µm. The numerical simulations based on the optogeometric properties of the fibers agree well with the experimental characterizations.

  13. Enhanced Two-Photon Absorption in a Hollow-Core Photonic Bandgap Fiber

    CERN Document Server

    Saha, Kasturi; Londero, Pablo; Gaeta, Alexander L

    2010-01-01

    We show that two-photon absorption (TPA) in Rubidium atoms can be greatly enhanced by the use of a hollow-core photonic bandgap fiber. We investigate off-resonant, degenerate Doppler-free TPA on the 5S1/2 - 5D5/2 transition and observe 1% absorption of a pump beam with a total power of only 1 mW in the fiber. These results are verified by measuring the amount of emitted blue fluorescence and are consistent with the theoretical predictions which indicate that transit time effects play an important role in determining the two-photon absorption cross-section in a confined geometry.

  14. Scattering loss analysis and structure optimization of hollow-core photonic bandgap fiber

    Science.gov (United States)

    Song, Jingming; Wu, Rong; Sun, Kang; Xu, Xiaoliang

    2016-06-01

    Effects of core structure in 7 cell hollow-core photonic bandgap fibers (HC-PBGFs) on scattering loss are analyzed by means of investigating normalized interface field intensity. Fibers with different core wall thickness, core radius and rounding corner of air hole are simulated. Results show that with thick core wall and expanded core radius, scattering loss could be greatly reduced. The scattering loss of the HC-PBGFs in the wavelength range of 1.5-1.56 μm could be decreased by about 50 % of the present level with optimized core structure design.

  15. Photolithography of thick photoresist coating for electrically controlled liquid crystal photonic bandgap fibre devices

    DEFF Research Database (Denmark)

    Wei, Lei; Khomtchenko, Elena; Alkeskjold, Thomas Tanggaard;

    2009-01-01

    Thick photoresist coating for electrode patterning in an anisotropically etched V-groove is investigated for electrically controlled liquid crystal photonic bandgap fibre devices. The photoresist step coverage at the convex corners is compared with and without soft baking after photoresist spin...

  16. Light Absorption Enhancement of Silicon-Based Photovoltaic Devices with Multiple Bandgap Structures of Porous Silicon

    Directory of Open Access Journals (Sweden)

    Kuen-Hsien Wu

    2015-09-01

    Full Text Available Porous-silicon (PS multi-layered structures with three stacked PS layers of different porosity were prepared on silicon (Si substrates by successively tuning the electrochemical-etching parameters in an anodization process. The three PS layers have different optical bandgap energy and construct a triple-layered PS (TLPS structure with multiple bandgap energy. Photovoltaic devices were fabricated by depositing aluminum electrodes of Schottky contacts on the surfaces of the developed TLPS structures. The TLPS-based devices exhibit broadband photoresponses within the spectrum of the solar irradiation and get high photocurrent for the incident light of a tungsten lamp. The improved spectral responses of devices are owing to the multi-bandgap structures of TLPS, which are designed with a layered configuration analog to a tandem cell for absorbing a wider energy range of the incidental sun light. The large photocurrent is mainly ascribed to an enhanced light-absorption ability as a result of applying nanoporous-Si thin films as the surface layers to absorb the short-wavelength light and to improve the Schottky contacts of devices. Experimental results reveal that the multi-bandgap PS structures produced from electrochemical-etching of Si wafers are potentially promising for development of highly efficient Si-based solar cells.

  17. Characteristics of Bragg Gratings in All-Solid Photonic Bandgap Fiber

    Institute of Scientific and Technical Information of China (English)

    Bai-Ou Guan; Zhi Wang; Yang Zhang; Da Chen

    2008-01-01

    We report on fiber Bragg gratings in all-solid photonie bandgap fiber that was composed of a triangular array of high-index Ge-doped rods in pure silica background with fluorine-doped index-depressed layer surrounding the Ge-doped rod. Fiber Bragg gratings were photowritten with 193 nm ArF excimer laser and characterized for their response to strain, temperature, bending, and torsion. These gratings couple light from the forward core mode to not only backward core mode but also backward rod modes. This results in multiple resonance peaks in the reflection spectrum. All resonance wavelengths exhibited the same temperature and strain response with coefficient similar to that of Bragg gratings in standard single-mode fiber. The strength of the resonance peaks corresponding to the backward rod modes showed high sensitivity to bending and torsion.

  18. Broadband orbital angular momentum transmission using a hollow-core photonic bandgap fiber.

    Science.gov (United States)

    Li, Haisu; Ren, Guobin; Lian, Yudong; Zhu, Bofeng; Tang, Min; Zhao, Yuanchu; Jian, Shuisheng

    2016-08-01

    We present the viability of exploiting a current hollow-core photonic bandgap fiber (HC-PBGF) to support orbital angular momentum (OAM) states. The photonic bandgap intrinsically provides a large refractive index spacing for guiding light, leading to OAM transmission with low crosstalk. From numerical simulations, a broad OAM±1 mode transmission window with satisfied effective index separations between vector modes (>10-4) and low confinement loss (power weight for OAM mode) is found to be affected by the modal effective area. Simulation results also show HC-PBGF based OAM transmission is immune to fabrication inaccuracies near the hollow core. This work illustrates that HC-PBGF is a competitive candidate for high-capacity communication harnessing OAM multiplexing. PMID:27472626

  19. Determining the Origin of Half-bandgap-voltage Electroluminescence in Bifunctional Rubrene/C60 Devices

    Science.gov (United States)

    Chen, Qiusong; Jia, Weiyao; Chen, Lixiang; Yuan, De; Zou, Yue; Xiong, Zuhong

    2016-01-01

    Lowering the driving voltage of organic light-emitting diodes (OLEDs) is an important approach to reduce their energy consumption. We have fabricated a series of bifunctional devices (OLEDs and photovoltaics) using rubrene and fullerene (C60) as the active layer, in which the electroluminescence threshold voltage(~1.1 V) was half the value of the bandgap of rubrene. Magneto-electroluminescence (MEL) response of planner heterojunction diodes exhibited a small increase in response to a low magnetic field strength (20 mT). When a hole-transport layer with a low mobility was included in these devices, the MEL response reversed in shape, and simultaneously, the EL threshold voltage became larger than the bandgap voltage. When bulk heterojunction device was examined, the amplitude of MEL curves presented an anomalous voltage-dependence. Following an analysis of the MEL responses of these devices, we proposed that the EL of half-bandgap-voltage device originated from bimolecular triplet-triplet annihilation in the rubrene film, rather than from singlet excitons that formed via an interface auger recombination. This work provides critical insight into the mechanisms of OLED emission and will help advance the applications of bifunctional devices. PMID:27142285

  20. Determining the Origin of Half-bandgap-voltage Electroluminescence in Bifunctional Rubrene/C60 Devices.

    Science.gov (United States)

    Chen, Qiusong; Jia, Weiyao; Chen, Lixiang; Yuan, De; Zou, Yue; Xiong, Zuhong

    2016-01-01

    Lowering the driving voltage of organic light-emitting diodes (OLEDs) is an important approach to reduce their energy consumption. We have fabricated a series of bifunctional devices (OLEDs and photovoltaics) using rubrene and fullerene (C60) as the active layer, in which the electroluminescence threshold voltage(~1.1 V) was half the value of the bandgap of rubrene. Magneto-electroluminescence (MEL) response of planner heterojunction diodes exhibited a small increase in response to a low magnetic field strength (20 mT). When a hole-transport layer with a low mobility was included in these devices, the MEL response reversed in shape, and simultaneously, the EL threshold voltage became larger than the bandgap voltage. When bulk heterojunction device was examined, the amplitude of MEL curves presented an anomalous voltage-dependence. Following an analysis of the MEL responses of these devices, we proposed that the EL of half-bandgap-voltage device originated from bimolecular triplet-triplet annihilation in the rubrene film, rather than from singlet excitons that formed via an interface auger recombination. This work provides critical insight into the mechanisms of OLED emission and will help advance the applications of bifunctional devices. PMID:27142285

  1. High sensitivity high temperature sensor based on SMS structure with large-core all-solid bandgap fiber as the multimode section

    Science.gov (United States)

    Franco, Marcos A. R.; Cruz, Alice L. S.; Serrão, Valdir A.; Barbosa, Carmem L.

    2014-05-01

    A fiber optic interferometric device based on a singlemode-multimode-singlemode (SMS) structure is proposed as a high sensitive high temperature sensor. The multimode section (MMF) consists of a large-core all-solid photonic bandgap fiber (AS-PBF) with silica as the background material and germanium-doped silica at the high index regions. The numerical analyses were carried out by beam propagation method. The numerical results indicate a constant high temperature sensitivity of ~-35 pm/°C over a large temperature range from 20oC to 930°C.

  2. 400-W near diffraction-limited single-frequency all-solid photonic bandgap fiber amplifier.

    Science.gov (United States)

    Pulford, Benjamin; Ehrenreich, Thomas; Holten, Roger; Kong, Fanting; Hawkins, Thomas W; Dong, Liang; Dajani, Iyad

    2015-05-15

    An ytterbium-doped large-mode area photonic bandgap fiber is used to demonstrate 400 W of single-frequency output at 1064 nm with excellent beam quality and minimal stimulated Brillouin scattering. The fiber possesses all-solid microstructures embedded in the cladding and a core composed of phosphosilicate with a diameter of ∼50  μm. As the signal power is pushed beyond 450 W, there is degradation in the beam quality due to the modal instability. We briefly discuss techniques to alleviate this problem in future designs. To the best of our knowledge, the 400-W single-frequency near diffraction-limited output far exceeds the current state-of-the-art from such type of fiber amplifier. PMID:26393723

  3. Fabrication and characterization of porous-core honeycomb bandgap THz fibers

    DEFF Research Database (Denmark)

    Bao, Hualong; Nielsen, Kristian; Rasmussen, Henrik K.;

    We have fabricated a porous-core honeycomb fiber in the cyclic olefin copolymer (COC) Topas® by drill-draw technology [1]. A cross-sectional image of the fabricated fiber is shown in the left Panel of Fig. 1. Simulation of the electromagnetic properties of the fiber shows two wide bandgaps within......-TDS system (Picometrix T-Ray 4000). The reference pulse before coupling into the fiber is shown in Fig. 1(a) and the time trace of the THz pulse after propagation through a 5-cm long segment of fiber is shown in Fig. 1(b) (blue curve). After adding some water on the outside of the fiber surface, the...... below approximately 0.6 THz are attenuated by adding a layer of water on the outside of the fiber surface, while the transmission in the two band gaps in the 0.7-1.1 THz and 1.3-1.7 THz regions are unaffected by the water, This observation demonstrates that the absorptive water layer effectively strips...

  4. Optical Fiber Devices in WDM Networks

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Crystal optics and fiber grating technology are two of the most important optical fiber device technologies. In this paper, we report several new devices developed in Accelink for WDM networks application.

  5. Physical simulation, fabrication and characterization of Wide bandgap semiconductor devices

    OpenAIRE

    Muniza Faraz, Sadia

    2011-01-01

    Wide band gap semiconductors, Zinc Oxide (ZnO), Gallium Nitride (GaN) and Silicon Carbide (SiC) have been emerged to be the most promising semiconductors for future applications in electronic, optoelectronic and power devices. They offer incredible advantages in terms of their optical properties, DC and microwave frequencies power handling capability, piezoelectric properties in building electromechanical coupled sensors and transducers, biosensors and bright light emission. For producing hig...

  6. Continuous generation of Rubidium vapor in hollow-core photonic band-gap fibers

    CERN Document Server

    Donvalkar, Prathamesh S; Clemmen, Stephane; Gaeta, Alexander L

    2015-01-01

    We demonstrate high optical depths (50+/-5), lasting for hours in Rubidium-filled hollow-core photonic band-gap fibers, which represents a 1000X improvement over operation times previously reported. We investigate the vapor generation mechanism using both a continuous-wave and a pulsed light source and find that the mechanism for generating the Rubidium atoms is primarily due to thermal vaporization. Continuous generation of large vapor densities should enable measurements at the single-photon level by averaging over longer time scales.

  7. Compression of realistic laser pulses in hollow-core photonic bandgap fibers

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper; Roberts, John

    2009-01-01

    Dispersive compression of chirped few-picosecond pulses at the microjoule level in a hollow-core photonic bandgap fiber is studied numerically. The performance of ideal parabolic input pulses is compared to pulses from a narrowband picosecond oscillator broadened by self-phase modulation during...... power, duration, and bandwidth. The same conclusion is found for the peak power and energy of solitons formed beyond the point of maximal compression. Long-pass filtering of these solitons is shown to be a promising route to clean solitonlike output pulses with peak powers of several MW....

  8. Wide bandgap semiconductors. Fundamental properties and modern photonic and electronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, K. [Nippon EMC Ltd. (Japan). R and D Center; Yoshikawa, A. [Chiba Univ. (Japan); Sandhu, A. (eds.) [Tokyo Institute of Technology (Japan)

    2007-07-01

    This book offers a comprehensive overview of the development, current state and future prospects of wide bandgap semiconductor materials and related optoelectronics devices. It includes an overview of recent developments in III-V nitride semiconductors, SiC, diamond, ZnO, II-VI materials and related devices including AIGaN/GaN FET, UV LDs, white light LEDs, and cold electron emitters. With 901 references, 333 figures and 21 tables, this book will serve as a one-stop source of knowledge on wide bandgap semiconductors and related optoelectronics devices. After review of the basic physics of WBGS and the relevance of the physical properties to the development of commercial devices, the book addresses the applications of WBGS devices for solid-state white-light illumination, medicine and gigahertz-high power telecommunications. In addition, description of recent development in the growth and applications of nitride semiconductors are complemented by chapters on the properties and device applications of SiC, diamond thin films, doping of ZnO, II-IVs and the novel BeZnSeTe/BAlGaAs material systems. Practical issues and problems such as the effect of defects on device performance are highlighted and solutions proposed based on recent studies. (orig.)

  9. Fiber-Optic Communication Technology Branching Devices

    Science.gov (United States)

    Williams, J. C.

    1985-02-01

    This tutorial review of fiber-optic branching devices covers example uses of branching devices, device types, device-performance characteristics, examples of current technology, and system-design methodology. The discussion is limited to passive single- and multimode devices fabricated from optical fibers or graded-index components. Integrated-optic, wavelength-division-multiplexing, and polarization-selective devices are not specifically addressed.

  10. Enhancement of the lifetime in organic light-emitting devices fabricated utilizing wide-bandgap-impurity-doped emitting layers

    International Nuclear Information System (INIS)

    The degradation behaviors of the electrical and the optical properties of organic light-emitting devices (OLEDs) fabricated with an emitting layer (EML) doped with or without a wide-bandgap-impurity were investigated. The OLEDs with a wide-bandgap-doped Alq3 EML were more stable than those with an undoped Alq3 EML. The existence of the doped wide-bandgap-impurity in the EML decreased the trap-charge density in the EML, resulting in an increase in the number of electrons in the Alq3 EML. That increases in the number of electron in the Alq3 EML for the OLEDs with a wide-bandgap-impurity decreased the staying time of the holes in the Alq3 EML, resulting in an enhanced lifetime for the OLEDs. These results indicate that OLEDs with a wide-bandgap-impurity-doped EML hold promise for potential applications in long-lifetime OLED displays

  11. Optical devices based on liquid crystal photonic bandgap fibers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard

    2005-01-01

    features directly caused by LC anisotropy has been identified. The main sources of loss is discussed and investigated through simulations and experimental verification. The thesis begins with an introduction to LCs and PCFs, with emphasis on the basic properties, which are useful for describing the...

  12. Wild Band Edges: The Role of Bandgap Grading and Band-Edge Fluctuations in High-Efficiency Chalcogenide Devices: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Repins, Ingrid; Mansfield, Lorelle; Kanevce, Ana; Jensen, Soren A.; Kuciauskas, Darius; Glynn, Stephen; Barnes, Teresa; Metzger, Wyatt; Burst, James; Jiang, Chun-Sheng; Dippo, Patricia; Harvey, Steve; Teeter, Glenn; Perkins, Craig; Egaas, Brian; Zakutayev, Andriy; Alsmeier, J.-H.; Lussky, T.; Korte, L.; Wilks, R. G.; Bar, M.; Yan, Y.; Lany, Stephan; Zawadzki, Pawel; Park, Ji-Sang; Wei, Suhuai

    2016-06-16

    Band-edge effects -- including grading, electrostatic fluctuations, bandgap fluctuations, and band tails -- affect chalcogenide device efficiency. These effects now require more careful consideration as efficiencies increase beyond 20%. Several aspects of the relationships between band-edge phenomena and device performance for NREL absorbers are examined. For Cu(In,Ga)Se2 devices, recent increases in diffusion length imply changes to optimum bandgap profile. The origin, impact, and modification of electrostatic and bandgap fluctuations are also discussed. The application of the same principles to devices based on CdTe, kesterites, and emerging absorbers (Cu2SnS3, CuSbS2), considering differences in materials properties and defect formation energies, is examined.

  13. High temperature performance of Wide Bandgap Semiconductors Devices for High Power Applications

    Directory of Open Access Journals (Sweden)

    B. N. Shashikala

    2010-12-01

    Full Text Available Wide bandgap III-Nitride semiconductor materials possess superior properties as compared to silicon and other IIIV compound materials. GaN has recently attracted a lot of interest for applications in high power electronics capable of operation at elevated temperatures. Modeling of the drift region properties of GaN Schottky rectifiers and power MOSFET to achieve breakdown voltages ranging from 200 to 5kV is presented. 1kV and 3kV Schottky rectifiers are simulated and the characteristics of the GaN devices compared with those of Si devices. The specific on- resistance Ron,sp of a GaN MOSFET is at least three orders of magnitude smaller than the corresponding n-resistance for a Si device. 5kV GaN Schottky rectifiers can deliver on-state current density of 100 A/cm2 at room temperature with aforward drop of only 1.29V because of very low drift region resistance. GaN devices would allow operation at higher breakdown voltages than the conventional Si devices.

  14. Polarization Properties of Elliptical-Hole Liquid Crystal Photonic Bandgap Fibers

    DEFF Research Database (Denmark)

    Tartarini, Giovanni; Pansera, Marco; Alkeskjold, Thomas Tanggaard;

    2007-01-01

    ellipticity allow some phenomena that are not predicted yet, such as polarization-dependent losses and birefringence sign change in the wavelength range used for standard telecom fibers. Control of these features allows the design of new devices for sensing or telecommunication applications......The characteristics of triangular photonic crystal fibers (PCFs) with elliptical holes filled with a nematic liquid crystal (LC) are investigated theoretically. The analysis that is carried out using the finite-element method, including material dispersion effects, shows that LC anisotropy and hole...

  15. Towards self-similar propagation in a dispersion tailored and highly nonlinear segmented bandgap fiber at 2.8 micron

    CERN Document Server

    Biswas, Piyali; Biswas, Abhijit; Pal, Bishnu P

    2016-01-01

    We numerically demonstrate self-similar propagation of parabolic optical pulses through a highly nonlinear and passive specialty photonic bandgap fiber at 2.8 micron. In this context, we have proposed a scheme endowed with a rapidly varying, but of nearly-mean-zero longitudinal dispersion and modulated nonlinear profile in order to achieve self-similarity of the formed parabolic pulse propagating over longer distances. To implement the proposed scheme, we have designed a segmented bandgap fiber with suitably tapered counterparts to realize such customized dispersion with chalchogenide glass materials. A self-similar parabolic pulse with full-width-at-half-maxima of 4.12 ps and energy of ~ 39 pJ as been achieved at the output. Along with a linear chirp spanning over the entire pulse duration, 3dB spectral broadening of about 38 nm at the output has been reported.

  16. Enhanced chemiluminescent detection scheme for trace vapor sensing in pneumatically-tuned hollow core photonic bandgap fibers.

    Science.gov (United States)

    Stolyarov, Alexander M; Gumennik, Alexander; McDaniel, William; Shapira, Ofer; Schell, Brent; Sorin, Fabien; Kuriki, Ken; Benoit, Gilles; Rose, Aimee; Joannopoulos, John D; Fink, Yoel

    2012-05-21

    We demonstrate an in-fiber gas phase chemical detection architecture in which a chemiluminescent (CL) reaction is spatially and spectrally matched to the core modes of hollow photonic bandgap (PBG) fibers in order to enhance detection efficiency. A peroxide-sensitive CL material is annularly shaped and centered within the fiber's hollow core, thereby increasing the overlap between the emission intensity and the intensity distribution of the low-loss fiber modes. This configuration improves the sensitivity by 0.9 dB/cm compared to coating the material directly on the inner fiber surface, where coupling to both higher loss core modes and cladding modes is enhanced. By integrating the former configuration with a custom-built optofluidic system designed for concomitant controlled vapor delivery and emission measurement, we achieve a limit-of-detection of 100 parts per billion (ppb) for hydrogen peroxide vapor. The PBG fibers are produced by a new fabrication method whereby external gas pressure is used as a control knob to actively tune the transmission bandgaps through the entire visible range during the thermal drawing process. PMID:22714227

  17. Bandgap Engineering of 1300 nm Quantum Dots/Quantum Well Nanostructures Based Devices

    KAUST Repository

    Alhashim, Hala H.

    2016-05-29

    The main objectives of this thesis are to develop viable process and/or device technologies for bandgap tuning of 1300-nm InGaAs/GaAs quantum-dot (QD) laser structures, and broad linewidth 1300-nm InGaAsP/InP quantum well (QW) superluminescent diode structures. The high performance bandgap-engineered QD laser structures were achieved by employing quantum-dot intermixing (QDI) based on impurity free vacancy diffusion (IFVD) technique for eventual seamless active-passive integration, and bandgap-tuned lasers. QDI using various dielectric-capping materials, such as HfO2, SrTiO3, TiO2, Al2O3 and ZnO, etc, were experimented in which the resultant emission wavelength can be blueshifted to ∼ 1100 nm ─ 1200 nm range depending on process conditions. The significant results extracted from the PL characterization were used to perform an extensive laser characterization. The InAs/GaAs quantum-dot lasers with QDs transition energies were blueshifted by ~185 nm, and lasing around ~1070 – 1190 nm was achieved. Furthermore, from the spectral analysis, a simultaneous five-state lasing in the InAs/InGaAs intermixed QD laser was experimentally demonstrated for the first time in the very important wavelength range from 1030 to 1125 nm. The QDI methodology enabled the facile formation of a plethora of devices with various emission wavelengths suitable for a wide range of applications in the infrared. In addition, the wavelength range achieved is also applicable for coherent light generation in the green – yellow – orange visible wavelength band via frequency doubling, which is a cost-effective way of producing compact devices for pico-projectors, semiconductor laser based solid state lighting, etc. [1, 2] In QW-based superluminescent diode, the problem statement lies on achieving a flat-top and ultra-wide emission bandwidth. The approach was to design an inhomogeneous active region with a comparable simultaneous emission from different transition states in the QW stacks, in

  18. Distributed optical fibre devices based on liquid crystal infiltrated photonic crystal fibers

    OpenAIRE

    Alkeskjold, Thomas Tanggaard; Broeng, Jes; Hermann, D.S.; Bjarklev, Anders Overgaard

    2004-01-01

    We describe a new class of hybrid photonic crystal fibers, which are liquid crystal infiltrated fibers. Using these fibers, we demonstrate 'distributed' tunable filter and switching functionalities operating by the photonic bandgap effect.

  19. Next Generation Solar Cells Based on Graded Bandgap Device Structures Utilising Rod-Type Nano-Materials

    Directory of Open Access Journals (Sweden)

    Imyhamy M. Dharmadasa

    2015-06-01

    Full Text Available Current solar cells under research and development utilise mainly one absorber layer limiting the photon harvesting capabilities. In order to develop next generation solar cells, research should move towards effective photon harvesting methods utilising low-cost solar energy materials. This will lead to reduce the $W−1 figure for direct solar energy conversion to electrical energy. In this work, a graded bandgap solar cell has been designed to absorb all photons from the UV, visible and IR regions. In addition, impurity PV effect and impact ionisation have been incorporated to enhance charge carrier creation within the same device. This new design has been experimentally tested using the most researched MOCVD grown GaAs/AlGaAs system, in order to confirm its validity. Devices with high Voc ~ 1175 mV and the highest possible FF ~ (0.85–0.87 have been produced, increasing the conversion efficiency to ~20% within only two growth runs. These devices were also experimentally tested for the existence of impurity PV effect and impact ionisation. The devices are PV active in complete darkness producing over 800 mV, Voc indicating the harvesting of IR radiation from the surroundings through impurity PV effect. The quantum efficiency measurements show over 140% signal confirming the contribution to PV action from impact ionisation. Since the concept is successfully proven, the low-cost and scalable electrodeposited semiconducting layers are used to produce graded bandgap solar cell structures. The utilisation of nano- and micro-rod type materials in graded bandgap devices are also presented and discussed in this paper. Preliminary work on glass/FTO/n-ZnS/n-CdS/n-CdTe/Au graded bandgap devices show 10%–12% efficient devices indicating extremely high Jsc values ~48 mA·cm−2, showing the high potential of these devices in achieving higher efficiencies. The detailed results on these low-cost and novel graded bandgap devices are presented in a separate

  20. Measurement and suppression of secondary waves caused by high-order modes in a photonic bandgap fiber-optic gyroscope.

    Science.gov (United States)

    Xu, Xiaobin; Gao, Fuyu; Song, Ningfang; Jin, Jing

    2016-05-16

    Air-core photonic bandgap fiber (PBF) is a good choice for fiber-optic gyroscopes (FOGs) owing to the fact that it can be adapted to a wide variety of environments. However, its multimode properties are disadvantageous for the application to FOGs. An interference-based method is proposed to precisely determine the secondary waves caused by the high-order modes and their coupling. Based on the method, two groups of secondary waves have been found, having optical path differences (OPDs) of ~1.859 m and ~0.85 m, respectively, relative to the primary waves in a PBFOG that consists of a 7-cell PBF coil, approximately 180 m in length. Multi-turn bends of the PBF at both ends of the PBF coil after the fusion splicing points are shown to suppress the intensity of these secondary waves by approximately 10 dB. PMID:27409849

  1. In-line Mach-Zehnder interferometer composed of microtaper and long-period grating in all-solid photonic bandgap fiber

    International Nuclear Information System (INIS)

    We report a compact in-line Mach-Zehnder interferometer combining a microtaper with a long-period grating (LPG) in a section of all-solid photonic bandgap fiber. Theoretical and experimental investigations reveal that the interferometer works from the interference between the fundamental core mode and the LP01 cladding supermodes. The mechanism underlying the mode coupling caused by the microtaper can be attributed to a bandgap-shifting as the fiber diameter is abruptly scaled down. In addition, the interferometer designed to strengthen the coupling ratio of the long-period grating has a promising practical application in the simultaneous measurement of curvature and temperature.

  2. Optical Measurement Techniques for Optical Fiber and Waveguide Devices

    Institute of Scientific and Technical Information of China (English)

    D.Y.; Kim; Y.; Park; N.H.; Seong; Y.C.Youk; J.Y.; Lee; S.; Moon; I.H.; Shin; H.S.; Ryu

    2003-01-01

    We describe three major optical characterization methods for fiber and fiber devices. A simple servo controlled scanning fiber-optic confocal microscope is proposed for determining the refractive index profile of an optical fiber. To measure the chromatic dispersion of a short length fiber a Mach-Zehnder fiber interferometer with a novel interferometric distance meter is introduced. At the end, a tomographic method is demonstrated for determining the 2-D stress profile of a fiber.

  3. Effect of Fresnel reflections in a hybrid air-core photonic-bandgap fiber ring-resonator gyro.

    Science.gov (United States)

    Yan, Yuchao; Ma, Huilian; Wang, Linglan; Li, Hanzhao; Jin, Zhonghe

    2015-11-30

    A novel hybrid polarization-maintaining (PM) air-core photonic bandgap fiber (PBF) ring resonator is firstly demonstrated by using a conventional solid-core PM fiber optical coupler formed by splicing a section of PM air-core PBF into the resonator. Due to Fresnel reflections exist at the two junctions between the air-core PBF and the solid-core fiber, the forward output signal of this hybrid ring resonator is the normal resonant curve with the superposition of the lightwaves that experienced even numbers of Fresnel reflections and the backward output signal is composed of lightwaves that experienced odd numbers of Fresnel reflections. Rigorous derivations of the forward and backward output signals are given out. The biggest resonant depth and finesse of the hybrid air-core PBF ring resonator predicted are 0.352 and 6.3 respectively by assuming a splice loss of 1.8 dB per junction. These predictions are finally confirmed by testing both the forward and backward output signals of the hybrid ring resonator. With the countermeasures against the influences of the odd numbers of Fresnel reflections, a bias stability of 0.007°/s is successfully demonstrated in a hybrid PM air-core PBF ring-resonator gyro. PMID:26698764

  4. Performance investigation of bandgap, gate material work function and gate dielectric engineered TFET with device reliability improvement

    Science.gov (United States)

    Raad, Bhagwan Ram; Nigam, Kaushal; Sharma, Dheeraj; Kondekar, P. N.

    2016-06-01

    This script features a study of bandgap, gate material work function and gate dielectric engineering for enhancement of DC and Analog/RF performance, reduction in the hot carriers effect (HCEs) and drain induced barrier lowering (DIBL) for better device reliability. In this concern, the use of band gap and gate material work function engineering improves the device performance in terms of the ON-state current and suppressed ambipolar behaviour with maintaining the low OFF-state current. With these advantages, the use of gate material work function engineering imposes restriction on the high frequency performance due to increment in the parasitic capacitances and also introduces the hot carrier effects. Hence, the gate dielectric engineering with bandgap and gate material work function engineering are used in this paper to overcome the cons of the gate material work function engineering by obtaining a superior performance in terms of the current driving capability, ambipolar conduction, HCEs, DIBL and high frequency parameters of the device for ultra-low power applications. Finally, the optimization of length for different work function is performed to get the best out of this.

  5. Highly efficient high power single-mode fiber amplifier utilizing the distributed mode filtering bandgap rod fiber

    DEFF Research Database (Denmark)

    Laurila, Marko; Alkeskjold, Thomas T.; Jørgensen, Mette Marie;

    2012-01-01

    high average output power levels and demonstrate a 44% power improvement before the threshold-like onset of mode instabilities by operating the rod fiber in a leaky waveguide regime. We investigate the guiding dynamics of the rod fiber and explain the improved performance by thermally induced......We report on an ytterbium doped single mode distributed mode filtering rod fiber in an amplifier configuration delivering high average output power, up to 292 watts, using a mode-locked 30ps source at 1032nm with good power conversion efficiency. We study the modal stability of the output beam at...

  6. 1178 nm all Yb-fiber laser source power-scaled by solid-core photonic bandgap fiber for 589nm generation

    DEFF Research Database (Denmark)

    Maruyama, H.; Shirakawa, A.; Ueda, K.I.;

    2009-01-01

    Here we report an 1178 nm all Yb-fiber laser source power-scaled by solid-core photonic bandgap fiber (SC-PBGF) for 589 nm generation. A 1.4 W output at 589 nm with an input power of 9 W at 1178 nm were obtained. One important advantage of PBGF is distributed filtering. Hence the gain spectrum can...... be designed artificially in an active-ion-doped SC-PBGF, desirable for long-wavelength Yb fiber laser operation. At first, 1178 nm amplification seeded with a non-polarized and linearly-polarized FRL was carried out with the core launched powers of 4 W and 2 W, respectively. As a result, an output...... power of 30 W at 1178 nm with was obtained with the slope efficiency of 58% and ASE free. A 25 W linearly-polarized output with dimensions. Thereby one can obtain lasing or amplification at longer avelengths (1100 nm - 1200 nm) as the amount of amplification in the fibre is shown to scale with the power...

  7. Tunable Fabry-Perot filter using hollow-core photonic bandgap fiber and micro-fiber for a narrow-linewidth laser.

    Science.gov (United States)

    Wang, Xiaozhen; Zhu, Tao; Chen, Liang; Bao, Xiaoyi

    2011-05-01

    A novel tunable fiber Fabry-Perot (FP) filter is proposed and demonstrated by using a hollow-core photonic bandgap fiber (HC-PBF) and a micro-fiber. The interference cavity is a hollow core of HC-PBF. One of the reflection mirrors is the splicing point between a section of HC-PBF and a single mode fiber. The other reflection mirror is a gold-coated end of micro-fiber that uses chemical etching process to obtain the similar diameter as the core of HC-PBF. Hence the movable mirror can be adjusted with long distance inside the hollow core of HC-PBF. Tunable FP filter is used as a mode selecting component in the reflection mode to implement stable single longitudinal mode (SLM) operation in a ring laser. With FP cavity length of 0.25 ± 0.14 mm, the wavelength of SLM laser can be tuned over 1554-1562 nm with a tuning step of 0.2-0.3 nm, a side-mode suppression ratio (SMSR) of 32-36 dB and a linewidth of 3.0-5.1 kHz. With FP cavity length of 2.37 ± 0.37 mm, the SLM laser can be tuned over 1557.3-1560.2 nm with a tuning step of 0.06-0.1 nm, a SMSR of 44-51 dB and a linewidth of 1.8-3.0 kHz. PMID:21643220

  8. Considerations of dopant-dependent bandgap narrowing for accurate device simulation in abrupt HBTs

    Institute of Scientific and Technical Information of China (English)

    Zhou Shouli; Xiong Deping; Qin Yali

    2009-01-01

    Heavy doping of the base in HBTs brings about a bandgap narrowing(BGN)effect,which modifies the intrinsic carrier density and disturbs the band offset,and thus leads to the change of the currents.Based on a thermionic-field-diffusion model that is used to the analyze the performance of all abrupt HBT with a heavydoped base,the conclusion is made that,although the BGN effect makes the currents obviously change due to the modification of the intrinsic carrier density,the band offsets disturbed by the BGN effect should also be taken into account in the analysis of the electrical characteristics of abrupt HBTs.In addition,the BGN effect changes the bias voltage for the onset of Kirk effects.

  9. Infiltrated microstructured fibers as tunable and nonlinear optical devices

    DEFF Research Database (Denmark)

    Rosberg, Christian Romer; Bennet, Francis; Neshev, Dragomir N.;

    We study the light guiding properties of microstructured optical fibers infiltrated with nonlinear liquids and demonstrate their applicability for spatial beam control in novel type tunable and nonlinear optical devices.......We study the light guiding properties of microstructured optical fibers infiltrated with nonlinear liquids and demonstrate their applicability for spatial beam control in novel type tunable and nonlinear optical devices....

  10. A novel electro-thermal model for wide bandgap semiconductor based devices

    DEFF Research Database (Denmark)

    Sintamarean, Nicolae Christian; Blaabjerg, Frede; Wang, Huai

    2013-01-01

    This paper propose a novel Electro-Thermal Model for the new generation of power electronics WBG-devices (by considering the SiC MOSFET-CMF20120D from CREE), which is able to estimate the device junction and case temperature. The Device-Model estimates the voltage drop and the switching energies by...... considering the device current, the off-state blocking voltage and junction temperature variation. Moreover, the proposed Thermal-Model is able to consider the thermal coupling within the MOSFET and its freewheeling diode, integrated into the same package, and the influence of the ambient temperature...... variation. The importance of temperature loop feedback in the estimation accuracy of device junction and case temperature is studied. Furthermore, the Safe Operating Area (SOA) of the SiC MOSFET is determined for 2L-VSI applications which are using sinusoidal PWM. Thus, by considering the heatsink thermal...

  11. Photonic crystal fibers, devices, and applications

    Institute of Scientific and Technical Information of China (English)

    Wei JIN; Jian JU; Hoi Lut HO; Yeuk Lai HOO; Ailing ZHANG

    2013-01-01

    This paper reviews different types of air-silica photonic crystal fibers (PCFs), discusses their novel properties, and reports recent advances in PCF components and sensors as well as techniques for splicing PCFs to standard telecomm fibers.

  12. 77 FR 65713 - Certain Optoelectronic Devices for Fiber Optic Communications, Components Thereof, and Products...

    Science.gov (United States)

    2012-10-30

    ... COMMISSION Certain Optoelectronic Devices for Fiber Optic Communications, Components Thereof, and Products... the United States after importation of certain optoelectronic devices for fiber optic communications... importation of certain optoelectronic devices for fiber optic communications, components thereof, and...

  13. Efficient fiber-optical interface for nanophotonic devices

    CERN Document Server

    Tiecke, T G; Thompson, J D; Peyronel, T; de Leon, N P; Vuletić, V; Lukin, M D

    2014-01-01

    We demonstrate a method for efficient coupling of guided light from a single mode optical fiber to nanophotonic devices. Our approach makes use of single-sided conical tapered optical fibers that are evanescently coupled over the last ~10 um to a nanophotonic waveguide. By means of adiabatic mode transfer using a properly chosen taper, single-mode fiber-waveguide coupling efficiencies as high as 97(1)% are achieved. Efficient coupling is obtained for a wide range of device geometries which are either singly-clamped on a chip or attached to the fiber, demonstrating a promising approach for integrated nanophotonic circuits, quantum optical and nanoscale sensing applications.

  14. Optical fiber-based devices and applications

    Institute of Scientific and Technical Information of China (English)

    Perry Ping SHUM; Jonathan C. KNIGHT; Jesper LAEGSGAARD; Dora Juan Juan HU

    2010-01-01

    @@ Optical fiber technology has undergone tremendous growth and development over the last 40 years. Optical fibers constitute an information super highway and are vital in enabling the proliferating use of the Internet. Optical fiber is also an enabling technology which can find applications in sensing, imaging, biomedical, machining, etc. There have been a few milestones in the advancement of optical fiber technology. Firstly, the invention and development of the laser some 50 years ago made optical communications possible. Secondly, the fabrication of low-loss optical fibers has been a key element to the success of optical communication.

  15. Investigation of High-Nonlinearity Glass Fibers for Potential Applications in Ultrafast Nonlinear Fiber Devices

    OpenAIRE

    Kim, Jong-Kook

    2005-01-01

    Nonlinear fiber devices have been attracting considerable attention in recent years, due to their inherent ultrafast response time and potential applications in optical communication systems. They usually require long fibers to generate sufficient nonlinear phase shifts, since nonlinearities of conventional silica-core silica-clad fibers are too low. These long devices, however, cause the serious problems of pulse walk-off, pulse broadening, and polarization fluctuation which are major limiti...

  16. Fiber-shaped energy harvesting and storage devices

    CERN Document Server

    Peng, Huisheng

    2015-01-01

    This comprehensive book covers flexible fiber-shaped devices in the area of energy conversion and storage. The first part of the book introduces recently developed materials, particularly, various nanomaterials and composite materials based on nanostructured carbon such as carbon nanotubes and graphene, metals and polymers for the construction of fiber electrodes. The second part of the book focuses on two typical twisted and coaxial architectures of fiber-shaped devices for energy conversion and storage. The emphasis is placed on dye-sensitized solar cells, polymer solar cells, lithium-ion b

  17. Silica optical fiber technology for devices and components design, fabrication, and international standards

    CERN Document Server

    Oh, Kyunghwan

    2012-01-01

    From basic physics to new products, Silica Optical Fiber Technology for Device and Components examines all aspects of specialty optical fibers. Moreover, the inclusion of the latest international standards governing optical fibers enables you to move from research to fabrication to commercialization. Reviews all the latest specialty optical fiber technologies, including those developed for high capacity WDM applications; broadband fiber amplifiers; fiber filleters based on periodic coupling; fiber branching devices; and fiber terminations Discusses key differences among sing

  18. The Challenge of Producing Fiber-Based Organic Electronic Devices

    Directory of Open Access Journals (Sweden)

    Tobias Könyves-Toth

    2014-07-01

    Full Text Available The implementation of organic electronic devices on fibers is a challenging task, not yet investigated in detail. As was shown earlier, a direct transition from a flat device structure to a fiber substrate is in principle possible. However, a more detailed investigation of the process reveals additional complexities than just the transition in geometry. It will be shown, that the layer formation of evaporated materials behaves differently due to the multi-angled incidence on the fibers surface. In order to achieve homogenous layers the evaporation process has to be adapted. Additionally, the fiber geometry itself facilitates damaging of its surface due to mechanical impact and leads to a high surface roughness, thereby often hindering commercial fibers to be used as substrates. In this article, a treatment of commercial polymer-coated glass fibers will be demonstrated that allows for the fabrication of rather flexible organic light-emitting diodes (OLEDs with cylindrical emission characteristics. Since OLEDs rely the most on a smooth substrate, fibers undergoing the proposed treatment are applicable for other organic electronic devices such as transistors and solar cells. Finally, the technique also supports the future fabrication of organic electronics not only in smart textiles and woven electronics but also in bent surfaces, which opens a wide range of applications.

  19. Low index-contrast aperiodically ordered photonic quasicrystals for the development of isotropic photonic band-gap devices

    Science.gov (United States)

    Priya Rose, T.; Di Gennaro, E.; Andreone, A.; Abbate, G.

    2010-05-01

    Photonic quasicrystals (PQCs) have neither true periodicity nor translational symmetry, however they can exhibit symmetries that are not achievable by conventional periodic structures. The arbitrarily high rotational symmetry of these materials can be practically exploited to manufacture isotropic band gap materials, which are perfectly suitable for hosting waveguides or cavities. In this work, formation and development of the photonic bandgap (PBG) in twodimensional 8-, 10- and 12-fold symmetry quasicrystalline lattices of low dielectric contrast (0.4-0.6) were measured in the microwave region and compared with the PBG properties of a conventional hexagonal crystal. Band-gap properties were also investigated by changing the direction of propagation of the incident beam inside the crystal. Various angles of incidence from 0° to 30° were used in order to investigate the isotropic nature of the band-gap.

  20. An integrated fiber and stone basket device for use in Thulium fiber laser lithotripsy

    Science.gov (United States)

    Wilson, Christopher R.; Hutchens, Thomas C.; Hardy, Luke A.; Irby, Pierce B.; Fried, Nathaniel M.

    2014-03-01

    The Thulium fiber laser (TFL) is being explored as an alternative laser lithotripter to the Holmium:YAG laser. The TFL's superior near-single mode beam profile enables higher power transmission through smaller fibers with reduced proximal fiber tip damage. Recent studies have also reported that attaching hollow steel tubing to the distal fiber tip decreases fiber degradation and burn-back without compromising stone ablation rates. However, significant stone retropulsion was observed, which increased with pulse rate. In this study, the hollow steel tip fiber design was integrated with a stone basket to minimize stone retropulsion during ablation. A device was constructed consisting of a 100-μm-core, 140-μm-OD silica fiber outfitted with 5-mm-long stainless steel tubing at the distal tip, and integrated with a 1.3-Fr (0.433-mm-OD) disposable nitinol wire basket, to form an overall 1.9-Fr (0.633-mm- OD) integrated device. This compact design may provide several potential advantages including increased flexibility, higher saline irrigation rates through the ureteroscope working channel, and reduced fiber tip degradation compared to separate fiber and stone basket manipulation. TFL pulse energy of 31.5 mJ with 500 μs pulse duration and pulse rate of 500 Hz was delivered through the integrated fiber/basket device in contact with human uric acid stones, ex vivo. TFL stone ablation rates measured 1.5 +/- 0.2 mg/s, comparable to 1.7 +/- 0.3 mg/s (P > 0.05) using standard bare fiber tips separately with a stone basket. With further development, this device may be useful for minimizing stone retropulsion, thus enabling more efficient TFL lithotripsy at higher pulse rates.

  1. Quantum efficiency and bandgap analysis for combinatorial photovoltaics: sorting activity of Cu-O compounds in all-oxide device libraries.

    Science.gov (United States)

    Anderson, Assaf Y; Bouhadana, Yaniv; Barad, Hannah-Noa; Kupfer, Benjamin; Rosh-Hodesh, Eli; Aviv, Hagit; Tischler, Yaakov R; Rühle, Sven; Zaban, Arie

    2014-02-10

    All-oxide-based photovoltaics (PVs) encompass the potential for extremely low cost solar cells, provided they can obtain an order of magnitude improvement in their power conversion efficiencies. To achieve this goal, we perform a combinatorial materials study of metal oxide based light absorbers, charge transporters, junctions between them, and PV devices. Here we report the development of a combinatorial internal quantum efficiency (IQE) method. IQE measures the efficiency associated with the charge separation and collection processes, and thus is a proxy for PV activity of materials once placed into devices, discarding optical properties that cause uncontrolled light harvesting. The IQE is supported by high-throughput techniques for bandgap fitting, composition analysis, and thickness mapping, which are also crucial parameters for the combinatorial investigation cycle of photovoltaics. As a model system we use a library of 169 solar cells with a varying thickness of sprayed titanium dioxide (TiO2) as the window layer, and covarying thickness and composition of binary compounds of copper oxides (Cu-O) as the light absorber, fabricated by Pulsed Laser Deposition (PLD). The analysis on the combinatorial devices shows the correlation between compositions and bandgap, and their effect on PV activity within several device configurations. The analysis suggests that the presence of Cu4O3 plays a significant role in the PV activity of binary Cu-O compounds. PMID:24410367

  2. Precise Balancing of Viscous and Radiation Forces on a Particle in Liquid-Filled Photonic Bandgap Fiber

    OpenAIRE

    Euser, T.G.; Garbos, M. K.; Chen, J. S. Y.; Russell, P. St. J.

    2009-01-01

    It is shown that, in the liquid-filled hollow core of a single-mode photonic crystal fiber, a micron-sized particle can be held stably against a fluidic counter-flow using radiation pressure, and moved to and fro (over 10s of cm) by ramping the laser power up and down. The results represent a major advance over previous work on particle transport in optically multimode liquid-filled fibers, in which the fluctuating transverse field pattern renders the radiation and trapping forces unpredictab...

  3. Precise Balancing of Viscous and Radiation Forces on a Particle in Liquid-Filled Photonic Bandgap Fiber

    CERN Document Server

    Euser, T G; Chen, J S Y; Russell, P St J

    2009-01-01

    It is shown that, in the liquid-filled hollow core of a single-mode photonic crystal fiber, a micron-sized particle can be held stably against a fluidic counter-flow using radiation pressure, and moved to and fro (over 10s of cm) by ramping the laser power up and down. The results represent a major advance over previous work on particle transport in optically multimode liquid-filled fibers, in which the fluctuating transverse field pattern renders the radiation and trapping forces unpredictable. The counter-flowing liquid can be loaded with sequences of chemicals in precisely controlled concentrations and doses, making possible studies of single particles, vesicles or cells.

  4. 太赫兹双芯光子带隙光纤定向耦合器%Terahertz dual-core photonic band-gap fiber directional coupler

    Institute of Scientific and Technical Information of China (English)

    白晋军; 王昌辉; 侯宇; 范飞; 常胜江

    2012-01-01

    提出了一种低损耗、宽频段太赫兹双芯光子带隙光纤定向耦合器,光纤的包层由亚波长尺度呈三角晶格排列的空气孔组成,两个纤芯分别由去掉7个空气孔构成.利用全矢量有限元法对光纤的色散、耦合特性以及损耗特性进行了理论分析.研究表明,这种耦合器的损耗系数小于0.021cm^-1更重要的是可以实现0.14THz范围内的宽频定向耦合.这种定向耦合器在太赫兹通信系统中滤波、波分复用、偏振分离和开关等技术中有潜在的应用价值.%A low-loss and broadband terahertz twin-core photonic band-gap fiber directional coupler is proposed, which consists of a cladding with a triangular lattice array of sub-wavelength air rods and two cores formed respectively by omitting seven nearby air rods. The group veIocity dispersion, the coupling and the loss of the fibers are investigated by using a full-vector finite element method. The numerical simulations show that the loss coefficient of the coupler is less than 0.021 cm^-1, and the coupling broadband of 0.14 THz can be realized. The directional coupler has potential applications in terahertz communication systems, such as filtering, wavelength-division multiplexing, polarization isolation, switching and so on.

  5. Characterization of the stress and refractive-index distributions in optical fibers and fiber-based devices

    Science.gov (United States)

    Hutsel, Michael R.

    2011-07-01

    Optical fiber technology continues to advance rapidly as a result of the increasing demands on communication systems and the expanding use of fiber-based sensing. New optical fiber types and fiber-based communications components are required to permit higher data rates, an increased number of channels, and more flexible installation requirements. Fiber-based sensors are continually being developed for a broad range of sensing applications, including environmental, medical, structural, industrial, and military. As optical fibers and fiber-based devices continue to advance, the need to understand their fundamental physical properties increases. The residual-stress distribution (RSD) and the refractive-index distribution (RID) play fundamental roles in the operation and performance of optical fibers. Custom RIDs are used to tailor the transmission properties of fibers used for long-distance transmission and to enable fiber-based devices such as long-period fiber gratings (LPFGs). The introduction and modification of RSDs enable specialty fibers, such as polarization-maintaining fiber, and contribute to the operation of fiber-based devices. Furthermore, the RSD and the RID are inherently linked through the photoelastic effect. Therefore, both the RSD and the RID need to be characterized because these fundamental properties are coupled and affect the fabrication, operation, and performance of fibers and fiber-based devices. To characterize effectively the physical properties of optical fibers, the RSD and the RID must be measured without perturbing or destroying the optical fiber. Furthermore, the techniques used must not be limited in detecting small variations and asymmetries in all directions through the fiber. Finally, the RSD and the RID must be characterized concurrently without moving the fiber to enable the analysis of the relationship between the RSD and the RID. Although many techniques exist for characterizing the residual stress and the refractive index in

  6. Characterization of the stress and refractive-index distributions in optical fibers and fiber-based devices

    Science.gov (United States)

    Hutsel, Michael R.

    2011-07-01

    Optical fiber technology continues to advance rapidly as a result of the increasing demands on communication systems and the expanding use of fiber-based sensing. New optical fiber types and fiber-based communications components are required to permit higher data rates, an increased number of channels, and more flexible installation requirements. Fiber-based sensors are continually being developed for a broad range of sensing applications, including environmental, medical, structural, industrial, and military. As optical fibers and fiber-based devices continue to advance, the need to understand their fundamental physical properties increases. The residual-stress distribution (RSD) and the refractive-index distribution (RID) play fundamental roles in the operation and performance of optical fibers. Custom RIDs are used to tailor the transmission properties of fibers used for long-distance transmission and to enable fiber-based devices such as long-period fiber gratings (LPFGs). The introduction and modification of RSDs enable specialty fibers, such as polarization-maintaining fiber, and contribute to the operation of fiber-based devices. Furthermore, the RSD and the RID are inherently linked through the photoelastic effect. Therefore, both the RSD and the RID need to be characterized because these fundamental properties are coupled and affect the fabrication, operation, and performance of fibers and fiber-based devices. To characterize effectively the physical properties of optical fibers, the RSD and the RID must be measured without perturbing or destroying the optical fiber. Furthermore, the techniques used must not be limited in detecting small variations and asymmetries in all directions through the fiber. Finally, the RSD and the RID must be characterized concurrently without moving the fiber to enable the analysis of the relationship between the RSD and the RID. Although many techniques exist for characterizing the residual stress and the refractive index in

  7. Active fiber optic technologies used as tamper-indicating devices

    International Nuclear Information System (INIS)

    The Sandia National Laboratories (SNL) Safeguards and Seals Evaluation Program is evaluating new fiber optic active seal technologies for use at Department of Energy (DOE) facilities. The goal of the program is to investigate active seal technologies that can monitor secured containers storing special nuclear materials (SNM) within DOE vaults. Specifically investigated were active seal technologies that can be used as tamper-indicating devices to monitor secured containers within vaults while personnel remain outside the vault area. Such a system would allow minimal access into vaults while ensuring container content accountability. The purpose of this report is to discuss tamper-indicating devices that were evaluated for possible DOE use. While previous seal evaluations (Phase I and II) considered overall facility applications, this discussion focuses specifically on their use in vault storage situations. The report will highlight general background information, specifications and requirements, and test procedures. Also discussed are the systems available from four manufacturers: Interactive Technologies, Inc., Fiber SenSys, Inc., Inovonics, Inc., and Valve Security Systems

  8. Active fiber optic technologies used as tamper-indicating devices

    Energy Technology Data Exchange (ETDEWEB)

    Horton, P.R.V.; Waddoups, I.G.

    1995-11-01

    The Sandia National Laboratories (SNL) Safeguards and Seals Evaluation Program is evaluating new fiber optic active seal technologies for use at Department of Energy (DOE) facilities. The goal of the program is to investigate active seal technologies that can monitor secured containers storing special nuclear materials (SNM) within DOE vaults. Specifically investigated were active seal technologies that can be used as tamper-indicating devices to monitor secured containers within vaults while personnel remain outside the vault area. Such a system would allow minimal access into vaults while ensuring container content accountability. The purpose of this report is to discuss tamper-indicating devices that were evaluated for possible DOE use. While previous seal evaluations (Phase I and II) considered overall facility applications, this discussion focuses specifically on their use in vault storage situations. The report will highlight general background information, specifications and requirements, and test procedures. Also discussed are the systems available from four manufacturers: Interactive Technologies, Inc., Fiber SenSys, Inc., Inovonics, Inc., and Valve Security Systems.

  9. Identifying the Electronic Properties Relevant to Improving the Performance of High Band-Gap Copper Based I-III-VI2 Chalcopyrite Thin Film Photovoltaic Devices: Final Subcontract Report, 27 April 2004-15 September 2007

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, J. D.

    2008-08-01

    This report summarizes the development and evaluation of higher-bandgap absorbers in the CIS alloy system. The major effort focused on exploring suitable absorbers with significant sulfur alloying in collaboration with Shafarman's group at the Institute of Energy Conversion. Three series of samples were examined; first, a series of quaternary CuIn(SeS)2-based devices without Ga; second, a series of devices with pentenary Cu(InGa)(SeS)2 absorbers in which the Se-to-S and In-to-Ga ratios were chosen to keep the bandgap nearly constant, near 1.52 eV. Third, based on the most-promising samples in those two series, we examined a series of devices with pentenary Cu(InGa)(SeS)2 absorbers with roughly 25 at.% S/(Se+S) ratios and varying Ga fractions. We also characterized electronic properties of several wide-bandgap CuGaSe2 devices from both IEC and NREL. The electronic properties of these absorbers were examined using admittance spectroscopy, drive-level capacitance profiling, transient photocapacitance, and transient photocurrent optical spectroscopies. The sample devices whose absorbers had Ga fraction below 40 at.% and S fractions above 20 at.% but below 40% exhibited the best electronic properties and device performance.

  10. Monolayer MoS2 Bandgap Modulation by Dielectric Environments and Tunable Bandgap Transistors

    Science.gov (United States)

    Ryou, Junga; Kim, Yong-Sung; KC, Santosh; Cho, Kyeongjae

    2016-01-01

    Semiconductors with a moderate bandgap have enabled modern electronic device technology, and the current scaling trends down to nanometer scale have introduced two-dimensional (2D) semiconductors. The bandgap of a semiconductor has been an intrinsic property independent of the environments and determined fundamental semiconductor device characteristics. In contrast to bulk semiconductors, we demonstrate that an atomically thin two-dimensional semiconductor has a bandgap with strong dependence on dielectric environments. Specifically, monolayer MoS2 bandgap is shown to change from 2.8 eV to 1.9 eV by dielectric environment. Utilizing the bandgap modulation property, a tunable bandgap transistor, which can be in general made of a two-dimensional semiconductor, is proposed. PMID:27378032

  11. Monolayer MoS2 Bandgap Modulation by Dielectric Environments and Tunable Bandgap Transistors.

    Science.gov (United States)

    Ryou, Junga; Kim, Yong-Sung; Kc, Santosh; Cho, Kyeongjae

    2016-01-01

    Semiconductors with a moderate bandgap have enabled modern electronic device technology, and the current scaling trends down to nanometer scale have introduced two-dimensional (2D) semiconductors. The bandgap of a semiconductor has been an intrinsic property independent of the environments and determined fundamental semiconductor device characteristics. In contrast to bulk semiconductors, we demonstrate that an atomically thin two-dimensional semiconductor has a bandgap with strong dependence on dielectric environments. Specifically, monolayer MoS2 bandgap is shown to change from 2.8 eV to 1.9 eV by dielectric environment. Utilizing the bandgap modulation property, a tunable bandgap transistor, which can be in general made of a two-dimensional semiconductor, is proposed. PMID:27378032

  12. Feasibility of detecting single atoms using photonic bandgap cavities

    CERN Document Server

    Lev, B I; Barclay, P; Painter, O J; Mabuchi, H; Lev, Benjamin; Srinivasan, Kartik; Barclay, Paul; Painter, Oskar; Mabuchi, Hideo

    2004-01-01

    We propose an atom-cavity chip that combines laser cooling and trapping of neutral atoms with magnetic microtraps and waveguides to deliver a cold atom to the mode of a fiber taper coupled photonic bandgap (PBG) cavity. The feasibility of this device for detecting single atoms is analyzed using both a semi-classical treatment and an unconditional master equation approach. Single-atom detection seems achievable in an initial experiment involving the non-deterministic delivery of weakly trapped atoms into the mode of the PBG cavity.

  13. Wide Bandgap Extrinsic Photoconductive Switches

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, James S. [State Univ. of New York (SUNY), Plattsburgh, NY (United States); Univ. of California, Davis, CA (United States)

    2012-01-20

    Photoconductive semiconductor switches (PCSS) have been investigated since the late 1970s. Some devices have been developed that withstand tens of kilovolts and others that switch hundreds of amperes. However, no single device has been developed that can reliably withstand both high voltage and switch high current. Yet, photoconductive switches still hold the promise of reliable high voltage and high current operation with subnanosecond risetimes. Particularly since good quality, bulk, single crystal, wide bandgap semiconductor materials have recently become available. In this chapter we will review the basic operation of PCSS devices, status of PCSS devices and properties of the wide bandgap semiconductors 4H-SiC, 6H-SiC and 2H-GaN.

  14. Two-Dimensional Fiber Positioning and Clamping Device for Product-Internal Microassembly

    NARCIS (Netherlands)

    Henneken, V.A.; Sassen, W.P.; Van der Vlist, W.; Wien, W.H.A.; Tichem, M.; Sarro, P.M.

    2008-01-01

    In this paper, we present a microelectromechanical systems-based two-degrees-of-freedom positioning device combined with a clamping structure for positioning and constraining an optical fiber. The fiber position can be controlled in the two directions perpendicular to the fiber axis using two specif

  15. 78 FR 16296 - Certain Optoelectronic Devices for Fiber Optic Communications, Components Thereof, and Products...

    Science.gov (United States)

    2013-03-14

    ... COMMISSION Certain Optoelectronic Devices for Fiber Optic Communications, Components Thereof, and Products... certain claims of U.S. Patent Nos. 6,947,456 and 5,596,595 (collectively, ``Asserted Patents''). 77 FR... complaint filed by Avago Technologies Fiber IP (Singapore) Pte. Ltd. of Singapore (``Avago Fiber...

  16. Suppressing sub-bandgap phonon-polariton heat transfer in near-field thermophotovoltaic devices for waste heat recovery

    Science.gov (United States)

    Chen, Kaifeng; Santhanam, Parthiban; Fan, Shanhui

    2015-08-01

    We consider a near-field thermophotovoltaic device with metal as the emitter and semiconductor as the photovoltaic cell. We show that when the cell is a III-V semiconductor, such as GaSb, parasitic phonon-polariton heat transfer reduces efficiency in the near-field regime, especially when the temperature of the emitter is not high enough. We further propose ways to avoid the phonon-polariton heat transfer by replacing the III-V semiconductor with a non-polar semiconductor such as Ge. Our work provides practical guidance on the design of near-field thermophotovoltaic systems for efficient harvesting of low-quality waste heat.

  17. Fiber optic device for sensing the presence of a gas

    Science.gov (United States)

    Benson, David K.; Bechinger, Clemens S.; Tracy, C. Edwin

    1998-01-01

    A fiber-optic device for sensing the presence of a gas in an environment is provided. The device comprises a light source for directing a light beam to a layer system having a first surface and a second surface opposite the first surface. The first surface is exposable to the light beam and the second surface is exposable to the environment. A first light portion encounters and reflects from the first surface at an angle of incidence free from optical wave guide resonance phenomenon and the second light portion encounters and reflects from the first surface at an angle of incidence enabling an optical wave guide resonance phenomenon. The layer system is selected to reversibly react with the gas to be detected. The reaction between the gas and the material changes the material's optical properties and the wavelength at which the optical wave guide resonance occurs. Furthermore, a mechanism for measuring the intensity of the reflected first light portion relative to the reflected second light portion is provided with the ratio of the first and second light portions indicating the concentration of the gas presence in the environment.

  18. Flexible fiber energy storage and integrated devices: recent progress and perspectives

    OpenAIRE

    Xianfu Wang; Kai Jiang; Guozhen Shen

    2015-01-01

    Flexible fiber-shaped energy storage devices have been studied and developed intensively over the past few years to meet the demands of modern electronics in terms of flexibility, weavability and being lightweight. In this review, fiber electrodes and flexible fiber energy storage devices containing solid-state supercapacitors (SCs) and lithium-ion batteries (LIBs) are carefully summarized with particular emphasis on their electrode fabrication, structure design and flexibility. In addition, ...

  19. Wide-Bandgap Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Chinthavali, M.S.

    2005-11-22

    With the increase in demand for more efficient, higher-power, and higher-temperature operation of power converters, design engineers face the challenge of increasing the efficiency and power density of converters [1, 2]. Development in power semiconductors is vital for achieving the design goals set by the industry. Silicon (Si) power devices have reached their theoretical limits in terms of higher-temperature and higher-power operation by virtue of the physical properties of the material. To overcome these limitations, research has focused on wide-bandgap materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond because of their superior material advantages such as large bandgap, high thermal conductivity, and high critical breakdown field strength. Diamond is the ultimate material for power devices because of its greater than tenfold improvement in electrical properties compared with silicon; however, it is more suited for higher-voltage (grid level) higher-power applications based on the intrinsic properties of the material [3]. GaN and SiC power devices have similar performance improvements over Si power devices. GaN performs only slightly better than SiC. Both SiC and GaN have processing issues that need to be resolved before they can seriously challenge Si power devices; however, SiC is at a more technically advanced stage than GaN. SiC is considered to be the best transition material for future power devices before high-power diamond device technology matures. Since SiC power devices have lower losses than Si devices, SiC-based power converters are more efficient. With the high-temperature operation capability of SiC, thermal management requirements are reduced; therefore, a smaller heat sink would be sufficient. In addition, since SiC power devices can be switched at higher frequencies, smaller passive components are required in power converters. Smaller heat sinks and passive components result in higher-power-density power converters

  20. Flexible fiber energy storage and integrated devices: recent progress and perspectives

    Directory of Open Access Journals (Sweden)

    Xianfu Wang

    2015-06-01

    Full Text Available Flexible fiber-shaped energy storage devices have been studied and developed intensively over the past few years to meet the demands of modern electronics in terms of flexibility, weavability and being lightweight. In this review, fiber electrodes and flexible fiber energy storage devices containing solid-state supercapacitors (SCs and lithium-ion batteries (LIBs are carefully summarized with particular emphasis on their electrode fabrication, structure design and flexibility. In addition, emerging wire-shaped integrated energy systems, combined energy storage and solar cells, as well as other electronic devices to realize self-charging and self-powered integrated systems are specifically highlighted.

  1. Modifying Poly(Vinyl Alcohol) (PVA) from Insulator to Small-Bandgap Polymer: A Novel Approach for Organic Solar Cells and Optoelectronic Devices

    Science.gov (United States)

    Aziz, Shujahadeen B.

    2016-01-01

    An innovative method has been used to reduce the bandgap of poly(vinyl alcohol) (PVA) polymer by addition of a nontoxic, inexpensive, and environmentally friendly material. The resulting materials are small-bandgap polymers, hence opening new frontiers in green chemistry. The doped PVA films showed a wide range of light absorption of the solar spectrum from 200 nm to above 800 nm. Nonsharp absorption behavior versus wavelength was observed for the samples. The refractive index exhibited a wide range of dispersion. Shift of the absorption edge from 6.2 eV to 1.5 eV was observed. The energy bandgap of PVA was diminished to 1.85 eV upon addition of black tea extract solution, lying in the range of small-bandgap polymers. Increase of the optical dielectric constant was observed with increasing tea solution addition. The results indicate that small-bandgap PVA with good film-forming ability could be useful in terms of cost-performance tradeoff, solving problems of short lifetime, cost, and flexibility associated with conjugated polymers. The decrease of the Urbach energy upon addition of black tea extract solution indicates modification of PVA from a disordered to ordered material. X-ray diffraction results confirm an increase of the crystalline fraction in the doped samples.

  2. Faceted ceramic fibers, tapes or ribbons and epitaxial devices therefrom

    Science.gov (United States)

    Goyal, Amit

    2013-07-09

    A crystalline article includes a single-crystal ceramic fiber, tape or ribbon. The fiber, tape or ribbon has at least one crystallographic facet along its length, which is generally at least one meter long. In the case of sapphire, the facets are R-plane, M-plane, C-plane or A-plane facets. Epitaxial articles, including superconducting articles, can be formed on the fiber, tape or ribbon.

  3. Photolithography of thick photoresist coating in anisotropically etched V-grooves for electrically controlled liquid crystal photonic bandgap fiber devices

    DEFF Research Database (Denmark)

    Wei, Lei; Khomtchenko, Elena; Alkeskjold, Thomas Tanggaard;

    2009-01-01

    Thick photoresist coating for electrode patterning in anisotropically etched v-grooves is investigated. The photoresist coverage is compared with and without soft baking. Two-step exposure is applied for a complete exposure and minimizing the resolution loss.......Thick photoresist coating for electrode patterning in anisotropically etched v-grooves is investigated. The photoresist coverage is compared with and without soft baking. Two-step exposure is applied for a complete exposure and minimizing the resolution loss....

  4. Properties of fiber composites for advanced flywheel energy storage devices

    Energy Technology Data Exchange (ETDEWEB)

    DeTeresa, S J; Groves, S E

    2001-01-12

    The performance of commercial high-performance fibers is examined for application to flywheel power supplies. It is shown that actual delivered performance depends on multiple factors such as inherent fiber strength, strength translation and stress-rupture lifetime. Experimental results for recent stress-rupture studies of carbon fibers will be presented and compared with other candidate reinforcement materials. Based on an evaluation of all of the performance factors, it is concluded that carbon fibers are preferred for highest performance and E-glass fibers for lowest cost. The inferior performance of the low-cost E-glass fibers can be improved to some extent by retarding the stress-corrosion of the material due to moisture and practical approaches to mitigating this corrosion are discussed. Many flywheel designs are limited not by fiber failure, but by matrix-dominated failure modes. Unfortunately, very few experimental results for stress-rupture under transverse tensile loading are available. As a consequence, significant efforts are made in flywheel design to avoid generating any transverse tensile stresses. Recent results for stress-rupture of a carbon fiber/epoxy composite under transverse tensile load reveal that these materials are surprisingly durable under the transverse loading condition and that some radial tensile stress could be tolerated in flywheel applications.

  5. Miniature micro-wire based optical fiber-field access device.

    Science.gov (United States)

    Pevec, Simon; Donlagic, Denis

    2012-12-01

    This paper presents an optical fiber-field access device suitable for use in different in-line fiber-optics' systems and fiber-based photonics' components. The proposed device utilizes a thin silica micro-wire positioned in-between two lead-in single mode fibers. The thin micro-wire acts as a waveguide that allows for low-loss interconnection between both lead-in fibers, while providing interaction between the guided optical field and the surrounding medium or other photonic structures. The field interaction strength, total loss, and phase matching conditions can be partially controlled by device-design. The presented all-fiber device is miniature in size and utilizes an all-silica construction. It has mechanical properties suitable for handling and packaging without the need for additional mechanical support or reinforcements. The proposed device was produced using a micromachining method that utilizes selective etching of a purposely-produced phosphorus pentoxide-doped optical fiber. This method is simple, compatible with batch processes, and has good high-volume manufacturing potential. PMID:23262732

  6. Nanostructure Core Fiber With Enhanced Performances: Design, Fabrication and Devices

    DEFF Research Database (Denmark)

    Yu, X.; Yan, Min; Ren, G.B.;

    2009-01-01

    We report a new type of silica-based all-solid fiber with a 2-D nanostructure core. The nanostructure core fiber (NCF) is formed by a 2-D array of high-index rods of sub-wavelength dimensions. We theoretically study the birefringence property of such fibers over a large wavelength range. Large......-mode-area (LMA) structure with a typical high birefringence in the order of 10(-4) can be easily realized. The attenuation of the fabricated NCF is as low as 3.5 dB/km at 1550 nm. Higher macro- and micro-bending losses compared with those of the single-mode fiber (SMF) due to the reduced index difference have...... been observed experimentally, which suggests that the NCF is potentially useful for curvature and strain sensing applications. A fiber Bragg grating (FBG) inscribed in such a novel fiber is side-polished to make use of its evanescent field for refractive index sensing. The refractive index sensitivity...

  7. Research progress in the key device and technology for fiber optic sensor network

    Science.gov (United States)

    Liu, Deming; Sun, Qizhen; Lu, Ping; Xia, Li; Sima, Chaotan

    2016-03-01

    The recent research progress in the key device and technology of the fiber optic sensor network (FOSN) is introduced in this paper. An architecture of the sensor optical passive network (SPON), by employing hybrid wavelength division multiplexing/time division multiplexing (WDM/TDM) techniques similar to the fiber communication passive optical network (PON), is proposed. The network topology scheme of a hybrid TDM/WDM/FDM (frequency division multiplexing) three-dimension fiber optic sensing system for achieving ultra-large capacity, long distance, and high resolution sensing performance is performed and analyzed. As the most important device of the FOSN, several kinds of light source are developed, including the wideband multi-wavelength fiber laser operating at C band, switchable and tunable 2 μm multi-wavelength fiber lasers, ultra-fast mode-locked fiber laser, as well as the optical wideband chaos source, which have very good application prospects in the FOSN. Meanwhile, intelligent management techniques for the FOSN including wideband spectrum demodulation of the sensing signals and real-time fault monitoring of fiber links are presented. Moreover, several typical applications of the FOSN are also discussed, such as the fiber optic gas sensing network, fiber optic acoustic sensing network, and strain/dynamic strain sensing network.

  8. Devices, components, and applications of low cost using polymer optical fibers

    Science.gov (United States)

    Lomer, Mauro; Baldwin-Olguin, Guillermo

    2004-10-01

    Low-cost optical devices, components a polymer optical fiber (POF) are demonstrated using technical of polished. Potentially low-cost components fabrication processes are described. Several components and devices are proposed for applications in comunications or industrial applications. Experimental results obtained with POF and diffraction grating are presented.

  9. Devices, components, and applications of low cost using polymer optical fibers

    OpenAIRE

    Lomer Barboza, Mauro Matías; Baldwin Olguín, Guillermo

    2004-01-01

    Low-cost optical devices, components a polymer optical fiber (POF) are demonstrated using technical of polished. Potentially low-cost components fabrication processes are described. Several components and devices are proposed for applications in comunications or industrial applications. Experimental results obtained with POF and diffraction grating are presented.

  10. Load bearing capacity of bone anchored fiber-reinforced composite device.

    Science.gov (United States)

    Ballo, Ahmed Mansour; Lassila, Lippo V; Vallittu, Pekka K; Närhi, Timo O

    2007-10-01

    The purpose of this study was to evaluate the push-out load-bearing capacity of threaded fiber-reinforced composite (FRC) devices for use as bone-anchored devices. The purpose was also to evaluate the possibility to use bioactive glass (BAG) granules on the experimental FRC devices in terms the mechanical behavior. Three experimental FRC devices (n = 15) were fabricated for the study: (a) threaded device with smooth surface; (b) threaded device with BAG granules (S53P4, Vivoxid Ltd, Turku, Finland) and supplementary retention grooves, and (c) unthreaded device with BAG granules. Threaded titanium devices were used as controls. The FRC devices were prepared from a light-polymerized dimethacrylate resin reinforced with preimpregnated unidirectional and bidirectional E-glass fibers (EverStick, StickTech Ltd, Turku, Finland). Experimental and control devices were embedded into dental plaster to simulate bone before the mechanical push-out test was carried out. ANOVA and Weibull analysis were used for the statistical evaluation. Threaded FRC devices had significantly higher push-out strength than the threaded titanium device (p < .001). The push-out forces exceeding 2,500 N were measured for threaded FRC devices with supplementary grooves and BAG coating. No thread failures were observed in any FRC devices. The unthreaded FRC devices with BAG lost 70% of glass particles during the test, while no BAG particles were lost from threaded FRC devices. It can be concluded that threaded FRC devices can withstand high push-out forces in the dental plaster without a risk of thread failure under physiological load. PMID:17558473

  11. Experimental arrangement to measure dispersion in optical fiber devices

    International Nuclear Information System (INIS)

    Dispersion is a quite important parameter in systems based on optical fiber, especially in pulsed emission lasers, where the temporal width is affected by such parameter. Therefore, it is necessary to consider the dispersion provoked by each component in the cavity. There are various experimental interferometric arrangements to evaluate this parameter. Generally, these systems modify the wavelength to obtain information about the n(λ) dependency, which is contained in the interferogram phase. However, this makes the system quite slow and it requires tunable and narrow bandwidth laser sources. In the present work, results obtained from an arrangement based on Mach-Zehnder interferometer where one of the arms is the optical fiber under study, while the reference one is air, are presented. In order to determine the n(λ) dependency, a wide spectrum light source was used in the wavelength range of interest. The phase information was evaluated from the interferometric signal measured by an optical spectrum analyzer.

  12. Experimental arrangement to measure dispersion in optical fiber devices

    Energy Technology Data Exchange (ETDEWEB)

    Armas Rivera, Ivan [Benemerita Universidad Autonoma de Puebla, Facultad de Ciencias de la Electronica (Mexico); Beltran Perez, Georgina; Castillo Mixcoatl, Juan; Munoz Aguirre, Severino [Benemerita Universidad Autonoma de Puebla, Facultad de Ciencias Fisico Matematicas (Mexico); Zaca Moran, Placido, E-mail: ivan_rr1@hotmail.com [Benemerita Universidad Autonoma de Puebla, Fisicoquimica de Materiales ICUAP (Mexico)

    2011-01-01

    Dispersion is a quite important parameter in systems based on optical fiber, especially in pulsed emission lasers, where the temporal width is affected by such parameter. Therefore, it is necessary to consider the dispersion provoked by each component in the cavity. There are various experimental interferometric arrangements to evaluate this parameter. Generally, these systems modify the wavelength to obtain information about the n({lambda}) dependency, which is contained in the interferogram phase. However, this makes the system quite slow and it requires tunable and narrow bandwidth laser sources. In the present work, results obtained from an arrangement based on Mach-Zehnder interferometer where one of the arms is the optical fiber under study, while the reference one is air, are presented. In order to determine the n({lambda}) dependency, a wide spectrum light source was used in the wavelength range of interest. The phase information was evaluated from the interferometric signal measured by an optical spectrum analyzer.

  13. Photonic crystal fibers -

    DEFF Research Database (Denmark)

    Libori, Stig E. Barkou

    2002-01-01

    possibilities, the thesis will attempot to offer a proof of concept, rather than an in-depth analysis, thus reflecting the present state of the art within the area of micro-structured fibers. Another important sub-class of micro-structured fibers is photonic bandgap fibers. Photonic bandgap fibers are far more......-structured fibers that guide light by simple index effects. However, photonic bandgap fibers offer more radical possibilities, such as core regions with an effective index that is lower than the surrounding effective cladding index one may guide light in air- and dispersion qualities that differ from both those of...

  14. Darcy Permeability of Hollow Fiber Membrane Bundles Made from Membrana Polymethylpentene Fibers Used in Respiratory Assist Devices.

    Science.gov (United States)

    Madhani, Shalv P; D'Aloiso, Brandon D; Frankowski, Brian; Federspiel, William J

    2016-01-01

    Hollow fiber membranes (HFMs) are used in blood oxygenators for cardiopulmonary bypass or in next generation artificial lungs. Flow analyses of these devices is typically done using computational fluid dynamics (CFD) modeling HFM bundles as porous media, using a Darcy permeability coefficient estimated from the Blake-Kozeny (BK) equation to account for viscous drag from fibers. We recently published how well this approach can predict Darcy permeability for fiber bundles made from polypropylene HFMs, showing the prediction can be significantly improved using an experimentally derived correlation between the BK constant (A) and bundle porosity (ε). In this study, we assessed how well our correlation for A worked for predicting the Darcy permeability of fiber bundles made from Membrana polymethylpentene (PMP) HFMs, which are increasingly being used clinically. Swatches in the porosity range of 0.4 to 0.8 were assessed in which sheets of fiber were stacked in parallel, perpendicular, and angled configurations. Our previously published correlation predicted Darcy within ±8%. A new correlation based on current and past measured permeability was determined: A = 497ε - 103; using this correlation measured Darcy permeability was within ±6%. This correlation varied from 8% to -3.5% of our prior correlation over the tested porosity range. PMID:26809086

  15. Fiber - Optic Devices as Temperature Sensors for Temperature Measurements in AC Magnetic Fields

    Science.gov (United States)

    Rablau, Corneliu; Lafrance, Joseph; Sala, Anca

    2007-10-01

    We report on the investigation of several fiber-optic devices as potential sensors for temperature measurements in AC magnetic fields. Common temperature sensors, such as thermocouples, thermistors or diodes, will create random and/or systematic errors when placed in a magnetic field. A DC magnetic field is susceptible to create a systematic offset to the measurement, while in an AC magnetic field of variable frequency random errors which cannot be corrected for can also be introduced. Fiber-Bragg-gratings and thin film filters have an inherent temperature dependence. Detrimental for their primary applications, the same dependence allows one to use such devices as temperature sensors. In an AC magnetic field, they present the advantage of being immune to electromagnetic interference. Moreover, for fiber-Bragg-gratings, the shape factor and small mass of the bare-fiber device make it convenient for temperature measurements on small samples. We studied several thin-film filters and fiber-Bragg-gratings and compared their temperature measurement capabilities in AC magnetic fields of 0 to 150 Gauss, 0 to 20 KHz to the results provided by off-the-shelf thermocouples and thermistor-based temperature measurement systems.

  16. Photomechanical actuator device based on disperse red 1 doped poly(methyl methacrylate) optical fiber

    Science.gov (United States)

    Ye, Xianjun

    The photomechanical effect is the phenomenon involving any mechanical property change of a material induced by light exposure. Photomechanical devices can be built with superior performance over traditional devices and offer versatile control tactics. Previous experiments show that disperse red 1 azobenzene (DR1) doped poly(methyl methacrylate) (PMMA) optical fiber has a fast photomechanical response upon asymmetrical 633nm laser irradiation originating in photoisomerization of the dopants between the cis and trans forms, which causes an elongation of the polymer fiber. In this work, laser light of 355nm wavelength is used to investigate the dynamics of the trans to cis photoisomerization process, which should result in length contraction of the DR1 doped PMMA polymer fiber. A three-point-contact optically-actuated beam controlling tilt mount is made and used as the measurement apparatus to study this process. The photomechanical fiber is observed to elongate upon UV irradiation. Numerical simulations, which take into account the coupled effect between the laser-induced temperature increase and population density change of the dye molecules, show that contraction of the fiber due to direct trans-cis photoisomerization is overwhelmed by elongation due to the photo-thermally-stimulated cis-trans isomerization under high intensity. An ink coated entrance face of the fiber is placed in the measurement tilt mount and is found to exhibit contraction in the fast process under low intensity without sacrificing the good signal to noise ratio enjoyed in the high intensity case.

  17. 78 FR 77166 - Certain Optoelectronic Devices for Fiber Optic Communications, Components Thereof, and Products...

    Science.gov (United States)

    2013-12-20

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Optoelectronic Devices for Fiber Optic Communications, Components Thereof, and Products Containing the Same; Notice of Request for Statements on the Public Interest AGENCY: U.S. International...

  18. Large-area single-mode photonic bandgap vcsels

    DEFF Research Database (Denmark)

    Birkedal, Dan; Gregersen, N.; Bischoff, S.; Madsen, M.; Romstad, F.; Oestergaard, J.

    We demonstrate that the photonic bandgap effect can be used to control the modes of large area vertical cavity surface emitting lasers. We obtain more than 20 dB side mode suppression ratios in a 10-micron area device.......We demonstrate that the photonic bandgap effect can be used to control the modes of large area vertical cavity surface emitting lasers. We obtain more than 20 dB side mode suppression ratios in a 10-micron area device....

  19. Hollow Fiber Membrane Dehumidification Device for Air Conditioning System

    Science.gov (United States)

    Zhao, Baiwang; Peng, Na; Liang, Canzeng; Yong, Wai Fen; Chung, Tai-Shung

    2015-01-01

    In order to provide a comfortable living and working environment indoors in tropical countries, the outdoor air often needs to be cooled and dehumidified before it enters the rooms. Membrane separation is an emerging technology for air dehumidification and it is based on the solution diffusion mechanism. Water molecules are preferentially permeating through the membranes due to its smaller kinetic diameter and higher condensability than the other gases. Compared to other dehumidification technologies such as direct cooling or desiccation, there is no phase transition involved in membrane dehumidification, neither the contact between the fresh air stream and the desiccants. Hence, membrane dehumidification would not only require less energy consumption but also avoid cross-contamination problems. A pilot scale air dehumidification system is built in this study which comprises nine pieces of one-inch PAN/PDMS hollow fiber membrane modules. A 150 h long-term test shows that the membrane modules has good water vapor transport properties by using a low vacuum force of only 0.78 bar absolute pressure at the lumen side. The water vapor concentration of the feed humid air decreases dramatically from a range of 18–22 g/m3 to a range of 13.5–18.3 g/m3. Most importantly, the total energy saving is up to 26.2% compared with the conventional air conditioning process. PMID:26580660

  20. Hollow Fiber Membrane Dehumidification Device for Air Conditioning System.

    Science.gov (United States)

    Zhao, Baiwang; Peng, Na; Liang, Canzeng; Yong, Wai Fen; Chung, Tai-Shung

    2015-01-01

    In order to provide a comfortable living and working environment indoors in tropical countries, the outdoor air often needs to be cooled and dehumidified before it enters the rooms. Membrane separation is an emerging technology for air dehumidification and it is based on the solution diffusion mechanism. Water molecules are preferentially permeating through the membranes due to its smaller kinetic diameter and higher condensability than the other gases. Compared to other dehumidification technologies such as direct cooling or desiccation, there is no phase transition involved in membrane dehumidification, neither the contact between the fresh air stream and the desiccants. Hence, membrane dehumidification would not only require less energy consumption but also avoid cross-contamination problems. A pilot scale air dehumidification system is built in this study which comprises nine pieces of one-inch PAN/PDMS hollow fiber membrane modules. A 150 h long-term test shows that the membrane modules has good water vapor transport properties by using a low vacuum force of only 0.78 bar absolute pressure at the lumen side. The water vapor concentration of the feed humid air decreases dramatically from a range of 18-22 g/m³ to a range of 13.5-18.3 g/m³. Most importantly, the total energy saving is up to 26.2% compared with the conventional air conditioning process. PMID:26580660

  1. Hollow Fiber Membrane Dehumidification Device for Air Conditioning System

    Directory of Open Access Journals (Sweden)

    Baiwang Zhao

    2015-11-01

    Full Text Available In order to provide a comfortable living and working environment indoors in tropical countries, the outdoor air often needs to be cooled and dehumidified before it enters the rooms. Membrane separation is an emerging technology for air dehumidification and it is based on the solution diffusion mechanism. Water molecules are preferentially permeating through the membranes due to its smaller kinetic diameter and higher condensability than the other gases. Compared to other dehumidification technologies such as direct cooling or desiccation, there is no phase transition involved in membrane dehumidification, neither the contact between the fresh air stream and the desiccants. Hence, membrane dehumidification would not only require less energy consumption but also avoid cross-contamination problems. A pilot scale air dehumidification system is built in this study which comprises nine pieces of one-inch PAN/PDMS hollow fiber membrane modules. A 150 h long-term test shows that the membrane modules has good water vapor transport properties by using a low vacuum force of only 0.78 bar absolute pressure at the lumen side. The water vapor concentration of the feed humid air decreases dramatically from a range of 18–22 g/m3 to a range of 13.5–18.3 g/m3. Most importantly, the total energy saving is up to 26.2% compared with the conventional air conditioning process.

  2. Lab-on-Fiber devices as an all around platform for sensing

    Science.gov (United States)

    Ricciardi, A.; Consales, M.; Quero, G.; Crescitelli, A.; Esposito, E.; Cusano, A.

    2013-12-01

    "Lab-on-Fiber" technology is an emerging field envisioning a novel class of advanced, multifunctional photonic devices and components arising from the integration onto optical fibers of different materials at micro and nano-scale with suitable physical, chemical and biological properties. This new fascinating and intriguing research field thus proposes a new technological platform where functionalized materials, devices and components are constructed, embedded all together in a single optical fiber providing the necessary physical connections and light matter interaction, exploitable in both communication and sensing applications. This technological innovation would open the way for the creation of a novel technological world completely integrated in a single optical fiber conferring unique and unprecedented performances and functionality degree. Although, the benefits provided by such a technology can be easily understood, many research efforts are, however, required to translate the vision in a technological reality. Indeed, the main issue to address concerns the identification and definition of viable fabrication methodologies, routes and strategies enabling the integration of a large set of functional materials at sub wavelength scale onto non conventional substrates as the case of optical fibers.

  3. 0.6-eV bandgap In0.69Ga0.31As thermophotovoltaic devices with compositionally undulating step-graded InAsyP1-ybuffers

    Institute of Scientific and Technical Information of China (English)

    Ji Lian; Lu Shu-Long; Jiang De-Sheng; Zhao Yong-Ming; Tan Ming; Zhu Ya-Qi; Dong Jian-Rong

    2013-01-01

    Single-junction,lattice-mismatched In0.69Ga0.31 As thermophotovoltaic (TPV) devices each with a bandgap of 0.6 eV are grown on InP substrate by metal-organic chemical vapour deposition (MOCVD).Compositionally undulating stepgraded InAsyPl-y buffer layers with a lattice mismatch of ~ 1.2% are used to mitigate the effect of lattice mismatch between the device layers and the InP substrate.With an optimized buffer thickness,the In0.69Ga0.31 As active layers grown on the buffer display a high crystal quality with no measurable tetragonal distortion.High-performance single-junction devices are demonstrated,with an open-circuit voltage of 0.215 V and a photovoltaic conversion efficiency of 6.9% at a short-circuit current density of 47.6 mA/cm2,which are measured under the standard solar simulator of air mass 1.5-global (AM 1.5 G).

  4. Electrically Tunable Bandgaps in Bilayer MoS₂.

    Science.gov (United States)

    Chu, Tao; Ilatikhameneh, Hesameddin; Klimeck, Gerhard; Rahman, Rajib; Chen, Zhihong

    2015-12-01

    Artificial semiconductors with manufactured band structures have opened up many new applications in the field of optoelectronics. The emerging two-dimensional (2D) semiconductor materials, transition metal dichalcogenides (TMDs), cover a large range of bandgaps and have shown potential in high performance device applications. Interestingly, the ultrathin body and anisotropic material properties of the layered TMDs allow a wide range modification of their band structures by electric field, which is obviously desirable for many nanoelectronic and nanophotonic applications. Here, we demonstrate a continuous bandgap tuning in bilayer MoS2 using a dual-gated field-effect transistor (FET) and photoluminescence (PL) spectroscopy. Density functional theory (DFT) is employed to calculate the field dependent band structures, attributing the widely tunable bandgap to an interlayer direct bandgap transition. This unique electric field controlled spontaneous bandgap modulation approaching the limit of semiconductor-to-metal transition can open up a new field of not yet existing applications. PMID:26560813

  5. A comparative study between SMS interferometers and lossy mode resonace optical fiber devices for sensing applications

    Science.gov (United States)

    Socorro, A. B.; Hernaez, M.; Del Villar, I.; Corres, J. M.; Arregui, F. J.; Matias, I. R.

    2015-05-01

    Optical fiber sensors are of great interest due to their intrinsic advantages over electronic sensors. In this work, the sensing characteristics of two different and novel optical fiber devices are compared, after simultaneously depositing a thin-film using the layer-by-layer assembly deposition process. The first one is an SMS structure, formed by splicing two single-mode fiber pigtails on both sides of a coreless multimode fiber segment. This structure induces an interferometric phenomenon that generates several attenuation and transmission bands along the spectrum. These bands are sensitive to variations in the surrounding refractive index, although this sensitivity has been enhanced by a TiO2/PSS thin-film. The other device is a 40 mm uncladded segment of a 200 μm-core multimode optical fiber. When coated by a TiO2/PSS thinfilm, part of the light transmitted into the uncladded core is coupled into the thin-film, generating a lossy mode resonance (LMR). The absorption peaks due to these phenomena red-shift as long as the thin-film thickness increases or the external RI becomes higher. The performance of these devices as refractometers and relative humidity sensors are tested. Results show that the LMR-based sensor is more sensitive in both situations, in spite of its lower sensitivity. Particularly, it presents a 7-fold sensitivity enhancement when measuring surrounding medium refractive index changes and a 10-fold sensitivity enhancement when measuring environmental relative humidity. To our knowledge, this is the first time that a comparative study between SMS and LMR sensors is performed.

  6. Optofluidic Temperature and Pressure Measurements with Fiber Bragg Gratings Embedded in Microfluidic Devices

    CERN Document Server

    Cooksey, Gregory A

    2016-01-01

    The integration of photonic sensors into microfluidic devices provides opportunities for dynamic measurement of chemical and physical properties of fluids in very small volumes. We previously reported on the use of commercially available Fiber Bragg Gratings (FBGs) and on-chip silicon waveguides for temperature sensing. In this report, we demonstrate the integration of FBGs into easy-to-fabricate microfluidic devices and report on their sensitivity for temperature and pressure measurement in microliter volumes. These sensors present new routes to measurement in microfluidic applications such as small-volume calorimetry and microflow metrology.

  7. Wide bandgap matrix switcher, amplifier and oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Sampayan, Stephen

    2016-08-16

    An electronic device comprising an optical gate, an electrical input an electrical output and a wide bandgap material positioned between the electrical input and the electrical output to control an amount of current flowing between the electrical input and the electrical output in response to a stimulus received at the optical gate can be used in wideband telecommunication applications in transmission of multi-channel signals.

  8. CMOS bandgap references and temperature sensors and their applications

    OpenAIRE

    Wang, G.

    2005-01-01

    Two main parts have been presented in this thesis: device characterization and circuit. In integrated bandgap references and temperature sensors, the IC(VBE, characteristics of bipolar transistors are used to generate the basic signals with high accuracy. To investigate the possibilities to fabricate high-precision bandgap references and temperature sensors in low-cost CMOS technology, the electrical characteristics of substrate bipolar pnp transistors have been investigated over a wide tempe...

  9. Photonic crystal fibers

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper; Hansen, K P; Nielsen, M D;

    2003-01-01

    Photonic crystal fibers having a complex microstructure in the transverse plane constitute a new and promising class of optical fibers. Such fibers can either guide light through total internal reflection or the photonic bandgap effect, In this paper, we review the different types and applications...... of photonic crystal fibers with particular emphasis on recent advances in the field....

  10. Localized surface plasmon fiber device coated with carbon nanotubes for the specific detection of CO2

    Science.gov (United States)

    Allsop, T.; Arif, R.; Neal, R.; Kalli, K.; Kundrát, V.; Rozhin, A.; Culverhouse, P.; Webb, D. J.

    2015-08-01

    We explored the potential of a carbon nanotube (CNT) coating working in conjunction with a recently developed localized surface plasmon (LSP) device (based upon a nanostructured thin film consisting of of nano-wires of platinum) with ultra-high sensitivity to changes in the surrounding index. The uncoated LSP sensor's transmission resonances exhibited a refractive index sensitivity of Δλ/Δn ~ -6200nm/RIU and ΔΙ/Δn ~5900dB/RIU, which is the highest reported spectral sensitivity of a fiber optic sensor to bulk index changes within the gas regime. The complete device provides the first demonstration of the chemically specific gas sensing capabilities of CNTs utilizing their optical characteristics. This is proven by investigating the spectral response of the sensor before and after the adhesion of CNTs to alkane gases along with carbon dioxide. The device shows a distinctive spectral response in the presence of gaseous CO2 over and above what is expected from general changes in the bulk refractive index. This fiber device yielded a limit of detection of 150ppm for CO2 at a pressure of one atmosphere. Additionally the adhered CNTs actually reduce sensitivity of the device to changes in bulk refractive index of the surrounding medium. The polarization properties of the LSP sensor resonances are also investigated and it is shown that there is a reduction in the overall azimuthal polarization after the CNTs are applied. These optical devices offer a way of exploiting optically the chemical selectivity of carbon nanotubes, thus providing the potential for real-world applications in gas sensing in many inflammable and explosive environments.

  11. Wireless electro-optic switching network for optical fiber sensor array using MEMS-IDT devices

    Science.gov (United States)

    Varadan, Vijay K.; Varadan, Vasundara V.

    1999-09-01

    Optical fiber arrays have been proposed for signal paths in various civilian and military controls as a means of offering advanced sensing functions not available in electronic systems. To implement optic fiber sensors on various control systems, a proper electro-optic architecture (EOA) with a bar- coded electro-optical switch needs to be studied. In this paper, a design of such EO switch is proposed which can be operated remotely. Lithium Niobate is chosen as the EO material. The MEMS-IDT device is designed with Lithium Niobate as a substrate with IDT and a set of floating reflectors. The reflectors can be programmable and thus a bar-coded switch can be fabricated. The electrostatic field between the reflectors and the Lithium Niobate serves as the fast acting switch in this application.

  12. Large Bandgap Semiconductors for Solar Water Splitting

    DEFF Research Database (Denmark)

    Malizia, Mauro

    Photoelectrochemical water splitting represents an eco-friendly technology that could enable the production of hydrogen using water as reactant and solar energy as primary energy source. The exploitation of solar energy for the production of hydrogen would help modern society to reduce the relian...... on fossil fuels as primary feedstock for hydrogen production and diminish the emission of greenhouse gases in the atmosphere, weakening the global warming phenomenon.The dissertation reports the development of GaP (gallium phosphide) photocathodes as a large bandgap semiconductor for...... photoelectrochemical water splitting devices having tandem design. The increase of the photovoltage produced by GaP under illumination was the main goal of this work. GaP has a bandgap of 2.25 eV and could in theory produce a photovoltage of approximately 1.7 V. Instead, the photovoltage produced by the semiconductor...... of BiVO4 (bismuth vanadate) was investigated in view of combining this 2.4 eV large bandgap semiconductor with a Si back-illuminated photocathode. A device obtained by mechanical stacking of BiVO4 photoanode and standard Si photocathode performs non-assisted water splitting under illumination with...

  13. Fiber

    Science.gov (United States)

    Diet - fiber; Roughage; Bulk ... Dietary fiber adds bulk to your diet. Because it makes you feel full faster, it can help with ... Elsevier Saunders; 2016:chap 213. National Research Council. ... Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids ( ...

  14. Fiber

    Science.gov (United States)

    Diet - fiber; Roughage; Bulk ... Dietary fiber adds bulk to your diet. Because it makes you feel full faster, it can help with weight control. Fiber aids digestion and helps prevent constipation . It is ...

  15. Structural refinement, band-gap analysis and optical properties of GdAlO3 nanophosphors influenced by Dy3+ ion concentrations for white light emitting device applications

    Science.gov (United States)

    Jisha, P. K.; Naik, Ramachandra; Prashantha, S. C.; Nagaswarupa, H. P.; Nagabhushana, H.; Basavaraj, R. B.; Sharma, S. C.; Prasad, Daruka

    2016-04-01

    Nanosized GdAlO3 phosphors activated with Dy3+ were prepared by a combustion method. Synthesized phosphors were calcined at 1000 °C for 3 h in order to achieve crystallinity. Powder x-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis was used to characterize the prepared product. The orthorhombic phase was observed in the XRD pattern. The particle size of the samples was calculated as around 25 nm. The SEM images show an irregular shape of the prepared nanophosphor. Functional groups of the phosphors were examined by Fourier transform infrared (FTIR) spectroscopy. Photoluminescence (PL) properties of Dy3+ doped GdAlO3 for near-ultraviolet excitation (352 nm) were studied in order to investigate the possibility of its use in white light emitting device applications. Judd–Ofelt intensity parameters, radiative transition rate (A T) and radiative lifetimes (τ rad) were evaluated from the emission spectrum by adopting a standard procedure. The Commission International de l’Eclairage (CIE) color coordinates and correlated color temperature (CCT) are studied for the optimized phosphor. It is found that the color coordinates of Dy3+ doped GdAlO3 powders fall in the white region of the CIE diagram, and the average CCT value was found to be about 6276 K. Therefore, the present phosphor is highly useful for display applications.

  16. Fiber free plug and play on-chip scattering cytometer module – for implementation in microfluidic point of care devices

    DEFF Research Database (Denmark)

    Jensen, Thomas Glasdam; Kutter, Jörg Peter

    -expert users and Point-Of-Care (POC) applications. It has been demonstrated that this device is capable of detecting and counting particles down to 1 μm at 100 particles per second. This device only depends on a single microfluidic channel. Hence, the device is easy to implement, or to use on its own.......In this paper, we report on recent progress toward the development of a plug and play on-chip cytometer based on light scattering. By developing a device that does not depend on the critical alignment and cumbersome handling of fragile optical fibers, we approach a device that is suitable for non...

  17. Thulium-doped silica fibers with enhanced 3H4 level lifetime: modelling the devices for 800-820 nm band

    CERN Document Server

    Peterka, Pavel; Dhar, Anirban; Dussardier, Bernard; Blanc, Wilfried; 10.1117/12.871756

    2012-01-01

    Silica-based thulium-doped fiber devices operating around 810 nm would extend the spectral range covered by high- power fiber devices. Using a comprehensive numerical model of the fiber we have shown that efficient lasing at 810 nm can be achieved for specific ranges of the laser cavity parameters in silica-based thulium-doped fibers with enhanced 3H4 lifetime up to 58 \\mus as measured in our highly alumina-codoped fibers. We present optimization of the thulium-doped fiber and laser cavity parameters and also potential applications of the developed host material in amplifiers and broadband sources.

  18. Fiber-optic add-drop device based on a silica microsphere-whispering gallery mode system

    OpenAIRE

    Ming CAI; Hunziker, Guido; Vahala, Kerry J.

    1999-01-01

    An all-optical passive four-port system including a fused silica microsphere and two tapered fibers is proposed and demonstrated for the application as a channel adding-dropping device. It is shown that channels can be selectively exchanged between two fibers by coupling to a whispering gallery mode resonance in the microsphere. Finesse in excess of 11150 is measured for the loaded whispering gallery modes.

  19. High brightness laser-diode device emitting 500 W from a 200 μm/NA0.22 fiber

    Science.gov (United States)

    Junhong, Yu; Linhui, Guo; Hualing, Wu; Zhao, Wang; Hao, Tan; Songxin, Gao; Deyong, Wu; Kai, Zhang

    2016-06-01

    A practical method of achieving high brightness and high power fiber-coupled laser-diode device is demonstrated both by experiment and ZEMAX software simulation, which is obtained by technologies of precision beam collimation, free space beam combining and polarization beam combining based on mini-bar diode laser chip. Using this method, fiber-coupled laser-diode module output power from the multimode fiber with 200 μm core diameter and 0.22 numerical aperture (NA) could reach 528 W, equalizing brightness is 11.0 MW/(cm2 sr) and electro-optical efficiency (defined as fiber output power divided by voltage and current of the module) is 43.0%. By this method, much wider applications of fiber-coupled laser-diode are anticipated.

  20. Resonant filtered fiber amplifiers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Laurila, Marko; Olausson, Christina Bjarnal Thulin;

    2013-01-01

    In this paper we present our recent result on utilizing resonant/bandgap fiber designs to achieve high performance ytterbium doped fiber amplifers for achieving diffraction limited beam quality in large mode area fibers, robust bending performance and gain shaping for long wavelength operation of...

  1. Platform for enhanced light-graphene interaction length and miniaturizing fiber stereo-devices

    CERN Document Server

    Xu, Fei; Chen, Jin-hui; Chen, Ye; Lu, Yan-qing

    2014-01-01

    Sufficient light-matter interactions are important for waveguide-coupled graphene optoelectronic devices. Using a microfiber-based lab-on-a-rod technique, we present a platform for ultra-long light-graphene interaction and design graphene-integrated helical microfiber (MF) devices. Using this approach, we experimentally demonstrate an in-line stereo polarizer by wrapping an MF on a rod pretreated with a graphene sheet. The device operates as a broadband (450 nm wavelength) polarizer capable of achieving an extinction ratio (ER) as high as ~8 dB/coil in the telecommunication band. Furthermore, we extend this approach to successfully demonstrate a high-Q graphene-based single-polarization resonator, which operates with an ER of ~11 dB with excellent suppression of polarization noise. The fiber-coil resonator shows great potential for sensing applications and gyro-integration. By specializing the rod surface and coil geometry, we believe the preliminary results reported herein could contribute to advancing the r...

  2. Hierarchical structural health monitoring system combining a fiber optic spinal cord network and distributed nerve cell devices

    Science.gov (United States)

    Minakuchi, Shu; Tsukamoto, Haruka; Takeda, Nobuo

    2009-03-01

    This study proposes novel hierarchical sensing concept for detecting damages in composite structures. In the hierarchical system, numerous three-dimensionally structured sensor devices are distributed throughout the whole structural area and connected with the optical fiber network through transducing mechanisms. The distributed "sensory nerve cell" devices detect the damage, and the fiber optic "spinal cord" network gathers damage signals and transmits the information to a measuring instrument. This study began by discussing the basic concept of the hierarchical sensing system thorough comparison with existing fiber optic based systems and nerve systems in the animal kingdom. Then, in order to validate the proposed sensing concept, impact damage detection system for the composite structure was proposed. The sensor devices were developed based on Comparative Vacuum Monitoring (CVM) system and the Brillouin based distributed strain sensing was utilized to gather the damage signals from the distributed devices. Finally a verification test was conducted using prototype devices. Occurrence of barely visible impact damage was successfully detected and it was clearly indicated that the hierarchical system has better repairability, higher robustness, and wider monitorable area compared to existing systems utilizing embedded optical fiber sensors.

  3. High performance, high bandgap, lattice-mismatched, GaInP solar cells

    Science.gov (United States)

    Wanlass, Mark W.; Carapella, Jeffrey J.; Steiner, Myles A.

    2014-07-08

    High performance, high bandgap, lattice-mismatched, photovoltaic cells (10), both transparent and non-transparent to sub-bandgap light, are provided as devices for use alone or in combination with other cells in split spectrum apparatus or other applications.

  4. Energy Bandgap and Edge States in an Epitaxially Grown Graphene/h-BN Heterostructure

    Science.gov (United States)

    Hwang, Beomyong; Hwang, Jeongwoon; Yoon, Jong Keon; Lim, Sungjun; Kim, Sungmin; Lee, Minjun; Kwon, Jeong Hoon; Baek, Hongwoo; Sung, Dongchul; Kim, Gunn; Hong, Suklyun; Ihm, Jisoon; Stroscio, Joseph A.; Kuk, Young

    2016-08-01

    Securing a semiconducting bandgap is essential for applying graphene layers in switching devices. Theoretical studies have suggested a created bulk bandgap in a graphene layer by introducing an asymmetry between the A and B sub-lattice sites. A recent transport measurement demonstrated the presence of a bandgap in a graphene layer where the asymmetry was introduced by placing a graphene layer on a hexagonal boron nitride (h-BN) substrate. Similar bandgap has been observed in graphene layers on metal substrates by local probe measurements; however, this phenomenon has not been observed in graphene layers on a near-insulating substrate. Here, we present bulk bandgap-like features in a graphene layer epitaxially grown on an h-BN substrate using scanning tunneling spectroscopy. We observed edge states at zigzag edges, edge resonances at armchair edges, and bandgap-like features in the bulk.

  5. Energy Bandgap and Edge States in an Epitaxially Grown Graphene/h-BN Heterostructure

    Science.gov (United States)

    Hwang, Beomyong; Hwang, Jeongwoon; Yoon, Jong Keon; Lim, Sungjun; Kim, Sungmin; Lee, Minjun; Kwon, Jeong Hoon; Baek, Hongwoo; Sung, Dongchul; Kim, Gunn; Hong, Suklyun; Ihm, Jisoon; Stroscio, Joseph A.; Kuk, Young

    2016-01-01

    Securing a semiconducting bandgap is essential for applying graphene layers in switching devices. Theoretical studies have suggested a created bulk bandgap in a graphene layer by introducing an asymmetry between the A and B sub-lattice sites. A recent transport measurement demonstrated the presence of a bandgap in a graphene layer where the asymmetry was introduced by placing a graphene layer on a hexagonal boron nitride (h-BN) substrate. Similar bandgap has been observed in graphene layers on metal substrates by local probe measurements; however, this phenomenon has not been observed in graphene layers on a near-insulating substrate. Here, we present bulk bandgap-like features in a graphene layer epitaxially grown on an h-BN substrate using scanning tunneling spectroscopy. We observed edge states at zigzag edges, edge resonances at armchair edges, and bandgap-like features in the bulk. PMID:27503427

  6. Wide Bandgap Extrinsic Photoconductive Switches

    Science.gov (United States)

    Sullivan, James Stephen

    Wide Bandgap Extrinsic Photoconductive Switches Semi-insulating Gallium Nitride, 4H and 6H Silicon Carbide are attractive materials for compact, high voltage, extrinsic, photoconductive switches due to their wide bandgap, high dark resistance, high critical electric field strength and high electron saturation velocity. These wide bandgap semiconductors are made semi-insulating by the addition of vanadium (4H and 6H-SiC) and iron (2H-GaN) impurities that form deep acceptors. These deep acceptors trap electrons donated from shallow donor impurities. The electrons can be optically excited from these deep acceptor levels into the conduction band to transition the wide bandgap semiconductor materials from a semi-insulating to a conducting state. Extrinsic photoconductive switches with opposing electrodes have been constructed using vanadium compensated 6H-SiC and iron compensated 2H-GaN. These extrinsic photoconductive switches were tested at high voltage and high power to determine if they could be successfully used as the closing switch in compact medical accelerators. The successful development of a vanadium compensated, 6H-SiC extrinsic photoconductive switch for use as a closing switch for compact accelerator applications was realized by improvements made to the vanadium, nitrogen and boron impurity densities. The changes made to the impurity densities were based on the physical intuition outlined and simple rate equation models. The final 6H-SiC impurity 'recipe' calls for vanadium, nitrogen and boron densities of 2.5 e17 cm-3, 1.25e17 cm-3 and ≤ 1e16 cm-3, respectively. This recipe was originally developed to maximize the quantum efficiency of the vanadium compensated 6H-SiC, while maintaining a thermally stable semi-insulating material. The rate equation models indicate that, besides increasing the quantum efficiency, the impurity recipe should be expected to also increase the carrier recombination time. Three generations of 6H-SiC materials were tested. The

  7. High brightness laser-diode device emitting 160 watts from a 100 μm/NA 0.22 fiber.

    Science.gov (United States)

    Yu, Junhong; Guo, Linui; Wu, Hualing; Wang, Zhao; Tan, Hao; Gao, Songxin; Wu, Deyong; Zhang, Kai

    2015-11-10

    A practical method of achieving a high-brightness and high-power fiber-coupled laser-diode device is demonstrated both by experiment and ZEMAX software simulation, which is obtained by a beam transformation system, free-space beam combining, and polarization beam combining based on a mini-bar laser-diode chip. Using this method, fiber-coupled laser-diode module output power from the multimode fiber with 100 μm core diameter and 0.22 numerical aperture (NA) could reach 174 W, with equalizing brightness of 14.2  MW/(cm2·sr). By this method, much wider applications of fiber-coupled laser-diodes are anticipated. PMID:26560762

  8. Photonic Bandgap (PBG) Shielding Technology

    Science.gov (United States)

    Bastin, Gary L.

    2007-01-01

    Photonic Bandgap (PBG) shielding technology is a new approach to designing electromagnetic shielding materials for mitigating Electromagnetic Interference (EM!) with small, light-weight shielding materials. It focuses on ground planes of printed wiring boards (PWBs), rather than on components. Modem PSG materials also are emerging based on planar materials, in place of earlier, bulkier, 3-dimensional PBG structures. Planar PBG designs especially show great promise in mitigating and suppressing EMI and crosstalk for aerospace designs, such as needed for NASA's Constellation Program, for returning humans to the moon and for use by our first human visitors traveling to and from Mars. Photonic Bandgap (PBG) materials are also known as artificial dielectrics, meta-materials, and photonic crystals. General PBG materials are fundamentally periodic slow-wave structures in I, 2, or 3 dimensions. By adjusting the choice of structure periodicities in terms of size and recurring structure spacings, multiple scatterings of surface waves can be created that act as a forbidden energy gap (i.e., a range of frequencies) over which nominally-conductive metallic conductors cease to be a conductor and become dielectrics. Equivalently, PBG materials can be regarded as giving rise to forbidden energy gaps in metals without chemical doping, analogous to electron bandgap properties that previously gave rise to the modem semiconductor industry 60 years ago. Electromagnetic waves cannot propagate over bandgap regions that are created with PBG materials, that is, over frequencies for which a bandgap is artificially created through introducing periodic defects

  9. Phosphorene nanoribbons: Passivation effect on bandgap and effective mass

    International Nuclear Information System (INIS)

    Highlights: • Hydrogenation and fluorination can passivate the metallic edge states of zPNRs. • The bandgap of each type of zPNRs decreases as the ribbon's width increases duo to the quantum confinement effect. • Two local configurations of passivated atoms can coexist in nanoribbons and affect the bandgap of narrow nanoribbons. • New passivation configuration can effectively reduce the effective mass of electrons. - Abstract: The edge passivation effect of phosphorene nanoribbons is systematically investigated using density functional theory. Hydrogen and fluorine atoms passivate the metallic edge states of nanoribbons and can open a bandgap up to 2.25 eV. The two configurations of passivated atoms can exist at two edges and affect the bandgap of narrow nanoribbons. The bandgap of each type of zPNRs decreases as the ribbon's width increases, which can be attributed to the quantum confinement effect. The new configuration, named Cb, can effectively reduce the effective mass of electrons, which benefits the future design of phosphorene-based electronic devices

  10. Photonic bandgap structures

    CERN Document Server

    Marco, Pisco; Antonello, Cutolo

    2012-01-01

    This E-Book covers the research and the development of a novel generation of photonic devices for sensing applications. Key features of this book include a brief review of basic PhCs related design and fabrication concepts, a selection of crossover topics for the development of novel technological platforms for physical, chemical and biological sensing and a description of the main PhCs sensors to date by representing many of the exciting sensing applications that utilize photonic crystal structures.

  11. A surface plasmon resonance probe without optical fibers as a portable sensing device

    International Nuclear Information System (INIS)

    A surface plasmon resonance (SPR) sensor integrating a small sensor probe, a laser emission diode, a photo detector, and a polarizer was developed as a portable sensing device. The sensor probe was made with a glass cylinder, 50 mm long and 1.5 mm in diameter, that was connected directly to a beam splitter without optical fibers. The SPR spectrum obtained with this probe system showed a 10% reflectivity minimum at 690 nm. Shifts of the SPR spectrum induced by refractive index (RI) changes in the sample were measured by detecting the reflection light intensity at 670 nm. When the sensitivity was compared using a BIAcoreTM SPR instrument, the lowest sensor response of 1 mV observed with the SPR probe system coincided with 1.4 x 10-6 of the RI changes. The RI resolution of the SPR probe was estimated with experimentally evaluated noise on the signal, and, consequently, it was concluded that the RI resolution was 1.2 x 10-5. Moreover, immunoreaction was demonstrated with adsorbed bovine serum albumin (BSA) and anti-BSA antibody as an analyte. As a result, 50 ng mL-1 of the lower detection limit was estimated

  12. X-ray inspection using digital devices applied to space engines using carbon fiber case

    International Nuclear Information System (INIS)

    'Full-text:' The VEGA European small launcher of new generation is made of four stages of which the first three are solid propellant engines of advanced technology. The long experience reached in the solid propellant Field through Ariane 3, 4 and 5 programme, identified AVIO how the manufacturer of the 1st, 2nd and 3rd stage of the launcher. With the aim of minimizing launcher cost, a new technology using a low weight motor case made of carbon fiber has been developed. Other than process of fabrication also process of control are involved in the development of the new technology and, in considering the large size of the engines, the latter fall heavily on the manufacturing time and cost. In view of the reducing the recurrent cost of the launcher, AVIO is particularly interested in new technologies having the potentiality to reduce control costs. Among Non-Destructive Tests, the X-ray inspection is irreplaceable for its effectiveness, therefore improvements in X-ray imaging techniques aimed at decreasing control cost without any performance reduction, is a challenge that AVIO intends to pursue. From this point of view Digital Radiography offers good opportunity to which AVIO is looking to define the applicability to the case of interest. This paper shows the status of art and summarizes the results obtained through tests performed in collaboration with the main suppliers of digital devices working in industrial high energy X-ray NonDestructive Testing Field. (author)

  13. Monolithic femtosecond Yb-fiber laser with photonic crystal fibers

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Lægsgaard, Jesper; Turchinovich, Dmitry

    We demonstrate a monolithic stable SESAM-modelocked self-starting Yb-fiber laser. A novel PM all-solid photonic bandgap fiber is used for intra-cavity of dispersion management. The ex-cavity final pulse compression is performed in a spliced-on PM hollow-core photonic crystal fiber. The laser...

  14. Bandgap engineering of GaN nanowires

    Science.gov (United States)

    Ming, Bang-Ming; Wang, Ru-Zhi; Yam, Chi-Yung; Xu, Li-Chun; Lau, Woon-Ming; Yan, Hui

    2016-05-01

    Bandgap engineering has been a powerful technique for manipulating the electronic and optical properties of semiconductors. In this work, a systematic investigation of the electronic properties of [0001] GaN nanowires was carried out using the density functional based tight-binding method (DFTB). We studied the effects of geometric structure and uniaxial strain on the electronic properties of GaN nanowires with diameters ranging from 0.8 to 10 nm. Our results show that the band gap of GaN nanowires depends linearly on both the surface to volume ratio (S/V) and tensile strain. The band gap of GaN nanowires increases linearly with S/V, while it decreases linearly with increasing tensile strain. These linear relationships provide an effect way in designing GaN nanowires for their applications in novel nano-devices.

  15. Wide bandgap materials in future electronic applications

    International Nuclear Information System (INIS)

    A brief overview of the impact that wide bandgap materials have, and will have in the future, on the development of (micro)electronic devices, circuits, and systems is presented. It is held that electronic control systems and thus their applications fall into three temperature domains, delineated by the maximum use temperature of the semiconductor systems with which they are equipped: the current low temperature (- 100 to 200 oC) domain dominated by silicon; a medium temperature range (200 - ∼600oC), in which GaN and AlN provide the transition to SiC; and a high temperature domain (600-1300 oC) not yet covered by any one material system and in which research and development of c-BN based composites can at first, as passives, enhance performance in all three temperature/application ranges. Current developments in most application areas are cost-not performance-driven. (author)

  16. Towards mid-infrared fiber-optic devices and systems for sensing, mapping and imaging

    Science.gov (United States)

    Jayasuriya, D.; Wilson, B.; Furniss, D.; Tang, Z.; Barney, E.; Benson, T. M.; Seddon, A. B.

    2016-03-01

    Novel chalcogenide glass-based fiber opens up the mid-infrared (MIR) range for real-time monitoring and control in medical diagnostics and chemical processing. Fibers with long wavelength cut-off are of interest here. Sulfide, selenide and telluride based chalcogenide glass are candidates, but there are differences in their glass forming region, thermal stability and in the short and long wavelength cut-off positions. In general sulfide and selenide glasses have greater glass stability, but shorter long-wavelength cut-off edge, compared to telluride glasses; selenide-telluride glasses are a good compromise. Low optical loss selenide-telluride based long wavelength fibers could play a substantial role in improving medical diagnostic systems, chemical sensing, and processing, and in security and agriculture. For biological tissue, the molecular finger print lies between ~3-15 μm wavelengths in the MIR region. Using MIR spectral mapping, information about diseased tissue may be obtained with improved accuracy and in vivo using bright broadband MIR super-continuum generation (SCG) fiber sources and low optical loss fiber for routing. The Ge-As-Se-Te chalcogenide glass system is a potential candidate for both MIR SCG and passive-routing fiber, with good thermal stability, wide intrinsic transparency from ~1.5 to 20 μm and low phonon energy. This paper investigates Ge-As-Se-Te glass system pairs for developing high numerical aperture (NA) small-core, step-index optical fiber for MIR SCG and low NA passive step-index optical fiber for an in vivo fiber probe. Control of fiber geometry of small-core optical fiber and methods of producing the glass material are also included in this paper.

  17. Development of a thermodynamic control system for the Fontan circulation pulsation device using shape memory alloy fibers.

    Science.gov (United States)

    Yamada, Akihiro; Shiraishi, Yasuyuki; Miura, Hidekazu; Hashem, Hashem Mohamed Omran; Tsuboko, Yusuke; Yamagishi, Masaaki; Yambe, Tomoyuki

    2015-09-01

    The Fontan procedure is one of the common surgical treatments for circulatory reconstruction in pediatric patients with congenital heart disease. In Fontan circulation, low pulsatility may induce localized lung ischemia and may impair the development of pulmonary peripheral endothelial cells. To promote pulmonary circulation in Fontan circulation, we have been developing a pediatric pulmonary circulatory pulsation device using shape memory alloy fibers attached from the outside of total cavopulmonary connection. In this study, we developed a new thermal control system for the device and examined its functions. We mounted on the device 16 fibers connected in parallel around an ePTFE graft circumferentially. To provide optimized contraction, we designed the new thermal control system. The system consisted of a thermistor, a pressure sensor, and a regulator that was controlled by the adaptive thermodynamic transfer functions. We monitored the parameters and calculated heat transfer function as well as pressure distribution on the graft surface. Then we examined and compared the dynamic contractile pressure and changes in surface temperature. As a result, by the application of the control based on the new feedback system analysis, the circumferential contractile pressure increased by 35%. The adaptive thermodynamic regulation was useful for the selection of alternative thresholds of the surface temperature of the graft. The system could achieve effective contraction for the pulsatile flow generation by the device. PMID:25894077

  18. Wide Bandgap Extrinsic Photoconductive Switches

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, James S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2013-07-03

    Semi-insulating Gallium Nitride, 4H and 6H Silicon Carbide are attractive materials for compact, high voltage, extrinsic, photoconductive switches due to their wide bandgap, high dark resistance, high critical electric field strength and high electron saturation velocity. These wide bandgap semiconductors are made semi-insulating by the addition of vanadium (4H and 6HSiC) and iron (2H-GaN) impurities that form deep acceptors. These deep acceptors trap electrons donated from shallow donor impurities. The electrons can be optically excited from these deep acceptor levels into the conduction band to transition the wide bandgap semiconductor materials from a semi-insulating to a conducting state. Extrinsic photoconductive switches with opposing electrodes have been constructed using vanadium compensated 6H-SiC and iron compensated 2H-GaN. These extrinsic photoconductive switches were tested at high voltage and high power to determine if they could be successfully used as the closing switch in compact medical accelerators.

  19. Design and Fabrication of Calibration Device for Scintillating Fibers of Tagger Microscope: For use in GlueX's QCD Experiment

    Science.gov (United States)

    Briere, Emily

    2012-10-01

    For decades, scientists have struggled to understand the chromo-electromagnetic field which confines quarks and gluons within the hadron. GlueX is a QCD experiment centered at Jefferson Lab, Virginia, seeking to better understand this gluonic field by exciting it and mapping the spectrum of exotic hybrid mesons that it generates. The experiment uses coherent bremsstrahlung radiation to produce a beam of photons, which due to their polarity act as virtual vector mesons. When incident on a liquid hydrogen target, these mesons are expected to form exotic hybrid mesons. Such particles quickly decay into new particles which are captured in a solenoid detector. The decays can then be reconstructed to examine the properties of the original exotic hybrid meson, although the initial energy of the photon is required to draw meaningful conclusions. The post-bremsstrahlung degraded electrons are bent from the main beam into the tagger microscope where they strike an array of scintillating optical fibers. Given the correlation between momentum and radial bend, the Silicon Photmultiplier sensors attached to the optical fibers are able to ``tag'' the electrons', and thus the photons', initial energies based on which fibers were hit. Providing central data for GlueX, the tagger microscope must be accurate. This paper details the design and fabrication of a scintillating fiber calibration device that moves horizontally above fiber bundles, using a green laser diode to direct light pulses into the fibers. This calibration method has been tested mechanically and via a Monte Carlo Matlab simulation, and has proven to be effective.

  20. Fiber

    Science.gov (United States)

    ... a fiber-rich sandwich with whole-grain bread, peanut butter, and bananas. Use whole-grain spaghetti and other ... cookies and muffins. Top whole-wheat crackers with peanut butter or low-fat cheese. Go easy on the ...

  1. New Light-Harvesting Materials Using Accurate and Efficient Bandgap Calculations

    DEFF Research Database (Denmark)

    Castelli, Ivano Eligio; Hüser, Falco; Pandey, Mohnish;

    2014-01-01

    materials for different applications where the bandgaps are used as descriptors for the efficiency of a photoelectrochemical device. Here, new light harvesting materials are proposed to be used in a one-photon photoelectrochemical device for water splitting by combining the estimation of the bandgaps with......Electronic bandgap calculations are presented for 2400 experimentally known materials from the Materials Project database and the bandgaps, obtained with different types of functionals within density functional theory and (partial) self-consistent GW approximation, are compared for 20 randomly...... chosen compounds forming an unconventional set of ternary and quaternary materials. It is shown that the computationally cheap GLLB-SC potential gives results in good agreement (around 15%) with the more advanced and demanding eigenvalue-self-consistent GW. This allows for a high-throughput screening of...

  2. Printable, wide band-gap chalcopyrite thin films for power generating window applications

    OpenAIRE

    Sung Hwan Moon; Se Jin Park; Yun Jeong Hwang; Doh-Kwon Lee; Yunae Cho; Dong-Wook Kim; Byoung Koun Min

    2014-01-01

    Printable, wide band-gap chalcopyrite compound films (CuInGaS2, CIGS) were synthesized on transparent conducting oxide substrates. The wide band-gap and defective nature of the films reveal semi-transparent and bifacial properties that are beneficial for power generating window applications. Importantly, solar cell devices with these films demonstrate a synergistic effect for bifacial illumination resulting in a 5.4–16.3% increase of the apparent power conversion efficiency compared to the si...

  3. Effects of sterilization methods on key properties of specialty optical fibers used in medical devices

    Science.gov (United States)

    Stolov, Andrei A.; Slyman, Brian E.; Burgess, David T.; Hokansson, Adam S.; Li, Jie; Allen, R. Steve

    2013-03-01

    Optical fibers with different types of polymer coatings were exposed to three sterilization conditions: multiple autoclaving, treatment with ethylene oxide and treatment with gamma rays. Effects of different sterilization techniques on key optical and mechanical properties of the fibers are reported. The primary attention is given to behavior of the coatings in harsh sterilization environments. The following four coating/buffer types were investigated: (i) dual acrylate, (ii) polyimide, (iii) silicone/PEEK and (iv) fluoroacrylate hard cladding/ETFE.

  4. Simultaneous detection of liquid level and refractive index with a long-period fiber grating based sensor device

    International Nuclear Information System (INIS)

    In this study, a long-period fiber grating (LPFG)-based optical fiber sensor device is proposed for simultaneous detection of liquid level and refractive index (RI). When part of the grating was submerged in an unknown liquid, the resonant wavelength of each cladding mode of the LPFG sensor varied linearly with the submerged length and nonlinearly with the RI of the liquid. By retaining the first-order (sensitivity) and second-order (cross sensitivity) terms of a Taylor expansion of the nonlinear relation, the changes in submerged length (or liquid level) and RI can be simultaneously evaluated from the changes in resonant wavelength of two cladding modes. The sensitivity coefficients to liquid level, RI, their cross effect and environmental effects were studied both analytically and experimentally. The maximum prediction error by the proposed evaluation algorithm was found to be 1 mm for liquid level and 0.005 for RI. (paper)

  5. A low-cost, manufacturable method for fabricating capillary and optical fiber interconnects for microfluidic devices.

    Science.gov (United States)

    Hartmann, Daniel M; Nevill, J Tanner; Pettigrew, Kenneth I; Votaw, Gregory; Kung, Pang-Jen; Crenshaw, Hugh C

    2008-04-01

    Microfluidic chips require connections to larger macroscopic components, such as light sources, light detectors, and reagent reservoirs. In this article, we present novel methods for integrating capillaries, optical fibers, and wires with the channels of microfluidic chips. The method consists of forming planar interconnect channels in microfluidic chips and inserting capillaries, optical fibers, or wires into these channels. UV light is manually directed onto the ends of the interconnects using a microscope. UV-curable glue is then allowed to wick to the end of the capillaries, fibers, or wires, where it is cured to form rigid, liquid-tight connections. In a variant of this technique, used with light-guiding capillaries and optical fibers, the UV light is directed into the capillaries or fibers, and the UV-glue is cured by the cone of light emerging from the end of each capillary or fiber. This technique is fully self-aligned, greatly improves both the quality and the manufacturability of the interconnects, and has the potential to enable the fabrication of interconnects in a fully automated fashion. Using these methods, including a semi-automated implementation of the second technique, over 10,000 interconnects have been formed in almost 2000 microfluidic chips made of a variety of rigid materials. The resulting interconnects withstand pressures up to at least 800psi, have unswept volumes estimated to be less than 10 femtoliters, and have dead volumes defined only by the length of the capillary. PMID:18369517

  6. Production of continuous piezoelectric ceramic fibers for smart materials and active control devices

    Science.gov (United States)

    French, Jonathan D.; Weitz, Gregory E.; Luke, John E.; Cass, Richard B.; Jadidian, Bahram; Bhargava, Parag; Safari, Ahmad

    1997-05-01

    Advanced Cerametrics Inc. has conceived of and developed the Viscous-Suspension-Spinning Process (VSSP) to produce continuous fine filaments of nearly any powdered ceramic materials. VSSP lead zirconate titanate (PZT) fiber tows with 100 and 790 filaments have been spun in continuous lengths exceeding 1700 meters. Sintered PZT filaments typically are 10 - 25 microns in diameter and have moderate flexibility. Prior to carrier burnout and sintering, VSSP PZT fibers can be formed into 2D and 3D shapes using conventional textile and composite forming processes. While the extension of PZT is on the order of 20 microns per linear inch, a woven, wound or braided structure can contain very long lengths of PZT fiber and generate comparatively large output strokes from relatively small volumes. These structures are intended for applications such as bipolar actuators for fiber optic assembly and repair, vibration and noise damping for aircraft, rotorcraft, automobiles and home applications, vibration generators and ultrasonic transducers for medical and industrial imaging. Fiber and component cost savings over current technologies, such as the `dice-and-fill' method for transducer production, and the range of unique structures possible with continuous VSSP PZT fiber are discussed. Recent results have yielded 1-3 type composites (25 vol% PZT) with d33 equals 340 pC/N, K equals 470, and g33 equals 80 mV/N, kt equals 0.54, kp equals 0.19, dh equals 50.1pC/N and gh equals 13 mV/N.

  7. Ultrahigh photoconductivity of bandgap-graded CdSxSe1‑x nanowires probed by terahertz spectroscopy

    Science.gov (United States)

    Liu, Hongwei; Lu, Junpeng; Yang, Zongyin; Teng, Jinghua; Ke, Lin; Zhang, Xinhai; Tong, Limin; Sow, Chorng Haur

    2016-06-01

    Superiorly high photoconductivity is desirable in optoelectronic materials and devices for information transmission and processing. Achieving high photoconductivity via bandgap engineering in a bandgap-graded semiconductor nanowire has been proposed as a potential strategy. In this work, we report the ultrahigh photoconductivity of bandgap-graded CdSxSe1‑x nanowires and its detailed analysis by means of ultrafast optical-pump terahertz-probe (OPTP) spectroscopy. The recombination rates and carrier mobility are quantitatively obtained via investigation of the transient carrier dynamics in the nanowires. By analysis of the terahertz (THz) spectra, we obtain an insight into the bandgap gradient and band alignment to carrier transport along the nanowires. The demonstration of the ultrahigh photoconductivity makes bandgap-graded CdSxSe1‑x nanowires a promising candidate as building blocks for nanoscale electronic and photonic devices.

  8. Development of Spintronic Bandgap Materials

    Energy Technology Data Exchange (ETDEWEB)

    Levy, Jeremy; Awschalom, David; Floro, Jerrold

    2014-02-16

    The development of Ge/Si quantum dots with high spatial precision has been pursued, with the goal of developing a platform for “spintronics bandgap materials”. Quantum dots assemblies were grown by molecular beam epitaxy on carbon-templated silicon substrates. These structures were characterized by atomic force microscopy. Vertically gated structures were created on systems with up to six well-defined quantum dots with a controlled geometric arrangement, and low-temperature (mK) transport experiments were performed. These experiments showed evidence for a crossover from diamagnetic to Zeeman energy shifts in resonant tunneling of electrons through electronic states in the quantum dots.

  9. Surface state photonic bandgap cavities

    OpenAIRE

    Rahachou, A. I.; Zozoulenko, I. V.

    2005-01-01

    We propose and analyze a new type of a resonant high-Q cavity for lasing, sensing or filtering applications, which is based on a surface states of a finite photonic crystal. We demonstrate that such the cavity can have a Q factor comparable with that one of conventional photonic band-gap defect mode cavities. At the same time, the distinguished feature of the surface mode cavity is that it is situated directly at the surface of the photonic crystal. This might open up new possibilities for de...

  10. Optimal design of tunable phononic bandgap plates under equibiaxial stretch

    Science.gov (United States)

    Hedayatrasa, Saeid; Abhary, Kazem; Uddin, M. S.; Guest, James K.

    2016-05-01

    Design and application of phononic crystal (PhCr) acoustic metamaterials has been a topic with tremendous growth of interest in the last decade due to their promising capabilities to manipulate acoustic and elastodynamic waves. Phononic controllability of waves through a particular PhCr is limited only to the spectrums located within its fixed bandgap frequency. Hence the ability to tune a PhCr is desired to add functionality over its variable bandgap frequency or for switchability. Deformation induced bandgap tunability of elastomeric PhCr solids and plates with prescribed topology have been studied by other researchers. Principally the internal stress state and distorted geometry of a deformed phononic crystal plate (PhP) changes its effective stiffness and leads to deformation induced tunability of resultant modal band structure. Thus the microstructural topology of a PhP can be altered so that specific tunability features are met through prescribed deformation. In the present study novel tunable PhPs of this kind with optimized bandgap efficiency-tunability of guided waves are computationally explored and evaluated. Low loss transmission of guided waves throughout thin walled structures makes them ideal for fabrication of low loss ultrasound devices and structural health monitoring purposes. Various tunability targets are defined to enhance or degrade complete bandgaps of plate waves through macroscopic tensile deformation. Elastomeric hyperelastic material is considered which enables recoverable micromechanical deformation under tuning finite stretch. Phononic tunability through stable deformation of phononic lattice is specifically required and so any topology showing buckling instability under assumed deformation is disregarded. Nondominated sorting genetic algorithm (GA) NSGA-II is adopted for evolutionary multiobjective topology optimization of hypothesized tunable PhP with square symmetric unit-cell and relevant topologies are analyzed through finite

  11. Phase Conjugated and Transparent Wavelength Conversions of Nyquist 16-QAM Signals Employing a Single-Layer Graphene Coated Fiber Device

    Science.gov (United States)

    Hu, Xiao; Zeng, Mengqi; Long, Yun; Liu, Jun; Zhu, Yixiao; Zou, Kaiheng; Zhang, Fan; Fu, Lei; Wang, Jian

    2016-01-01

    We fabricate a nonlinear optical device based on a fiber pigtail cross-section coated with a single-layer graphene grown by chemical vapor deposition (CVD) method. Using the fabricated graphene-assisted nonlinear optical device and employing Nyquist 16-ary quadrature amplitude modulation (16-QAM) signal, we experimentally demonstrate phase conjugated wavelength conversion by degenerate four-wave mixing (FWM) and transparent wavelength conversion by non-degenerate FWM in graphene. We study the conversion efficiency as functions of the pump power and pump wavelength and evaluate the bit-error rate (BER) performance. We also compare the time-varying symbol sequence for graphene-assisted phase conjugated and transparent wavelength conversions of Nyquist 16-QAM signal. PMID:26932470

  12. Study of lineal and non-lineal transmission of an optical fiber Sagnac interferometer as a bidirectional device

    International Nuclear Information System (INIS)

    The optical fiber Sagnac interferometer is a versatile system that has been investigated for a variety of applications such as optical switchers, filters, demultiplexers and passive mode-locked laser. In many cases, this arrangement is designed using a symmetrical coupler with two of their ports connected making a loop and generally the analysis have been focused in the transmission of the signal propagated in only one direction. Therefore in the present work a complementary study of the system considering the analysis for the lineal and non-lineal transmission as a bidirectional device has been performed. The experimental setup consists of different optical fiber lengths inside the cavity loop (between 100 and 500 m) with highly twisted singlemode fiber, a quarter wave retarder placed asymmetrically in one arm and a 50/50 coupler. The results have shown that for low optical powers, it is possible to adjust the system transmission in both propagation directions with the rotation of the retarder wave. On the other hand, in high optical power levels, this arrangement showed that the transmission increases slowly for the case when both the input and the output beams have the same polarization. This behavior can be used for pedestal suppression in a light pulse. Furthermore, for the case when the output signal polarization is orthogonal respect to the input one, the transmission changes quite fast. This effect can be used for applications such as the passive mode-locking.

  13. Study of lineal and non-lineal transmission of an optical fiber Sagnac interferometer as a bidirectional device

    Energy Technology Data Exchange (ETDEWEB)

    Ramos-Beltran, J [Benemerita Universidad Autonoma de Puebla, Facultad de Ciencias de la Electronica (Mexico); Beltran-Perez, G; Castillo-Mixcoatl, J; Munoz-Aguirre, S [Benemerita Universidad Autonoma de Puebla, Facultad de Ciencias Fisco-Matematicas (Mexico); Zaca-Moran, P [Benemerita Universidad Autonoma de Puebla, Fisicoquimica de Materiales, ICUAP (Mexico); Felipe, C, E-mail: squall_rb@hotmail.com [Departamento de biociencias e ingenieria, CIIEMAD, Instituto Politecnico Nacional (Mexico)

    2011-01-01

    The optical fiber Sagnac interferometer is a versatile system that has been investigated for a variety of applications such as optical switchers, filters, demultiplexers and passive mode-locked laser. In many cases, this arrangement is designed using a symmetrical coupler with two of their ports connected making a loop and generally the analysis have been focused in the transmission of the signal propagated in only one direction. Therefore in the present work a complementary study of the system considering the analysis for the lineal and non-lineal transmission as a bidirectional device has been performed. The experimental setup consists of different optical fiber lengths inside the cavity loop (between 100 and 500 m) with highly twisted singlemode fiber, a quarter wave retarder placed asymmetrically in one arm and a 50/50 coupler. The results have shown that for low optical powers, it is possible to adjust the system transmission in both propagation directions with the rotation of the retarder wave. On the other hand, in high optical power levels, this arrangement showed that the transmission increases slowly for the case when both the input and the output beams have the same polarization. This behavior can be used for pedestal suppression in a light pulse. Furthermore, for the case when the output signal polarization is orthogonal respect to the input one, the transmission changes quite fast. This effect can be used for applications such as the passive mode-locking.

  14. Platform for enhanced light-graphene interaction length and miniaturizing fiber stereo-devices

    OpenAIRE

    Xu, Fei; Kou, Jun-Long; Chen, Jin-Hui; Chen, Ye; Lu, Yan-Qing

    2014-01-01

    Sufficient light-matter interactions are important for waveguide-coupled graphene optoelectronic devices. Using a microfiber-based lab-on-a-rod technique, we present a platform for ultra-long light-graphene interaction and design graphene-integrated helical microfiber (MF) devices. Using this approach, we experimentally demonstrate an in-line stereo polarizer by wrapping an MF on a rod pretreated with a graphene sheet. The device operates as a broadband (450 nm wavelength) polarizer capable o...

  15. THz waveguides, devices and hybrid polymer-chalcogenide photonic crystal fibers

    DEFF Research Database (Denmark)

    Bao, Hualong; Markos, Christos; Nielsen, Kristian; Rasmussen, Henrik K.; Jepsen, Peter Uhd; Bang, Ole

    In this contribution, we review our recent activities in the design, fabrication and characterization of polymer THz waveguides. Besides the THz waveguides, we finally will also briefly show some of our initial results on a novel hybrid polymer photonic crystal fiber with integrated chalcogenide ...

  16. Eat-by-light: fiber-optic and micro-optic devices for food safety and quality assessment

    Science.gov (United States)

    Mignani, A. G.; Ciaccheri, L.; Cucci, C.; Mencaglia, A. A.; Cimato, A.; Attilio, C.; Thienpont, H.; Ottevaere, H.; Paolesse, R.; Mastroianni, M.; Monti, D.; Buonocore, G.; Del Nobile, A.; Mentana, A.; Dall'Asta, C.; Faccini, A.; Galaverna, G.; Dossena, A.

    2007-07-01

    A selection of fiber-optic and micro-optic devices is presented designed and tested for monitoring the quality and safety of typical foods, namely the extra virgin olive oil, the beer, and the milk. Scattered colorimetry is used for the authentication of various types of extra virgin olive oil and beer, while a fiber-optic-based device for UV-VIS-NIR absorption spectroscopy is exploited in order to obtain the hyperspectral optical signature of olive oil. This is done not only for authentication purposes, but also so as to correlate the spectral data with the content of fatty acids that are important nutritional factors. A micro-optic sensor for the detection of olive oil aroma is presented. It is capable of distinguishing different ageing levels of extra virgin olive oil. It shows effective potential for acting as a smart cap of bottled olive oil in order to achieve a non-destructive olfactory perception of oil ageing. Lastly, a compact portable fluorometer is experimented for the rapid monitoring of the carcinogenic M1 aflatoxin in milk.

  17. Eat-by-light fiber-optic and micro-optic devices for food quality and safety assessment

    Science.gov (United States)

    Mignani, A. G.; Ciaccheri, L.; Cucci, C.; Mencaglia, A. A.; Cimato, A.; Attilio, C.; Thienpont, H.; Ottevaere, H.; Paolesse, R.; Mastroianni, M.; Monti, D.; Buonocore, G.; Del Nobile, A.; Mentana, A.; Grimaldi, M. F.; Dall'Asta, C.; Faccini, A.; Galaverna, G.; Dossena, A.

    2007-06-01

    A selection is presented of fiber-optic and micro-optic devices that have been designed and tested for guaranteeing the quality and safety of typical foods, such as extra virgin olive oil, beer, and milk. Scattered colorimetry is used to authenticate various types of extra virgin olive oil and beer, while a fiber-optic-based device for UV-VIS-NIR absorption spectroscopy is exploited in order to obtain the hyperspectral optical signature of olive oil. This is done not only for authentication purposes, but also so as to correlate the spectral data with the content of fatty acids, which are important nutritional factors. A micro-optic sensor for the detection of olive oil aroma that is capable of distinguishing different ageing levels of extra virgin olive oil is also presented. It shows effective potential for acting as a smart cap of bottled olive oil in order to achieve a non-destructive olfactory perception of oil ageing. Lastly, a compact portable fluorometer for the rapid monitoring of the carcinogenic M1 aflatoxin in milk, is experimented.

  18. Comprehensive study of an optical fiber plasmonic microsensor in a microfluidic device

    OpenAIRE

    2011-01-01

    Abstract In the last decade, surface plasmon resonance (SPR) has become a very sensitive technique for real-time detection of chemical and biochemical targets in many application areas. Considering the important needs for analyzing biomolecular reactions through automated and miniaturized components, optical fiber sensors based on the SPR effects are presently considered as an alternative in the development of microsensors. In the present work, a microfluidic system associated with...

  19. Comprehensive study of an optical fiber plasmonic microsensor in a microfluidic device

    OpenAIRE

    Makiabadi, T.; Le Nader, V.; Kanso, M.; Louarn, G.

    2011-01-01

    International audience In the last decade, surface plasmon resonance (SPR) has become a very sensitive technique for real-time detection of chemical and biochemical targets in many application areas. Considering the important needs for analyzing biomolecular reactions through automated and miniaturized components, optical fiber sensors based on the SPR effects are presently considered as an alternative in the development of microsensors. In the present work, a microfluidic system associate...

  20. Method and device for detecting impact events on a security barrier which includes a hollow rebar allowing insertion and removal of an optical fiber

    Science.gov (United States)

    Pies, Ross E.

    2016-03-29

    A method and device for the detection of impact events on a security barrier. A hollow rebar is farmed within a security barrier, whereby the hollow rebar is completely surrounded by the security barrier. An optical fiber passes through the interior of the hollow rebar. An optical transmitter and an optical receiver are both optically connected to the optical fiber and connected to optical electronics. The optical electronics are configured to provide notification upon the detection of an impact event at the security barrier based on the detection of disturbances within the optical fiber.

  1. Optical Deposition of Carbon Nanotubes for Fiber-based Device Fabrication

    OpenAIRE

    Kashiwagi, Ken; Yamashita, Shinji

    2010-01-01

    In this chapter, we have proposed and demonstrated the optical deposition method of CNTs. After brief introduction of this chapter (section 1), we explained the general characteristics, optical properties, and optical devices based on CNTs in section 2. From

  2. ZnMgO by APCVD Enabling High-Performance Mid-bandgap CIGS on Polyimide Modules: October 2009--October 2010

    Energy Technology Data Exchange (ETDEWEB)

    Woods, L.

    2011-04-01

    This Pre-Incubator project was designed to increase the 'real world' CIGS based photovoltaic module performance and decrease the Levelized Cost of Energy (LCOE) of systems utilizing those modules compared to our traditional CIGS based photovoltaic modules. This was enabled by a) increasing the CIGS bandgap and b) developing better matched device finishing layers to the mid-bandgap CIGS based photovoltaics; including window and buffer layers (and eventually the TCO). Incremental progress in the novel device performance was demonstrated throughout the program, and ultimately achieved performance results that exceeded the milestones ahead of schedule. Metal-oxide buffer layer devices with mid-bandgap CIGS alloys on polyimide substrates were produced with efficiencies of over 12%. Corresponding mid-bandgap devices with CdS buffers produced over 13% efficient devices. Furthermore, no obvious degradation in the device performance has been observed to date, after proper storage ambient of the different types of unencapsulated devices were identified.

  3. Single mode optical fiber based devices and systems for mid-infrared light generation, communication and metrology

    Science.gov (United States)

    Kulkarni, Ojas P.

    Fiber-optic systems and devices for broadband mid-infrared light generation, communication and optical metrology are developed in this thesis. Using the nonlinear properties of low mid-infrared loss ZrF4-BaF 2-LaF3-AlF3-NaF (ZBLAN) fiber, a mid-infrared supercontinuum (SC) laser based on a thulium-doped fiber amplifier (TDFA) with spectrum extending from ˜1.9-4.5 microm is demonstrated. A higher efficiency, power-scalable, all-fiber integrated mid-infrared light source is realized capable of generating ˜0.7 W time-average power in wavelengths beyond 3.8 microm. The novelty of the laser lies in its two-step spectral shifting architecture. First, amplified laser diode pulses at 1.55 microm are used to generate a SC extending beyond 2 microm in standard SMF using modulation-instability initiated pulse break-up. A TDFA stage is then used to amplify the ˜2 microm components in the standard SMF continuum. By subsequently coupling the amplified ˜2 microm pulses in to a ZBLAN fiber, an SC with up to ˜2.6 W average power, and ˜9% optical conversion efficiency from the power-amp pump to mid-IR output is demonstrated. The two-step methodology leads to extension in the long wavelength edge of the SC from 4.2 microm to ˜4.5 microm, compared to previously demonstrated systems and ˜2.5 times higher optical efficiency in generating wavelengths beyond 3.8 microm. Numerical simulations are also presented based on solving the generalized non-linear Schrodinger equation to verify and extend experimental results. A broadband surface-normal optical modulator for communication applications with operation demonstrated over 1200--2400 nm is also presented. The modulator uses free-carrier effect in GaAs and mode selectivity of SMF to generate up to ˜43% modulation depth with a maximum operating speed of ˜270 MHz. The broad wavelength range of operation of the modulator can potentially enable higher throughput wavelength-division multiplexed optical network architectures based on

  4. Bandgap tunability at single-layer molybdenum disulphide grain boundaries

    KAUST Repository

    Huang, Yu Li

    2015-02-17

    Two-dimensional transition metal dichalcogenides have emerged as a new class of semiconductor materials with novel electronic and optical properties of interest to future nanoelectronics technology. Single-layer molybdenum disulphide, which represents a prototype two-dimensional transition metal dichalcogenide, has an electronic bandgap that increases with decreasing layer thickness. Using high-resolution scanning tunnelling microscopy and spectroscopy, we measure the apparent quasiparticle energy gap to be 2.40±0.05 eV for single-layer, 2.10±0.05 eV for bilayer and 1.75±0.05 eV for trilayer molybdenum disulphide, which were directly grown on a graphite substrate by chemical vapour deposition method. More interestingly, we report an unexpected bandgap tunability (as large as 0.85±0.05 eV) with distance from the grain boundary in single-layer molybdenum disulphide, which also depends on the grain misorientation angle. This work opens up new possibilities for flexible electronic and optoelectronic devices with tunable bandgaps that utilize both the control of two-dimensional layer thickness and the grain boundary engineering.

  5. Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes

    Science.gov (United States)

    Comfort, Everett; Lee, Ji Ung

    2016-06-01

    The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range.

  6. Materials Research Society Symposium Proceedings. Volume 339: Diamond, SiC and nitride wide bandgap semiconductors

    Science.gov (United States)

    Carter, Calvin H.; Gildenblat, Gennady; Nakamura, Shuji; Nemanich, Robert J.

    1994-04-01

    This symposium was directed toward the potential of using diamond, SiC, and nitride wide bandgap semiconductors. The symposium emphasized materials issues related to the semiconducting properties of these wide bandgap materials. Both experimental and theoretical studies were presented. Solid advances were reported in the growth techniques of all three materials groups. Contributions demonstrated the critical importance of surfaces, interfaces, doping, defects, and impurities Reports demonstrated potential device applications ranging from unique electronic devices to blue/UV light emitters/detectors and even novel structures employing a negative electron affinity. The overall theme of the symposium was that materials research into wide bandgap semiconductors will make available exciting new applications, and that we are just beginning to understand the potential of these materials.

  7. Tuning the hybridization bandgap by meta-molecules with in-unit interaction

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yongqiang; Li, Yunhui, E-mail: liyunhui@tongji.edu.cn; Wu, Qian; Jiang, Haitao; Zhang, Yewen; Chen, Hong [Key Laboratory of Advanced Micro-Structured Materials, Ministry of Education, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China)

    2015-09-07

    In this paper, we demonstrate that the hybridization bandgap (HBG) can be tuned conveniently by deep subwavelength meta-molecules with in-unit interaction. Spontaneous-emission-cancellation-like (SEC-like) effect is realized in a meta-molecule by introducing the destructive interference of two detuned meta-atoms. The meta-atoms consisting of subwavelength zero-index-metamaterial-based resonators are side-coupled to a microstrip. Compared to conventional HBG configurations, the presence of in-unit interaction between meta-atoms provides more flexibility in tuning the bandgap properties, keeping the device volume almost unchanged. Both numerical simulations and microwave experiments confirm that the width, depth, and spectrum shape of HBG can be tuned by simply introducing SEC-like interaction into the meta-molecule. Due to these features, our design may be promising to be applied in microwave or optics communications systems with strict limitation of device volume and flexible bandgap properties.

  8. Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes.

    Science.gov (United States)

    Comfort, Everett; Lee, Ji Ung

    2016-01-01

    The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range. PMID:27339272

  9. Colloidal Bandpass and Bandgap Filters

    Science.gov (United States)

    Yellen, Benjamin; Tahir, Mukarram; Ouyang, Yuyu; Nori, Franco

    2013-03-01

    Thermally or deterministically-driven transport of objects through asymmetric potential energy landscapes (ratchet-based motion) is of considerable interest as models for biological transport and as methods for controlling the flow of information, material, and energy. Here, we provide a general framework for implementing a colloidal bandpass filter, in which particles of a specific size range can be selectively transported through a periodic lattice, whereas larger or smaller particles are dynamically trapped in closed-orbits. Our approach is based on quasi-static (adiabatic) transition in a tunable potential energy landscape composed of a multi-frequency magnetic field input signal with the static field of a spatially-periodic magnetization. By tuning the phase shifts between the input signal and the relative forcing coefficients, large-sized particles may experience no local energy barriers, medium-sized particles experience only one local energy barrier, and small-sized particles experience two local energy barriers. The odd symmetry present in this system can be used to nudge the medium-sized particles along an open pathway, whereas the large or small beads remain trapped in a closed-orbit, leading to a bandpass filter, and vice versa for a bandgap filter. NSF CMMI - 0800173, Youth 100 Scholars Fund

  10. Wide Bandgap Nanostructured Space Photovoltaics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Firefly, in collaboration with Rochester Institute of Technology, proposes an STTR program for the development of a wide-bandgap GaP-based space solar cell capable...

  11. Tuning the Bandgap of a Ternary Semiconductor

    OpenAIRE

    2005-01-01

    This interactive tutorial covers the following: The relationship between bandgap energy and the long wavelength cut-off of a detector response., The changes expected in long wavelength cut-off in response to changes in alloy composition and operating temperature.The interactions in this tutorial involve students using sliding scales to change the values of alloy composition, bandgap energy, cut-off wavelength, temperature, and intrinsic carrier concentration, and make observations of correspo...

  12. Advanced devices based on fibers, integrated optics and liquid crystals for WDM networks

    OpenAIRE

    Contreras Lallana, Pedro

    2011-01-01

    The increment of bandwidth required for new services offered to users make necessary the use of optical fibres in data transmission. Glass optical fibres are widely used in long distance communications, and there are many devices implemented for using in these networks, but these technologies are sometimes expensive for their used in local loops. Different systems implemented over the established technology are used for increasing local loops bandwidth, but more services are demanded at home....

  13. A device for uranium series leaching from glass fiber in HEPA filter

    International Nuclear Information System (INIS)

    For the disposal of a high efficiency particulate air (HEPA) glass filter into the environment, the glass fiber should be leached to lower its radioactive concentration to the clearance level. To derive an optimum method for the removal of uranium series from a HEPA glass fiber, five methods were applied in this study. That is, chemical leaching by a 4.0 M HNO3-0.1 M Ce(IV) solution, chemical leaching by a 5 wt% NaOH solution, chemical leaching by a 0.5 M H2O2-1.0 M Na2CO3 solution, chemical consecutive chemical leaching by a 4.0 M HNO3 solution, and repeated chemical leaching by a 4.0 M HNO3 solution were used to remove the uranium series. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after leaching for 5 h by the 4.0 M HNO3-0.1 M Ce(IV) solution were 2.1, 0.3, 1.1, and 1.2 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after leaching for 36 h by 4.0 M HNO3-0.1 M Ce(IV) solution were 76.9, 3.4, 63.7, and 71.9 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after leaching for 8 h by a 0.5 M H2O2-1.0 M Na2CO3 solution were 8.9, 0.0, 1.91, and 6.4 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after consecutive leaching for 8 h by the 4.0 M HNO3 solution were 2.08, 0.12, 1.55, and 2.0 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after three repetitions of leaching for 3 h by the 4.0 M HNO3 solution were 0.02, 0.02, 0.29, and 0.26 Bq/g. Meanwhile, the removal efficiencies of 238U, 235U, 226Ra, and 234Th from the waste solution after its precipitation-filtration treatment with NaOH and alum for reuse of the 4.0 M HNO3 waste solution were 100, 100, 93.3, and 100%. (author)

  14. Towards in vivo laser coagulation and concurrent optical coherence tomography through double-clad fiber devices

    Science.gov (United States)

    Beaudette, Kathy; Lo, William; Villiger, Martin; Shishkov, Milen; Godbout, Nicolas; Bouma, Brett E.; Boudoux, Caroline

    2016-03-01

    There is a strong clinical need for an optical coherence tomography (OCT) system capable of delivering concurrent coagulation light enabling image-guided dynamic laser marking for targeted collection of biopsies, as opposed to a random sampling, to reduce false-negative findings. Here, we present a system based on double-clad fiber (DCF) capable of delivering pulsed laser light through the inner cladding while performing OCT through the core. A previously clinically validated commercial OCT system (NVisionVLE, Ninepoint Medical) was adapted to enable in vivo esophageal image-guided dynamic laser marking. An optimized DCF coupler was implemented into the system to couple both modalities into the DCF. A DCF-based rotary joint was used to couple light to the spinning DCF-based catheter for helical scanning. DCF-based OCT catheters, providing a beam waist diameter of 62μm at a working distance of 9.3mm, for use with a 17-mm diameter balloon sheath, were used for ex vivo imaging of a swine esophagus. Imaging results using the DCF-based clinical system show an image quality comparable with a conventional system with minimal crosstalk-induced artifacts. To further optimize DCF catheter optical design in order to achieve single-pulse marking, a Zemax model of the DCF output and its validation are presented.

  15. A Device for Uranium series Leaching from Glass Fiber in HEPA Filter

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Gye Nam; Lee, Suk Chol; Yang, Hee Chul; Yoon, In Ho; Choi, Wang Kyu; Lee, Kune Woo; Moon, Jei Kwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-10-15

    A great amount of radioactive waste has been generated during the operation of nuclear facilities. Recently, the storage space of a radioactive waste storage facility in the Korea Atomic Energy Research Institute (KAERI) was almost saturated with many radioactive wastes. To derive an optimum method for the removal of uranium series from HEPA glass fiber, five methods were applied in this study. That is, chemical leaching by 4.0 M HNO{sub 3}-0.1M Ce(IV) solution, chemical leaching by 5 wt% NaOH solution, chemical leaching by 0.5M H{sub 2}O{sub 2}-1.0M Na{sub 2}CO{sub 3} solution, chemical consecutive leaching by 4.0 M HNO{sub 3} solution, and chemical repeated leaching by 4.0 M HNO{sub 3} solution were used to remove uranium series. Also, in order to reuse the leaching waste-solution contaminated with {sup 238}U, {sup 235}U, {sup 226}Ra, and {sup 234}Th, the precipitation-filtration experiment was carried out with NaOH and alum as precipitants

  16. 0.6-eV bandgap In0.69Ga0.31As thermophotovoltaic devices with compositionally undulating step-graded InAsyP1−ybuffers

    International Nuclear Information System (INIS)

    Single-junction, lattice-mismatched In0.69Ga0.31As thermophotovoltaic (TPV) devices each with abandgap of 0.6 eV are grown on InP substrate by metal—organic chemical vapour deposition (MOCVD). Compositionally undulating step-graded InAsyP1−y buffer layers with a lattice mismatch of ∼1.2% are used to mitigate the effect of lattice mismatch between the device layers and the InP substrate. With an optimized buffer thickness, the In0.69Ga0.31As active layers grown on the buffer display a high crystal quality with no measurable tetragonal distortion. High-performance single-junction devices are demonstrated, with an open-circuit voltage of 0.215 V and a photovoltaic conversion efficiency of 6.9% at a short-circuit current density of 47.6 mA/cm2, which are measured underthe standard solar simulator of air mass 1.5-global (AM 1.5 G). (condensed matter: structural, mechanical, and thermal properties)

  17. Controlling terahertz waves with meta-materials and photonic bandgap structures

    Energy Technology Data Exchange (ETDEWEB)

    Shchegolkov, Dmitry [Los Alamos National Laboratory; Azad, Abul [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory; Moody, Nathan A [Los Alamos National Laboratory; Simakov, Evgenya I [Los Alamos National Laboratory

    2010-12-07

    We will describe research conducted at Los Alamos National Laboratory towards developing components for controlling terahertz waves. We employ meta-materials and, particularly, meta-films, as very compact absorbers for controlling quasioptical beams. We believe that dielectric photonic bandgap structures could replace ordinary metal waveguide devices at THz, since metal structures become extremely lossy in this frequency range.

  18. Electrical and Optical Measurements of the Bandgap Energy of a Light-Emitting Diode

    Science.gov (United States)

    Petit, Matthieu; Michez, Lisa; Raimundo, Jean-Manuel; Dumas, Philippe

    2016-01-01

    Semiconductor materials are at the core of electronics. Most electronic devices are made of semiconductors. The operation of these components is well described by quantum physics which is often a difficult concept for students to understand. One of the intrinsic parameters of semiconductors is their bandgap energy E[subscript g]. In the case of…

  19. Tunable all-optical devices based on liquid-filled photonic crystal fibers

    DEFF Research Database (Denmark)

    Rosberg, Christian Romer; Bennet, Francis; Neshev, Dragomir N.;

    of discrete and nonlinear light propagation in extended two-dimensional periodic systems. We experimentally demonstrate strongly tunable beam diffraction in a triangular waveguide array created by infiltration of a high index liquid into the cladding holes of a standard PCF, and employ the thermal...... nonlinearity of the liquid to achieve beam self-defocusing at higher light intensity. Based on the observed effects we devise a compact all-optical power limiter device with tunable characteristics. The use of commercially available PCFs in combination with liquid infiltration avoids the need for specialized...... high-precision fabrication procedures, and provides high tunability and nonlinearity at moderate laser powers while taking advantage of a compact experimental setup. The increasingly broad range of PCF structures available could stimulate further efforts in applying them in discrete nonlinear optics...

  20. Self-assembled guanine ribbons as wide-bandgap semiconductors

    Science.gov (United States)

    di Felice, Rosa; Calzolari, Arrigo; Molinari, Elisa; Garbesi, Anna; Rinaldi, Ross; Maruccio, Giuseppe; Cingolani, Roberto

    2002-03-01

    We present a new class of biomolecular wide-bandgap semiconductors, that spontaneously form by the self-assembling of deoxyguanosine molecules (a modified DNA base) in the solid state. Their deposition onto planar metallic nanocircuits allows the fabrication of hybrid nanodiodes and metal/semiconductor/metal devices. By means of first-principle calculations, we describe the structure and the electronic properties of stacked guanine ribbons. We discuss the formation of extended Bloch orbitals, resulting from the superposition of base-localized states, as a function of H-bonding and π-π coupling. The oveall band-like conduction is affected by a dipole-field that spontaneously arise along the ribb n axis. Our theoretical model explains both the basic transport mechanism and the current-voltage characteristics of the devices.

  1. Machine learning bandgaps of double perovskites

    Science.gov (United States)

    Pilania, G.; Mannodi-Kanakkithodi, A.; Uberuaga, B. P.; Ramprasad, R.; Gubernatis, J. E.; Lookman, T.

    2016-01-01

    The ability to make rapid and accurate predictions on bandgaps of double perovskites is of much practical interest for a range of applications. While quantum mechanical computations for high-fidelity bandgaps are enormously computation-time intensive and thus impractical in high throughput studies, informatics-based statistical learning approaches can be a promising alternative. Here we demonstrate a systematic feature-engineering approach and a robust learning framework for efficient and accurate predictions of electronic bandgaps of double perovskites. After evaluating a set of more than 1.2 million features, we identify lowest occupied Kohn-Sham levels and elemental electronegativities of the constituent atomic species as the most crucial and relevant predictors. The developed models are validated and tested using the best practices of data science and further analyzed to rationalize their prediction performance.

  2. Porous silicon bandgap broadening at natural oxidation

    International Nuclear Information System (INIS)

    Emission and excitation photoluminescence spectra of porous silicon thin layers have been investigated at natural oxidation. The shift of both types of spectra to high-energy region with time has been shown. Analysis of excitation spectra points out the indirect behavior of electron transitions responsible for visible photoluminescence, which remains unaltered at natural oxidation. The value of optical bandgap is estimated in each case. It is shown that the optical bandgap broadens during oxidation due to size reduction of silicon nanocrystallites. - Highlights: → Porous silicon emission and excitation spectra blue shifted at natural oxidation. → Excitation spectra points out the indirect behavior of electron transitions. → Optical bandgap broadens during oxidation due to Si nanoparticles size reduction.

  3. Electric gating induced bandgaps and enhanced Seebeck effect in zigzag bilayer graphene ribbons

    Science.gov (United States)

    Vu, Thanh-Tra; Tran, Van-Truong

    2016-08-01

    We theoretically investigate the effect of a transverse electric field generated by side gates and a vertical electric field generated by top/back gates on energy bands and transport properties of zigzag bilayer graphene ribbons (Bernal stacking). Using atomistic tight binding calculations and Green’s function formalism we demonstrate that a bandgap is opened when either field is applied and even enlarged under simultaneous influence of the two fields. Interestingly, although vertical electric fields are widely used to control the bandgap in bilayer graphene, here we show that transverse fields exhibit a more positive effect in terms of modulating a larger range of bandgap and retaining good electrical conductance. The Seebeck effect is also demonstrated to be enhanced strongly—by about 13 times for a zigzag bilayer graphene ribbon with 16 chain lines. These results may motivate new designs of devices made of bilayer graphene ribbons using electric gates.

  4. The impact of sodium on the sub-bandgap states in CZTSe and CZTS

    Science.gov (United States)

    Gershon, By Talia; Lee, Yun Seog; Mankad, Ravin; Gunawan, Oki; Gokmen, Tayfun; Bishop, Doug; McCandless, Brian; Guha, Supratik

    2015-03-01

    We compare the optically active sub-bandgap states in polycrystalline Cu2ZnSnSe4 (CZTSe) and Cu2ZnSnS4 (CZTS) thin films as a function of sodium content. In all samples studied, we find that CZTSe has a lower concentration of radiative defect-derived states compared to CZTS and that the states are also shallower in CZTSe compared to CZTS. Further, we find that sodium impacts the relative ratios of two sub-bandgap peaks in the 4 K photoluminescence (PL) spectra of CZTSe (one at ˜0.85 eV and another at ˜0.92 eV). We propose that both of these sub-bandgap peaks stem from intrinsic point defects in CZTSe rather than from electronic states introduced by sodium; this is supported by a measurement on a sodium-free single-crystal of CZTSe. We also show that films with stronger emission through the shallower sub-bandgap states at 4 K display room-temperature PL closer to the bandgap energy. For all sodium quantities studied, one broad PL peak is observed in the 4 K PL spectrum of CZTS which also shifts towards the band edge with increasing sodium. A reduced overall defect density and the fact that the states that are present are shallower together may help account for the lower VOC deficits in CZTSe and the empirical observations that sodium improves device performance.

  5. Water Fibers

    CERN Document Server

    Douvidzon, Mark L; Martin, Leopoldo L; Carmon, Tal

    2016-01-01

    Fibers constitute the backbone of modern communication and are used in laser surgeries; fibers also genarate coherent X-ray, guided-sound and supercontinuum. In contrast, fibers for capillary oscillations, which are unique to liquids, were rarely considered in optofluidics. Here we fabricate fibers by water bridging an optical tapered-coupler to a microlensed coupler. Our water fibers are held in air and their length can be longer than a millimeter. These hybrid fibers co-confine two important oscillations in nature: capillary- and electromagnetic-. We optically record vibrations in the water fiber, including an audio-rate fundamental and its 3 overtones in a harmonic series, that one can hear in soundtracks attached. Transforming Micro-Electro-Mechanical-Systems [MEMS] to Micro-Electro-Capillary-Systems [MECS], boosts the device softness by a million to accordingly improve its response to minute forces. Furthermore, MECS are compatible with water, which is a most important liquid in our world.

  6. Quasi-Fermi level splitting and sub-bandgap absorptivity from semiconductor photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Katahara, John K.; Hillhouse, Hugh W., E-mail: h2@uw.edu [Department of Chemical Engineering, University of Washington, Seattle, Washington 98105 (United States)

    2014-11-07

    A unified model for the direct gap absorption coefficient (band-edge and sub-bandgap) is developed that encompasses the functional forms of the Urbach, Thomas-Fermi, screened Thomas-Fermi, and Franz-Keldysh models of sub-bandgap absorption as specific cases. We combine this model of absorption with an occupation-corrected non-equilibrium Planck law for the spontaneous emission of photons to yield a model of photoluminescence (PL) with broad applicability to band-band photoluminescence from intrinsic, heavily doped, and strongly compensated semiconductors. The utility of the model is that it is amenable to full-spectrum fitting of absolute intensity PL data and yields: (1) the quasi-Fermi level splitting, (2) the local lattice temperature, (3) the direct bandgap, (4) the functional form of the sub-bandgap absorption, and (5) the energy broadening parameter (Urbach energy, magnitude of potential fluctuations, etc.). The accuracy of the model is demonstrated by fitting the room temperature PL spectrum of GaAs. It is then applied to Cu(In,Ga)(S,Se){sub 2} (CIGSSe) and Cu{sub 2}ZnSn(S,Se){sub 4} (CZTSSe) to reveal the nature of their tail states. For GaAs, the model fit is excellent, and fitted parameters match literature values for the bandgap (1.42 eV), functional form of the sub-bandgap states (purely Urbach in nature), and energy broadening parameter (Urbach energy of 9.4 meV). For CIGSSe and CZTSSe, the model fits yield quasi-Fermi leveling splittings that match well with the open circuit voltages measured on devices made from the same materials and bandgaps that match well with those extracted from EQE measurements on the devices. The power of the exponential decay of the absorption coefficient into the bandgap is found to be in the range of 1.2 to 1.6, suggesting that tunneling in the presence of local electrostatic potential fluctuations is a dominant factor contributing to the sub-bandgap absorption by either purely electrostatic (screened Thomas-Fermi) or

  7. Hollow core photonic bandgap fibers for medical applications

    OpenAIRE

    Vural, Mert

    2009-01-01

    Ankara : The Department of Materials Science and Nanotechnology and the Institute of Engineering and Sciences of Bilkent University, 2009. Thesis (Master's) -- Bilkent University, 2009. Includes bibliographical references leaves 87-95. Vural, Mert Master's

  8. Proceedings of the international conference on specialty glass and optical fiber: materials, technology and devices - book of abstracts

    International Nuclear Information System (INIS)

    The present conference on Specialty Glass and Optical Fiber (ICGF-2011) was organized during 4-6 August, 2011 as a part of Institute's year long Diamond Jubilee celebration.The development and commercialization of specialty glasses and optical fibers has become a rightful index of a country's progress in today's competitive global scenario. The conference covers topics on modeling, manufacturing and processing of glass with novel design and composition as well as specialty optical fiber and technologies, papers on innovative, cutting-edge topics in the fields of specialty glass and optical fiber foregrounding the recent technical advances. Papers relevant to INIS are indexed separately

  9. Petahertz optical drive with wide-bandgap semiconductor

    Science.gov (United States)

    Mashiko, Hiroki; Oguri, Katsuya; Yamaguchi, Tomohiko; Suda, Akira; Gotoh, Hideki

    2016-08-01

    High-speed photonic and electronic devices at present rely on radiofrequency electric fields to control the physical properties of a semiconductor, which limits their operating speed to terahertz frequencies (1012 Hz ref. ). Using the electric field from intense light pulses, however, could extend the operating frequency into the petahertz regime (1015 Hz ref. ). Here we demonstrate optical driving at a petahertz frequency in the wide-bandgap semiconductor gallium nitride. Few-cycle near-infrared pulses are shown to induce electric interband polarization though a multiphoton process. Dipole oscillations with a periodicity of 860 as are revealed in the gallium nitride electron and hole system by using the quantum interference between the two transitions from the valence and conduction band states, which are probed by an extremely short isolated attosecond pulse with a coherent broadband spectrum. In principle, this shows that the conductivity of the semiconductor can be manipulated on attosecond timescales, which corresponds to instantaneous light-induced switching from insulator to conductor. The resultant dipole frequency reaches 1.16 PHz, showing the potential for future high-speed signal processing technologies based on wide-bandgap semiconductors.

  10. Research on micro-sized acoustic bandgap structures.

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, James Grant; McCormick, Frederick Bossert; Su, Mehmet F.; El-Kady, Ihab Fathy; Olsson, Roy H., III; Tuck, Melanie R.

    2010-01-01

    Phononic crystals (or acoustic crystals) are the acoustic wave analogue of photonic crystals. Here a periodic array of scattering inclusions located in a homogeneous host material forbids certain ranges of acoustic frequencies from existence within the crystal, thus creating what are known as acoustic (or phononic) bandgaps. The vast majority of phononic crystal devices reported prior to this LDRD were constructed by hand assembling scattering inclusions in a lossy viscoelastic medium, predominantly air, water or epoxy, resulting in large structures limited to frequencies below 1 MHz. Under this LDRD, phononic crystals and devices were scaled to very (VHF: 30-300 MHz) and ultra (UHF: 300-3000 MHz) high frequencies utilizing finite difference time domain (FDTD) modeling, microfabrication and micromachining technologies. This LDRD developed key breakthroughs in the areas of micro-phononic crystals including physical origins of phononic crystals, advanced FDTD modeling and design techniques, material considerations, microfabrication processes, characterization methods and device structures. Micro-phononic crystal devices realized in low-loss solid materials were emphasized in this work due to their potential applications in radio frequency communications and acoustic imaging for medical ultrasound and nondestructive testing. The results of the advanced modeling, fabrication and integrated transducer designs were that this LDRD produced the 1st measured phononic crystals and phononic crystal devices (waveguides) operating in the VHF (67 MHz) and UHF (937 MHz) frequency bands and established Sandia as a world leader in the area of micro-phononic crystals.

  11. Plasma-Enhanced Pulsed Laser Deposition of Wide Bandgap Nitrides for Space Power Applications

    Science.gov (United States)

    Triplett, G. E., Jr.; Durbin, S. M.

    2004-01-01

    The need for a reliable, inexpensive technology for small-scale space power applications where photovoltaic or chemical battery approaches are not feasible has prompted renewed interest in radioisotope-based energy conversion devices. Although a number of devices have been developed using a variety of semiconductors, the single most limiting factor remains the overall lifetime of the radioisotope battery. Recent advances in growth techniques for ultra-wide bandgap III-nitride semiconductors provide the means to explore a new group of materials with the promise of significant radiation resistance. Additional benefits resulting from the use of ultra-wide bandgap materials include a reduction in leakage current and higher operating voltage without a loss of energy transfer efficiency. This paper describes the development of a novel plasma-enhanced pulsed laser deposition system for the growth of cubic boron nitride semiconducting thin films, which will be used to construct pn junction devices for alphavoltaic applications.

  12. Fabrication and optical properties of lead silicate glass holey fibers

    OpenAIRE

    Ebendorff-Heidepriem, H.; Petropoulos, P.; Moore, R.; Frampton, K.; Monro, T.M.

    2003-01-01

    Since the first microstructured optical fiber was made in 1996, holey fibers (HFs) have attracted growing attention. Compared with conventional fibers, they offer a significantly broader range of optical properties such as photonic bandgap guiding, shift of anomalous dispersion into the visible, high nonlinearity in small core fibers and high power delivery in large mode area fibers. Therefore, HFs have a wide range of potential applications in optical technologies. The vast majority of resea...

  13. Main Factors for Affecting Photonic Bandgap of Photonic Crystals

    Institute of Scientific and Technical Information of China (English)

    LI Xia; XUE Wei; JIANG Yu-rong; YU Zhi-nong; WANG Hua-qing

    2007-01-01

    The factors affecting one dimensional (1D) and two dimensional (2D) photonic crystals (PhCs) are systemically analyzed in this paper by numerical simulation.Transfer matrix method (TMM) is employed for 1D PCs, both finite difference time domain method (FDTD) and plane wave expansion method (PWE) are employed for 2D PCs.The result shows that the photonic bandgaps (PBG) are directly affected by crystal type, crystal lattice constant, modulation of refractive index and periodicity, and it is should be useful for design of different type photonic crystals with the required PBG and functional devices.Finally, as an example, a near-IR 1D PCs narrow filter was designed.

  14. Hybrid photonic-bandgap accelerating cavities

    CERN Document Server

    Di Gennaro, E; Savo, S; Andreone, A; Masullo, M R; Castaldi, G; Gallina, I; Galdi, V

    2009-01-01

    In a recent investigation, we studied two-dimensional point-defected photonic bandgap cavities composed of dielectric rods arranged according to various representative periodic and aperiodic lattices, with special emphasis on possible applications to particle acceleration (along the longitudinal axis). In this paper, we present a new study aimed at highlighting the possible advantages of using hybrid structures based on the above dielectric configurations, but featuring metallic rods in the outermost regions, for the design of extremely-high quality factor, bandgap-based, accelerating resonators. In this framework, we consider diverse configurations, with different (periodic and aperiodic) lattice geometries, sizes, and dielectric/metal fractions. Moreover, we also explore possible improvements attainable via the use of superconducting plates to confine the electromagnetic field in the longitudinal direction. Results from our comparative studies, based on numerical full-wave simulations backed by experimental...

  15. Advances in Fiber Optic Sensors Technology Development for temperature and strain measurements in Superconducting magnets and devices

    CERN Document Server

    Chiuchiolo, A.; Bajko, M.; Bottura, L.; Consales, M.; Cusano, A.; Giordano, M.; Perez, J. C.

    2016-01-01

    Fiber optic sensors (FOS) based on Fiber Bragg Grating (FBG) technology have been embedded in the coils of the Short Model Coil (SMC) magnet. The FBG sensitivity to both temperature and strain required the development of a solution able to separate the mechanical and temperature effects. This work presents the feasibility study of the implementation of embedded FBG sensors for the temperature and strain monitoring of the 11 T type conductor. We aim to monitor and register these...

  16. Printable, wide band-gap chalcopyrite thin films for power generating window applications

    Science.gov (United States)

    Moon, Sung Hwan; Park, Se Jin; Hwang, Yun Jeong; Lee, Doh-Kwon; Cho, Yunae; Kim, Dong-Wook; Min, Byoung Koun

    2014-03-01

    Printable, wide band-gap chalcopyrite compound films (CuInGaS2, CIGS) were synthesized on transparent conducting oxide substrates. The wide band-gap and defective nature of the films reveal semi-transparent and bifacial properties that are beneficial for power generating window applications. Importantly, solar cell devices with these films demonstrate a synergistic effect for bifacial illumination resulting in a 5.4-16.3% increase of the apparent power conversion efficiency compared to the simple sum of the efficiencies of the front and rear side illumination only. We also confirmed that this extra output power acquisition due to bifacial irradiation is apparently not influenced by the light intensity of the rear side illumination, which implies that weak light (e.g., indoor light) can be efficiently utilized to improve the overall solar cell efficiency of bifacial devices.

  17. Graded-Bandgap Solar Cells Using All-Electrodeposited ZnS, CdS and CdTe Thin-Films

    OpenAIRE

    Obi K. Echendu; Imyhamy M. Dharmadasa

    2015-01-01

    A 3-layer graded-bandgap solar cell with glass/FTO/ZnS/CdS/CdTe/Au structure has been fabricated using all-electrodeposited ZnS, CdS and CdTe thin layers. The three semiconductor layers were electrodeposited using a two-electrode system for process simplification. The incorporation of a wide bandgap amorphous ZnS as a buffer/window layer to form glass/FTO/ZnS/CdS/CdTe/Au solar cell resulted in the formation of this 3-layer graded-bandgap device structure. This has yielded corresponding impro...

  18. High peak-power monolithic femtosecond ytterbium fiber chirped pulse amplifier with a spliced-on hollow core fiber compressor.

    Science.gov (United States)

    Verhoef, A J; Jespersen, K; Andersen, T V; Grüner-Nielsen, L; Flöry, T; Zhu, L; Baltuška, A; Fernández, A

    2014-07-14

    We demonstrate a monolithic Yb-fiber chirped pulse amplifier that uses a dispersion matched fiber stretcher and a spliced-on hollow core photonic bandgap fiber compressor. For an output energy of 77 nJ, 220 fs pulses with 92% of the energy contained in the main pulse, can be obtained with minimal nonlinearities in the system. 135 nJ pulses are obtained with 226 fs duration and 82 percent of the energy in the main pulse. Due to the good dispersion match of the stretcher to the hollow core photonic bandgap fiber compressor, the duration of the output pulses is within 10% of the Fourier limited duration. PMID:25090494

  19. Anisotropic nanostructures directly written by fs pulses in wide-bandgap materials

    OpenAIRE

    Baumberg, J. J.; Mills, J. D.; Kazansky, P. G.; Bricchi, E.

    2003-01-01

    The use of lasers to directly pattern optoelectronic devices primarily utilizes direct irradiation by UV light. We present here an alternative route using multi-photon absorption within a spherical focus in 3D space, thus allowing complex embedded structures to be directly written. In wide-bandgap materials such as chalcogenide, fluoride and silica glasses, our observations suggest free electrons are produced within the focus of a high-power infrared ultrashort pulse. The anisotropic interact...

  20. Bandgap Engineering of Double Perovskites for One- and Two-photon Water Splitting

    DEFF Research Database (Denmark)

    Castelli, Ivano Eligio; Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel

    2013-01-01

    Computational screening is becoming increasingly useful in the search for new materials. We are interested in the design of new semiconductors to be used for light harvesting in a photoelectrochemical cell. In the present paper, we study the double perovskite structures obtained by combining 46...... the volume has an effect on the size of the bandgap. In addition, we suggest some new candidate materials that can be used as photocatalysts in one- and two-photon water splitting devices....

  1. Tunable bandgaps and excitons in doped semiconducting carbon nanotubes made possible by acoustic plasmons

    OpenAIRE

    Spataru, Catalin D.; Léonard, François

    2010-01-01

    Doping of semiconductors is essential in modern electronic and photonic devices. While doping is well understood in bulk semiconductors, the advent of carbon nanotubes and nanowires for nanoelectronic and nanophotonic applications raises some key questions about the role and impact of doping at low dimensionality. Here we show that for semiconducting carbon nanotubes, bandgaps and exciton binding energies can be dramatically reduced upon experimentally relevant doping, and can be tuned gradua...

  2. A new photonic bandgap cover for a patch antenna with a photonic bandgap substrate

    Institute of Scientific and Technical Information of China (English)

    林青春; 朱方明; 何赛灵

    2004-01-01

    A new photonic bandgap (PBG) cover for a patch antenna with a photonic bandgap substrate is introduced. The plane wave expansion method and the FDTD method were used to calculate such an antenna system. Numerical results for the input return loss, radiation pattern, surface wave, and the directivity of the antennas are presented. A comparison between the conventional patch antenna and the new PBG antenna is given. It is shown that the new PBG cover is very efficient for improving the radiation directivity. The physical reasons for the improvement are also given.

  3. Method for effectively utilizing tunable one-pump fiber parametric wavelength converters as an enabling device for WDM routers.

    Science.gov (United States)

    Cui, Sheng; Liu, Deming; Wang, Ying; Tu, Feng

    2009-02-01

    In this paper a method is proposed to maximize the bandwidth of the WDM router based on one-pump fiber parametric wavelength converters. It is proved that for such converters there exists an optimum signal (idler) frequency at which the output (input) tuning range can be maximized. Analytical expressions of the optimum frequency and the maximal tuning range are deduced. Then a two-stage bidirectional wavelength conversion method is proposed. With this method the bandwidth of the WDM router based on such a converter can be significantly improved compared to the one-stage ones by 252% if ordinary highly nonlinear fibers are used or 390% if fibers with optimal fourth order dispersion are used. PMID:19188974

  4. Dissipative rogue waves induced by long-range chaotic multi-pulse interactions in a fiber laser with a topological insulator-deposited microfiber photonic device.

    Science.gov (United States)

    Liu, Meng; Cai, Ze-Rong; Hu, Song; Luo, Ai-Ping; Zhao, Chu-Jun; Zhang, Han; Xu, Wen-Cheng; Luo, Zhi-Chao

    2015-10-15

    We reported on the generation of dissipative rogue waves (DRWs) induced by long-range chaotic multi-pulse interactions in a fiber laser based on a topological insulator (TI)-deposited microfiber photonic device. By virtue of the simultaneous saturable absorption effect and high nonlinearity provided by the TI-deposited microfiber, a localized, chaotic multi-pulse wave packet with strong long-range nonlinear interactions could be obtained, which gives rise to the formation of DRWs. The results might enhance the understanding of DRWs in optical systems, and further demonstrated that the TI-deposited microfiber could be considered as an excellent photonic device with both saturable absorption and highly nonlinear effects for the application field of nonlinear optics. PMID:26469615

  5. Narrow-linewidth and tunable fiber lasers

    OpenAIRE

    Morkel, P.R.

    1993-01-01

    1. Introduction 2. Line-narrowed fiber laser devices Integral fiber reflective Bragg grating lasers Intra-cavity etalon laser 3. Tunable, line narrowed fiber laser devices Ring lasers using wavelength selective couplers Tunable lasers using bulk-optic components a) Mechanical tuning b) Electronic tuning 4. Single frequency fiber lasers Integral fiber reflective Bragg grating laser Interferometric cavity laser Injection locked laser Travellin...

  6. Intermediate Bandgap Solar Cells From Nanostructured Silicon

    Energy Technology Data Exchange (ETDEWEB)

    Black, Marcie [Bandgap Engineering, Lincoln, MA (United States)

    2014-10-30

    This project aimed to demonstrate increased electronic coupling in silicon nanostructures relative to bulk silicon for the purpose of making high efficiency intermediate bandgap solar cells using silicon. To this end, we formed nanowires with controlled crystallographic orientation, small diameter, <111> sidewall faceting, and passivated surfaces to modify the electronic band structure in silicon by breaking down the symmetry of the crystal lattice. We grew and tested these silicon nanowires with <110>-growth axes, which is an orientation that should produce the coupling enhancement.

  7. Highly dispersive photonic band-gap prism

    International Nuclear Information System (INIS)

    We propose the concept of a photonic band-gap (PBG) prism based on two-dimensional PBG structures and realize it in the millimeter-wave spectral regime. We recognize the highly nonlinear dispersion of PBG materials near Brillouin zone edges and utilize the dispersion to achieve strong prism action. Such a PBG prism is very compact if operated in the optical regime, ∼20μm in size for λ∼700nm, and can serve as a dispersive element for building ultracompact miniature spectrometers. copyright 1996 Optical Society of America

  8. Highly dispersive photonic band-gap prism.

    Science.gov (United States)

    Lin, S Y; Hietala, V M; Wang, L; Jones, E D

    1996-11-01

    We propose the concept of a photonic band-gap (PBG) prism based on two-dimensional PBG structures and realize it in the millimeter-wave spectral regime. We recognize the highly nonlinear dispersion of PBG materials near Brillouin zone edges and utilize the dispersion to achieve strong prism action. Such a PBG prism is very compact if operated in the optical regime, ~20 mm in size for lambda ~ 700 nm, and can serve as a dispersive element for building ultracompact miniature spectrometers. PMID:19881796

  9. Switchable Electromagnetic Bandgap Surface Wave Antenna

    Directory of Open Access Journals (Sweden)

    Qiang Bai

    2014-01-01

    Full Text Available This paper presents a novel switchable electromagnetic bandgap surface wave antenna that can support both a surface wave and normal mode radiation for communications at 2.45 GHz. In the surface wave mode, the antenna has a monopole-like radiation pattern with a measured gain of 4.4 dBi at ±49° and a null on boresight. In the normal mode, the antenna operates like a back-fed microstrip patch antenna.

  10. The impact of sodium on the sub-bandgap states in CZTSe and CZTS

    Energy Technology Data Exchange (ETDEWEB)

    Gershon, By Talia, E-mail: tsgersho@us.ibm.com; Lee, Yun Seog; Mankad, Ravin; Gunawan, Oki; Gokmen, Tayfun; Guha, Supratik [Physical Sciences Department, IBM T.J. Watson Research Center, 1101 Kitchawan Rd, Yorktown Heights, New York 10598 (United States); Bishop, Doug; McCandless, Brian [Institute of Energy Conversion, University of Delaware, Newark, Delaware 19716 (United States)

    2015-03-23

    We compare the optically active sub-bandgap states in polycrystalline Cu{sub 2}ZnSnSe{sub 4} (CZTSe) and Cu{sub 2}ZnSnS{sub 4} (CZTS) thin films as a function of sodium content. In all samples studied, we find that CZTSe has a lower concentration of radiative defect-derived states compared to CZTS and that the states are also shallower in CZTSe compared to CZTS. Further, we find that sodium impacts the relative ratios of two sub-bandgap peaks in the 4 K photoluminescence (PL) spectra of CZTSe (one at ∼0.85 eV and another at ∼0.92 eV). We propose that both of these sub-bandgap peaks stem from intrinsic point defects in CZTSe rather than from electronic states introduced by sodium; this is supported by a measurement on a sodium-free single-crystal of CZTSe. We also show that films with stronger emission through the shallower sub-bandgap states at 4 K display room-temperature PL closer to the bandgap energy. For all sodium quantities studied, one broad PL peak is observed in the 4 K PL spectrum of CZTS which also shifts towards the band edge with increasing sodium. A reduced overall defect density and the fact that the states that are present are shallower together may help account for the lower V{sub OC} deficits in CZTSe and the empirical observations that sodium improves device performance.

  11. Development of High-Bandgap AlGaInP Solar Cells Grown by Organometallic Vapor-Phase Epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Perl, Emmett E.; Simon, John; Geisz, John F.; Olavarria, Waldo; Young, Michelle; Duda, Anna; Friedman, Daniel J.; Steiner, Myles A.

    2016-05-01

    AlGaInP solar cells with bandgaps between 1.9 and 2.2 eV are investigated for use in next-generation multijunction photovoltaic devices. This quaternary alloy is of great importance to the development of III-V solar cells with five or more junctions and for cells optimized for operation at elevated temperatures because of the high bandgaps required in these designs. In this work, we explore the conditions for the organometallic vapor-phase epitaxy growth of AlGaInP and study their effects on cell performance. Initial efforts focused on developing -2.0-eV AlGaInP solar cells with a nominal aluminum composition of 12%. Under the direct spectrum at 1000 W/m2 (AM1.5D), the best of these samples had an open-circuit voltage of 1.59 V, a bandgap-voltage offset of 440 mV, a fill factor of 88.0%, and an efficiency of 14.8%. We then varied the aluminum composition of the alloy from 0% to 24% and were able to tune the bandgap of the AlGaInP layers from -1.9 to -2.2 eV. While the samples with a higher aluminum composition exhibited a reduced quantum efficiency and increased bandgap-voltage offset, the bandgap-voltage offset remained at 500 mV or less, up to a bandgap of -2.1 eV.

  12. Hybrid photonic-bandgap accelerating cavities

    Energy Technology Data Exchange (ETDEWEB)

    Di Gennaro, E [CNISM and Department of Physics, University of Naples ' Federico II' , Naples (Italy); Zannini, C; Savo, S; Andreone, A [CNR-INFM ' Coherentia' and Department of Physics, University of Naples ' Federico II' , Naples (Italy); Masullo, M R [INFN-Naples Unit, Naples (Italy); Castaldi, G; Gallina, I; Galdi, V [Waves Group, Department of Engineering, University of Sannio, Benevento (Italy)], E-mail: masullo@na.infn.it

    2009-11-15

    In a recent investigation, we studied two-dimensional (2D) point-defected photonic bandgap cavities composed of dielectric rods arranged according to various representative periodic and aperiodic lattices, with special emphasis on possible applications to particle acceleration (along the longitudinal axis). In this paper, we present a new study aimed at highlighting the possible advantages of using hybrid structures based on the above dielectric configurations, but featuring metallic rods in the outermost regions, for the design of extremely high quality factor, bandgap-based, accelerating resonators. In this framework, we consider diverse configurations, with different (periodic and aperiodic) lattice geometries, sizes and dielectric/metal fractions. Moreover, we also explore possible improvements attainable via the use of superconducting plates to confine the electromagnetic field in the longitudinal direction. Results from our comparative studies, based on numerical full-wave simulations backed by experimental validations (at room and cryogenic temperatures) in the microwave region, identify the candidate parametric configurations capable of yielding the highest quality factor.

  13. Hybrid photonic-bandgap accelerating cavities

    Science.gov (United States)

    Di Gennaro, E.; Zannini, C.; Savo, S.; Andreone, A.; Masullo, M. R.; Castaldi, G.; Gallina, I.; Galdi, V.

    2009-11-01

    In a recent investigation, we studied two-dimensional (2D) point-defected photonic bandgap cavities composed of dielectric rods arranged according to various representative periodic and aperiodic lattices, with special emphasis on possible applications to particle acceleration (along the longitudinal axis). In this paper, we present a new study aimed at highlighting the possible advantages of using hybrid structures based on the above dielectric configurations, but featuring metallic rods in the outermost regions, for the design of extremely high quality factor, bandgap-based, accelerating resonators. In this framework, we consider diverse configurations, with different (periodic and aperiodic) lattice geometries, sizes and dielectric/metal fractions. Moreover, we also explore possible improvements attainable via the use of superconducting plates to confine the electromagnetic field in the longitudinal direction. Results from our comparative studies, based on numerical full-wave simulations backed by experimental validations (at room and cryogenic temperatures) in the microwave region, identify the candidate parametric configurations capable of yielding the highest quality factor.

  14. Hybrid photonic-bandgap accelerating cavities

    International Nuclear Information System (INIS)

    In a recent investigation, we studied two-dimensional (2D) point-defected photonic bandgap cavities composed of dielectric rods arranged according to various representative periodic and aperiodic lattices, with special emphasis on possible applications to particle acceleration (along the longitudinal axis). In this paper, we present a new study aimed at highlighting the possible advantages of using hybrid structures based on the above dielectric configurations, but featuring metallic rods in the outermost regions, for the design of extremely high quality factor, bandgap-based, accelerating resonators. In this framework, we consider diverse configurations, with different (periodic and aperiodic) lattice geometries, sizes and dielectric/metal fractions. Moreover, we also explore possible improvements attainable via the use of superconducting plates to confine the electromagnetic field in the longitudinal direction. Results from our comparative studies, based on numerical full-wave simulations backed by experimental validations (at room and cryogenic temperatures) in the microwave region, identify the candidate parametric configurations capable of yielding the highest quality factor.

  15. Direct-bandgap electroluminescence from a horizontal Ge p-i-n ridge waveguide on Si(001) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhi; Li, Yaming; He, Chao; Li, Chuanbo; Xue, Chunlai; Zuo, Yuhua; Cheng, Buwen, E-mail: cbw@semi.ac.cn; Wang, Qiming [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2014-05-12

    Horizontal injection Ge p-i-n ridge waveguide light emitting diodes (LEDs) were fabricated on n{sup −}-Si(001) substrates by ultrahigh vacuum chemical vapor deposition. The direct-bandgap electroluminescence (EL) of Ge waveguide LEDs under a continuous/pulse electrical pump was studied. The heating effect from a continuous electrical pump was found to significantly enhance the emission of devices. The top surface EL intensity of the Ge waveguide LEDs significantly depended on the position. Most direct-bandgap radiative recombination of Ge p-i-n waveguide LEDs occurred near the N{sup +} region of the junction. This interesting phenomenon could be explained by the carrier distribution in the junction and the pseudo-direct bandgap of Ge.

  16. Direct-bandgap electroluminescence from a horizontal Ge p-i-n ridge waveguide on Si(001) substrate

    International Nuclear Information System (INIS)

    Horizontal injection Ge p-i-n ridge waveguide light emitting diodes (LEDs) were fabricated on n−-Si(001) substrates by ultrahigh vacuum chemical vapor deposition. The direct-bandgap electroluminescence (EL) of Ge waveguide LEDs under a continuous/pulse electrical pump was studied. The heating effect from a continuous electrical pump was found to significantly enhance the emission of devices. The top surface EL intensity of the Ge waveguide LEDs significantly depended on the position. Most direct-bandgap radiative recombination of Ge p-i-n waveguide LEDs occurred near the N+ region of the junction. This interesting phenomenon could be explained by the carrier distribution in the junction and the pseudo-direct bandgap of Ge

  17. Ultraviolet laser quantum well intermixing based prototyping of bandgap tuned heterostructures for the fabrication of superluminescent diodes

    Science.gov (United States)

    Beal, Romain; Moumanis, Khalid; Aimez, Vincent; Dubowski, Jan J.

    2016-04-01

    The ultraviolet laser induced quantum well intermixing process has been investigated for prototyping of multiple bandgap quantum well (QW) wafers designed for the fabrication of superluminescent diodes (SLDs). The process takes advantage of a krypton fluoride excimer laser (λ=248 nm) that by irradiating an InP layer capping GaInAs/GaInAsP QW heterostructure leads to the modification of its surface chemical composition and formation of point defects. A subsequent rapid thermal annealing step results in the selective area intermixing of the investigated heterostructures achieving a high quality bandgap tuned material for the fabrication of broad spectrum SLDs. The devices made from a 3-bandgap material are characterized by ~100 nm wide emission spectra with relatively flat profiles and emission exceeding 1 mW.

  18. Oxygen-activated growth and bandgap tunability of large single-crystal bilayer graphene

    Science.gov (United States)

    Hao, Yufeng; Wang, Lei; Liu, Yuanyue; Chen, Hua; Wang, Xiaohan; Tan, Cheng; Nie, Shu; Suk, Ji Won; Jiang, Tengfei; Liang, Tengfei; Xiao, Junfeng; Ye, Wenjing; Dean, Cory R.; Yakobson, Boris I.; McCarty, Kevin F.; Kim, Philip; Hone, James; Colombo, Luigi; Ruoff, Rodney S.

    2016-05-01

    Bernal (AB)-stacked bilayer graphene (BLG) is a semiconductor whose bandgap can be tuned by a transverse electric field, making it a unique material for a number of electronic and photonic devices. A scalable approach to synthesize high-quality BLG is therefore critical, which requires minimal crystalline defects in both graphene layers and maximal area of Bernal stacking, which is necessary for bandgap tunability. Here we demonstrate that in an oxygen-activated chemical vapour deposition (CVD) process, half-millimetre size, Bernal-stacked BLG single crystals can be synthesized on Cu. Besides the traditional ‘surface-limited’ growth mechanism for SLG (1st layer), we discovered new microscopic steps governing the growth of the 2nd graphene layer below the 1st layer as the diffusion of carbon atoms through the Cu bulk after complete dehydrogenation of hydrocarbon molecules on the Cu surface, which does not occur in the absence of oxygen. Moreover, we found that the efficient diffusion of the carbon atoms present at the interface between Cu and the 1st graphene layer further facilitates growth of large domains of the 2nd layer. The CVD BLG has superior electrical quality, with a device on/off ratio greater than 104, and a tunable bandgap up to ∼100 meV at a displacement field of 0.9 V nm‑1.

  19. Oxygen-activated growth and bandgap tunability of large single-crystal bilayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Yufeng; Wang, Lei; Liu, Yuanyue; Chen, Hua; Wang, Xiaohan; Tan, Cheng; Nie, Shu; Suk, Ji Won; Jiang, Tengfei; Liang, Tengfei; Xiao, Junfeng; Ye, Wenjing; Dean, Cory R.; Yakobson, Boris I.; McCarty, Kevin F.; Kim, Philip; Hone, James; Colombo, Luigi; Ruoff, Rodney S.

    2016-02-01

    Bernal (AB)-stacked bilayer graphene (BLG) is a semiconductor whose bandgap can be tuned by a transverse electric field, making it a unique material for a number of electronic and photonic devices. A scalable approach to synthesize high-quality BLG is therefore critical, which requires minimal crystalline defects in both graphene layers and maximal area of Bernal stacking, which is necessary for bandgap tunability. Here we demonstrate that in an oxygen-activated chemical vapour deposition (CVD) process, half-millimetre size, Bernal-stacked BLG single crystals can be synthesized on Cu. Besides the traditional 'surface-limited' growth mechanism for SLG (1st layer), we discovered new microscopic steps governing the growth of the 2nd graphene layer below the 1st layer as the diffusion of carbon atoms through the Cu bulk after complete dehydrogenation of hydrocarbon molecules on the Cu surface, which does not occur in the absence of oxygen. Moreover, we found that the efficient diffusion of the carbon atoms present at the interface between Cu and the 1st graphene layer further facilitates growth of large domains of the 2nd layer. The CVD BLG has superior electrical quality, with a device on/off ratio greater than 104, and a tunable bandgap up to -100 meV at a displacement field of 0.9 V nm-1.

  20. Oxygen-activated growth and bandgap tunability of large single-crystal bilayer graphene.

    Science.gov (United States)

    Hao, Yufeng; Wang, Lei; Liu, Yuanyue; Chen, Hua; Wang, Xiaohan; Tan, Cheng; Nie, Shu; Suk, Ji Won; Jiang, Tengfei; Liang, Tengfei; Xiao, Junfeng; Ye, Wenjing; Dean, Cory R; Yakobson, Boris I; McCarty, Kevin F; Kim, Philip; Hone, James; Colombo, Luigi; Ruoff, Rodney S

    2016-05-01

    Bernal (AB)-stacked bilayer graphene (BLG) is a semiconductor whose bandgap can be tuned by a transverse electric field, making it a unique material for a number of electronic and photonic devices. A scalable approach to synthesize high-quality BLG is therefore critical, which requires minimal crystalline defects in both graphene layers and maximal area of Bernal stacking, which is necessary for bandgap tunability. Here we demonstrate that in an oxygen-activated chemical vapour deposition (CVD) process, half-millimetre size, Bernal-stacked BLG single crystals can be synthesized on Cu. Besides the traditional 'surface-limited' growth mechanism for SLG (1st layer), we discovered new microscopic steps governing the growth of the 2nd graphene layer below the 1st layer as the diffusion of carbon atoms through the Cu bulk after complete dehydrogenation of hydrocarbon molecules on the Cu surface, which does not occur in the absence of oxygen. Moreover, we found that the efficient diffusion of the carbon atoms present at the interface between Cu and the 1st graphene layer further facilitates growth of large domains of the 2nd layer. The CVD BLG has superior electrical quality, with a device on/off ratio greater than 10(4), and a tunable bandgap up to ∼100 meV at a displacement field of 0.9 V nm(-1). PMID:26828845

  1. Stability and bandgaps of layered perovskites for one- and two-photon water splitting

    International Nuclear Information System (INIS)

    Direct production of hydrogen from water and sunlight requires stable and abundantly available semiconductors with well positioned band edges relative to the water red-ox potentials. We have used density functional theory (DFT) calculations to investigate 300 oxides and oxynitrides in the Ruddlesden–Popper phase of the layered perovskite structure. Based on screening criteria for the stability, bandgaps and band edge positions, we suggest 20 new materials for the light harvesting photo-electrode of a one-photon water splitting device and 5 anode materials for a two-photon device with silicon as photo-cathode. In addition, we explore a simple rule relating the bandgap of the perovskite to the number of octahedra in the layered structure and the B-metal ion. Finally, the quality of the GLLB-SC potential used to obtain the bandgaps, including the derivative discontinuity, is validated against G0W0@LDA gaps for 20 previously identified oxides and oxynitrides in the cubic perovskite structure. (paper)

  2. Stability and bandgaps of layered perovskites for one- and two-photon water splitting

    Science.gov (United States)

    Castelli, Ivano E.; María García-Lastra, Juan; Hüser, Falco; Thygesen, Kristian S.; Jacobsen, Karsten W.

    2013-10-01

    Direct production of hydrogen from water and sunlight requires stable and abundantly available semiconductors with well positioned band edges relative to the water red-ox potentials. We have used density functional theory (DFT) calculations to investigate 300 oxides and oxynitrides in the Ruddlesden-Popper phase of the layered perovskite structure. Based on screening criteria for the stability, bandgaps and band edge positions, we suggest 20 new materials for the light harvesting photo-electrode of a one-photon water splitting device and 5 anode materials for a two-photon device with silicon as photo-cathode. In addition, we explore a simple rule relating the bandgap of the perovskite to the number of octahedra in the layered structure and the B-metal ion. Finally, the quality of the GLLB-SC potential used to obtain the bandgaps, including the derivative discontinuity, is validated against G0W0@LDA gaps for 20 previously identified oxides and oxynitrides in the cubic perovskite structure.

  3. Fiber Singular Optics

    OpenAIRE

    A. V. Volyar

    2002-01-01

    The present review is devoted to the optical vortex behavior both in free space and optical fibers. The processes of the vortex transformations in perturbed optical fibers are analyzed on the base of the operator of the spin – orbit interaction in order to forecast the possible ways of manufacturing the vortex preserving fibers and their applications in supersensitive optical devices.

  4. Applications of monolithic fiber interferometers and actively controlled fibers

    OpenAIRE

    Rugeland, Patrik

    2013-01-01

    The objective of this thesis was to develop applications of monolithic fiber devices and actively controlled fibers. A special twin-core fiber known as a ‘Gemini’ fiber was used to construct equal arm-length fiber interferometers, impervious to temperature and mechanical perturbations. A broadband add/drop multiplexer was constructed by inscribing fiber Bragg gratings in the arms of a Gemini Mach-Zehnder interferometer. A broadband interferometric nanosecond switch was constructed from a micr...

  5. Comparison of retinal nerve fiber layer and macular thickness measurements with Stratus OCT and OPKO/OTI OCT devices in healthy subjects

    Institute of Scientific and Technical Information of China (English)

    Ahmet; Ozkok; Julide; Canan; Umurhan; Akkan; Nevbahar; Tamcelik; Mehmet; Erdogan; Didar; Ucar; Comlekoglu; Rengin; Yildirim

    2015-01-01

    AIM: To compare retinal nerve fiber layer(RNFL) and macular thickness measurements obtained with the Stratus optical coherence tomography(OCT) and OPKO/OTI OCT devices.METHODS: Included in the study were 59 eyes of 30 participants. All measurements for each eye were done on the same day with both devices. Student’s paired t-tests were used to compare the central macular thickness and RNFL measurements of the Stratus OCT and OPKO/OTI OCT. Pearson correlation was used to assess the relationship between the devices. Coefficient of variation(COV) was calculated to assess intersession repeatability.RESULTS: Using both the Stratus OCT and OPKO/OTI OCT, respectively, the measured mean average RNFL thicknesses were 98.9±11.1 μm and 115.1±9.6 μm(P =0.001),and the measured mean central retinal thicknesses(CRT)were 196.2 ±18.8 μm and 204.5 ±21.1 μm(P <0.001).Measured by the two devices, the RNFL thickness values were correlated in all quadrants, as were the retinal thickness values except the inferior outer sector. COV for average RNFL and CRT thickness were 2.9% and 4.6%for Stratus OCT, and 2.1% and 4.2% for OPKO/OTI OCT,respectively.CONCLUSION: We found good reproducibility of RNFL and retina thickness measurements for both Stratus OCT and OPKO/OTI OCT devices. However, even though the two OCT systems provided statistically correlated results,the values for both RNFL and macular thickness were statistically different. RNFL and macular thickness measurements with the OPKO/OTI OCT were higher than that of the Stratus OCT; therefore, the two OCT systems cannot be used interchangeably for the measurements of RNFL and macular thickness.

  6. Characterization of a fiber-taper charge-coupled device system for plastic scintillation dosimetry and comparison with the traditional lens system

    International Nuclear Information System (INIS)

    Purpose: To compare the signal-to-noise ratio (SNR), dose sensitivity and stability, and reproducibility of a lens-less charge-coupled device (CCD) photon-counting system with those of a traditional CCD + lens photon-counting system for plastic scintillation detectors (PSDs). Methods: The PSD used in this study was made from a 1-mm diameter, 2-mm long BCF60 scintillating fiber (emission peak at 530 nm) coupled to a 2.6-m Eska GH-4001 clear plastic fiber. This PSD was coupled to either a fiber-taper-based photon-counting system (FTS) or a lens-based photon-counting system (LS). In the FTS, the fiber-taper was attached to a 2048 × 2048 pixel, uncooled Alta 4020 polychromatic CCD camera. The LS consisted of a 1600 × 1200 pixel Alta 2020 polychromatic CCD camera (cooled to −18 °C) with a 50-mm lens with f/# = 1. Dose measurements were made under the same conditions for each system (isocentric setup; depth of 1.5 cm in solid water using a 10 × 10 cm2 field size and 6-MV photon beam). The performance of each system was determined and compared, using the chromatic Čerenkov removal method to account for the stem effects produced in the clear plastic fiber. Results: The FTS increased the light collected by a factor of 4 compared with the LS, for the same dose measurements. This gain was possible because the FTS was not limited by the optical aberration that comes with a lens system. Despite a 45 °C operating temperature difference between the systems, the SNR was 1.8–1.9 times higher in the FTS than in the LS, for blue and green channels respectively. Low-dose measurements of 1.0 and 0.5 cGy were obtained with an accuracy of 3.4% and 5.6%, respectively, in the FTS, compared with 5.8% and 15.9% in the LS. The FTS provided excellent dose measurement stability as a function of integration time, with at most a 1% difference at 5 cGy. Under the same conditions, the LS system produced a measurement difference between 2 and 3%. Conclusion: Our results showed that

  7. Two-dimensional complex source point solutions: application to propagationally invariant beams, optical fiber modes, planar waveguides, and plasmonic devices.

    Science.gov (United States)

    Sheppard, Colin J R; Kou, Shan S; Lin, Jiao

    2014-12-01

    Highly convergent beam modes in two dimensions are considered based on rigorous solutions of the scalar wave (Helmholtz) equation, using the complex source point formalism. The modes are applicable to planar waveguide or surface plasmonic structures and nearly concentric microcavity resonator modes in two dimensions. A novel solution is that of a vortex beam, where the direction of propagation is in the plane of the vortex. The modes also can be used as a basis for the cross section of propagationally invariant beams in three dimensions and bow-tie-shaped optical fiber modes. PMID:25606756

  8. Novel 1-D Sandwich Photonic Bandgap Structure

    Institute of Scientific and Technical Information of China (English)

    庞云波; 高葆新

    2004-01-01

    A sandwich photonic bandgap (PBG) structure is a novel PBG structure whose periodic lattice is buried in the middle of a substrate. Neither drilling nor suspending the substrate is required, and the integrity of the ground plane is maintained. This paper presents several modification techniques for sandwich PBG structure fabrication. The forbidden gap can be improved by adopting the chirping technique, applying the tapering technique, enlarging the periodic elements, adjusting the location of the periodic lattice in the substrate, and using different dielectric media H-shape elements. A finite difference time domain method is applied to analyze the structures. Deep and wide stopbands can be obtained using the modified sandwich structures. Experimental measurement results agree well with the theoretical analysis.

  9. Sub-300 femtosecond soliton tunable fiber laser with all-anomalous dispersion passively mode locked by black phosphorus.

    Science.gov (United States)

    Chen, Yu; Chen, Shuqing; Liu, Jun; Gao, Yanxia; Zhang, Wenjing

    2016-06-13

    By using evanescent field optical deposition method, we had successfully fabricated an effective optoelectronic device based on multi-layer black phosphorus (BP), which is been heavily investigating 2 dimensional (2D) semiconducting material with similar structure as graphene and thickness dependent direct band-gap. By placing this BP-based optoelectronic device inside a highly compact all-anomalous dispersion fiber laser cavity, stable passive mode-locking operation could be ensured and eventually a record 280 fs transmission limited soliton pulse with tunable central wavelength had been obtained through finely tailoring the cavity length. Other operation states, like bound soliton and noise-like state, had also been observed as well. This work demonstrates the enormous potential of BP for ultra-short pulse generation as an effective optoelectronic device. PMID:27410348

  10. In-line sample concentration by evaporation through porous hollow fibers and micromachined membranes embedded in microfluidic devices.

    Science.gov (United States)

    Zhang, Hainan; Tiggelaar, Roald M; Schlautmann, Stefan; Bart, Jacob; Gardeniers, Han

    2016-02-01

    Two types of microfluidic systems, a porous hollow fiber and a thin supported membrane with an array of micromachined holes, are investigated for concentrating mass-limited analyte samples. Water evaporation is driven by the partial pressure difference across the hydrophobic membrane, induced by dry sweeping gas on the permeate side. An analytical model permitting clarification of the contribution of design and process parameters on acquisition of concentrated solution and prediction of achievable concentration factors is presented. Concentrating an exemplary solution utilizing the two systems has been studied at different experimental conditions to validate the model. The results show that the hollow fiber gives controllable concentration factors of more than 10. For the micromachined membrane concentrator concentration factors of 6-8 were achieved, at much lower flow rates than predicted by the model. Because of the asymptotic dependence of concentration factor on flow rate, accurate control of the liquid feed is extremely critical in the flow rate range where high concentration factors are obtained, and the smallest variations in liquid flow rate may easily lead to supersaturation and deposition of solutes in the pores. This changes membrane porosity in an unpredictable way and limits the maximum attainable concentration factor. PMID:26331575

  11. Review of long period fiber gratings written by CO2 laser

    OpenAIRE

    Wang, Yiping

    2010-01-01

    This paper presents a systematic review of long period fiber gratings (LPFGs) written by the CO2 laser irradiation technique. First, various fabrication techniques based on CO2 laser irradiations are demonstrated to write LPFGs in different types of optical fibers such as conventional glass fibers, solid-core photonic crystal fibers, and air-core photonic bandgap fibers. Second, possible mechanisms, e.g., residual stress relaxation, glass structure changes, and physical deformation, of refrac...

  12. Microstructured optical fibers - Fundamentals and applications

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper; Bjarklev, Anders Overgaard

    2006-01-01

    In recent years optical fibers having a complex microstructure in the transverse plane have attracted much attention from both researchers and industry. Such fibers can either guide light through total internal reflection or the photonic bandgap effect. Among the many unique applications offered by...... these fibers are mode guidance in air, highly flexible dispersion engineering, and the use of very heterogeneous material combinations. In this paper, we review the different types and applications of microstructured optical fibers, with particular emphasis on recent advances in the field....

  13. Compound semiconductor alloys: From atomic-scale structure to bandgap bowing

    International Nuclear Information System (INIS)

    Compound semiconductor alloys such as InxGa1−xAs, GaAsxP1−x, or CuInxGa1−xSe2 are increasingly employed in numerous electronic, optoelectronic, and photonic devices due to the possibility of tuning their properties over a wide parameter range simply by adjusting the alloy composition. Interestingly, the material properties are also determined by the atomic-scale structure of the alloys on the subnanometer scale. These local atomic arrangements exhibit a striking deviation from the average crystallographic structure featuring different element-specific bond lengths, pronounced bond angle relaxation and severe atomic displacements. The latter, in particular, have a strong influence on the bandgap energy and give rise to a significant contribution to the experimentally observed bandgap bowing. This article therefore reviews experimental and theoretical studies of the atomic-scale structure of III-V and II-VI zincblende alloys and I-III-VI2 chalcopyrite alloys and explains the characteristic findings in terms of bond length and bond angle relaxation. Different approaches to describe and predict the bandgap bowing are presented and the correlation with local structural parameters is discussed in detail. The article further highlights both similarities and differences between the cubic zincblende alloys and the more complex chalcopyrite alloys and demonstrates that similar effects can also be expected for other tetrahedrally coordinated semiconductors of the adamantine structural family

  14. Photonic crystal fibers: fundamentals to emerging applications

    DEFF Research Database (Denmark)

    Bjarklev, Anders Overgaard

    2005-01-01

    A review of the fundamental properties of photonic crystal fibers is presented. Special focus is held on the emerging fields of application within areas such as actively controlled fiber devices and high-power fiber lasers.......A review of the fundamental properties of photonic crystal fibers is presented. Special focus is held on the emerging fields of application within areas such as actively controlled fiber devices and high-power fiber lasers....

  15. Design for maximum band-gaps in beam structures

    DEFF Research Database (Denmark)

    Olhoff, Niels; Niu, Bin; Cheng, Gengdong

    2012-01-01

    This paper aims to extend earlier optimum design results for transversely vibrating Bernoulli-Euler beams by determining new optimum band-gap beam structures for (i) different combinations of classical boundary conditions, (ii) much larger values of the orders n and n-1 of adjacent upper and lower...... eigenfrequencies of maximized band-gaps, and (iii) different values of a minimum cross-sectional area constraint. The periodicity of the optimum beams and the attenuation of their band-gaps are also discussed....

  16. Fiber-optic Fourier transform infrared (FO-FTIR) spectroscopy for detecting endotoxin contamination in ophthalmic viscosurgical devices (OVDS) (Conference Presentation)

    Science.gov (United States)

    Hassan, Moinuddin; Ilev, Ilko

    2016-03-01

    Ophthalmic Viscosurgical Devices (OVDs) in clinical setting are a major health risk factor for potential endotoxin contamination in the eye, due to their extensive applications in cataract surgery for space creation, stabilization and protection of intraocular tissue and intraocular lens (IOL) during implantation. Endotoxin contamination of OVDs is implicated in toxic anterior syndrome (TASS), a severe complication of cataract surgery that leads to intraocular damage and even blindness. Current standard methods for endotoxin contamination detection utilize rabbit assay or Limulus amoebocyte lysate (LAL) assays. These endotoxin detection strategies are extremely difficult for gel-like type devices such as OVDs. To overcome the endotoxin detection limitations in OVDs, we have developed an alternative optical detection methodology for label-free and real-time sensing of bacterial endotoxin in OVDs, based on fiber-optic Fourier transform infrared (FO-FTIR) transmission spectrometry in the mid-IR spectral range from 2.5 micron to 12 micron. Endotoxin contaminated OVD test samples were prepared by serial dilutions of endotoxins on OVDs. The major results of this study revealed two salient spectral peak shifts (in the regions 2925 to 2890 cm^-1 and 1125 to 1100 cm^-1), which are associated with endotoxin in OVDs. In addition, FO-FTIR experimental results processed using a multivariate analysis confirmed the observed specific peak shifts associated with endotoxin contamination in OVDs. Thus, employing the FO-FTIR sensing methodology integrated with a multivariate analysis could potentially be used as an alternative endotoxin detection technique in OVD.

  17. Fused-Polished Fiber Couplers

    Institute of Scientific and Technical Information of China (English)

    Sien; Chi; Shiao-Min; Tseng

    2003-01-01

    We report on fused-polished fiber couplers with a new fabrication method. This structure so fabricated is promising while achieving high-performance all-fiber WDM devices. Potential advantages and prospects of our works are presented.

  18. The Tunable Bandgap of AB-Stacked Bilayer Graphene on SiO2 with H2O Molecule Adsorption

    Institute of Scientific and Technical Information of China (English)

    WANG Tao; GUO Qing; AO Zhi-Min; LIU Yan; WANG Wen-Bo; SHENG Kuang; YU Bin

    2011-01-01

    The atomic and electronic structures of AB-stacking bilayer graphene (BLG) in the presence of H2O molecules are investigated by density functional theory calculations.For free-standing BLG,the bandgap is opened to 0.101 eV with a single H2O molecule adsorbed on its surface.The perfectly suspended BLG is sensitive to H2O adsorbates,which break the BLG lattice symmetry and open an energy gap.While a single H2O molecule is adsorbed on the BLG surface with a SiO2 substrate,the bandgap widens to 0.363eV.Both the H2O molecule adsorption and the oxide substrate contribute to the BLG bandgap opening.The phenomenon is interpreted with the charge transfer process in 2D carbon nanostructures.With its demonstrated unique electron transport properties,graphene has becomes one of the research hot spots with great potential in replacing silicon for future-generation nanoscale electronic devices.[1-3]Among graphene derivatives,AB-stacking bilayer graphene (BLG) exhibits fantastic properties.For example,the IBM research group successfully demonstrated a BLG-based transistor with a working frequency from 24.7 to 100GHz and highlighted suppressed electronic noise in devices.[4-6] With one additional layer added on single-layer graphene,BLG has a completely different band structure.However,pristine BLG still suffers from the same zero-bandgap (Eg) issue as single-layer graphene,hampering the implementation of logic switch devices with sufficient onto-off current ratios.%The atomic and electronic structures of AB-stacking bilayer graphene (BLG) in the presence of H2O molecules are investigated by density functional theory calculations. For free-standing BLG, the bandgap is opened to 0.101 eV with a single H2O molecule adsorbed on its surface. The perfectly suspended BLG is sensitive to H2O adsorbates, which break the BLG lattice symmetry and open an energy gap. While a single H2O molecule is adsorbed on the BLG surface with a S1O2 substrate, the bandgap widens to 0.363eV. Both the H2O

  19. High Power Wide Bandgap Engineered MMW MMIC Transceiver Project

    Data.gov (United States)

    National Aeronautics and Space Administration — During this phase I SBIR effort unique proven lattice and bandgap engineering techniques will be utilized to epitaxially grow InAlAs / InGaAs on GaN substrate for...

  20. Bandgap tuning in armchair MoS2 nanoribbon

    Science.gov (United States)

    Yue, Qu; Chang, Shengli; Kang, Jun; Zhang, Xueao; Shao, Zhengzheng; Qin, Shiqiao; Li, Jingbo

    2012-08-01

    We report on the first-principles calculations of bandgap modulation in armchair MoS2 nanoribbon (AMoS2NR) by transverse and perpendicular electric fields respectively. In the monolayer AMoS2NR case, it is shown that the bandgap can be significantly reduced and be closed by transverse field, whereas the bandgap modulation is absent under perpendicular field. The critical strength of transverse field for gap closure decreases as ribbon width increases. In the multilayer AMoS2NR case, in contrast, it is shown that the bandgap can be effectively reduced by both transverse and perpendicular fields. Nevertheless, it seems that the two fields exhibit different modulation effects on the gap. The critical strength of perpendicular field for gap closure decreases with increasing number of layers, while the critical strength of transverse field is almost independent of it.

  1. Specialty optical fibers: revisited

    Science.gov (United States)

    Romaniuk, Ryszard S.

    2011-10-01

    The paper contains description of chosen aspects of analysis and design of tailored optical fibers. By specialty optical fibers we understand here the fibers which have complex construction and which serve for the functional processing of optical signal rather than long distance transmission. Thus, they are called also instrumentation optical fibers. The following issues are considered: transmission properties, transformation of optical signal, fiber characteristics, fiber susceptibility to external reactions. The technology of tailored optical fibers offers a wider choice of the design tools for the fiber itself, and then various devices made from these fiber, than classical technology of communication optical fibers. The consequence is different fiber properties, nonstandard dimensions and different metrological problems. The price to be paid for wider design possibilities are bigger optical losses of these fibers and weaker mechanical properties, and worse chemical stability. These fibers find their applications outside the field of telecommunications. The applications of instrumentation optical fibers combine other techniques apart from the photonics ones like: electronic, chemical and mechatronic.

  2. Degradation of wide band-gap electrolumienscent materials by exciton-polaron interactions (Presentation Recording)

    Science.gov (United States)

    Aziz, Hany; Wang, Qi

    2015-10-01

    The limited performance stability and gradual loss in the electroluminescence efficiency of OLEDs utilizing wide band-gap materials, such as blue-emitting phosphorescent and fluorescent devices, continues to be a challenge for wider technology adoption. We recently found that interactions between excitons and polarons play an important role in the aging behavior of electroluminescent materials, and that a correlation exists between the susceptibility of these materials to this aging mode and their band-gap. This degradation mode is also found to be often associated with the emergence of new bands - at longer wavelength - in the electroluminescence spectra of the materials, that can often be detected after prolonged electrical driving. Such bands contribute to the increased spectral broadening and color purity loss often observed in these devices over time. Exciton-polaron interactions, and the associated degradation, are also found to occur most significantly in the vicinity of device inter-layer interfaces such as at the interface between the emitter layer and the electron or hole transport layers. New results obtained from investigations of these phenomena in a wide range of commonly used host and guest OLED materials will be presented.

  3. Fiber optic communication technology; Proceedings of the Meeting, San Diego, CA, August 23, 24, 1984

    Science.gov (United States)

    Kleekamp, C. W.

    Fiber optic components are considered, taking into account a review of developments related to optical fibers, a review of fiber optic cable technology, aspects of fiber system testing, fiber optic splices, a critical review of fiber optic connectors, and fiber optic communication technology branching devices. Developments concerning fiber optic systems are also discussed, giving attention to optoelectronic issues in fiber optic communications, digital fiber optic systems, wideband analog fiber optic systems, fiber optic local area networks, and wavelength division multiplexing.

  4. Semiconductor nanostructures for optoelectronic devices processing, characterization and applications

    CERN Document Server

    Yi, Gyu-Chul

    2012-01-01

    This book summarizes the current state of semiconductor nanodevice development, examining nanowires, nanorods, hybrid semiconductor nanostructures, wide bandgap nanostructures for visible light emitters and graphene and describing their device applications.

  5. Local resonance bandgaps in periodic media: theory and experiment.

    Science.gov (United States)

    Raghavan, L; Phani, A Srikantha

    2013-09-01

    Periodic composites such as acoustic metamaterials use local resonance phenomenon in designing low frequency sub-Bragg bandgaps. These bandgaps emerge from a resonant scattering interaction between a propagating wave and periodically arranged resonators. This paper develops a receptance coupling technique to combine the dynamics of the resonator with the unit cell dynamics of the background medium to analyze flexural wave transmission in a periodic structure, involving a single degree of freedom coupling between the medium and the resonator. Receptance techniques allow for a straightforward extension to higher dimensional systems with multiple degrees of freedom coupling and for easier experimental measurements. Closed-form expressions for the location and width of sub-Bragg bandgaps are obtained. Rigid body modes of the unit cell of the background medium are shown to set the bounding frequencies for local resonance bandgaps. Results from the receptance analysis compare well with Bloch wave analysis and experiments performed on a finite structural beam with periodic masses and resonators. Stronger coupling and inertia of the resonator increase the local resonance bandgap width. Two-fold periodicity widens the Bragg bandgap, narrowed by local resonators, thus expanding the design space and highlighting the advantages of hierarchical periodicity. PMID:23967928

  6. Paper-based energy-storage devices comprising carbon fiber-reinforced polypyrrole-cladophora nanocellulose composite electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Razaq, Aamir; Sjoedin, Martin; Stroemme, Maria; Mihranyan, Albert [Nanotechnology and Functional Materials, Department of Engineering Sciences, Uppsala (Sweden); Department of Chemistry, Angstroem Laboratory, Uppsala (Sweden); Nyholm, Leif [Department of Chemistry, Angstroem Laboratory, Uppsala (Sweden)

    2012-04-15

    Composites of polypyrrole (PPy) and Cladophora nanocellulose, reinforced with 8 {mu}m-thick chopped carbon filaments, can be used as electrode materials to obtain paper-based energy-storage devices with unprecedented performance at high charge and discharge rates. Charge capacities of more than 200 C g{sup -1} (PPy) are obtained for paper-based electrodes at potential scan rates as high as 500 mV s{sup -1}, whereas cell capacitances of {proportional_to}60-70 F g{sup -1} (PPy) are reached for symmetric supercapacitor cells with capacitances up to 3.0 F (i.e.,0.48 F cm{sup -2}) when charged to 0.6 V using current densities as high as 31 A g{sup -1} based on the PPy weight (i.e., 99 mA cm{sup -2}). Energy and power densities of 1.75 Wh kg{sup -1} and 2.7 kW kg{sup -1}, respectively, are obtained when normalized with respect to twice the PPy weight of the smaller electrode. No loss in cell capacitance is seen during charging/discharging at 7.7 A g{sup -1} (PPy) over 1500 cycles. It is proposed that the nonelectroactive carbon filaments decrease the contact resistances and the resistance of the reduced PPy composite. The present straightforward approach represents significant progress in the development of low-cost and environmentally friendly paper-based energy-storage devices for high-power applications. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Ab initio study of the bandgap engineering of Al1−xGaxN for optoelectronic applications

    KAUST Repository

    Amin, B.

    2011-01-19

    A theoretical study of Al1−xGaxN, based on the full-potential linearized augmented plane wave method, is used to investigate the variations in the bandgap,optical properties, and nonlinear behavior of the compound with the change in the Ga concentration. It is found that the bandgap decreases with the increase in Ga. A maximum value of 5.50 eV is determined for the bandgap of pure AlN, which reaches a minimum value of 3.0 eV when Al is completely replaced by Ga. The static index of refraction and dielectric constant decreases with the increase in the bandgap of the material, assigning a high index of refraction to pure GaN when compared to pure AlN. The refractive index drops below 1 for higher energy photons, larger than 14 eV. The group velocity of these photons is larger than the vacuum velocity of light. This astonishing result shows that at higher energies the optical properties of the material shifts from linear to nonlinear. Furthermore, frequency dependent reflectivity and absorption coefficients show that peak values of the absorption coefficient and reflectivity shift toward lower energy in the ultraviolet (UV) spectrum with the increase in Ga concentration. This comprehensive theoretical study of the optoelectronic properties predicts that the material can be effectively used in the optical devices working in the visible and UV spectrum.

  8. Defects induced luminescence and tuning of bandgap energy narrowing in ZnO nanoparticles doped with Li ions

    KAUST Repository

    Awan, Saif Ullah

    2014-08-28

    Microstructural and optical properties of Zn1-yLiyO (0.00 ≤y ≤0.10) nanoparticles are investigated. Li incorporation leads to substantial changes in the structural characterization. From micro-structural analysis, no secondary phases or clustering of Li was detected. Elemental maps confirmed homogeneous distribution of Li in ZnO. Sharp UV peak due to the recombination of free exciton and defects based luminescence broad visible band was observed. The transition from the conduction band to Zinc vacancy defect level in photoluminescence spectra is found at 518±2.5nm. The yellow luminescence was observed and attributed to Li related defects in doped samples. With increasing Li doping, a decrease in energy bandgap was observed in the range 3.26±0.014 to 3.17±0.018eV. The bandgap narrowing behavior is explained in terms of the band tailing effect due to structural disorder, carrier-impurities, carrier-carrier, and carrier-phonon interactions. Tuning of the bandgap energy in this class of wide bandgap semiconductor is very important for room temperature spintronics applications and optical devices. © 2014 AIP Publishing LLC.

  9. On the Suppression Band and Bandgap of Planar Electromagnetic Bandgap Structures

    Directory of Open Access Journals (Sweden)

    Baharak Mohajer-Iravani

    2014-01-01

    Full Text Available Electromagnetic bandgap structures are considered a viable solution for the problem of switching noise in printed circuit boards and packages. Less attention, however, has been given to whether or not the introduction of EBGs affects the EMI potential of the circuit to couple unwanted energy to neighboring layers or interconnects. In this paper, we show that the bandgap of EBG structures, as generated using the Brillouin diagram, does not necessarily correspond to the suppression bandwidth typically generated using S-parameters. We show that the reactive near fields radiating from openings within the EBG layers can be substantial and are present in the entire frequency band including propagating and nonpropagating mode regions. These fields decay fast with distance; however, they can couple significant energy to adjacent layers and to signal lines. The findings are validated using full-wave three-dimensional numerical simulation. Based on this work, design guidelines for EBG structures can be drawn to insure not only suppression of switching noise but also minimization of EMI and insuring signal integrity.

  10. Nickel (II Preconcentration and Speciation Analysis During Transport from Aqueous Solutions Using a Hollow-fiber Permeation Liquid Membrane (HFPLM Device

    Directory of Open Access Journals (Sweden)

    Jan Åke Jönsson

    2011-08-01

    Full Text Available Nickel (II preconcentration and speciation analysis using a hollow fiber supported liquid membrane (HFSLM device was studied. A counterflow of protons coupled to complexation with formate provided the driving force of the process, while Kelex 100 was employed as carrier. The influence of variables related to module configuration (acceptor pH and carrier concentration and to the sample properties (donor pH on the preconcentration factor, E, was simultaneously studied and optimized using a 3 factor Doehlert matrix response surface methodology. The effect of metal concentration was studied as well. Preconcentration factors as high as 4240 were observed  depending on the values of the different variables. The effects of the presence of inorganic anions (NO2-, SO42-, Cl-, NO3-, CO32-, CN- and dissolved organic matter (DOM in the form of humic acids were additionally considered in order to carry out a speciation analysis study. Nickel preconcentration was observed to be independent of both effects, except when cyanide was present in the donor phase. A characterization of the transport regime was performed through the analysis of the dependence of E on the temperature. E increases with the increase in temperature according to the equation E(K = -8617.3 + 30.5T with an activation energy of 56.7 kJ mol-1 suggesting a kinetic-controlled regime. Sample depletion ranged from 12 to 1.2% depending on the volume of the donor phase (100 to 1000 mL, respectively.

  11. Monolithic Yb-fiber femtosecond laser with intracavity all-solid PBG fiber and ex-cavity HC-PCF

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Liu, Xiaomin; Lægsgaard, Jesper

    2010-01-01

    (PM) photonic bandgap fiber (PBG) is used in the cavity of the master oscillator for dispersion compensation and stabilization of modelocking. The final compression of an chirped-pulse-amplified laser signal is performed in a hollow PM PCF, yielding final fiber-delivered pulse energy of around 7 n......We demonstrate an all-fiber femtosecond master oscillator / power amplifier operating at the central wavelength of 1033 nm, based on Yb-doped fiber as gain medium, and two different kinds of photonic crystal fibers for dispersion control and stabilization. An all-solid (AS) polarization maintaining...

  12. High-Efficiency Solar Cells Using Photonic-Bandgap Materials

    Science.gov (United States)

    Dowling, Jonathan; Lee, Hwang

    2005-01-01

    Solar photovoltaic cells would be designed to exploit photonic-bandgap (PBG) materials to enhance their energy-conversion efficiencies, according to a proposal. Whereas the energy-conversion efficiencies of currently available solar cells are typically less than 30 percent, it has been estimated that the energy-conversion efficiencies of the proposed cells could be about 50 percent or possibly even greater. The primary source of inefficiency of a currently available solar cell is the mismatch between the narrow wavelength band associated with the semiconductor energy gap (the bandgap) and the broad wavelength band of solar radiation. This mismatch results in loss of power from both (1) long-wavelength photons, defined here as photons that do not have enough energy to excite electron-hole pairs across the bandgap, and (2) short-wavelength photons, defined here as photons that excite electron- hole pairs with energies much above the bandgap. It follows that a large increase in efficiency could be obtained if a large portion of the incident solar energy could be funneled into a narrow wavelength band corresponding to the bandgap. In the proposed approach, such funneling would be effected by use of PBG materials as intermediaries between the Sun and photovoltaic cells.

  13. Wideband saturable absorption in few-layer molybdenum diselenide (MoSe2) for Q-switching Yb-, Er- and Tm-doped fiber lasers

    CERN Document Server

    Woodward, R I; Runcorn, T H; Hu, G; Torrisi, F; Kelleher, E J R; Hasan, T

    2015-01-01

    We fabricate a free-standing molybdenum diselenide (MoSe2) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe2 flakes into a polymer film. The MoSe2-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe2, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe2 to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices.

  14. Hierarchically Structured Electrospun Fibers

    Directory of Open Access Journals (Sweden)

    Nicole E. Zander

    2013-01-01

    Full Text Available Traditional electrospun nanofibers have a myriad of applications ranging from scaffolds for tissue engineering to components of biosensors and energy harvesting devices. The generally smooth one-dimensional structure of the fibers has stood as a limitation to several interesting novel applications. Control of fiber diameter, porosity and collector geometry will be briefly discussed, as will more traditional methods for controlling fiber morphology and fiber mat architecture. The remainder of the review will focus on new techniques to prepare hierarchically structured fibers. Fibers with hierarchical primary structures—including helical, buckled, and beads-on-a-string fibers, as well as fibers with secondary structures, such as nanopores, nanopillars, nanorods, and internally structured fibers and their applications—will be discussed. These new materials with helical/buckled morphology are expected to possess unique optical and mechanical properties with possible applications for negative refractive index materials, highly stretchable/high-tensile-strength materials, and components in microelectromechanical devices. Core-shell type fibers enable a much wider variety of materials to be electrospun and are expected to be widely applied in the sensing, drug delivery/controlled release fields, and in the encapsulation of live cells for biological applications. Materials with a hierarchical secondary structure are expected to provide new superhydrophobic and self-cleaning materials.

  15. On the Integration of Wide Band-gap Semiconductors in Single Phase Boost PFC Converters

    DEFF Research Database (Denmark)

    Hernandez Botella, Juan Carlos

    compared to Si semiconductors. Moreover, both semiconductor materials are particularly interesting for high temperature operation. These characteristics makes integration of SiC and GaN devices as the next logical step to further increase efficiency and power density in SMPS. This work is part of the Ph...... diodes, or the introduction of silicon carbide (SiC) diodes, provided large steps in miniaturization and efficiency improvement of switched mode power converters. Gallium nitride (GaN) and SiC semiconductor devices have already been around for some years. The first one proliferated due to the necessity...... of high frequency operation in optoelectronics applications. On the other hand, Schottky SiC power diodes were introduced in 2001 as an alternative to eliminate reverse recovery issues in Si rectifiers. Wide band-gap semiconductors offer an increased electrical field strength and electron mobility...

  16. Optimum design of band-gap beam structures

    DEFF Research Database (Denmark)

    Olhoff, Niels; Niu, Bin; Cheng, Gengdong

    2012-01-01

    of a single, linearly elastic material without damping. Numerical results are presented for different combinations of classical boundary conditions, prescribed orders of the upper and lower natural frequencies of maximized natural frequency gaps, and a given minimum constraint value for the beam......The design of band-gap structures receives increasing attention for many applications in mitigation of undesirable vibration and noise emission levels. A band-gap structure usually consists of a periodic distribution of elastic materials or segments, where the propagation of waves is impeded or...... significantly suppressed for a range of external excitation frequencies. Maximization of the band-gap is therefore an obvious objective for optimum design. This problem is sometimes formulated by optimizing a parameterized design model which assumes multiple periodicity in the design. However, it is shown in...

  17. Sustained hole inversion layer in a wide-bandgap metal-oxide semiconductor with enhanced tunnel current

    Science.gov (United States)

    Shoute, Gem; Afshar, Amir; Muneshwar, Triratna; Cadien, Kenneth; Barlage, Douglas

    2016-02-01

    Wide-bandgap, metal-oxide thin-film transistors have been limited to low-power, n-type electronic applications because of the unipolar nature of these devices. Variations from the n-type field-effect transistor architecture have not been widely investigated as a result of the lack of available p-type wide-bandgap inorganic semiconductors. Here, we present a wide-bandgap metal-oxide n-type semiconductor that is able to sustain a strong p-type inversion layer using a high-dielectric-constant barrier dielectric when sourced with a heterogeneous p-type material. A demonstration of the utility of the inversion layer was also investigated and utilized as the controlling element in a unique tunnelling junction transistor. The resulting electrical performance of this prototype device exhibited among the highest reported current, power and transconductance densities. Further utilization of the p-type inversion layer is critical to unlocking the previously unexplored capability of metal-oxide thin-film transistors, such applications with next-generation display switches, sensors, radio frequency circuits and power converters.

  18. STM/STS Study of Surface Modification Effect on Bandgap Structure of Ti2C with -OH, -F, and -H

    Science.gov (United States)

    Jung, Seong Jun; Lai, Shen; Jeong, Taehwan; Lee, Sungjoo; Song, Young Jae

    In this presentation, we present Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) study of bandgap structures of surface-modified Ti2C with -OH, -F, and -O in atomic scale. Since the discovery of new two dimensional (2D) materials like graphene, various 2D materials including transition metal dichalcogenide (TMD) have been intensively investigated. There are, however, still scientific issues to apply them to the device fabrications for controlling the appropriate bandgap structure with high field effect mobility. Recently another 2D materials of transition metal carbide (TMC), Ti2CTx with modifiable surface group Tx(-OH, -F, and -O) was suggested. [S. Lai et. al, Nanoscale (2015), DOI: 10.1039/C5NR06513E]. This 2D material shows that the mobility at room temperature is less sensitive to the measured transport bandgap, which can imply that Ti2CTx can be a strong candidate of 2D TMC for application to the future electronic devices. Surface modification on the electronic structure of Ti2C by -OH, -F, and -O is, therefore, investigated by STM and STS in atomic scale. More scientific results will be further discussed in the presentation. This research was supported by Basic Science Research Program through the National Research Foundation of Korea funded by the Korean government (Grant Numbers: 2015R1A1A1A05027585, 2011­0030046, IBS- R011­D1, 2014M3C1A3053024 and 2015M3A7B4050455).

  19. 21 CFR 895.101 - Prosthetic hair fibers.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Prosthetic hair fibers. 895.101 Section 895.101...) MEDICAL DEVICES BANNED DEVICES Listing of Banned Devices § 895.101 Prosthetic hair fibers. Prosthetic hair fibers are devices intended for implantation into the human scalp to simulate natural hair or...

  20. 21 CFR 872.4620 - Fiber optic dental light.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Fiber optic dental light. 872.4620 Section 872...) MEDICAL DEVICES DENTAL DEVICES Surgical Devices § 872.4620 Fiber optic dental light. (a) Identification. A fiber optic dental light is a device that is a light, usually AC-powered, that consists of glass...

  1. Distributed mode filtering rod fiber amplifier delivering 292W with improved mode stability

    DEFF Research Database (Denmark)

    Laurila, Marko; Jørgensen, Mette Marie; Hansen, Kristian Rymann; Alkeskjold, Thomas T.; Broeng, Jes; Lægsgaard, Jesper

    2012-01-01

    We demonstrate a high power fiber (85μm core) amplifier delivering up to 292Watts of average output power using a mode-locked 30ps source at 1032nm. Utilizing a single mode distributed mode filter bandgap rod fiber, we demonstrate 44% power improvement before the threshold-like onset of mode...

  2. Processing of nanocrystalline diamond thin films for thermal management of wide-bandgap semiconductor power electronics

    International Nuclear Information System (INIS)

    Highlights: → Studied effect of nanocrystalline diamond (NCD) deposition on device metallization. → Deposited NCD on to top of High Electron Mobility Transistors (HEMTs) and Si devices. → Temperatures below 290 deg. C for Si devices and 320 deg. C for HEMTs prevent metal damage. → Development of novel NCD-based thermal management for power electronics feasible. - Abstract: High current densities in wide-bandgap semiconductor electronics operating at high power levels results in significant self-heating of devices, which necessitates the development thermal management technologies to effectively dissipate the generated heat. This paper lays the foundation for the development of such technology by ascertaining process conditions for depositing nanocrystalline diamond (NCD) on AlGaN/GaN High Electron Mobility Transistors (HEMTs) with no visible damage to device metallization. NCD deposition is carried out on Si and GaN HEMTs with Au/Ni metallization. Raman spectroscopy, optical and scanning electron microscopy are used to evaluate the quality of the deposited NCD films. Si device metallization is used as a test bed for developing process conditions for NCD deposition on AlGaN/GaN HEMTs. Results indicate that no visible damage occurs to the device metallization for deposition conditions below 290 deg. C for Si devices and below 320 deg. C for the AlGaN/GaN HEMTs. Possible mechanisms for metallization damage above the deposition temperature are enumerated. Electrical testing of the AlGaN/GaN HEMTs indicates that it is indeed possible to deposit NCD on GaN-based devices with no significant degradation in device performance.

  3. Effect of Dielectric Constant Contrast and Filling Factor to Photonic Bandgap

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The effect of dielectric constant contrast and the filling factor to the photonic bandgap in a 2-D square lattice photonic crystal is discussed. The location, width and number of photonic bandgap can be modulated.

  4. Optically controlled photonic bandgap structures for microstrip circuits

    CERN Document Server

    Cadman, D A

    2003-01-01

    This thesis is concerned with the optical control of microwave photonic bandgap circuits using high resistivity silicon. Photoconducting processes that occur within silicon are investigated. The influence of excess carrier density on carrier mobility and lifetime is examined. In addition, electron-hole pair recombination mechanisms (Shockley-Read-Hall, Auger, radiative and surface) are investigated. The microwave properties of silicon are examined, in particular the variation of silicon reflectivity with excess carrier density. Filtering properties of microstrip photonic bandgap structures and how they may be controlled optically are studied. A proof-of-concept microstrip photonic bandgap structure with optical control is designed, simulated and measured. With no optical illumination incident upon the silicon, the microstrip photonic bandgap structure's filtering properties are well-defined; a 3dB stopband width of 2.6GHz, a 6dB bandwidth of 2GHz and stopband depth of -11.6dB at the centre frequency of 9.9GHz...

  5. Bandgap properties of low index contrast aperiodically ordered photonic quasicrystals

    CERN Document Server

    Zito, Gianluigi; Di Gennaro, Emiliano; Andreone, Antonello; Santamato, Enrico; Abbate, Giancarlo

    2009-01-01

    We numerically analyze, using Finite Difference Time Domain simulations, the bandgap properties of photonic quasicrystals with a low index contrast. We compared 8-, 10- and 12-fold symmetry aperiodically ordered lattices with different spatial tiling. Our results show that tiling design, more than symmetry, determines the transmission properties of these structures.

  6. Automating Energy Bandgap Measurements in Semiconductors Using LabVIEW

    Science.gov (United States)

    Garg, Amit; Sharma, Reena; Dhingra, Vishal

    2010-01-01

    In this paper, we report the development of an automated system for energy bandgap and resistivity measurement of a semiconductor sample using Four-Probe method for use in the undergraduate laboratory of Physics and Electronics students. The automated data acquisition and analysis system has been developed using National Instruments USB-6008 DAQ…

  7. Bandgap Opening in Graphene Induced by Patterned Hydrogen Adsorption

    DEFF Research Database (Denmark)

    Balog, Richard; Jørgensen, Bjarke; Nilsson, Louis;

    2010-01-01

    fermions, and graphene shows ballistic charge transport, turning it into an ideal material for circuit fabrication. However, graphene lacks a bandgap around the Fermi level, which is the defining concept for semiconductor materials and essential for controlling the conductivity by electronic means. Theory...

  8. Optically controlled photonic bandgap structures for microstrip circuits

    International Nuclear Information System (INIS)

    This thesis is concerned with the optical control of microwave photonic bandgap circuits using high resistivity silicon. Photoconducting processes that occur within silicon are investigated. The influence of excess carrier density on carrier mobility and lifetime is examined. In addition, electron-hole pair recombination mechanisms (Shockley-Read-Hall, Auger, radiative and surface) are investigated. The microwave properties of silicon are examined, in particular the variation of silicon reflectivity with excess carrier density. Filtering properties of microstrip photonic bandgap structures and how they may be controlled optically are studied. A proof-of-concept microstrip photonic bandgap structure with optical control is designed, simulated and measured. With no optical illumination incident upon the silicon, the microstrip photonic bandgap structure's filtering properties are well-defined; a 3dB stopband width of 2.6GHz, a 6dB bandwidth of 2GHz and stopband depth of -11.6dB at the centre frequency of 9.9GHz. When the silicon is illuminated, the structure's filtering properties are suppressed. Under illumination the experimental results display an increase in S21 of 6.5dB and a reduction in S11 of more than 10dB at 9.9GHz. A comparison of measured and simulated results reveal that the photogenerated excess carrier density is between 4 x 1015 cm-3 and 1.1 x 1016 cm-3. (author)

  9. Synthesis of low-bandgap alternating copolymers with thienothiadiazole units

    Czech Academy of Sciences Publication Activity Database

    Kmínek, Ivan; Výprachtický, Drahomír; Cimrová, Věra

    Istanbul : Istanbul Technical University, 2011. s. 197. [IUPAC International Conference on Advanced Polymers via Macromolecular Engineering /9./ - APME 2011. 05.09.2011-08.09.2011, Nevsehir, Cappadocia] R&D Projects: GA MŠk(CZ) 1M06031 Institutional research plan: CEZ:AV0Z40500505 Keywords : thienothiadiazole * low bandgap * copolymer Subject RIV: BM - Solid Matter Physics ; Magnetism

  10. A generation/recombination model assisted with two trap centers in wide band-gap semiconductors

    Science.gov (United States)

    Yamaguchi, Ken; Kuwabara, Takuhito; Uda, Tsuyoshi

    2013-03-01

    A generation/recombination (GR) model assisted with two trap centers has been proposed for studying reverse current on pn junctions in wide band-gap semiconductors. A level (Et1) has been assumed to be located near the bottom of the conduction band and the other (Et2) to be near the top of the valence band. The GR model has been developed by assuming (1) a high-electric field; F, (2) a short distance; d, between trap centers, (3) reduction in an energy-difference; Δeff = |Et1 - Et2| - eFd, and (4) hopping or tunneling conductions between trap centers with the same energy-level (Δeff ≈ 0). The GR rate has been modeled by trap levels, capture cross-sections, trap densities, and transition rate between trap centers. The GR rate, about 1010 greater than that estimated from the single-level model, has been predicted on pn junctions in a material with band-gap of 3.1 eV. Device simulations using the proposed GR model have been demonstrated for SiC diodes with and without a guard ring. A reasonable range for reverse current at room temperature has been simulated and stable convergence has been obtained in a numerical scheme for analyzing diodes with an electrically floating region.

  11. Optimization of Beam Properties with Respect to Maximum Band-Gap

    DEFF Research Database (Denmark)

    Halkjær, Søren; Sigmund, Ole

    2004-01-01

    We study numerically the frequency band-gap phenomenon for bending waves in an infinite periodic beam. The outcome of the analysis is then subjected to an optimization problem in order to maximize these band-gaps. The band-gap maximization may be performed with respect to material parameters and...

  12. Fabrication of micro-optical devices at the end of a multimode optical fiber with negative tone lift-off EBL

    International Nuclear Information System (INIS)

    A fabrication method based on negative tone lift off EBL is developed for constructing nano-structures at end faces of multimode optical fibers. With this new approach, precise and robust nano-structures with high spatial resolutions can be fabricated with minimum damage to the optical fiber face during the fabrication process. Based on this approach, high numerical aperture micro Fresnel zone plates (MZP) with focal lengths ∼3 µm were fabricated on the face of an optical fiber. The focusing characteristics of the fabricated MZP showed good consistency with the numerical simulations at the specified wavelength (∼405 nm). (paper)

  13. Graded-Bandgap Solar Cells Using All-Electrodeposited ZnS, CdS and CdTe Thin-Films

    Directory of Open Access Journals (Sweden)

    Obi K. Echendu

    2015-05-01

    Full Text Available A 3-layer graded-bandgap solar cell with glass/FTO/ZnS/CdS/CdTe/Au structure has been fabricated using all-electrodeposited ZnS, CdS and CdTe thin layers. The three semiconductor layers were electrodeposited using a two-electrode system for process simplification. The incorporation of a wide bandgap amorphous ZnS as a buffer/window layer to form glass/FTO/ZnS/CdS/CdTe/Au solar cell resulted in the formation of this 3-layer graded-bandgap device structure. This has yielded corresponding improvement in all the solar cell parameters resulting in a conversion efficiency >10% under AM1.5 illumination conditions at room temperature, compared to the 8.0% efficiency of a 2-layer glass/FTO/CdS/CdTe/Au reference solar cell structure. These results demonstrate the advantages of the multi-layer graded-bandgap device architecture over the conventional 2-layer structure. In addition, they demonstrate the effective application of the two-electrode system as a simplification to the conventional three-electrode system in the electrodeposition of semiconductors with the elimination of the reference electrode as a possible impurity source.

  14. Experimental Studies of Charge Transport in Single Crystal Diamond Devices

    OpenAIRE

    Majdi, Saman

    2012-01-01

    Diamond is a promising material for high-power, high-frequency and high- temperature electronics applications, where its outstanding physical properties can be fully exploited. It exhibits an extremely high bandgap, very high carrier mobilities, high breakdown field strength, and the highest thermal conductivity of any wide bandgap material. It is therefore an outstanding candidate for the fastest switching, the highest power density, and the most efficient electronic devices obtainable, with...

  15. 21 CFR 880.5300 - Medical absorbent fiber.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Medical absorbent fiber. 880.5300 Section 880.5300... Devices § 880.5300 Medical absorbent fiber. (a) Identification. A medical absorbent fiber is a device intended for medical purposes that is made from cotton or synthetic fiber in the shape of a ball or a...

  16. Compact and broadband waveguide taper based on partial bandgap photonic crystals

    Institute of Scientific and Technical Information of China (English)

    Jin Hou; Dingshan Gao; Huaming Wu; Zhiping Zhou

    2009-01-01

    Partial bandgap characteristics of parallelogram lattice photonic crystals are proposed to suppress the radiation modes in a compact dielectric waveguide taper so as to obtain high transmittance in a large wavelength range. Band structure of the photonic crystals shows that there exists a partial bandgap. The photonic crystals with partial bandgap are then used as the cladding of a waveguide taper to reduce the radiation loss efficiently. In comparison with the conventional dielectric taper and the complete bandgap photonic crystal taper, the partial bandgap photonic crystal taper has a high transmittance of above 85% with a wide band of 170 nm.

  17. Wide bandgap, strain-balanced quantum well tunnel junctions on InP substrates

    Science.gov (United States)

    Lumb, M. P.; Yakes, M. K.; González, M.; Bennett, M. F.; Schmieder, K. J.; Affouda, C. A.; Herrera, M.; Delgado, F. J.; Molina, S. I.; Walters, R. J.

    2016-05-01

    In this work, the electrical performance of strain-balanced quantum well tunnel junctions with varying designs is presented. Strain-balanced quantum well tunnel junctions comprising compressively strained InAlAs wells and tensile-strained InAlAs barriers were grown on InP substrates using solid-source molecular beam epitaxy. The use of InAlAs enables InP-based tunnel junction devices to be produced using wide bandgap layers, enabling high electrical performance with low absorption. The impact of well and barrier thickness on the electrical performance was investigated, in addition to the impact of Si and Be doping concentration. Finally, the impact of an InGaAs quantum well at the junction interface is presented, enabling a peak tunnel current density of 47.6 A/cm2 to be realized.

  18. Quantum well effect based on hybridization bandgap in deep subwavelength coupled meta-atoms

    Science.gov (United States)

    Chen, Yongqiang; Li, Yunhui; Wu, Qian; Jiang, Haitao; Zhang, Yewen; Chen, Hong

    2015-09-01

    In this paper, quantum well (QW) effect in a hybridization bandgap (HBG) structure via hiring deep subwavelength coupled meta-atoms is investigated. Subwavelength zero-index-metamaterial-based resonators acting as meta-atoms are side-coupled to a microstrip, forming the HBG structure. Both numerical and microwave experimental results confirm that, through properly hiring another set of meta-atoms, band mismatch between two HBGs can be introduced resulting in the HBG QW effect. Compared with the conventional QW structure based on Bragg interferences in photonic crystal, the device length of the proposed HBG QW structure can be reduced to only 1/4, demonstrating well the deep subwavelength property. Therefore, the above features make our design of HBG QW structures suitable to be utilized as multi-channel filters or multiplexers in microwave and optical communication system.

  19. Near-Infrared Sub-Bandgap All-Silicon Photodetectors: State of the Art and Perspectives

    Directory of Open Access Journals (Sweden)

    Luigi Sirleto

    2010-11-01

    Full Text Available Due to recent breakthroughs, silicon photonics is now the most active discipline within the field of integrated optics and, at the same time, a present reality with commercial products available on the market. Silicon photodiodes are excellent detectors at visible wavelengths, but the development of high-performance photodetectors on silicon CMOS platforms at wavelengths of interest for telecommunications has remained an imperative but unaccomplished task so far. In recent years, however, a number of near-infrared all-silicon photodetectors have been proposed and demonstrated for optical interconnect and power-monitoring applications. In this paper, a review of the state of the art is presented. Devices based on mid-bandgap absorption, surface-state absorption, internal photoemission absorption and two-photon absorption are reported, their working principles elucidated and their performance discussed and compared.

  20. Non-resonant below-bandgap two-photon absorption in quantum dot solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tian; Dagenais, Mario, E-mail: dage@ece.umd.edu [Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742 (United States)

    2015-04-27

    We study the optically nonlinear sub-bandgap photocurrent generation facilitated by an extended tailing distribution of states in an InAs/GaAs quantum dots (QDs) solar cell. The tailing states function as both the energy states for low energy photon absorption and the photocarriers extraction pathway. One of the biggest advantages of our method is that it can clearly differentiate the photocurrent due to one-photon absorption (1PA) process and two-photon absorption (2PA) process. Both 1PA and 2PA photocurrent generation efficiency in an InAs/GaAs QD device operated at 1550 nm have been quantitatively evaluated. A two-photon absorption coefficient β = 5.7 cm/GW is extracted.

  1. Diamond Electronic Devices

    International Nuclear Information System (INIS)

    For high-power and high-voltage applications, silicon is by far the dominant semiconductor material. However, silicon has many limitations, e.g. a relatively low thermal conductivity, electric breakdown occurs at relatively low fields and the bandgap is 1.1 eV which effectively limits operation to temperatures below 175 deg.n C. Wide-bandgap materials, such as silicon carbide (SiC), gallium nitride (GaN) and diamond offer the potential to overcome both the temperature and power handling limitations of silicon. Diamond is the most extreme in this class of materials. By the fundamental material properties alone, diamond offers the largest benefits as a semiconductor material for power electronic applications. On the other hand, diamond has a problem with a large carrier activation energy of available dopants which necessitates specialised device concepts to allow room temperature (RT) operation. In addition, the role of common defects on the charge transport properties of diamond is poorly understood. Notwithstanding this, many proof-of-principle two-terminal and three-terminal devices have been made and tested. Two-terminal electronic diamond devices described in the literature include: p-n diodes, p-i-n diodes, various types of radiation detectors, Schottky diodes and photoconductive or electron beam triggered switches. Three terminal devices include e.g. MISFETs and JFETs. However, the development of diamond devices poses great challenges for the future. A particularly interesting way to overcome the doping problem, for which there has been some recent progress, is to make so-called delta doped (or pulse-doped) devices. Such devices utilise very thin (∼1 nm) doped layers in order to achieve high RT activation.

  2. Diamond Electronic Devices

    Science.gov (United States)

    Isberg, J.

    2010-11-01

    For high-power and high-voltage applications, silicon is by far the dominant semiconductor material. However, silicon has many limitations, e.g. a relatively low thermal conductivity, electric breakdown occurs at relatively low fields and the bandgap is 1.1 eV which effectively limits operation to temperatures below 175° C. Wide-bandgap materials, such as silicon carbide (SiC), gallium nitride (GaN) and diamond offer the potential to overcome both the temperature and power handling limitations of silicon. Diamond is the most extreme in this class of materials. By the fundamental material properties alone, diamond offers the largest benefits as a semiconductor material for power electronic applications. On the other hand, diamond has a problem with a large carrier activation energy of available dopants which necessitates specialised device concepts to allow room temperature (RT) operation. In addition, the role of common defects on the charge transport properties of diamond is poorly understood. Notwithstanding this, many proof-of-principle two-terminal and three-terminal devices have been made and tested. Two-terminal electronic diamond devices described in the literature include: p-n diodes, p-i-n diodes, various types of radiation detectors, Schottky diodes and photoconductive or electron beam triggered switches. Three terminal devices include e.g. MISFETs and JFETs. However, the development of diamond devices poses great challenges for the future. A particularly interesting way to overcome the doping problem, for which there has been some recent progress, is to make so-called delta doped (or pulse-doped) devices. Such devices utilise very thin (˜1 nm) doped layers in order to achieve high RT activation.

  3. Electronic structure characterization and bandgap engineering of solar hydrogen materials

    International Nuclear Information System (INIS)

    Bandgap, band edge positions as well as the overall band structure of semiconductors are of crucial importance in photoelectrochemical and photocatalytic applications. The energy position of the band edge level can be controlled by the electronegativity of the dopants, the pH of the solution (flatband potential variation of 60 mV per pH unit), as well as by quantum confinement effects. Accordingly, band edges and bandgap can be tailored to achieve specific electronic, optical or photocatalytic properties. Synchrotron radiation with photon energy at or below 1 keV is giving new insight into such areas as condensed matter physics and extreme ultraviolet optics technology. In the soft x-ray region, the question tends to be, what are the electrons doing as they migrated between the atoms. In this paper, I will present a number of soft x-ray spectroscopic study of nanostructured 3d metal compounds Fe2O3 and ZnO

  4. Increased Functionality Porous Optical Fiber Structures

    OpenAIRE

    Wooddell, Michael Gary

    2007-01-01

    A novel fiber optic structure, termed stochastic ordered hole fibers, has been developed that contains an ordered array of six hollow tubes surrounding a hollow core, combined with a nanoporous glass creating a unique fully three dimensional pore/fiber configuration. The objective of this study is to increase the functionality of these stochastic ordered hole fibers, as well as porous clad fibers, by integrating electronic device components such as conductors, and semiconductor...

  5. Photon absorption and photocurrent in solar cells below semiconductor bandgap due to electron photoemission from plasmonic nanoantennas

    DEFF Research Database (Denmark)

    Novitsky, Andrey; Uskov, Alexander; Gritti, Claudia; Protsenko, I. E.; Kardynal, Beata; Lavrinenko, Andrei

    2014-01-01

    continuous metal films. Optimally designed metal nanoparticles can provide an effectivemechanismfor the photon absorption in the infrared range below the semiconductor bandgap, resulting in the generation of a photocurrent in addition to the photocurrent from band-to-band absorption in a semiconductor. Such......We model the electron photoemission frommetal nanoparticles into a semiconductor in a Schottky diode with a conductive oxide electrode hosting the nanoparticles. We show that plasmonic effects in the nanoparticles lead to a substantial enhancement in photoemission compared with devices with...

  6. Phonon Bandgap Engineering of Strained Monolayer MoS2

    OpenAIRE

    Jiang, Jin-Wu

    2014-01-01

    The phonon band structure of monolayer MoS2 is characteristic for a large energy gap between acoustic and optical branches, which protects the vibration of acoustic modes from being scattered by optical phonon modes. Therefore, the phonon bandgap engineering is of practical significance for the manipulation of phonon-related mechanical or thermal properties in monolayer MoS2. We perform both phonon analysis and molecular dynamics simulations to investigate the tension effect on the phonon ban...

  7. Direct bandgap silicon: tensile-strained silicon nanocrystals

    Czech Academy of Sciences Publication Activity Database

    Kůsová, Kateřina; Hapala, Prokop; Valenta, J.; Jelínek, Pavel; Cibulka, Ondřej; Ondič, Lukáš; Pelant, Ivan

    2014-01-01

    Roč. 1, č. 2 (2014), "1300042-1"-"1300042-9". ISSN 2196-7350 R&D Projects: GA ČR(CZ) GBP108/12/G108; GA ČR GPP204/12/P235; GA ČR GAP204/10/0952 Institutional support: RVO:68378271 Keywords : silicon nanocrystals * badstructure * light emission * direct bandgap * surface capping Subject RIV: BM - Solid Matter Physics ; Magnetism

  8. Three-dimensional metallic photonic crystals with optical bandgaps.

    Science.gov (United States)

    Vasilantonakis, Nikos; Terzaki, Konstantina; Sakellari, Ioanna; Purlys, Vytautas; Gray, David; Soukoulis, Costas M; Vamvakaki, Maria; Kafesaki, Maria; Farsari, Maria

    2012-02-21

    The fabrication of fully three-dimensional photonic crystals with a bandgap at optical wavelengths is demonstrated by way of direct femtosecond laser writing of an organic-inorganic hybrid material with metal-binding moieties, and selective silver coating using electroless plating. The crystals have 600-nm intralayer periodicity and sub-100 nm features, and they exhibit well-defined diffraction patterns. PMID:22278944

  9. Dietary Fiber

    Science.gov (United States)

    Fiber is a substance in plants. Dietary fiber is the kind you eat. It's a type of carbohydrate. You may also see it listed on a food label as soluble fiber or insoluble fiber. Both types have important health benefits. Good sources of dietary fiber include Whole grains Nuts ...

  10. Evaluation of the measurement of Cu(II) bioavailability in complex aqueous media using a hollow-fiber supported liquid membrane device (HFSLM) and two microalgae species (Pseudokirchneriella subcapitata and Scenedesmus acutus).

    Science.gov (United States)

    Rodríguez-Morales, Erik A; Rodríguez de San Miguel, Eduardo; de Gyves, Josefina

    2015-11-01

    The environmental bioavailability of copper was determined using a hollow-fiber supported liquid membrane (HFSLM) device as a chemical surrogate and two microalgae species (Scenedesmus acutus and Pseudokirchneriella subcapitata). Several experimental conditions were studied: pH, the presence of organic matter, inorganic anions, and concomitant cations. The results indicated a strong relationship between the response given by the HFSLM and the microalgae species with free copper concentrations measured by an ion selective electrode (ISE), in accordance with the free-ion activity model (FIAM). A significant positive correlation was evident when comparing the bioavailability results measured by the HFSLM and the S. acutus microalga species, showing that the synthetic device may emulate biological uptake and, consequently, be used as a chemical test for bioavailability measurements using this alga as a biological reference. PMID:26431807

  11. Thulium-doped silica fibers with enhanced 3H4 level lifetime: modelling the devices for 800-820 nm band

    Czech Academy of Sciences Publication Activity Database

    Peterka, Pavel; Kašík, Ivan; Dhar, Anirban; Dussardier, B.; Blanc, W.

    Vol. 7843. Bellingham : SPIE, 2010 - (Upendra, S.), 7843A-1-7843A-9 ISBN 978-0-8194-8373-7. ISSN 0277-786X. [Conference on High-Power Laser s and Applications V. Beijing (CN), 18.10.2010-19.10.2010] R&D Projects: GA MŠk(CZ) ME10119; GA ČR GPP102/10/P554 Institutional research plan: CEZ:AV0Z20670512 Keywords : Fiber laser s * amplifiers * optical fiber Subject RIV: BH - Optics, Masers, Laser s

  12. Single mode fiber and twin-core fiber connection technique for in-fiber integrated interferometer

    Science.gov (United States)

    Yuan, Tingting; Zhang, Xiaotong; Guan, Chunying; Yang, Xinghua; Yuan, Libo

    2015-09-01

    A novel twin-core fiber connector has been made by two side-polished fibers. By using side polishing technique, we present a connector based on the twin-core fiber (TCF) and two D-shaped single-core fibers. After simple alignment and splicing, all fiber miniaturizing connector can be obtained. Two cores can operate independently and are non-interfering. The coupling loss of this connector is low and the fabrication technologies are mature. The connector device could be used for sensors or particle trapping.

  13. Efficient photovoltaic cells from low band-gap fluorene-based copolymer

    Institute of Scientific and Technical Information of China (English)

    Tian Ren-Yu; Yang Ren-Qiang; Peng Jun-Biao; Cao Yong

    2005-01-01

    Polymer photovoltaic cells based on low band-gap copolymer, poly [2,7-(9,9-dioctyl) fluorene-co-5,5'-(4,7-diselenophenyl)-2,2'-yl-2,1,3-benzothiadiazole] (PFSeBT) are investigated, focusing on the effects of cathode and blend concentration on device performance. The best device, with active layer from PFSeBT:PCBM=1:2 blend and with LiF/Al as cathode, achieves an open-circuit voltage of 1.00V, a short-circuit current density of 4.42mA/cm2, and energy conversion efficiency of 1.67% under AM1.5 illumination (100mW/cm2).The short-circuit current density indicates the dependence of power law on the incident light intensity with a power index of 0.887. All devices have a spectral response up to 680nm. The results indicate that PFSeBT is a potential polymer functioning as an electron donor in polymer photovoltaic cells.

  14. Application of Adsorption Device of Activated Carbon Fiber to Recovery of CFCs%活性炭纤维吸附装置在发泡剂CFCs回收中的应用

    Institute of Scientific and Technical Information of China (English)

    薛全民; 崔贵芹; 赵胜

    2012-01-01

    In the process of waste refrigerator disassembly, polyurethane foam would release large quantity of CFC - 11. CFCs was one of important greenhouse gases, so it was important to recycle CFCs from the exhaust gas of waste refrigerator disassembly. The device used activated carbon fiber for adsorption material was described, which had many virtues of automatically, advanced technology, and the use of efficient adsorbents - activated carbon fiber. The operation practice showed that CFCs from waste refrigerator disassembly could be disposed by the device.%在冰箱拆卸过程中,聚氨酯硬质泡沫会释放出大量CFCs,而CFCs是重要的温室气体之一,因此,冰箱拆卸过程中尾气中CFCs回收受到大家重视。本文介绍了利用活性炭纤维回收家电拆卸过程中释放出氟里昂的装置。该装置自动运行,工艺先进,并且利用高效的吸附剂一活性炭纤维。运行实践表明,利用该装置可以有效的处理冰箱拆卸过程中释放出的CFCs。

  15. Monitored separation device

    Science.gov (United States)

    Jackson, George William (Inventor); Willson, Richard Coale (Inventor); Fox, George Edward (Inventor)

    2011-01-01

    A device for separating and purifying useful quantities of particles comprises: a. an anolyte reservoir connected to an anode, the anolyte reservoir containing an electrophoresis buffer; b. a catholyte reservoir connected to a cathode, the catholyte reservoir also containing the electrophoresis buffer; c. a power supply connected to the anode and to the cathode; d. a column having a first end inserted into the anolyte reservoir, a second end inserted into the catholyte reservoir, and containing a separation medium; e. a light source; f. a first optical fiber having a first fiber end inserted into the separation medium, and having a second fiber end connected to the light source; g. a photo detector; h. a second optical fiber having a third fiber end inserted into the separation medium, and having a fourth fiber end connected to the photo detector; and i. an ion-exchange membrane in the anolyte reservoir.

  16. Optical fiber rotation sensing

    CERN Document Server

    Burns, William K; Kelley, Paul

    1993-01-01

    Optical Fiber Rotation Sensing is the first book devoted to Interferometric Fiber Optic Gyros (IFOG). This book provides a complete overview of IFOGs, beginning with a historical review of IFOG development and including a fundamental exposition of basic principles, a discussion of devices and components, and concluding with industry reports on state-of-the-art activity. With several chapters contributed by principal developers of this solid-state device, the result is an authoritative work which will serve as the resource for researchers, students, and users of IFOGs.* * State-of-t

  17. Grazing incidence angle based sensing approach integrated with fiber-optic Fourier transform infrared (FO-FTIR) spectroscopy for remote and label-free detection of medical device contaminations

    International Nuclear Information System (INIS)

    Contamination of medical devices has become a critical and prevalent public health safety concern since medical devices are being increasingly used in clinical practices for diagnostics, therapeutics and medical implants. The development of effective sensing methods for real-time detection of pathogenic contamination is needed to prevent and reduce the spread of infections to patients and the healthcare community. In this study, a hollow-core fiber-optic Fourier transform infrared spectroscopy methodology employing a grazing incidence angle based sensing approach (FO-FTIR-GIA) was developed for detection of various biochemical contaminants on medical device surfaces. We demonstrated the sensitivity of FO-FTIR-GIA sensing approach for non-contact and label-free detection of contaminants such as lipopolysaccharide from various surface materials relevant to medical device. The proposed sensing system can detect at a minimum loading concentration of approximately 0.7 μg/cm2. The FO-FTIR-GIA has the potential for the detection of unwanted pathogen in real time

  18. Grazing incidence angle based sensing approach integrated with fiber-optic Fourier transform infrared (FO-FTIR) spectroscopy for remote and label-free detection of medical device contaminations

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, Moinuddin, E-mail: moinuddin.hassan@fda.hhs.gov; Ilev, Ilko [Optical Therapeutics and Medical Nanophotonics Laboratory, Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland 20993 (United States)

    2014-10-15

    Contamination of medical devices has become a critical and prevalent public health safety concern since medical devices are being increasingly used in clinical practices for diagnostics, therapeutics and medical implants. The development of effective sensing methods for real-time detection of pathogenic contamination is needed to prevent and reduce the spread of infections to patients and the healthcare community. In this study, a hollow-core fiber-optic Fourier transform infrared spectroscopy methodology employing a grazing incidence angle based sensing approach (FO-FTIR-GIA) was developed for detection of various biochemical contaminants on medical device surfaces. We demonstrated the sensitivity of FO-FTIR-GIA sensing approach for non-contact and label-free detection of contaminants such as lipopolysaccharide from various surface materials relevant to medical device. The proposed sensing system can detect at a minimum loading concentration of approximately 0.7 μg/cm{sup 2}. The FO-FTIR-GIA has the potential for the detection of unwanted pathogen in real time.

  19. Wide bandgap engineering of (AlGa)2O3 films

    International Nuclear Information System (INIS)

    Bandgap tunable (AlGa)2O3 films were deposited on sapphire substrates by pulsed laser deposition (PLD). The deposited films are of high transmittance as measured by spectrophotometer. The Al content in films is almost the same as that in targets. The measurement of bandgap energies by examining the onset of inelastic energy loss in core-level atomic spectra using X-ray photoelectron spectroscopy is proved to be valid for determining the bandgap of (AlGa)2O3 films as it is in good agreement with the bandgap values from transmittance spectra. The measured bandgap of (AlGa)2O3 films increases continuously with the Al content covering the whole Al content range from about 5 to 7 eV, indicating PLD is a promising growth technology for growing bandgap tunable (AlGa)2O3 films.

  20. Temperature level fiber sensor network

    OpenAIRE

    López Higuera, José Miguel; Rodríguez Cobo, Luis; Castrellón Uribe, Jesús; Quintela Incera, Antonio; Lomer Barboza, Mauro Matías

    2013-01-01

    A temperature level fiber sensor network is proposed and demonstrated. Each inline transducer is based on a FBG-SMA wire structure working as an on/off optical device being interrogated using a time domain technique.

  1. Amplitude-modulated fiber-ring laser

    DEFF Research Database (Denmark)

    Caputo, J. G.; Clausen, Carl A. Balslev; Sørensen, Mads Peter; Bischoff, Svend

    2000-01-01

    Soliton pulses generated by a fiber-ring laser are investigated by numerical simulation and perturbation methods. The mathematical modeling is based on the nonlinear Schrödinger equation with perturbative terms. We show that active mode locking with an amplitude modulator leads to a self-starting......Soliton pulses generated by a fiber-ring laser are investigated by numerical simulation and perturbation methods. The mathematical modeling is based on the nonlinear Schrödinger equation with perturbative terms. We show that active mode locking with an amplitude modulator leads to a self......-starting of stable solitonic pulses from small random noise, provided the modulation depth is small. The perturbative analysis leads to a nonlinear coupled return map for the amplitude, phase, and position of the soliton pulses circulating in the fiber-ring laser. We established the validity of this approach...... by comparison with the full numerical simulations. Finally, we discuss possible sources of instability that are due to resonances in the device....

  2. High-efficiency, monolithic, multi-bandgap, tandem photovoltaic energy converters

    Science.gov (United States)

    Wanlass, Mark W.

    2011-11-29

    A monolithic, multi-bandgap, tandem solar photovoltaic converter has at least one, and preferably at least two, subcells grown lattice-matched on a substrate with a bandgap in medium to high energy portions of the solar spectrum and at least one subcell grown lattice-mismatched to the substrate with a bandgap in the low energy portion of the solar spectrum, for example, about 1 eV.

  3. A wide bandgap silicon carbide (SiC) gate driver for high-temperature and high-voltage applications

    Energy Technology Data Exchange (ETDEWEB)

    Lamichhane, Ranjan [University of Arkansas; Ericson, Milton Nance [ORNL; Frank, Steven Shane [ORNL; BRITTONJr., CHARLES L. [Oak Ridge National Laboratory (ORNL); Marlino, Laura D [ORNL; Mantooth, Alan [University of Arkansas; Francis, Matt [APEI, Inc.; Shepherd, Dr. Paul [University of Arkansas; Glover, Dr. Michael [University of Arkansas; Podar, Mircea [ORNL; Perez, M [University of Arkansas; Mcnutt, Tyler [APEI, Inc.; Whitaker, Mr. Bret [APEI, Inc.; Cole, Mr. Zach [APEI, Inc.

    2014-01-01

    Limitations of silicon (Si) based power electronic devices can be overcome with Silicon Carbide (SiC) because of its remarkable material properties. SiC is a wide bandgap semiconductor material with larger bandgap, lower leakage currents, higher breakdown electric field, and higher thermal conductivity, which promotes higher switching frequencies for high power applications, higher temperature operation, and results in higher power density devices relative to Si [1]. The proposed work is focused on design of a SiC gate driver to drive a SiC power MOSFET, on a Cree SiC process, with rise/fall times (less than 100 ns) suitable for 500 kHz to 1 MHz switching frequency applications. A process optimized gate driver topology design which is significantly different from generic Si circuit design is proposed. The ultimate goal of the project is to integrate this gate driver into a Toyota Prius plug-in hybrid electric vehicle (PHEV) charger module. The application of this high frequency charger will result in lighter, smaller, cheaper, and a more efficient power electronics system.

  4. Tunable bandgap energy of fluorinated nanocrystals for flash memory applications produced by low-damage plasma treatment

    International Nuclear Information System (INIS)

    A plasma system with a complementary filter to shield samples from damage during tetrafluoromethane (CF4) plasma treatment was proposed in order to incorporate fluorine atoms into gadolinium oxide nanocrystals (Gd2O3-NCs) for flash memory applications. X-ray photoelectron spectroscopy confirmed that fluorine atoms were successfully introduced into the Gd2O3-NCs despite the use of a filter in the plasma-enhanced chemical vapour deposition system to shield against several potentially damaging species. The number of incorporated fluorine atoms can be controlled by varying the treatment time. The optimized memory window of the resulting flash memory devices was twice that of devices treated by a filterless system because more fluorine atoms were incorporated into the Gd2O3-NCs film with very little damage. This enlarged the bandgap energy from 5.48 to 6.83 eV, as observed by ultraviolet absorption measurements. This bandgap expansion can provide a large built-in electric field that allows more charges to be stored in the Gd2O3-NCs. The maximum improvement in the retention characteristic was >60%. Because plasma damage during treatment is minimal, maximum fluorination can be achieved. The concept of simply adding a filter to a plasma system to prevent plasma damage exhibits great promise for functionalization or modification of nanomaterials for advanced nanoelectronics while introducing minimal defects. (paper)

  5. Analysis of photonic band-gap structures in stratified medium

    DEFF Research Database (Denmark)

    Tong, Ming-Sze; Yinchao, Chen; Lu, Yilong;

    2005-01-01

    Purpose - To demonstrate the flexibility and advantages of a non-uniform pseudo-spectral time domain (nu-PSTD) method through studies of the wave propagation characteristics on photonic band-gap (PBG) structures in stratified medium Design/methodology/approach - A nu-PSTD method is proposed in...... the occasions where the spatial distributions contain step of up to five times larger than the original size, while simultaneously the flexibility of non-uniform sampling offers further savings on computational storage. Research limitations/implications - Research has been mainly limited to the simple...

  6. Bandgap isotropy in photonic quasicrystals with low-index contrast

    Science.gov (United States)

    Andreone, Antonello; Abbate, Giancarlo; Di Gennaro, Emiliano; Rose Thankamani, Priya

    2012-05-01

    Formation and development of the photonic band gap in two-dimensional 8-, 10-, and 12-fold symmetry quasicrystalline lattices of low-index contrast are reported. Finite-size structures made of dielectric cylindrical rods are studied and measured in the microwave region, and their properties are compared with a conventional hexagonal crystal. Band-gap characteristics are investigated by changing the direction of propagation of the incident beam inside the crystal. Various angles of incidence are used to investigate the isotropic nature of the band gap.

  7. Advances in wide bandgap SiC for optoelectronics

    DEFF Research Database (Denmark)

    Ou, Haiyan; Ou, Yiyu; Argyraki, Aikaterini;

    2014-01-01

    Silicon carbide (SiC) has played a key role in power electronics thanks to its unique physical properties like wide bandgap, high breakdown field, etc. During the past decade, SiC is also becoming more and more active in optoelectronics thanks to the progress in materials growth and nanofabrication....... This paper will review the advances in fluorescent SiC for white light-emitting diodes, covering the poly-crystalline doped SiC source material growth, single crystalline epitaxy growth of fluorescent SiC, and nanofabrication of SiC to enhance the extraction efficiency for fluorescent SiC based white...

  8. New Curvature-Compensated CMOS Bandgap Voltage Reference

    Institute of Scientific and Technical Information of China (English)

    Lu Shen; Ning Ning; Qi Yu; Yan Luo; Chun-Sheng Li

    2007-01-01

    A novel curvaturecompensated CMOS bandgap voltage reference is presented. The reference utilizes two first order temperature compensations generated from the nonlinearity of the finite current gain β of vertical pnp bipolar transistor. The proposed circuit,designed in a standard 0.18 μm CMOS process, achieves a good temperature coefficient of 2.44 ppm/℃ with temperature range from 40 ℃ to 85 ℃, and about 4 mV supply voltage variation in the range from 1.4 V to 2.4 V. With a 1.8 V supply voltage, the power supply rejection ratio is 56 dB at 10 MHz.

  9. Fiber dielectrophoresis

    International Nuclear Information System (INIS)

    Dielectrophoresis is the motion of uncharged particles in nonuniform electric fields. We find that the theoretical dielectrophoretic velocity of a conducting fiber in an insulating medium is proportional to the square of the fiber length, and is virtually independent of fiber diameter. This prediction has been verified experimentally. The results point to the development of a fiber length classifier based on dielectrophoresis. (author)

  10. True photonic band-gap mode-control in VCSEL structures

    DEFF Research Database (Denmark)

    Romstad, F.; Madsen, M.; Birkedal, Dan;

    2003-01-01

    Photonic band-gap mode confinement in novel nano-structured large area VCSEL structures is confirmed by the amplified spontaneous emission spectrum. Both guide and anti-guide VCSEL structures are experimentally characterised to verify the photonic band-gap effect.......Photonic band-gap mode confinement in novel nano-structured large area VCSEL structures is confirmed by the amplified spontaneous emission spectrum. Both guide and anti-guide VCSEL structures are experimentally characterised to verify the photonic band-gap effect....

  11. Narrow bandgap host material for high quantum efficiency yellow phosphorescent organic light-emitting diodes doped with iridium(III) bis(4-phenylthieno[3,2-c]pyridine)acetylacetonate

    Energy Technology Data Exchange (ETDEWEB)

    Yook, Kyoung Soo; Lee, Jun Yeob, E-mail: leej17@skku.edu

    2015-05-15

    A narrow bandgap host material, 4,5-di(9H-carbazol-9-yl)phthalonitrile (2CzPN), was used as a bipolar host material to improve the device performances of yellow phosphorescent organic light-emitting diodes(PHOLEDs). The device performances of the yellow PHOLEDs were optimized at a low doping concentration of 1%. A low turn-on voltage of 3.0 V and high quantum efficiency of 19.3% were achieved using the 2CzPN host material and no efficiency roll-off of the device was observed up to 1000 cd/m{sup 2} compared with 25% of reference device. - Highlights: • High quantum efficiency in yellow phosphorescent organic light-emitting diodes. • Narrow bandgap host material with donor–acceptor structure for low driving voltage. • Low optimum doping concentration of 1% for high quantum efficiency and power efficiency.

  12. Using Protection Layers for a 2-Photon Water Splitting Device

    DEFF Research Database (Denmark)

    Seger, Brian; Mei, Bastian Timo; Frydendal, Rasmus;

    2015-01-01

    optimized to absorb low energy photons (small bandgap). To a large degree this approach has been hindered by corrosion issues. In this talk I will first discuss how our computational screening of 2,400 materials showed that very few materials can efficiently absorb light without corroding in water splitting......The 2-photon tandem device for photocatalytic water splitting has been theoretically shown to provide a higher efficiency than a single photon device(1). This increased efficiency can be achieved by having one material optimized to absorb high energy photons (large bandgap) and another material...

  13. Improved double-gate armchair silicene nanoribbon field-effect-transistor at large transport bandgap

    Science.gov (United States)

    Mohsen, Mahmoudi; Zahra, Ahangari; Morteza, Fathipour

    2016-01-01

    The electrical characteristics of a double-gate armchair silicene nanoribbon field-effect-transistor (DG ASiNR FET) are thoroughly investigated by using a ballistic quantum transport model based on non-equilibrium Green’s function (NEGF) approach self-consistently coupled with a three-dimensional (3D) Poisson equation. We evaluate the influence of variation in uniaxial tensile strain, ribbon temperature and oxide thickness on the on-off current ratio, subthreshold swing, transconductance and the delay time of a 12-nm-length ultranarrow ASiNR FET. A novel two-parameter strain magnitude and temperature-dependent model is presented for designing an optimized device possessing balanced amelioration of all the electrical parameters. We demonstrate that employing HfO2 as the gate insulator can be a favorable choice and simultaneous use of it with proper combination of temperature and strain magnitude can achieve better device performance. Furthermore, a general model power (GMP) is derived which explicitly provides the electron effective mass as a function of the bandgap of a hydrogen passivated ASiNR under strain.

  14. Photo-Induced Bandgap Renormalization Governs the Ultrafast Response of Single-Layer MoS2.

    Science.gov (United States)

    Pogna, Eva A A; Marsili, Margherita; De Fazio, Domenico; Dal Conte, Stefano; Manzoni, Cristian; Sangalli, Davide; Yoon, Duhee; Lombardo, Antonio; Ferrari, Andrea C; Marini, Andrea; Cerullo, Giulio; Prezzi, Deborah

    2016-01-26

    Transition metal dichalcogenides (TMDs) are emerging as promising two-dimensional (2D) semiconductors for optoelectronic and flexible devices. However, a microscopic explanation of their photophysics, of pivotal importance for the understanding and optimization of device operation, is still lacking. Here, we use femtosecond transient absorption spectroscopy, with pump pulse tunability and broadband probing, to monitor the relaxation dynamics of single-layer MoS2 over the entire visible range, upon photoexcitation of different excitonic transitions. We find that, irrespective of excitation photon energy, the transient absorption spectrum shows the simultaneous bleaching of all excitonic transitions and corresponding red-shifted photoinduced absorption bands. First-principle modeling of the ultrafast optical response reveals that a transient bandgap renormalization, caused by the presence of photoexcited carriers, is primarily responsible for the observed features. Our results demonstrate the strong impact of many-body effects in the transient optical response of TMDs even in the low-excitation-density regime. PMID:26691058

  15. Fiber optic gas sensor

    Science.gov (United States)

    Chen, Peng (Inventor); Buric, Michael P. (Inventor); Swinehart, Philip R. (Inventor); Maklad, Mokhtar S. (Inventor)

    2010-01-01

    A gas sensor includes an in-fiber resonant wavelength device provided in a fiber core at a first location. The fiber propagates a sensing light and a power light. A layer of a material is attached to the fiber at the first location. The material is able to absorb the gas at a temperature dependent gas absorption rate. The power light is used to heat the material and increases the gas absorption rate, thereby increasing sensor performance, especially at low temperatures. Further, a method is described of flash heating the gas sensor to absorb more of the gas, allowing the sensor to cool, thereby locking in the gas content of the sensor material, and taking the difference between the starting and ending resonant wavelengths as an indication of the concentration of the gas in the ambient atmosphere.

  16. Wide-bandgap epitaxial heterojunction windows for silicon solar cells

    Science.gov (United States)

    Landis, Geoffrey A.; Loferski, Joseph J.; Beaulieu, Roland; Sekula-Moise, Patricia A.; Vernon, Stanley M.

    1990-01-01

    It is shown that the efficiency of a solar cell can be improved if minority carriers are confined by use of a wide-bandgap heterojunction window. For silicon (lattice constant a = 5.43 A), nearly lattice-matched wide-bandgap materials are ZnS (a = 5.41 A) and GaP (a = 5.45 A). Isotype n-n heterojuntions of both ZnS/Si and GaP/Si were grown on silicon n-p homojunction solar cells. Successful deposition processes used were metalorganic chemical vapor deposition (MO-CVD) for GaP and ZnS, and vacuum evaporation of ZnS. Planar (100) and (111) and texture-etched - (111)-faceted - surfaces were used. A decrease in minority-carrier surface recombination compared to a bare surface was seen from increased short-wavelength spectral response, increased open-circuit voltage, and reduced dark saturation current, with no degradation of the minority carrier diffusion length.

  17. Rare-earth-activated wide bandgap materials for scintillators

    International Nuclear Information System (INIS)

    Open f-shell rare-earth (RE) ions in wide bandgap host materials are usually characterized by closely spaced electronic levels due to various electron configurations and charge states. These levels provide convenient luminescent transitions that can be excited by efficient recombination of charge carriers generated in the host material by ionizing radiation. Therefore, it is the area of ionizing radiation detectors, where search for new, fast and efficient scintillator materials for high-energy physics and nuclear medicine, has yielded much of the recent advances in the understanding of radioluminescence and scintillation mechanism in some solid state, UV and VUV luminescent, RE-activated materials. In this paper we shall present selected results of basic experiments such as radioluminescence, VUV spectroscopy, time profiles and thermoluminescence, on barium fluoride (activated with Ce, Pr, Nd, Tb) and two aluminum perovskites, YAlO3 and LuAlO3, activated with Ce. We shall demonstrate that these results point to consecutive carrier capture and recombination at RE ions as the basic mechanism of radioluminescence and scintillation in these materials, despite the strong self-trapping and poor charge transport properties. Consequently, various electron and/or hole traps that intercept and retain for some time the recombining charge carriers play an active role influencing both the scintillation light yield and time profiles of scintillation pulses in these and many other wide bandgap RE-activated luminescent materials

  18. DEVELOPMENT OF A CANDLE FILTER FAILURE SAFEGUARD DEVICE

    Energy Technology Data Exchange (ETDEWEB)

    G.J. Bruck; E.E. Smeltzer; Z.N. Sanjana

    2002-06-06

    Development, testing and optimization of advanced metal and ceramic, barrier and fiber safeguard devices (SGDs) is described. Metal barrier devices are found prone to manufacturing defects and premature blinding. Fiber devices are found to be satisfactory if fine fibers are used. Durable alloys are identified for both oxidation and gasification conditions. Ceramic honeycomb SGDs were found to perform as excellent barrier devices. Optimization has shown such devices to be durable. Field testing of ceramic honeycomb SGDs from two different manufacturers is being pursued.

  19. Effects of the optical energy bandgap and metal work function on the contact resistivity in a-SiGe : H

    International Nuclear Information System (INIS)

    Amorphous silicon based materials, especially a-SiGe : H, have provided a variety of applications in display backplane and sensor materials. The ultimate goal is the development of device architectures that offer improved properties and functionality. In this article, the electrical contact resistivity (ρc) of a-SiGe : H is investigated in terms of the optical energy bandgap modulated by Ge incorporation and the work function of the contact metals. Firstly, the ρc is found to be dependent on the optical bandgap, and this originates from the reduced potential difference between the Fermi level at the metal/a-Si : H interface and the electron mobility edge (Ec), with the decrease in the optical bandgap, which reduces the barrier height. Secondly, the barrier height of the Ti/Cu contact is higher than that of the Mo/Al/Mo contact. In particular, an abundance of Ge atoms is found to have been out-diffused towards the surface and to have formed a mixed interfacial layer, having higher work function than that of the Mo/Al/Mo contact. These results provide evidence that the ρc in a-SiGe : H depends on the work function of the contact layer and is potentially useful for improving device performances. (paper)

  20. Conversion of above- and below-bandgap photons via InAs quantum dot media embedded into GaAs solar cell

    International Nuclear Information System (INIS)

    Quantum dots (QDs) provide photovoltaic conversion of below-bandgap photons due to multistep electron transitions. QDs also increase conversion efficiency of the above-bandgap photons due to extraction of electrons from QDs via Coulomb interaction with hot electrons excited by high-energy photons. Nanoscale potential profile (potential barriers) and nanoscale band engineering (AlGaAs atomically thin barriers) allow for suppression of photoelectron capture to QDs. To study these kinetic effects and to distinguish them from the absorption enhancement due to light scattering on QDs, we investigate long, 3-μm base GaAs devices with various InAs QD media with 20 and 40 QD layers. Quantum efficiency measurements show that, at least at low doping, the multistep processes in QD media are strongly affected by the wetting layer (WL). The QD media with WLs provide substantial conversion of below-bandgap photons and for devices with 40 QD layers the short circuit current reaches 29.2 mA/cm2. The QD media with band-engineered AlGaAs barriers and reduced wetting layers (RWL) enhance conversion of high-energy photons and decrease the relaxation (thermal) losses.

  1. Radiation effects in optoelectronic devices

    International Nuclear Information System (INIS)

    A summary is given of studies on radiation effects in light-emitting diodes, laser diodes, detectors, optical isolators and optical fibers. It is shown that the study of radiation damage in these devices can provide valuable information concerning the nature of the devices themselves, as well as methods of hardening these devices for applications in radiation environments

  2. High dno/dT liquid crystals and their applications in a thermally tunable liquid crystal photonic crystal fiber

    DEFF Research Database (Denmark)

    Li, J.; Gauza, S.; Wu, S.-T.;

    2006-01-01

    crystal mixtures, designated as UCF-1 and UCF-2. The dn(o)/dT of UCF-1 is similar to 4x higher than that of 5CB at room temperature. By infiltrating UCF-1 into the air holes of a three-rod core photonic crystal fiber, we demonstrate a thermally tunable photonic bandgap fiber with tuning sensitivity of 27...

  3. Bandgap engineering of colloidal zinc oxysulfide via lattice substitution with sulfur

    Science.gov (United States)

    Pandey, Shiv K.; Pandey, Shipra; Parashar, Vyom; Yadav, Raghvendra S.; Mehrotra, G. K.; Pandey, Avinash C.

    2014-01-01

    Zinc oxysulfide nanocrystals with zinc blende phase are synthesized through a wet-chemical method. An affirmation of the crystal structure, elemental homogeneity and phase transformation is obtained by X-ray diffraction and authenticated by electron micrographic studies. Theoretical observations have strongly supported the thermodynamic solubility limit for its (30%) formation. An anomalous bandgap bowing with modulation in bandgap from 3.74 eV (ZnO) to 3.93 eV (ZnS) was observed with a minimum bandgap of 2.7 eV. Tunable bandgap and a wide range of visible emission ascertain it as a potential material for optoelectronic and solar cell applications due to its large bandgap offsets.Zinc oxysulfide nanocrystals with zinc blende phase are synthesized through a wet-chemical method. An affirmation of the crystal structure, elemental homogeneity and phase transformation is obtained by X-ray diffraction and authenticated by electron micrographic studies. Theoretical observations have strongly supported the thermodynamic solubility limit for its (30%) formation. An anomalous bandgap bowing with modulation in bandgap from 3.74 eV (ZnO) to 3.93 eV (ZnS) was observed with a minimum bandgap of 2.7 eV. Tunable bandgap and a wide range of visible emission ascertain it as a potential material for optoelectronic and solar cell applications due to its large bandgap offsets. Electronic supplementary information (ESI) available: Experimental procedure, characterization techniques, lattice strain, XPS, TEM/HRTEM, HRSEM, EDAX, bandgap and bowing parameters calculation and PL study for whole composition. See DOI: 10.1039/c3nr04457b

  4. All-fiber sensor of angular velocity

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, A.TS.; Vlasenko, O.A.; Dianov, E.M.; Diankov, G.L.; Zafirova, B.S.

    1989-06-01

    The paper reports the construction of an all-fiber optical sensor of angular velocity whose operation is based on the Sagnac effect in a fiber ring interferometer. An all-fiber system does not require the use of external discrete optical elements; division, polarization, and modulation functions are performed by the fiber waveguide itself. The fiber elements and sensor are constructed on the basis of slightly anisotropic fiber waveguides. The sensitivity of the device was 0.0077 deg/sq rt hr, while the zero drift was 0.5 deg/hr. 6 refs.

  5. Investigating Bandgap Energies, Materials, and Design of Light-Emitting Diodes

    Science.gov (United States)

    Wagner, Eugene P., II

    2016-01-01

    A student laboratory experiment to investigate the intrinsic and extrinsic bandgaps, dopant materials, and diode design in light-emitting diodes (LEDs) is presented. The LED intrinsic bandgap is determined by passing a small constant current through the diode and recording the junction voltage variation with temperature. A second visible…

  6. Investigations into low band-gap, semiconducting polymers

    International Nuclear Information System (INIS)

    The physical and electronic characteristics of the low band-gap polymers, poly(4-dicyanomethylene-4H-cyclopenta[1,2-b;3,4-b']dithiophene) (PCDM) and poly(7-benzo[1,3]dithiol-2-ylidine-7H-3,4-dithia-cyclopenta[a]pentalene) (PBDT), have been examined. The polymers were studied using microscopic and spectroscopic methods to determine the chemical and morphological properties of the polymer films. Micrographs of the polymer surfaces revealed PCDM to consist of a relatively smooth surface covered by large aggregations. PBDT had a much rougher surface with a large surface area, possibly suitable for the production of a polymeric battery. Polymer band-gaps were estimated using UV-vis spectra to be 1.38 eV and 1.29 eV respectively for PCDM and PBDT. XPS measurements allied with the PCDM and PBDT band-gaps have been used to produce preliminary band diagrams for ITO/polymer/Al diodes. Diodes of PCDM and PBDT were fabricated to allow study of the electrical behaviour of the polymers using DC current-voltage (I-V) measurements and AC impedance spectroscopy. Equivalent RC circuits of ITO/PCDM/Al diodes have been used to model the presence of 2 dispersions in the admittance plots and to explain the effects of increasing temperature, polymer film thickness and contact material. The DC electrical measurements for PCDM reveal almost symmetrical current-voltage characteristics. A hysteresis effect dependent on the direction of the voltage sweep observed in the DC characteristics has a potential application in the production of a polymeric ''memory element''. For sweep voltages starting above approximately ±4 V, ''high'' and ''low'' conductance states occur when sweeping from negative to positive and positive to negative bias respectively. The ''low'' state is stable for many months whereas the ''high'' state decays exponentially with time constants of approximately 2000 s. Characteristic values for PCDM films have been estimated using the experimental results. An investigation of

  7. Research on bandgaps in two-dimensional phononic crystal with two resonators.

    Science.gov (United States)

    Gao, Nansha; Wu, Jiu Hui; Yu, Lie

    2015-02-01

    In this paper, the bandgap properties of a two-dimensional phononic crystal with the two resonators is studied and embedded in a homogenous matrix. The resonators are not connected with the matrix but linked with connectors directly. The dispersion relationship, transmission spectra, and displacement fields of the eigenmodes of this phononic crystal are studied with finite-element method. In contrast to the phononic crystals with one resonators and hollow structure, the proposed structures with two resonators can open bandgaps at lower frequencies. This is a very interesting and useful phenomenon. Results show that, the opening of the bandgaps is because of the local resonance and the scattering interaction between two resonators and matrix. An equivalent spring-pendulum model can be developed in order to evaluate the frequencies of the bandgap edge. The study in this paper is beneficial to the design of opening and tuning bandgaps in phononic crystals and isolators in low-frequency range. PMID:25216625

  8. Compressed lead-based perovskites reaching optimal Shockley-Queisser bandgap with prolonged carrier lifetime

    CERN Document Server

    Liu, Gang; Gong, Jue; Yang, Wenge; Mao, Ho-kwang; Liu, Zhenxian; Schaller, Richard D; Zhang, Dongzhou; Xu, Tao

    2016-01-01

    Atomic structure of materials plays a decisive role in the light-matter interaction. Yet, despite its unprecedented progress, further efficiency boost of Lead-based organic-inorganic perovskite solar cells is hampered by its greater bandgap than the optimum value according to Shockley-Queisser limit. Here, we report the experimental achievement of bandgap narrowing in formamidinium lead triiodide from 1.489 to 1.337 eV by modulating the lattice constants under hydraulic compression, reaching the optimized bandgap for single-junction solar cells. Strikingly, such bandgap narrowing is accomplished with improved, instead of sacrificed carrier lifetime. More attractively, the narrowed bandgap is partially retainable after the release of pressure. This work opens a new dimension in basic science understanding of structural photonics and paves an alternative pathway towards more efficient photovoltaic materials.

  9. Larger bandgap of elliptical cylinders in two-dimensional double-layer photonic crystals

    International Nuclear Information System (INIS)

    We investigate the bandgap properties of two-dimensional double-layer photonic crystals composed of elliptical cylinders in square and triangular lattices, considering cylinders formed of dielectric cores surrounded by interfacial layers of air in magnesium fluoride background. Using the plane-wave numerical expansion method, the bandgap spectrum for the cylinders covered by air rings is obtained for different structural parameters, such as the radius, orientation angle, and lattice constant. The results show that the bandgap of the two-dimensional double-layer photonic crystal is greatly improved compared with traditional two-dimensional photonic crystal and the triangular lattice presents a larger bandgap than the square lattice. The optimal structure parameters to broaden the bandgap are presented. (paper)

  10. Liquid Crystal Devices for Optical Communications and Sensing Applications

    OpenAIRE

    Mathews, Sunish

    2011-01-01

    This thesis is focussed on the design and development of liquid crystal based tunable photonic devices for applications in optical communications and optical sensing, with an emphasis on all-fiber device configuration. The infiltration of liquid crystals into photonic crystal fiber provides a suitable common platform to design and fabricate simple and compact all-fiber tunable photonic devices which can be easily integrated with optical fiber networks and sensing systems. Based on the infiltr...

  11. Developments of DPF systems with mesh laminated structures. Performances of DPF systems which consist of the metal-mesh laminated filter combustion with the alumina-fiber mesh, and the combustion device of trapped diesel particles; Mesh taso kozo no DPF no kaihatsu. Kinzokusen to arumina sen`i mesh ni yoru fukugo filter to filter heiyo heater ni yoru DPF no seino

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, T.; Tange, A.; Matsuda, K. [NHK Spring Co. Ltd., Yokohama (Japan)

    1997-10-01

    For the purpose of continuous run without any maintenance, new DPF (diesel particulate filter)systems laminated by both metal-wire mesh and alumina-fiber mesh alternately, are under the developments. The perfect combustion of trapped diesel particulate can be achieved by a couple of the resistance heating devices inserted into the filter. 5 refs., 7 figs., 3 tabs.

  12. Frequency conversion through spontaneous degenerate four wave mixing in large mode area hybrid photonic crystal fibers

    DEFF Research Database (Denmark)

    Petersen, Sidsel Rübner; Alkeskjold, Thomas Tanggaard; Olausson, Christina Bjarnal Thulin;

    2014-01-01

    Frequency conversion through spontaneous degenerate four wave mixing (FWM) is investigated in large mode area hybrid photonic crystal fibers. Different FWM processes are observed, phasematching between fiber modes of orthogonal polarization, intermodal phasematching across bandgaps, and intramodal...... phasematching within the same transmission band as the one containing the pump laser. Furthermore first and second order Raman scattering is observed. The interplay between the different FWM processes and Raman scattering are investigated....

  13. Cavity quantum electrodynamics with three-dimensional photonic bandgap crystals

    CERN Document Server

    Vos, W L

    2015-01-01

    This paper gives an overview of recent work on three-dimensional (3D) photonic crystals with a "full and complete" 3D photonic band gap. We review five main aspects: 1) spontaneous emission inhibition, 2) spatial localization of light within a tiny nanoscale volume (aka "a nanobox for light"), 3) the introduction of a gain medium leading to thresholdless lasers, 4) breaking of the weak-coupling approximation of cavity QED, both in the frequency and in the time-domain, 5) decoherence, in particular the shielding of vacuum fluctuations by a 3D photonic bandgap. In addition, we list and evaluate all known photonic crystal structures with a demonstrated 3D band gap.

  14. One-dimensional photonic bandgap structure in abalone shell

    Institute of Scientific and Technical Information of China (English)

    LI Bo; ZHOU Ji; LI Longtu; LI Qi; HAN Shuo; HAO Zhibiao

    2005-01-01

    @@ Photonic bandgap (PBG) materials are periodic com- posites of dielectric materials in which electromagnetic waves of certain frequency range cannot propagate in any or a special direction. Recently, there has been great inter- est in synthetic PBG materials due to their ability in ma- nipulation of photons. Since 500 million years ago, the natural world has been exploiting photonic structures for specific biological purposes[1]. Different types of biologi- cal PBG materials have been discovered in recent years, such as the one-dimension PBG structure in the sea mouse Aphrodita[2], and the fruits Elaeocarpus[3,4]; two-dimension PBG structure in the male peacock Pavo muticus feathers[5], Indonesian male Papilio palinurus butterfly[6], Thaumantis diores butterfly[7] and the male Ancyluris meliboeus Fabricius butterflies[8]; and three-dimension PBG structure in the weevil Pachyrhynchus argus[9].

  15. Photonic bandgap via nonlinear modulation assisted by spontaneously generated coherence

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Yin-Ping; Zhang, Tong-Yi [State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); Kou, Jun [Quantum Engineering Center, Beijing Institute of Control Device, Beijing 100854 (China); Wan, Ren-Gang, E-mail: wrg@opt.ac.cn [State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China)

    2013-09-02

    A four-level double-ladder atomic system with two upper states coupled to the excited state by a standing-wave trigger field is explored to generate photonic bandgap (PBG) structure. With the assistance of spontaneously generated coherence (SGC) from the two decay pathways, we can obtain single or double fully developed PBG when the trigger field is far away from resonance or resonant. While in the absence of SGC, the atomic medium becomes strong absorptive to the probe field, and therefore the resulting PBGs are severely malformed or even cannot be opened up. Numerical results show that the PBG structure is originated from the third-order cross Kerr nonlinear modulation between the probe and trigger fields. This mechanism differs from the recent schemes based on linear modulation.

  16. A new diagnostic device for in-situ determination of conventional strength and modulus of deformability in compression of wood parallel to fiber

    Czech Academy of Sciences Publication Activity Database

    Kloiber, Michal; Kunecký, Jiří; Tippner, J.; Sebera, V.

    Mexico City: Instituto de Ingeniería UNAM, 2014 - (Peña, F.; Chávez, M.) ISBN N R&D Projects: GA MK(CZ) DF11P01OVV001; GA MŠk(CZ) LO1219 Keywords : semi-destructive device * in-situ measurement * finite element analysis * compression Subject RIV: JN - Civil Engineering http://hdl.handle.net/11104/0238193

  17. A Fiber Supercapacitor with High Energy Density Based on Hollow Graphene/Conducting Polymer Fiber Electrode.

    Science.gov (United States)

    Qu, Guoxing; Cheng, Jianli; Li, Xiaodong; Yuan, Demao; Chen, Peining; Chen, Xuli; Wang, Bin; Peng, Huisheng

    2016-05-01

    A hollow graphene/conducting polymer composite fiber is created with high mechanical and electronic properties and used to fabricate novel fiber-shaped supercapacitors that display high energy densities and long life stability. The fiber supercapacitors can be woven into flexible powering textiles that are particularly promising for portable and wearable electronic devices. PMID:27001216

  18. Alternative approaches of SiC & related wide bandgap materials in light emitting & solar cell applications

    Science.gov (United States)

    Wellmann, Peter; Syväjärvi, Mikael; Ou, Haiyan

    2014-03-01

    silicon oxycarbide material can provide potential applications of the Eu luminescent materials to challenging conditions like high temperatures or aggressive environments where the silica has weaknesses. In some approaches, silicon rich silicon oxide that contain silicon nanoclusters emit red to near infrared luminescence due to quantum confinement effects while luminescence at shorter wavelength is difficult due to the interplay of defects and quantum confinement effects. In addition it is applicable as low-k dielectric, etch-stop and passivation layers. It also has an optical band-gap that is smaller than that of SiO2 which may facilitate carrier injection at lower voltages that is suitable for optoelectronics. From materials perspective of emerging materials, it seems distant to consider system related issues. The future demands on communication and lighting devices require higher information flows in modernized optical devices, for example by replacing electrical interconnects with their optical counterparts and tunable backgrounds filters for integrated optics or photonics applications. However, there are materials issues related to such device performance, for example by a non-linearity, that provide the possibility for selective removal or addition of wavelengths using hetero structures in which one side of the structure enhances the light-to-dark sensitivity of long and medium wavelength channels and diminish others, and an opposite behavior in other face of the structure. Certainly materials may be applied in various innovative ways to provide new performances in devices and systems. In any materials and device evaluation, reliability issues in passivation and packaging of semiconductor device structures provide a base knowledge that may be used to evaluate new concepts. Fundamental aspects of dielectric constant, bandgap and band offsets between the valence and conduction band edges between the passivation layer and the semiconductor create a foundation for

  19. Optical fiber telecommunications IIIb

    CERN Document Server

    Koch, Thomas L

    2012-01-01

    Updated to include the latest information on light wave technology, Optical Fiber Telecommunication III, Volumes A & B are invaluable for scientists, students, and engineers in the modern telecommunications industry. This two-volume set includes the most current research available in optical fiber telecommunications, light wave technology, and photonics/optoelectronics. The authors cover important background concepts such as SONET, coding device technology, andWOM components as well as projecting the trends in telecommunications for the 21st century.Key Features* One of the hottest subjects of

  20. Microfiber-based few-layer black phosphorus saturable absorber for ultra-fast fiber laser

    CERN Document Server

    Luo, Zhi-Chao; Guo, Zhi-Nan; Jiang, Xiao-Fang; Luo, Ai-Ping; Zhao, Chu-Jun; Yu, Xue-Feng; Xu, Wen-Cheng; Zhang, Han

    2015-01-01

    Few-layer black phosphorus (BP), as the most alluring graphene analogue owing to its similar structure as graphene and thickness dependent direct band-gap, has now triggered a new wave of research on two-dimensional (2D) materials based photonics and optoelectronics. However, a major obstacle of practical applications for few-layer BPs comes from their instabilities of laser-induced optical damage. Herein, we demonstrate that, few-layer BPs, fabricated through the liquid exfoliation approach, can be developed as a new and practical saturable absorber (SA) by depositing few-layer BPs with microfiber. The saturable absorption property of few-layer BPs had been verified through an open-aperture z-scan measurement at the telecommunication band and the microfiber-based BP device had been found to show a saturable average power of ~4.5 mW and a modulation depth of 10.9%, which is further confirmed through a balanced twin detection measurement. By further integrating this optical SA device into an erbium-doped fiber...

  1. Characterization of bandgap reference circuits designed for high energy physics applications

    Science.gov (United States)

    Traversi, G.; De Canio, F.; Gaioni, L.; Manghisoni, M.; Mattiazzo, S.; Ratti, L.; Re, V.; Riceputi, E.

    2016-07-01

    The objective of this work is to design a high performance bandgap voltage reference circuit in a standard commercial 65 nm CMOS technology capable of operating in harsh radiation environments. A prototype circuit based on three different devices (diode, bipolar transistor and MOSFET) was fabricated and tested. Measurement results show a temperature variation as low as ±3.4 mV over a temperature range of 170 ° C (-30 °C to 140 °C) and a line regulation at room temperature of 5.2%/V. Measured VREF is 690 mV±15 mV (3σ) for 26 samples on the same wafer. Circuits correctly operate with supply voltages in the range from 1.32 V down to 0.78 V. A reference voltage shift of only 7.6 mV (around 1.1%) was measured after irradiation with 10 keV X-rays up to an integrated dose of 225 Mrad (SiO2).

  2. Near-elliptic core triangular-lattice and square-lattice PCFs: a comparison of birefringence, cut-off and GVD characteristics towards fiber device application

    CERN Document Server

    Maji, Partha Sona

    2014-01-01

    In this work, detailed numerical analysis of the near-elliptic core index-guiding triangular-lattice and square-lattice photonic crystal fiber (PCFs) are reported for birefringence, single mode, cut-off behavior, group velocity dispersion and effective area properties. For the same relative values of d/P, triangular-lattice PCFs show higher birefringence whereas the square-lattice PCFs show a wider range of single-mode operation. Square-lattice PCF was found to be endlessly single-mode for higher air-filling fraction (d/P). Smaller lengths of triangular-lattice PCF are required for dispersion compensation whereas PCFs with square-lattice with nearer relative dispersion slope (RDS) can better compensate the broadband dispersion. Square-lattice PCFs show ZDW red-shifted, making it preferable for mid-IR supercontinuum generation (SCG) with highly non-linear chalcogenide material. Square-lattice PCFs show higher dispersion slope that leads to compression of the broadband, thus accumulating more power in the pulse...

  3. Electrochromic devices based on wide band-gap nanocrystalline semiconductors functionalized with mononuclear charge transfer compounds

    DEFF Research Database (Denmark)

    Biancardo, M.; Argazzi, R.; Bignozzi, C.A.

    2006-01-01

    A series of ruthenium and iron mononuclear complexes were prepared and their spectroeletrochemical behavior characterized oil Optically Transparent Thin Layer Electrodes (OTTLE) and on Fluorine Doped SnO2 (FTO) conductive glasses coated with Sb-doped nanocrystalline SnO2. These systems display a ...

  4. Thermal Emission Control via Bandgap Engineering in Aperiodically Designed Nanophotonic Devices

    OpenAIRE

    Enrique Maciá

    2015-01-01

    Aperiodic photonic crystals can open up novel routes for more efficient photon management due to increased degrees of freedom in their design along with the unique properties brought about by the long-range aperiodic order as compared to their periodic counterparts. In this work we first describe the fundamental notions underlying the idea of thermal emission/absorption control on the basis of the systematic use of aperiodic multilayer designs in photonic quasicrystals. Then, we illustrate th...

  5. An all-fiber approach for in-phase supermode phase-locked operation of multicore fiber lasers

    Science.gov (United States)

    Li, L.; Schülzgen, A.; Temyanko, V. L.; Li, H.; Moloney, J. V.; Peyghambarian, N.

    2007-02-01

    An all-fiber approach is utilized to phase lock and select the in-phase supermode of compact multicore fiber lasers. Based on the principles of Talbot imaging and waveguide multimode interference, the fundamental supermode is selectively excited within a completely monolithic fiber device. The all-fiber device is constructed by simply fusion splicing passive non-core optical fibers of controlled lengths at both ends of a piece of multicore fiber. Experimental results upon in-house-made 19- and 37-core fibers are demonstrated, which generate output beams with high-brightness far-field intensity distributions. The whole fabricated multicore fiber laser device can in principle be a single fiber chain that is only ~10 cm in length, aligning-free in operation, and robust against environmental disturbance.

  6. Feasibility of tunable MEMS photonic crystal devices

    International Nuclear Information System (INIS)

    Periodic photonic crystal structures channel electromagnetic waves much as semiconductors (quantum) wells channel electrons. Photonic bandgap crystals (PBC) are fabricated by arranging sub-wavelength alternating materials with high and low dielectric constants to produce a desired effective bandgap. Photons with energy within this bandgap cannot propagate through the structure. This property has made these structures useful for microwave applications such as frequency-selective surfaces, narrowband filters, and antenna substrates when the dimensions are on the order of millimeters. They are also potentially very useful, albeit much more difficult to fabricate, in the visible-near-infrared region for various applications when the smallest dimensions are at the edge of current micro-lithography fabrication tools. We micro-fabricated suspended free standing micro-structure bridge waveguides to serve as substrates for PBC features. These micro-bridges were fabricated onto commercial silicon-on-insulator wafers. Nanoscale periodic features were fabricated onto these micro-structure bridges to form a tunable system. When this combined structure is perturbed, such as mechanical deflection of the suspended composite structure at resonance, there can be a realtime shift in the material effective bandgap due to slight geometric alterations due to the induced mechanical stress. Extremely high resonance frequencies device speeds are possible with these very small dimension MEMS

  7. A narrow bandgap SiGe channel superlattice bandgap engineered 1T DRAM cell for low voltage operation and extended hole retention time

    International Nuclear Information System (INIS)

    We propose a SiGe channel superlattice bandgap engineered (SiGe SBE) 1-transistor dynamic random access memory (1T DRAM) cell structure for improved generation and extended retention of hot holes adopting a narrow bandgap Si0.8Ge0.2 channel even with an extremely short gate length of 30 nm. The proposed SiGe channel SBE 1T DRAM shows longer retention time than the Si channel SBE 1T DRAM. It also provides improved design flexibility by optimizing the structural and process parameters, so the retention characteristics get better. Especially, it should be noted that the retention time can be further improved if the doping concentration of the Si buffer layer decreases. The narrow bandgap SiGe channel SBE structure also allows the 1T DRAM cell to generate more electron–hole pairs during the write '1' operation through the impact ionization in the channel under a high electric field. In addition to the long retention time with the SBE structure, the narrow bandgap SiGe channel SBE 1T DRAM cell enables the 1T DRAM cell to have a fast write speed and to operate at lower voltage, thanks to the narrow bandgap Si0.8Ge0.2 channel

  8. Synthesis and Characterization of Small Band-gap Conjugated Polymers - Poly(pyrrolyl methines)

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A kind of small band-gap conjugated polymers-poly (pyrrolyl methines) and their precursors-(poly pyrrolyl methanes) have been synthesized by a simple method and characterized by 1HNMR, FT-IR, TGA and UV-Vis. These polymers can be dissolved in high polar solvents such as DMSO, DMF or NMP. The results reveals that the band-gap of the synthesized conjugated polymers are in the range of 0.96~1.14 eV and they all belong to the small band-gap polymers. The conductivity of doped products with iodine is in the range of semiconductor.

  9. Wide-Band Spatially Tunable Photonic Bandgap in Visible Spectral Range and Laser based on a Polymer Stabilized Blue Phase

    Science.gov (United States)

    Lin, Jia-De; Wang, Tsai-Yen; Mo, Ting-Shan; Huang, Shuan-Yu; Lee, Chia-Rong

    2016-07-01

    This work successfully develops a largely-gradient-pitched polymer-stabilized blue phase (PSBP) photonic bandgap (PBG) device with a wide-band spatial tunability in nearly entire visible region within a wide blue phase (BP) temperature range including room temperature. The device is fabricated based on the reverse diffusion of two injected BP-monomer mixtures with a low and a high chiral concentrations and afterwards through UV-curing. This gradient-pitched PSBP can show a rainbow-like reflection appearance in which the peak wavelength of the PBG can be spatially tuned from the blue to the red regions at room temperature. The total tuning spectral range for the cell is as broad as 165 nm and covers almost the entire visible region. Based on the gradient-pitched PSBP, a spatially tunable laser is also demonstrated in this work. The temperature sensitivity of the lasing wavelength for the laser is negatively linear and approximately ‑0.26 nm/°C. The two devices have a great potential for use in applications of photonic devices and displays because of their multiple advantages, such as wide-band tunability, wide operated temperature range, high stability and reliability, no issue of hysteresis, no need of external controlling sources, and not slow tuning speed (mechanically).

  10. Low noise wide bandgap SiC based IMPATT diodes at sub-millimeter wave frequencies and at high temperature

    International Nuclear Information System (INIS)

    We have presented a comparative account of the high frequency prospective as well as noise behaviors of wide-bandgap 4H-SiC and 6H-SiC based on different structures of IMPATT diodes at sub-millimeter-wave frequencies up to 2.18 THz. The computer simulation study establishes the feasibility of the SiC based IMPATT diode as a high power density terahertz source. The most significant feature lies in the noise behavior of the SiC IMPATT diodes. It is noticed that the 6H-SiC DDR diode shows the least noise measure of 26.1 dB as compared to that of other structures. Further, it is noticed that the noise measure of the SiC IMPATT diode is less at a higher operating frequency compared to that at a lower operating frequency. (semiconductor devices)

  11. Bandgap engineering of InGaAsP/InP laser structure by photo-absorption-induced point defects

    Science.gov (United States)

    Kaleem, Mohammad; Nazir, Sajid; Saqib, Nazar Abbas

    2016-03-01

    Integration of photonic components on the same photonic wafer permits future optical communication systems to be dense and advanced performance. This enables very fast information handling between photonic active components interconnected through passive optical low loss channels. We demonstrate the UV-Laser based Quantum Well Intermixing (QWI) procedure to engineer the band-gap of compressively strained InGaAsP/InP Quantum Well (QW) laser material. We achieved around 135nm of blue-shift by simply applying excimer laser (λ= 248nm). The under observation laser processed material also exhibits higher photoluminescence (PL) intensity. Encouraging experimental results indicate that this simple technique has the potential to produce photonic integrated devices and circuits.

  12. Effects of corrugation shape on frequency band-gaps for longitudinal wave motion in a periodic elastic layer

    DEFF Research Database (Denmark)

    Sorokin, Vladislav

    2016-01-01

    one, the mth, harmonic in the corrugation series. The revealed insights into the mechanism of band-gap formation can be used to predict locations and widths of all frequency band-gaps featured by any corrugation shape. These insights are general and can be valid also for other types of wave motion in......The paper concerns determining frequency band-gaps for longitudinal wave motion in a periodic waveguide. The waveguide may be considered either as an elastic layer with variable thickness or as a rod with variable cross section. As a result, widths and locations of all frequency band-gaps are...... determined by means of the method of varying amplitudes. For the general symmetric corrugation shape, the width of each odd band-gap is controlled only by one harmonic in the corrugation series with its number being equal to the number of the band-gap. Widths of even band-gaps, however, are influenced by all...

  13. Polymer fiber waveguides for terahertz radiation

    DEFF Research Database (Denmark)

    Nielsen, Kristian

    Terahertz radiation offers many exciting applications noticeably in spectroscopy and it is showing promising results in imaging, mainly for security applications. In this project the study of using structured polymer fibers for THz waveguiding is presented. The inspiration for the THz fiber is...... taken from microstructured polymer optical fibers (mPOFs) used at optical wavelengths for sensing and communication. The fibers investigated can be divided into two groups, the solid core fibers and the hollow core fibers. The solid core fibers offer the broadest bandwidth with the best dispersion......-fill fraction. Finally, an example of an application is presented in the form of a broadband 3-dB directional fiber coupler. The device is numerically investigated and designed in such a way that it is manufacturable....

  14. Optical fiber communications

    CERN Document Server

    Keiser, Gerd

    2008-01-01

    The fourth edition of this popular text and reference book presents the fundamental principles for understanding and applying optical fiber technology to sophisticated modern telecommunication systems. Optical-fiber-based telecommunication networks have become a major information-transmission-system, with high capacity links encircling the globe in both terrestrial and undersea installations. Numerous passive and active optical devices within these links perform complex transmission and networking functions in the optical domain, such as signal amplification, restoration, routing, and switching. Along with the need to understand the functions of these devices comes the necessity to measure both component and network performance, and to model and stimulate the complex behavior of reliable high-capacity networks.

  15. Picosecond pump-probe measurement of bandgap changes in SiO2/TiO2 one-dimensional photonic bandgap structures

    Science.gov (United States)

    Hwang, Jisoo; Kim, Min Jung; Wu, J. W.; Mook Lee, Seung; Rhee, Bum Ku

    2006-02-01

    A picosecond pump-probe nonlinear optical measurement is performed in SiO2/TiO2 one-dimensional photonic bandgap structures fabricated by a solgel method. Both high and low band edges were examined by varying the probe wavelengths and angle tuning was also employed to further clarify the mechanism of a nonlinear optical response. The third-order nonlinear optical response in one-dimensional photonic bandgap structures that comprise TiO2 films is responsible for the nonlinear optical transmissions at both bandgap edges, with an 8% decrease at the low-energy edge and a 4.5% increase at the high-energy edge for a 355 nm pump intensity of 430 MW/cm2.

  16. Negative voltage bandgap reference with multilevel curvature compensation technique

    Science.gov (United States)

    Xi, Liu; Qian, Liu; Xiaoshi, Jin; Yongrui, Zhao; Lee, Jong-Ho

    2016-05-01

    A novel high-order curvature compensation negative voltage bandgap reference (NBGR) based on a novel multilevel compensation technique is introduced. Employing an exponential curvature compensation (ECC) term with many high order terms in itself, in a lower temperature range (TR) and a multilevel curvature compensation (MLCC) term in a higher TR, a flattened and better effect of curvature compensation over the TR of 165 °C (‑40 to 125 °C) is realised. The MLCC circuit adds two convex curves by using two sub-threshold operated NMOS. The proposed NBGR implemented in the Central Semiconductor Manufacturing Corporation (CSMC) 0.5 μm BCD technology demonstrates an accurate voltage of ‑1.183 V with a temperature coefficient (TC) as low as 2.45 ppm/°C over the TR of 165 °C at a ‑5.0 V power supply; the line regulation is 3 mV/V from a ‑5 to ‑2 V supply voltage. The active area of the presented NBGR is 370 × 180 μm2. Project supported by the Fund of Liaoning Province Education Department (No. L2013045).

  17. Angle-dependent bandgap engineering in gated graphene superlattices

    Science.gov (United States)

    García-Cervantes, H.; Gaggero-Sager, L. M.; Sotolongo-Costa, O.; Naumis, G. G.; Rodríguez-Vargas, I.

    2016-03-01

    Graphene Superlattices (GSs) have attracted a lot of attention due to its peculiar properties as well as its possible technological implications. Among these characteristics we can mention: the extra Dirac points in the dispersion relation and the highly anisotropic propagation of the charge carriers. However, despite the intense research that is carried out in GSs, so far there is no report about the angular dependence of the Transmission Gap (TG) in GSs. Here, we report the dependence of TG as a function of the angle of the incident Dirac electrons in a rather simple Electrostatic GS (EGS). Our results show that the angular dependence of the TG is intricate, since for moderated angles the dependence is parabolic, while for large angles an exponential dependence is registered. We also find that the TG can be modulated from meV to eV, by changing the structural parameters of the GS. These characteristics open the possibility for an angle-dependent bandgap engineering in graphene.

  18. Optoelectronic Characterization of Narrow Bandgap Nanostructures through Scanning Photocurrent Microscopy

    Science.gov (United States)

    Miller, Christopher Vincent

    Scanning Photocurrent Microscopy is a powerful technique that studies the carrier transport and dynamics in nanostructures. It is capable of measuring diffusion lengths, drift lengths, electric field distributions, and metal-semiconductor barrier heights. In this dissertation, the carrier dynamics of Lead Sulfide nanowires, Vanadium Dioxide nanobeams, and Lead Selenide quantum dot thin films are investigated through Scanning Photocurrent Microscopy. For the Lead Sulfide nanowires, the minority carrier diffusion length was determined to be around 1 micron. This photocurrent decay length is highly dependant on the applied internal field, indicating a drift dominant carrier transport at high bias. This is explained through an intuitive charge transport simulation that accurately predicts this field dependent photocurrent decay length. For the Vanadium Dioxide nanobeams, a Schottky barrier height of ˜0.3 eV is extracted between the metal and insulator phases of VO2, providing direct evidence of the nearly symmetric bandgap opening upon the phase transition. There was also an unusually long photocurrent decay length in the insulating phase, indicating an unexpectedly long minority carrier lifetimes on the order of microseconds. For the Lead Selenide quantum dot thin films, Scanning Photocurrent Microscopy reveals a long photocurrent decay length of 1.7 microns at moderate positive gate bias. The diffusion of long-lifetime carriers accounts for this long photocurrent decay length via a Shockley-Read-Hall recombination mechanism through charge traps. In addition, the application of gold nanoparticles, acting as a plasmonic resonator, greatly enhances the photocurrent at the contacts.

  19. Bandgap engineering of monolayer MoS2 under strain: A DFT study

    Science.gov (United States)

    Li, Can; Fan, Bowen; Li, Weiyi; Wen, Luowei; Liu, Yan; Wang, Tao; Sheng, Kuang; Yin, You

    2015-06-01

    In this paper, density functional theory calculations are used to investigate the monolayer MoS2 in terms of the strain by analyzing the structure parameters: the bandgap, the density of states (DOS) and the Milliken charges. The calculations indicate that an increasing external stain tends to depress the ripple structure with a shorter S-S interlayer spacing and to enlarge the length of the Mo-S bond. Tensile strain dramatically alteres the bandgap; however, compressive strain almost does not. The change in the bandgap is explained by an analysis of the DOS, the partial density of states (PDOS), the structure parameters and the Mulliken charge distribution. The effects of strain on the Mulliken charge and the length of the Mo-S band cause bandgap differences under tensile and compressive strain.

  20. Fringe structures and tunable bandgap width of 2D boron nitride nanosheets.

    Science.gov (United States)

    Feng, Peter; Sajjad, Muhammad; Li, Eric Yiming; Zhang, Hongxin; Chu, Jin; Aldalbahi, Ali; Morell, Gerardo

    2014-01-01

    We report studies of the surface fringe structures and tunable bandgap width of atomic-thin boron nitride nanosheets (BNNSs). BNNSs are synthesized by using digitally controlled pulse deposition techniques. The nanoscale morphologies of BNNSs are characterized by using scanning electron microscope (SEM), and transmission electron microscopy (TEM). In general, the BNNSs appear microscopically flat in the case of low temperature synthesis, whereas at high temperature conditions, it yields various curved structures. Experimental data reveal the evolutions of fringe structures. Functionalization of the BNNSs is completed with hydrogen plasma beam source in order to efficiently control bandgap width. The characterizations are based on Raman scattering spectroscopy, X-ray diffraction (XRD), and FTIR transmittance spectra. Red shifts of spectral lines are clearly visible after the functionalization, indicating the bandgap width of the BNNSs has been changed. However, simple treatments with hydrogen gas do not affect the bandgap width of the BNNSs. PMID:25161852

  1. Effects of relevant parameters on the bandgaps of acoustic metamaterials with multi-resonators

    Science.gov (United States)

    Zhou, Xiaoqin; Wang, Jun; Wang, Rongqi; Lin, Jieqiong

    2016-04-01

    Locally resonant acoustic metamaterials with multi-resonators are generally regarded as a fine trend for managing the bandgaps, the different effects of relevant structural parameters on the bandgaps, which will be numerically investigated in this paper. A two-step homogenization method is extended to achieve the effective mass of multi-resonators metamaterial in the lattice system. As comparison, the dispersive wave propagation in lattice system and continuum model is studied. Then, the different effects of relevant parameters on the center frequencies and bandwidth of bandgaps are perfectly revealed, and the steady-state responses in the continuum models with purposed relevant parameters are additionally clarified. The related results can well confirm that the bandgaps exist around the undamped natural frequencies of internal resonators, and also their bandwidth can be efficiently controlled with the ensured center frequencies. Moreover, the design of purposed multi-resonators acoustic metamaterial in vibration control is presented and discussed by an example.

  2. Continuous fiber thermoplastic prepreg

    Science.gov (United States)

    Wilson, Maywood L. (Inventor); Johnson, Gary S. (Inventor)

    1993-01-01

    A pultrusion machine employing a corrugated impregnator vessel to immerse multiple, continuous strand, fiber tow in an impregnating material, and an adjustable metered exit orifice for the impregnator vessel to control the quantity of impregnating material retained by the impregnated fibers, is provided. An adjustable height insert retains transverse rod elements within each depression of the corrugated vessel to maintain the individual fiber tows spread and in contact with the vessel bottom. A series of elongated heating dies, transversely disposed on the pultrusion machine and having flat heating surfaces with radiused edges, ensure adequate temperature exposed dwell time and exert adequate pressure on the impregnated fiber tows, to provide the desired thickness and fiber/resin ratio in the prepreg formed. The prepreg passing through the pulling mechanism is wound on a suitable take-up spool for subsequent use. A formula is derived for determining the cross sectional area opening of the metering device. A modification in the heating die system employs a heated nip roller in lieu of one of the pressure applying flat dies.

  3. Degenerate four wave mixing in large mode area hybrid photonic crystal fibers

    DEFF Research Database (Denmark)

    Petersen, Sidsel Rübner; Alkeskjold, Thomas Tanggaard; Lægsgaard, Jesper

    2013-01-01

    Spontaneous degenerate four wave mixing (FWM) is investigated in large mode area hybrid photonic crystal fibers, in which photonic bandgap guidance and index guidance is combined. Calculations show the parametric gain is maximum on the edge of a photonic bandgap, for a large range of pump...... wavelengths. The FWM products are observed on the edges of a transmission band experimentally, in good agreement with the numerical results. Thereby the bandedges can be used to control the spectral positions of FWM products through a proper fiber design. The parametric gain control combined with a large mode...... area fiber design potentially allows for power scaling of light at wavelengths not easily accessible with e.g. rare earth ions....

  4. Degenerate four wave mixing in large mode area hybrid photonic crystal fibers.

    Science.gov (United States)

    Petersen, Sidsel R; Alkeskjold, Thomas T; Lægsgaard, Jesper

    2013-07-29

    Spontaneous degenerate four wave mixing (FWM) is investigated in large mode area hybrid photonic crystal fibers, in which photonic bandgap guidance and index guidance is combined. Calculations show the parametric gain is maximum on the edge of a photonic bandgap, for a large range of pump wavelengths. The FWM products are observed on the edges of a transmission band experimentally, in good agreement with the numerical results. Thereby the bandedges can be used to control the spectral positions of FWM products through a proper fiber design. The parametric gain control combined with a large mode area fiber design potentially allows for power scaling of light at wavelengths not easily accessible with e.g. rare earth ions. PMID:23938682

  5. Direct writing of fiber optic components in photonic crystal fibers and other specialty fibers

    Science.gov (United States)

    Fernandes, Luis Andre; Sezerman, Omur; Best, Garland; Ng, Mi Li; Kane, Saidou

    2016-04-01

    Femtosecond direct laser writing has recently shown great potential for the fabrication of complex integrated devices in the cladding of optical fibers. Such devices have the advantage of requiring no bulk optical components and no breaks in the fiber path, thus reducing the need for complicated alignment, eliminating contamination, and increasing stability. This technology has already found applications using combinations of Bragg gratings, interferometers, and couplers for the fabrication of optical filters, sensors, and power monitors. The femtosecond laser writing method produces a local modification of refractive index through non-linear absorption of the ultrafast laser pulses inside the dielectric material of both the core and cladding of the fiber. However, fiber geometries that incorporate air or hollow structures, such as photonic crystal fibers (PCFs), still present a challenge since the index modification regions created by the writing process cannot be generated in the hollow regions of the fiber. In this work, the femtosecond laser method is used together with a pre-modification method that consists of partially collapsing the hollow holes using an electrical arc discharge. The partial collapse of the photonic band gap structure provides a path for femtosecond laser written waveguides to couple light from the core to the edge of the fiber for in-line power monitoring. This novel approach is expected to have applications in other specialty fibers such as suspended core fibers and can open the way for the integration of complex devices and facilitate miniaturization of optical circuits to take advantage of the particular characteristics of the PCFs.

  6. Semi-transparent polymer solar cells with excellent sub-bandgap transmission for third generation photovoltaics

    KAUST Repository

    Beiley, Zach M.

    2013-10-07

    Semi-transparent organic photovoltaics are of interest for a variety of photovoltaic applications, including solar windows and hybrid tandem photovoltaics. The figure shows a photograph of our semi-transparent solar cell, which has a power conversion efficiency of 5.0%, with an above bandgap transmission of 34% and a sub-bandgap transmission of 81%. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Wide Bandgap Semiconductor One-Dimensional Nanostructures for Applications in Nanoelectronics and Nanosensors

    OpenAIRE

    Pearton, Stephen J.; Fan Ren

    2013-01-01

    Wide bandgap semiconductor ZnO, GaN and InN nanowires have displayed the ability to detect many types of gases and biological and chemical species of interest. In this review, we give some recent examples of using these nanowires for applications in pH sensing, glucose detection and hydrogen detection at ppm levels. The wide bandgap materials offer advantages in terms of sensing because of their tolerance to high temperatures, environmental stability and the fact that ...

  8. Properties of photonic bandgap in one-dimensional multicomponent photonic crystal

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi; WANG Qi

    2006-01-01

    Properties of photonic band gap and light propagation in one-dimensional multicomponent photonic crystal have been studied with the optical transfer matrix method.We mainly analyze the relation of photonic band-gap property with the arrangement of components,the refractive index and the geometrical thickness.In this study,the methods to change the width and the location of the existing photonic band-gaps in multicomponent photonic crystal are proposed.

  9. 基于PLC的光纤喷胶装置空气压力控制系统设计∗%Air Pressure Control System Design about Optical Fiber Glue Spray Device Based on PLC

    Institute of Scientific and Technical Information of China (English)

    马保吉; 刘坤

    2016-01-01

    Stable air pressure is one of the effective ways to improve the accuracy of winding optical fiber glue spray device, and achieving air pressure stability under different conditions. Using the advantages of Siemens S7-200PLC PID control mod-ule of PI regulator can realize air pressure control system fast response speed, simple operation and good spraying effect. It plays an important role in the effective solution of the problems such as the vibration of the liquid atomization and the uneven particles.%提高制导光纤线包喷胶精度的有效办法之一就是稳定空气压力供给,实现不同工况下空气压力稳定。使用西门子S7-200PLC中PID控制模块的PI调节具有空气压力控制系统响应速度快,操作简便,喷胶效果良好等优点,对有效解决胶液雾化抖动、雾化颗粒不均匀等问题有重要作用。

  10. Graphene nano-devices and nano-composites for structural, thermal and sensing applications

    Science.gov (United States)

    Yavari, Fazel

    In this dissertation we have developed graphene-based nano-devices for applications in integrated circuits and gas sensors; as well as graphene-based nano-composites for applications in structures and thermal management. First, we have studied the bandgap of graphene for semiconductor applications. Graphene as a zero-bandgap material cannot be used in the semiconductor industry unless an effective method is developed to open the bandgap in this material. We have demonstrated that a bandgap of 0.206 eV can be opened in graphene by adsorption of water vapor molecules on its surface. Water molecules break the molecular symmetries of graphene resulting in a significant bandgap opening. We also illustrate that the lack of bandgap in graphene can be used to our advantage by making sensors that are able to detect low concentrations of gas molecules mixed in air. We have shown that 1-2 layers of graphene synthesized by chemical vapor deposition enables detection of trace amounts of NO 2 and NH3 in air at room temperature and atmospheric pressure. The gas species are detected by monitoring changes in electrical resistance of the graphene film due to gas adsorption. The sensor response time is inversely proportional to the gas concentration. Heating the film expels chemisorbed molecules from the graphene surface enabling reversible operation. The detection limits of ~100 parts-per-billion (ppb) for NO2 and ~500 ppb for NH3 obtained using this device are markedly superior to commercially available NO2 and NH3 detectors. This sensor is fabricated using individual graphene sheets that are exquisitely sensitive to the chemical environment. However, the fabrication and operation of devices that use individual nanostructures for sensing is complex, expensive and suffers from poor reliability due to contamination and large variability from sample-to-sample. To overcome these problems we have developed a gas sensor based on a porous 3D network of graphene sheets called graphene foam

  11. Large enhancement of the photovoltaic effect in ferroelectric complex oxides through bandgap reduction

    Science.gov (United States)

    An, Hyunji; Han, Jun Young; Kim, Bongjae; Song, Jaesun; Jeong, Sang Yun; Franchini, Cesare; Bark, Chung Wung; Lee, Sanghan

    2016-01-01

    Tuning the bandgap in ferroelectric complex oxides is a possible route for improving the photovoltaic activity of materials. Here, we report the realization of this effect in epitaxial thin films of the ferroelectric complex oxide Bi3.25La0.75Ti3O12 (BLT) suitably doped by Fe and Co. Our study shows that Co (BLCT) doping and combined Fe, Co (BLFCT) doping lead to a reduction of the bandgap by more than 1 eV compared to undoped BLT, accompanied by a surprisingly more efficient visible light absorption. Both BLCT and BLFCT films can absorb visible light with a wavelength of up to 500 nm while still exhibiting ferroelectricity, whereas undoped BLT only absorbs UV light with a wavelength of less than 350 nm. Correlated with its bandgap reduction, the BLFCT film shows a photocurrent density enhanced by 25 times compared to that of BLT films. Density functional theory calculations indicate that the bandgap contraction is caused by the formation of new energy states below the conduction bands due to intermixed transition metal dopants (Fe, Co) in BLT. This mechanism of tuning the bandgap by simple doping can be applied to other wide-bandgap complex oxides, thereby enabling their use in solar energy conversion or optoelectronic applications. PMID:27313099

  12. Wide Band-Gap 3,4-Difluorothiophene-Based Polymer with 7% Solar Cell Efficiency: an Alternative to P3HT

    KAUST Repository

    Wolf, Jannic

    2015-05-27

    We report on a wide band-gap polymer donor composed of benzo[1,2-b:4,5-b\\']dithiophene (BDT) and 3,4-difluorothiophene ([2F]T) units (Eopt ~2.1 eV), and show that the fluorinated analog PBDT[2F]T performs significantly better than its non-fluorinated counterpart PBDT[2H]T in BHJ solar cells with PC71BM. While control P3HT- and PBDT[2H]T-based devices yield PCEs of ca. 4% and 3% (Max.) respectively, PBDT[2F]T-based devices reach PCEs of ca. 7%, combining a large Voc of ca. 0.9 V and short-circuit current values (ca. 10.7 mA/cm2) comparable to those of the best P3HT-based control devices.

  13. Interference of selective higher-order modes in optical fibers

    Institute of Scientific and Technical Information of China (English)

    Li Enbang; Peng Gangding

    2007-01-01

    The interference of selective higher-order modes in optical fibers is investigated both theoretically and experimentally.It has been demonstrated that by coupling the LP01 mode in a step-index single-mode fiber(SMF)to the LPom modes in step-index muhimode fibers(MMFs)with different parameters,one can selectively generate higher-order modes and construct all-fiber interferometers.The research presented in this paper forms a basis of a new type of fiber devices with potential applications in fiber sensing,optical fiber communications,and optical signal processing.

  14. Devices, systems, and methods for harvesting energy and methods for forming such devices

    Energy Technology Data Exchange (ETDEWEB)

    Kotter, Dale K.; Novack, Steven D.

    2012-12-25

    Energy harvesting devices include a substrate coupled with a photovoltaic material and a plurality of resonance elements associated with the substrate. The resonance elements are configured to collect energy in at least visible and infrared light spectra. Each resonance element is capacitively coupled with the photovoltaic material, and may be configured to resonate at a bandgap energy of the photovoltaic material. Systems include a photovoltaic material coupled with a feedpoint of a resonance element. Methods for harvesting energy include exposing a resonance element having a resonant electromagnetic radiation having a frequency between approximately 20 THz and approximately 1,000 THz, absorbing at least a portion of the electromagnetic radiation with the resonance element, and resonating the resonance element at a bandgap energy of an underlying photovoltaic material. Methods for forming an energy harvesting device include forming resonance elements on a substrate and capacitively coupling the resonance elements with a photovoltaic material.

  15. High-power picosecond pulse delivery through hollow core photonic band gap fibers

    DEFF Research Database (Denmark)

    Michieletto, Mattia; Johansen, Mette Marie; Lyngsø, Jens Kristian;

    2016-01-01

    setup. It provided 22ps pulses with a maximum average power of 95W, 40MHz repetition rate at 1032nm (~2.4μJ pulse energy), with M2 <1.3. We determined the facet damage threshold for a 7-cells hollow core photonic bandgap fiber and showed up to 59W average power output for a 5 meters fiber. The damage......We demonstrated robust and bend insensitive fiber delivery of high power laser with diffraction limited beam quality for two different kinds of hollow core band gap fibers. The light source for this experiment consists of ytterbium-doped double clad fiber aeroGAIN-ROD-PM85 in a high power amplifier...... threshold for a 19-cell hollow core photonic bandgap fiber exceeded the maximum power provided by the light source and up to 76W average output power was demonstrated for a 1m fiber. In both cases, no special attention was needed to mitigate bend sensitivity. The fibers were coiled on 8 centimeters radius...

  16. Ultra-large bandwidth hollow-core guiding in all-silica bragg fibers with nano-supports

    DEFF Research Database (Denmark)

    Vienne, Guillaume; Xu, Yong; Jakobsen, Christian;

    2004-01-01

    We demonstrate a new class of hollow-core Bragg fibers that are composed of concentric cylindrical silica rings separated by nanoscale support bridges. We theoretically predict and experimentally observe hollow-core confinement over an octave frequency range. The bandwidth of bandgap guiding in...

  17. Study on the preparation of optical fiber-film type CWDM device%光纤-薄膜型粗波分复用器件制备技术研究

    Institute of Scientific and Technical Information of China (English)

    徐进; 陈抱雪; 周建忠

    2013-01-01

    Experiment is carried out for the research of the preparation technology of a Curing sealing CWDM device with low-cost polymer binder,and glue-free light path.The device is widely used in CWDM system.In order to meet its technical parameters of wavelength division,and based on the high precision structure adjustment of automatic adjustment core instrument,and the high stability and low cost of the EMI3410 curing glue,the process involved in the on-line monitoring of the light path adjustment method,the component fixed method,moisture isolation methods is discussed.Using the technology of symmetric filling quartz fiber,the impact characteristic of the device in high and low temperature is effectively improved.The all-glass all-glue process is employed in the experiments to prepare the sample,and its optical properties conform to the industry index,and have passed the reliability test.%实验研究了一种低成本的聚合物粘结剂固化封口的、光路不合胶的粗波分复用(CWDM)器件的制备技术,器件大量用于CWDM系统中,为了满足其对波分的各种技术指标要求,基于自动调芯仪的高精度结构微调,以及EMI3410固化胶的高热稳定性和低成本,讨论了工艺过程中涉及的在线监测的光路调节方法、元器件固定方法、湿气隔离手段等.采用了独到的对称填充石英纤维的技术,有效改善了器件的抗高低温冲击特性.实验中采用全玻璃全胶工艺所制备样品,其光学特性数据达到行业指标,并通过了可靠性试验.

  18. Effects of corrugation shape on frequency band-gaps for longitudinal wave motion in a periodic elastic layer.

    Science.gov (United States)

    Sorokin, Vladislav S

    2016-04-01

    The paper concerns determining frequency band-gaps for longitudinal wave motion in a periodic waveguide. The waveguide may be considered either as an elastic layer with variable thickness or as a rod with variable cross section. As a result, widths and locations of all frequency band-gaps are determined by means of the method of varying amplitudes. For the general symmetric corrugation shape, the width of each odd band-gap is controlled only by one harmonic in the corrugation series with its number being equal to the number of the band-gap. Widths of even band-gaps, however, are influenced by all the harmonics involved in the corrugation series, so that the lower frequency band-gaps can emerge. These are band-gaps located below the frequency corresponding to the lowest harmonic in the corrugation series. For the general non-symmetric corrugation shape, the mth band-gap is controlled only by one, the mth, harmonic in the corrugation series. The revealed insights into the mechanism of band-gap formation can be used to predict locations and widths of all frequency band-gaps featured by any corrugation shape. These insights are general and can be valid also for other types of wave motion in periodic structures, e.g., transverse or torsional vibration. PMID:27106336

  19. Novel spatial solitons in light-induced photonic bandgap structures

    Institute of Scientific and Technical Information of China (English)

    Ci-bo LOU; Li-qin TANG; Dao-hong SONG; Xiao-sheng WANG; Jing-jun XU; Zhi-gang CHEN

    2008-01-01

    The study of wave propagation in periodic sys-tems is at the frontiers of physics, from fluids to condensed matter physics, and from photonic crystals to Bose-Einstein condensates. In optics, a typical example of periodic system is a closely-spaced waveguide array, in which collective behavior of wave propagation exhibits many intriguing phenomena that have no counterpart in homogeneous media. Even in a linear waveguide array, the diffraction property of a light beam changes due to evanescent coupling between nearby waveguide sites, leading to normal and anomalous discrete diffraction. In a nonlinear waveguide array, a bal-ance between diffraction and self-action gives rise to novel localized states such as spatial "discrete solitons" in the semi-infinite (or total-internal-reflection) gap or spatial "gap solitons" in the Bragg reflection gaps, Recently, in a series of experiments, we have "fabricated" closely-spaced waveguide arrays (photonic lattices) by optical induction. Such photonic structures have attracted great interest due to their novel physics, link to photonic crystals, as well as po-tential applications in optical switching and navigation. In this review article, we present a brief overview on our ex-perimental demonstrations of a number of novel spatial soliton phenomena in light-induced photonic bandgap structures, including self-trapping of fundamental discrete solitons and more sophisticated lattice gap solitons. Much of our work has direct impact on the study of similar discrete phenomena in systems beyond optics, including sound waves, water waves, and matter waves (Bose-Einstein con-densates) propagating in periodic potentials.

  20. Ultra-Thin, Triple-Bandgap GaInP/GaAs/GaInAs Monolithic Tandem Solar Cells

    Science.gov (United States)

    Wanlass, M. W.; Ahrenkiel, S. P.; Albin, D. S.; Carapella, J. J.; Duda, A.; Emery, K.; Geisz, J. F.; Jones, K.; Kurtz, Sarah; Moriarty, T.; Romero, M. J.

    2007-01-01

    The performance of state-of-the-art, series-connected, lattice-matched (LM), triple-junction (TJ), III-V tandem solar cells could be improved substantially (10-12%) by replacing the Ge bottom subcell with a subcell having a bandgap of approx.1 eV. For the last several years, research has been conducted by a number of organizations to develop approx.1-eV, LM GaInAsN to provide such a subcell, but, so far, the approach has proven unsuccessful. Thus, the need for a high-performance, monolithically integrable, 1-eV subcell for TJ tandems has remained. In this paper, we present a new TJ tandem cell design that addresses the above-mentioned problem. Our approach involves inverted epitaxial growth to allow the monolithic integration of a lattice-mismatched (LMM) approx.1- eV GaInAs/GaInP double-heterostructure (DH) bottom subcell with LM GaAs (middle) and GaInP (top) upper subcells. A transparent GaInP compositionally graded layer facilitates the integration of the LM and LMM components. Handle-mounted, ultra-thin device fabrication is a natural consequence of the inverted-structure approach, which results in a number of advantages, including robustness, potential low cost, improved thermal management, incorporation of back-surface reflectors, and possible reclamation/reuse of the parent crystalline substrate for further cost reduction. Our initial work has concerned GaInP/GaAs/GaInAs tandem cells grown on GaAs substrates. In this case, the 1- eV GaInAs experiences 2.2% compressive LMM with respect to the substrate. Specially designed GaInP graded layers are used to produce 1-eV subcells with performance parameters nearly equaling those of LM devices with the same bandgap (e.g., LM, 1-eV GaInAsP grown on InP). Previously, we reported preliminary ultra-thin tandem devices (0.237 cm2) with NREL-confirmed efficiencies of 31.3% (global spectrum, one sun) (1), 29.7% (AM0 spectrum, one sun) (2), and 37.9% (low-AOD direct spectrum, 10.1 suns) (3), all at 25 C. Here, we include

  1. Two Fiber Optical Fiber Thermometry

    Science.gov (United States)

    Jones, Mathew R.; Farmer, Jeffery T.; Breeding, Shawn P.

    2000-01-01

    An optical fiber thermometer consists of an optical fiber whose sensing tip is given a metallic coating. The sensing tip of the fiber is essentially an isothermal cavity, so the emission from this cavity will be approximately equal to the emission from a blackbody. Temperature readings are obtained by measuring the spectral radiative heat flux at the end of the fiber at two wavelengths. The ratio of these measurements and Planck's Law are used to infer the temperature at the sensing tip. Optical fiber thermometers have high accuracy, excellent long-term stability and are immune to electromagnetic interference. In addition, they can be operated for extended periods without requiring re-calibration. For these reasons. it is desirable to use optical fiber thermometers in environments such as the International Space Station. However, it has recently been shown that temperature readings are corrupted by emission from the fiber when extended portions of the probe are exposed to elevated temperatures. This paper will describe several ways in which the reading from a second fiber can be used to correct the corrupted temperature measurements. The accuracy and sensitivity to measurement uncertainty will be presented for each method.

  2. Tapered fibers embedded in silica aerogel.

    Science.gov (United States)

    Xiao, Limin; Grogan, Michael D W; Leon-Saval, Sergio G; Williams, Rhys; England, Richard; Wadsworth, Willam J; Birks, Tim A

    2009-09-15

    We have embedded thin tapered fibers (with diameters down to 1 microm) in silica aerogel with low loss. The aerogel is rigid but behaves refractively like air, protecting the taper without disturbing light propagation along it. This enables a new class of fiber devices exploiting volume evanescent interactions with the aerogel itself or with dopants or gases in the pores. PMID:19756084

  3. The Development of Advanced Optical Fibers for Long-Wave Infrared Transmission

    Directory of Open Access Journals (Sweden)

    Pierre Lucas

    2013-12-01

    Full Text Available Long-wave infrared fibers are used in an increasing number of applications ranging from thermal imaging to bio-sensing. However, the design of optical fiber with low-loss in the far-infrared requires a combination of properties including good rheological characteristics for fiber drawing and low phonon energy for wide optical transparency, which are often mutually exclusive and can only be achieved through fine materials engineering. This paper presents strategies for obtaining low loss fibers in the far-infrared based on telluride glasses. The composition of the glasses is systematically investigated to obtained fibers with minimal losses. The fiber attenuation is shown to depend strongly on extrinsic impurity but also on intrinsic charge carrier populations in these low band-gap amorphous semiconductor materials.

  4. Detection of analyte refractive index and concentration using liquid-core photonic Bragg fibers

    Science.gov (United States)

    Li, Jingwen; Qu, Hang; Skorobogatiy, Maksim

    2016-03-01

    We demonstrate detection of liquid analyte refractive index by using a hollow-core photonic Bragg fiber. We apply this fiber sensor to monitor concentrations of commercial cooling oil. The sensor operates on a spectral modality. Variation in the analyte refractive index modifies the bandgap guidance of a fiber, leading to spectral shifts in the fiber transmission spectrum. The sensitivity of the sensor to changes in the analyte refractive index filling in the fiber core is found to be 1460nm/Refractive index unit (RIU). By using the spectral modality and effective medium theory, we determine the concentrations of commercial fluid from the measured refractive indices with an accuracy of ~0.42%. The presented fiber sensor can be used for on-line monitoring of concentration of many industrial fluids and dilutions with sub-1%v accuracy.

  5. Fast, Large-Area, Wide-Bandgap UV Photodetector for Cherenkov Light Detection

    Science.gov (United States)

    Wrbanek, John D.; Wrbanek, Susan Y.

    2013-01-01

    Due to limited resources available for power and space for payloads, miniaturizing and integrating instrumentation is a high priority for addressing the challenges of manned and unmanned deep space missions to high Earth orbit (HEO), near Earth objects (NEOs), Lunar and Martian orbits and surfaces, and outer planetary systems, as well as improvements to high-altitude aircraft safety. New, robust, and compact detectors allow future instrumentation packages more options in satisfying specific mission goals. A solid-state ultraviolet (UV) detector was developed with a theoretical fast response time and large detection area intended for application to Cherenkov detectors. The detector is based on the wide-bandgap semiconductor zinc oxide (ZnO), which in a bridge circuit can detect small, fast pulses of UV light like those required for Cherenkov detectors. The goal is to replace the role of photomultiplier tubes in Cherenkov detectors with these solid-state devices, saving on size, weight, and required power. For improving detection geometry, a spherical detector to measure high atomic number and energy (HZE) ions from any direction has been patented as part of a larger space radiation detector system. The detector will require the development of solid-state UV photodetectors fast enough (2 ns response time or better) to detect the shockwave of Cherenkov light emitted as the ions pass through a quartz, sapphire, or acrylic ball. The detector must be small enough to fit in the detector system structure, but have an active area large enough to capture enough Cherenkov light from the sphere. The detector is fabricated on bulk single-crystal undoped ZnO. Inter - digitated finger electrodes and contact pads are patterned via photolithography, and formed by sputtered metal of silver, platinum, or other high-conductivity metal.

  6. Optical bistability in tunable fiber laser using fiber Mach-Zehnder interferometer

    Institute of Scientific and Technical Information of China (English)

    Guohui Lü; Hongan Ye; Junqing Li; Xiudong Sun; Xinming Zhang; Cheng Li

    2005-01-01

    @@ In this letter, a novel mechanism of hybrid optical bistability is proposed by using nonlinear mechanism in the frequency domain. This device is based on electro-optical feedback through the fiber Bragg grating on piezoelectric transducer (PZT) to tune continuous wave (CW) fiber laser. The optical bistable characteristics for two manners of separately alternating input power and bias voltage are discussed. The smallest wavelength shift of the order of 0.001 nm needed to realize a switching process in this optical bistability device is estimated. The potential applications of this device in the optical fiber sensor technique are also discussed.

  7. Nematic droplets on fibers.

    Science.gov (United States)

    Batista, V M O; Silvestre, N M; Telo da Gama, M M

    2015-12-01

    The emergence of new techniques for the fabrication of nematic droplets with nontrivial topology provides new routes for the assembly of responsive devices. Here we explore some of the properties of nematic droplets on fibers, which constitute the basic units of a type of device that is able to respond to external stimuli, including the detection of gases. We perform a numerical study of spherical nematic droplets on fibers. We analyze the equilibrium textures for homogeneous and hybrid boundary conditions and find that in some cases the nematic avoids the nucleation of topological defects, which would provide a different optical response. We consider in detail a homeotropic nematic droplet wrapped around a fiber with planar anchoring. We investigate the effect of an electric field on the texture of this droplet. In the presence of a dc field, the system undergoes an orientational transition above a given threshold E(c), for which a ring defect is transformed into a figure-eight defect. We also consider ac fields, at high and low frequencies, and find that the textures are similar to those observed for static fields, in contrast with recently reported experiments. PMID:26764711

  8. Alternative approaches of SiC and related wide bandgap materials in light emitting and solar cell applications

    International Nuclear Information System (INIS)

    silicon oxycarbide material can provide potential applications of the Eu luminescent materials to challenging conditions like high temperatures or aggressive environments where the silica has weaknesses. In some approaches, silicon rich silicon oxide that contain silicon nanoclusters emit red to near infrared luminescence due to quantum confinement effects while luminescence at shorter wavelength is difficult due to the interplay of defects and quantum confinement effects. In addition it is applicable as low-k dielectric, etch-stop and passivation layers. It also has an optical band-gap that is smaller than that of SiO2 which may facilitate carrier injection at lower voltages that is suitable for optoelectronics. From materials perspective of emerging materials, it seems distant to consider system related issues. The future demands on communication and lighting devices require higher information flows in modernized optical devices, for example by replacing electrical interconnects with their optical counterparts and tunable backgrounds filters for integrated optics or photonics applications. However, there are materials issues related to such device performance, for example by a non-linearity, that provide the possibility for selective removal or addition of wavelengths using hetero structures in which one side of the structure enhances the light-to-dark sensitivity of long and medium wavelength channels and diminish others, and an opposite behavior in other face of the structure. Certainly materials may be applied in various innovative ways to provide new performances in devices and systems. In any materials and device evaluation, reliability issues in passivation and packaging of semiconductor device structures provide a base knowledge that may be used to evaluate new concepts. Fundamental aspects of dielectric constant, bandgap and band offsets between the valence and conduction band edges between the passivation layer and the semiconductor create a foundation for

  9. Fiber-bragg grating-loop ringdown method and apparatus

    Science.gov (United States)

    Wang, Chuji

    2008-01-29

    A device comprising a fiber grating loop ringdown (FGLRD) system of analysis is disclosed. A fiber Bragg grating (FBG) or Long-Period grating (LPG) written in a section of single mode fused silica fiber is incorporated into a fiber loop. By utilizing the wing areas of the gratings' bandwidth as a wavelength dependent attenuator of the light transmission, a fiber grating loop ringdown concept is formed. One aspect of the present invention is temperature sensing, which has been demonstrated using the disclosed device. Temperature measurements in the areas of accuracy, stability, high temperature, and dynamic range are also described.

  10. Silicene nanomeshes: bandgap opening by bond symmetry breaking and uniaxial strain

    Science.gov (United States)

    Jia, Tian-Tian; Fan, Xin-Yu; Zheng, Meng-Meng; Chen, Gang

    2016-02-01

    Based on the first-principles calculations, we have investigated in detail the bandgap opening of silicene nanomeshes. Different to the mechanism of bandgap opening induced by the sublattice equivalence breaking, the method of degenerate perturbation through breaking the bond symmetry could split the π-like bands in the inversion symmetry preserved silicene nanomeshes, resulting into the πa1 - πa2 and πz1 - πz2 band sets with sizable energy intervals. Besides the bandgap opening in the nanomeshes with Dirac point being folded to Γ point, the split energy intervals are however apart away from Fermi level to leave the semimetal nature unchanged for the other nanomeshes with Dirac points located at opposite sides of Γ point as opposite pseudo spin wave valleys. A mass bandgap could be then opened at the aid of uniaxial strain to transfer the nanomesh to be semiconducting, whose width could be continuously enlarged until reaching its maximum Emax. Moreover, the Emax could also be tuned by controlling the defect density in silicene nanomeshes. These studies could contribute to the understanding of the bandgap engineering of silicene-based nanomaterials to call for further investigations on both theory and experiment.

  11. Dirac cone move and bandgap on/off switching of graphene superlattice

    Science.gov (United States)

    Jia, Tian-Tian; Zheng, Meng-Meng; Fan, Xin-Yu; Su, Yan; Li, Shu-Juan; Liu, Hai-Ying; Chen, Gang; Kawazoe, Yoshiyuki

    2016-01-01

    Using the density functional theory with generalized gradient approximation, we have studied in detail the cooperative effects of degenerate perturbation and uniaxial strain on bandgap opening in graphene. The uniaxial strain could split π bands into πa and πz bands with an energy interval Es to move the Dirac cone. The inversion symmetry preserved antidot would then further split the πa (πz) bands into πa1 (πz1) and πa2 (πz2) bands with an energy interval Ed, which accounts for the bandgap opening in a kind of superlattices with Dirac cone being folded to Γ point. However, such antidot would not affect the semimetal nature of the other superlattices, showing a novel mechanism for bandstructure engineering as compared to the sublattice-equivalence breaking. For a superlattice with bandgap of ~Ed opened at Γ point, the Es could be increased by strengthening strain to close the bandgap, suggesting a reversible switch between the high velocity properties of massless Fermions attributed to the linear dispersion relation around Dirac cone and the high on/off ratio properties associated with the sizable bandgap. Moreover, the gap width actually could be continuously tuned by controlling the strain, showing attractive application potentials.

  12. Wide band-gap materials for high power electronics

    International Nuclear Information System (INIS)

    The wide gap semiconductors are the basis for the third generation of microelectronics and specially for the high end of the temperature range. In this presentation we will review the prospects and status of two members of this group: Diamond and Silicon Carbide (SiC). The two are at different stages of technological development and their respective modes of application at present are quite different. SiC devices can operate at up to 105 deg C. High power and high frequency devices have been demonstrated. Diamond is not yet ready for real electronic devices but its many extreme properties find their applications in several cases. The prospects of the future applications will be described in view of the semiconducting characteristics of these materials

  13. Energy bandgap variation in oblique angle-deposited indium tin oxide

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyurin; Kim, Hyunsoo; Cho, Jaehee, E-mail: jcho@chonbuk.ac.kr [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Park, Jun Hyuk; Kim, Jong Kyu [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 54896 (Korea, Republic of); Fred Schubert, E. [Future Chips Constellation, Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2016-01-25

    Indium tin oxide (ITO) thin films deposited using the oblique angle deposition (OAD) technique exhibit a strong correlation between structural and optical properties, especially the optical bandgap energy. The microstructural properties of ITO thin films are strongly influenced by the tilt angle used during the OAD process. When changing the tilt angle, the refractive index, porosity, and optical bandgap energy of ITO films also change due to the existence of a preferential growth direction at the interface between ITO and the substrate. Experiments reveal that the ITO film's optical bandgap varies from 3.98 eV (at normal incident deposition) to 3.87 eV (at a 60° tilt angle)

  14. Effects of weak nonlinearity on dispersion relations and frequency band-gaps of periodic structures

    DEFF Research Database (Denmark)

    Sorokin, Vladislav; Thomsen, Jon Juel

    2015-01-01

    The analysis of the behaviour of linear periodic structures can be traced back over 300 years, to Sir Isaac Newton, and still attracts much attention. An essential feature of periodic struc-tures is the presence of frequency band-gaps, i.e. frequency ranges in which waves cannot propagate....... Determination of band-gaps and the corresponding attenuation levels is an im-portant practical problem. Most existing analytical methods in the field are based on Floquet theory; e.g. this holds for the classical Hill’s method of infinite determinants, and the method of space-harmonics. However, application of...... accounted for. The present work deals with analytically predicting dynamic responses for nonlinear continuous elastic periodic structures. Specifically, the effects of weak nonlinearity on the dispersion re-lation and frequency band-gaps of a periodic Bernoulli-Euler beam performing bending os...

  15. Energy bandgap variation in oblique angle-deposited indium tin oxide

    International Nuclear Information System (INIS)

    Indium tin oxide (ITO) thin films deposited using the oblique angle deposition (OAD) technique exhibit a strong correlation between structural and optical properties, especially the optical bandgap energy. The microstructural properties of ITO thin films are strongly influenced by the tilt angle used during the OAD process. When changing the tilt angle, the refractive index, porosity, and optical bandgap energy of ITO films also change due to the existence of a preferential growth direction at the interface between ITO and the substrate. Experiments reveal that the ITO film's optical bandgap varies from 3.98 eV (at normal incident deposition) to 3.87 eV (at a 60° tilt angle)

  16. Photoconductivity of amorphous As2S8 chalcogenide film under bandgap light irradiation

    Directory of Open Access Journals (Sweden)

    L. E. Zou

    2013-06-01

    Full Text Available The photoconductivity of amorphous As2S8 chalcogenide film under the irradiation of bandgap light is investigated. In the temperature range 300–350 K, the dark conductivity and photoconductivity of the annealed As2S8 film increase with the temperature, and the dependence of the both on temperature shows that the conduction in As2S8 film is an activated process having single activation energy. Under the irradiation of bandgap light, the photocurrents of the annealed and illuminated As2S8 film increase with the irradiation intensity, and their difference indicates the existence of the light-soaked effect. Meanwhile, the photoconductivity degradation during the irradiation and the photocurrent decay after stopping the irradiation are observed. By adding the irradiation of the sub-bandgap light, the enhancement of photoinduced voltage occurs.

  17. Research progress of the resonant fiber optic gyroscope technology

    Science.gov (United States)

    Wang, Linglan; Yan, Yuchao; Ma, Huilian; Jin, Zhonghe

    2015-10-01

    The resonant fiber optic gyro (RFOG) is a high accuracy inertial rotation sensor based on the Sagnac effect. The existence of various noises, including the nonreciprocal noises such as the polarization noise and the Kerr noise as well as the reciprocal circuit noise, limits the performance improvement of the RFOG. An improved scheme by inserting two in-line polarizers in the polarization maintaining fiber transmission-type resonator has been proposed to suppress the polarization-fluctuation induced drift. Furthermore, the adoption of the air-core photonic bandgap fibers (PBFs) offers a novel solution to reduce the optical Kerr effect. In addition, A digital signal processor is designed to reduce the reciprocal noises and detect the rotation information. A minimum actual rotation of 0.001°/s is achieved. The dynamic range is improved by a factor of 7 and the scale factor nonlinearity is decreased by a factor of 60.

  18. Transverse Anderson Localization in Disordered Glass Optical Fibers: A Review

    OpenAIRE

    Arash Mafi; Salman Karbasi; Koch, Karl W.; Thomas Hawkins; John Ballato

    2014-01-01

    Disordered optical fibers show novel waveguiding properties that can be used for various device applications, such as beam-multiplexed optical communications and endoscopic image transport. The strong transverse scattering from the transversely disordered optical fibers results in transversely confined beams that can freely propagate in the longitudinal direction, similar to conventional optical fibers, with the advantage that any point in the cross section of the fiber can be used for beam t...

  19. Distributed sensing employing stimulated Brillouin scattering in optical fibers

    OpenAIRE

    Antman, Yair; Thévenaz, Luc; Zadok, Avinoam

    2012-01-01

    Disclosed are methods and devices for distributed sensing of a measurable parameter employing stimulated Brillouin scattering in an optical fiber. A frequency-modulated or phase-modulated light wave is transmitted into the optical fiber. A scattered light wave in the optical fiber is monitored for sensing a measurable parameter. In some embodiments, the calculating step may include calculating a distance of a sensed location along the optical fiber using the monitored time of arrival.

  20. CARBONIZED STARCH MICROCELLULAR FOAM-CELLULOSE FIBER COMPOSITE STRUCTURES

    OpenAIRE

    Andrew R. Rutledge; Richard A. Venditti; Joel J. Pawlak; Sameer Patel; Janderson L. Cibils

    2008-01-01

    The production of microporous carbon foams from renewable starch microcellular foam-fiber (SMCF-Fiber) composites is described. Carbon foams are used in applications such as thermal insulation, battery electrodes, filters, fuel cells, and medical devices. SMCF-Fiber compos-ites were created from an aquagel. The water in the aquagel was exchanged with ethanol and then dried and carbonized. Higher amylose content starches and fiber contents of up to 4% improved the processability of the foam. ...

  1. Design and fabrication of customized fiber gratings to improve the interrogation of optical fiber sensors

    OpenAIRE

    Ricchiuti, Amelia Lavinia

    2016-01-01

    [EN] Fiber grating sensors and devices have demonstrated outstanding capabilities in both telecommunications and sensing areas, due to their well-known advantageous characteristics. Therefore, one of the most important motivations lies in the potential of customized fiber gratings to be suitably employed for improving the interrogation process of optical fiber sensors and systems. This Ph.D. dissertation is focused on the study, design, fabrication and performance evaluation of customized...

  2. Preparation of optical fibers with non-circular cross-section for fiber lasers and amplifiers

    Czech Academy of Sciences Publication Activity Database

    Podrazký, Ondřej; Kašík, Ivan; Peterka, Pavel; Aubrecht, Jan; Cajzl, Jakub; Proboštová, Jana; Matějec, Vlastimil

    Bellingham: SPIE, 2015, 94501A. ISBN 9781628415667. ISSN 0277-786X. [8th International Conference on Photonics, Devices, and System VI. Praha (CZ), 27.08.2014-29.08.2014] R&D Projects: GA ČR GA14-35256S Institutional support: RVO:67985882 Keywords : Optical fiber drawing * Non-circular optical fiber * Double-clad optical fiber Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  3. Relationship between dopant energy levels and device performances of triplet mixed host devices

    International Nuclear Information System (INIS)

    Device performances of phosphorescent organic light-emitting diodes (PHOLEDs) with triplet mixed host structure were correlated with dopant energy levels and mixed host composition. A mixed host of 4,4',4''-tris-(N-carbazolyl)triphenylamine (TCTA) and spirobifluorene type host (PH1) was used and three different dopants with different bandgap were doped in the mixed host. Optimum quantum efficiency was obtained in TCTA:PH1 (50:50) mixed host device in the case of green dopants, while the optimum host composition for red and orange dopants was TCTA:PH1 (25:75)

  4. Effect of Heavily Doped Boron on Bandgap Narrowing of Strained SiGe Layers

    Institute of Scientific and Technical Information of China (English)

    YAO Fei; XUE Chun-Lai; CHENG Bu-Wen; WANG Qi-Ming

    2007-01-01

    Taking into account the compensation effect of B to Ge in strained SiGe layers for the first time, the effect of heavily doped boron on the bandgap narrowing of strained SiGe layers is calculated, and the classical Jain-Roulston (J-R) model is modified. The results show that our modified J-R model well fits the experimental values. Based on the modified J-R model, the real bandgap narrowing distribution between the conduction and valence bands is further calculated, which has great influence on modelling the electrical characteristics of SiGe heterojunction bipolar transistors.

  5. Linewidth of Cyclotron Absorption in Band-Gap Graphene: Relaxation Time Approximation vs. Monte Carlo Method

    Directory of Open Access Journals (Sweden)

    S.V. Kryuchkov

    2015-03-01

    Full Text Available The power of the elliptically polarized electromagnetic radiation absorbed by band-gap graphene in presence of constant magnetic field is calculated. The linewidth of cyclotron absorption is shown to be non-zero even if the scattering is absent. The calculations are performed analytically with the Boltzmann kinetic equation and confirmed numerically with the Monte Carlo method. The dependence of the linewidth of the cyclotron absorption on temperature applicable for a band-gap graphene in the absence of collisions is determined analytically.

  6. One-dimensional tunable magnetic photonic band-gap materials at microwave frequency

    International Nuclear Information System (INIS)

    The microwave transmission characteristics of one-dimensional magnetic photonic band-gap (MPBG) materials, in which a ferromagnetic composite layer is sandwiched by periodic dielectric layers, are studied. The magnetic photonic band gaps (MBPGs) are obtained related to the existence of ferromagnetic resonance (FMR) in the vicinity of the band-gap frequency. We investigate the effects of period structure and the applied magnetic field on the MPBGs as well as the ferromagnetic resonance. The photonic band gaps of the TE mode shift to lower frequencies. The MPBG effect is strongly dependent on the periodic structure of the MPBG materials. While the FMR effect is dominated by the applied magnetic field

  7. Nonlinear switching in a concentric ring core chalcogenide glass optical fiber for passively mode-locking a fiber laser

    CERN Document Server

    Nazemosadat, Elham

    2014-01-01

    We propose an all-fiber mode-locking device which operates based on nonlinear switching in a novel concentric ring core fiber structure. The design is particularly attractive given the ease of fabrication and coupling to other components in a mode-locked fiber laser cavity. The nonlinear switching in this coupler is studied and the relative power transmission is obtained. The analysis shows that this nonlinear switch is practical for mode-locking fiber lasers and is forgiving to fabrication errors.

  8. Nonlinear switching in a concentric ring core chalcogenide glass optical fiber for passively mode-locking a fiber laser

    OpenAIRE

    Nazemosadat, Elham; Mafi, Arash

    2014-01-01

    We propose an all-fiber mode-locking device which operates based on nonlinear switching in a novel concentric ring core fiber structure. The design is particularly attractive given the ease of fabrication and coupling to other components in a mode-locked fiber laser cavity. The nonlinear switching in this coupler is studied and the relative power transmission is obtained. The analysis shows that this nonlinear switch is practical for mode-locking fiber lasers and is forgiving to fabrication e...

  9. Bandgap engineering of the amorphous wide bandgap semiconductor (SiC)1-x(AlN)x doped with terbium and its optical emission properties

    International Nuclear Information System (INIS)

    Amorphous wide bandgap semiconductor thin films of the pseudobinary compound (SiC)1-x(AlN)x doped with terbium were grown by trial rf magnetron sputtering on CaF2 and glass substrates. The optical bandgap of the films in dependence of the composition x has been determined from transmission measurements using the (αhν)2 versus energy plot and the Tauc-plot. The bandgap varies from 2.2 eV for x = 0 (SiC) to 4.7 eV for x = 0.94 (almost pure AlN) and can be described by Vegard's law using the bowing parameter (3.18 ± 1.01) eV. Cathodoluminescence measurements show the typical terbium emission pattern. Thermal activation of the thin films with isochronical annealing from 300 deg. C to 1150 deg. C leads to strong increase of the emission with an optimal annealing temperature of 1100 deg. C.

  10. Soluble vs. insoluble fiber

    Science.gov (United States)

    Insoluble vs. soluble fiber; Fiber - soluble vs. insoluble ... There are two different types of fiber -- soluble and insoluble. Both are important for health, digestion, and preventing diseases. Soluble fiber attracts water and turns to gel during digestion. ...

  11. Band-gap engineering at a semiconductor - crystalline oxide interface

    OpenAIRE

    Moghadam, J.; Ahmadi-Majlan, K.; Shen, X; Droubay, T.; Bowden, M; Chrysler, M.; Su, D.; Chambers, S. A.; Ngai, J. H.

    2014-01-01

    The epitaxial growth of crystalline oxides on semiconductors provides a pathway to introduce new functionalities to semiconductor devices. Key to electrically coupling crystalline oxides with semiconductors to realize functional behavior is controlling the manner in which their bands align at interfaces. Here we apply principles of band gap engineering traditionally used at heterojunctions between conventional semiconductors to control the band offset between a single crystalline oxide and a ...

  12. Novel manufacturing method of optical fiber coupler

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Based on the coupling mode theory that the coupling ratio of fiber coupler changes periodically with canter distance of two optical fibers, a novel manufacturing method of optical fiber couplers was developed with fused biconical taper experimental system. Its fabrication process is that the fiber is fused but not stretched when light begins to split, and the reduction of diameter of fiber is dependent on the rheological characteristic of the fused fiberglass. The performance of the coupler was tested. The results show that the performance of the novel optical fiber coupler meets the performance expectations, and its diameter of coupling region (about 30 μm) is twice as long as that of classical fused biconical taper coupler (about 16 μm), so the default, that is, the device is easy to fracture, is restrained and the reliability is greatly improved.

  13. Cross-correlated imaging of single-mode photonic crystal rod fiber with distributed mode filtering

    DEFF Research Database (Denmark)

    Laurila, Marko; Barankov, Roman; Jørgensen, Mette Marie;

    2013-01-01

    Photonic crystal bandgap fibers employing distributed mode filtering design provide near diffraction-limited light outputs, a critical property of fiber-based high-power lasers. Microstructure of the fibers is tailored to achieve single-mode operation at specific wavelength by resonant mode...... coupling of higher-order modes. We analyze the modal regimes of the fibers having a mode field diameter of 60 µm by the cross-correlated (C2) imaging method in different wavelength ranges and evaluate the sensitivity of the modal content to various input-coupling conditions. As a result, we experimentally...... identify regimes of resonant coupling between higher-order core modes and cladding band. We demonstrate a passive fiber design in which the higher-order modal content inside the single-mode guiding regime is suppressed by at least 20 dB even for significantly misaligned input-coupling configurations....

  14. Highly Conductive Graphene/Ag Hybrid Fibers for Flexible Fiber-Type Transistors

    Science.gov (United States)

    Yoon, Sang Su; Lee, Kang Eun; Cha, Hwa-Jin; Seong, Dong Gi; Um, Moon-Kwang; Byun, Joon-Hyung; Oh, Youngseok; Oh, Joon Hak; Lee, Wonoh; Lee, Jea Uk

    2015-11-01

    Mechanically robust, flexible, and electrically conductive textiles are highly suitable for use in wearable electronic applications. In this study, highly conductive and flexible graphene/Ag hybrid fibers were prepared and used as electrodes for planar and fiber-type transistors. The graphene/Ag hybrid fibers were fabricated by the wet-spinning/drawing of giant graphene oxide and subsequent functionalization with Ag nanoparticles. The graphene/Ag hybrid fibers exhibited record-high electrical conductivity of up to 15,800 S cm-1. As the graphene/Ag hybrid fibers can be easily cut and placed onto flexible substrates by simply gluing or stitching, ion gel-gated planar transistors were fabricated by using the hybrid fibers as source, drain, and gate electrodes. Finally, fiber-type transistors were constructed by embedding the graphene/Ag hybrid fiber electrodes onto conventional polyurethane monofilaments, which exhibited excellent flexibility (highly bendable and rollable properties), high electrical performance (μh = 15.6 cm2 V-1 s-1, Ion/Ioff > 104), and outstanding device performance stability (stable after 1,000 cycles of bending tests and being exposed for 30 days to ambient conditions). We believe that our simple methods for the fabrication of graphene/Ag hybrid fiber electrodes for use in fiber-type transistors can potentially be applied to the development all-organic wearable devices.

  15. Ytterbium-doped large-mode-area photonic crystal fiber amplifier with gain shaping for use at long wavelengths

    DEFF Research Database (Denmark)

    Petersen, Sidsel Rübner; Alkeskjold, Thomas T.; Poli, Federica; Coscelli, Enrico; Jørgensen, Mette Marie; Laurila, Marko; Lægsgaard, Jesper; Broeng, Jes

    2012-01-01

    A large-mode-area Ytterbium-doped photonic crystal fiber amplifier with efficient suppression of amplified spontaneous emission is presented. The fiber cladding consists of a hexagonal lattice of air holes, where three rows are replaced with circular high-index inclusions. Seven missing air holes...... define the large-mode-area core. Light confinement is achieved by combined index and bandgap guiding, which allows for single-mode operation and distributed spectral filtering of amplified spontaneous. The fiber properties give control of the gain shape and are ideal for amplification in the long...

  16. Lab-on-fiber technology

    CERN Document Server

    Cusano, Andrea; Crescitelli, Alessio; Ricciardi, Armando

    2014-01-01

    This book focuses on a research field that is rapidly emerging as one of the most promising ones for the global optics and photonics community: the "lab-on-fiber" technology. Inspired by the well-established 'lab on-a-chip' concept, this new technology essentially envisages novel and highly functionalized devices completely integrated into a single optical fiber for both communication and sensing applications.Based on the R&D experience of some of the world's leading authorities in the fields of optics, photonics, nanotechnology, and material science, this book provides a broad and accurate de

  17. Fiber Bragg Grating Based Thermometry

    CERN Document Server

    Ahmed, Zeeshan; Guthrie, William; Quintavalle, John

    2016-01-01

    In recent years there has been considerable interest in developing photonic temperature sensors such as the Fiber Bragg gratings (FBG) as an alternative to resistance thermometry. In this study we examine the thermal response of FBGs over the temperature range of 233 K to 393 K. We demonstrate, in a hermetically sealed dry Argon environment, that FBG devices show a quadratic dependence on temperature with expanded uncertainties (k = 2) of ~500 mK. Our measurements indicate that the combined measurement uncertainty is dominated by uncertainty in determining the peak center fitting and by thermal aging of polyimide coated fibers.

  18. Fiber optic diffraction grating maker

    Science.gov (United States)

    Deason, Vance A.; Ward, Michael B.

    1991-01-01

    A compact and portable diffraction grating maker comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent beam splitters, and collimating lenses or mirrors directing the split beam at an appropriate photosensitive material. The collimating optics, the output ends of the fiber optic coupler and the photosensitive plate holder are all mounted on an articulated framework so that the angle of intersection of the beams can be altered at will without disturbing the spatial filter, collimation or beam quality, and assuring that the beams will always intersect at the position of the plate.

  19. Size dependence of the bandgap of plasma synthesized silicon nanoparticles through direct introduction of sulfur hexafluoride

    Science.gov (United States)

    Theingi, S.; Guan, T. Y.; Kendrick, C.; Klafehn, G.; Gorman, B. P.; Taylor, P. C.; Lusk, M. T.; Stradins, P.; Collins, R. T.

    2015-10-01

    Developing silicon nanoparticle (SiNP) synthesis techniques that allow for straightforward control of nanoparticle size and associated optical properties is critical to potential applications of these materials. In addition, it is, in general, hard to probe the absorption threshold in these materials due to silicon's low absorption coefficient. In this study, size is controlled through direct introduction of sulfur hexafluoride (SF6) into the dilute silane precursor of plasma synthesized SiNPs. Size reduction by nearly a factor of two with high crystallinity independent of size is demonstrated. The optical absorption spectra of the SiNPs in the vicinity of the bandgap are measured using photothermal deflection spectroscopy. Bandgap as a function of size is extracted taking into account the polydispersity of the samples. A systematic blue shift in absorption edge due to quantum confinement in the SiNPs is observed with increasing flow of SF6. Photoluminescence (PL) spectra show a similar blue shift with size. However, a ˜300 meV difference in energy between emission and absorption for all sizes suggests that PL emission involves a defect related process. This shows that, while PL may allow size-induced shifts in the bandgap of SiNPs to be monitored, it cannot be relied on to give an accurate value for the bandgap as a function of size.

  20. Size dependence of the bandgap of plasma synthesized silicon nanoparticles through direct introduction of sulfur hexafluoride

    Energy Technology Data Exchange (ETDEWEB)

    Theingi, S.; Guan, T. Y.; Klafehn, G.; Taylor, P. C.; Lusk, M. T.; Collins, R. T., E-mail: rtcollin@mines.edu [Department of Physics, Colorado School of Mines, Golden, Colorado 80401 (United States); Renewable Energy Materials Research Science and Engineering Center, Colorado School of Mines, Golden, Colorado 80401 (United States); Kendrick, C. [Department of Physics, Colorado School of Mines, Golden, Colorado 80401 (United States); Renewable Energy Materials Research Science and Engineering Center, Colorado School of Mines, Golden, Colorado 80401 (United States); Electrical and Computer Engineering, Michigan Technological University, Houghton, Michigan 49931 (United States); Gorman, B. P. [Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado 80401 (United States); Stradins, P. [Renewable Energy Materials Research Science and Engineering Center, Colorado School of Mines, Golden, Colorado 80401 (United States); National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

    2015-10-19

    Developing silicon nanoparticle (SiNP) synthesis techniques that allow for straightforward control of nanoparticle size and associated optical properties is critical to potential applications of these materials. In addition, it is, in general, hard to probe the absorption threshold in these materials due to silicon's low absorption coefficient. In this study, size is controlled through direct introduction of sulfur hexafluoride (SF{sub 6}) into the dilute silane precursor of plasma synthesized SiNPs. Size reduction by nearly a factor of two with high crystallinity independent of size is demonstrated. The optical absorption spectra of the SiNPs in the vicinity of the bandgap are measured using photothermal deflection spectroscopy. Bandgap as a function of size is extracted taking into account the polydispersity of the samples. A systematic blue shift in absorption edge due to quantum confinement in the SiNPs is observed with increasing flow of SF{sub 6}. Photoluminescence (PL) spectra show a similar blue shift with size. However, a ∼300 meV difference in energy between emission and absorption for all sizes suggests that PL emission involves a defect related process. This shows that, while PL may allow size-induced shifts in the bandgap of SiNPs to be monitored, it cannot be relied on to give an accurate value for the bandgap as a function of size.

  1. Size Dependence of the Bandgap of Plasma Synthesized Silicon Nanoparticles Through Direct Introduction of Sulfur Hexafluoride

    Energy Technology Data Exchange (ETDEWEB)

    Theingi, S.; Guan, T. Y.; Kendrick, C.; Klafehn, G.; Gorman, B. P.; Taylor, P. C.; Lusk, M. T.; Stradins, Pauls; Collins, R. T.

    2015-10-19

    Developing silicon nanoparticle (SiNP) synthesis techniques that allow for straightforward control of nanoparticle size and associated optical properties is critical to potential applications of these materials. In addition, it is, in general, hard to probe the absorption threshold in these materials due to silicon's low absorption coefficient. In this study, size is controlled through direct introduction of sulfur hexafluoride (SF6) into the dilute silane precursor of plasma synthesized SiNPs. Size reduction by nearly a factor of two with high crystallinity independent of size is demonstrated. Optical absorption spectra of the SiNPs in the vicinity of the bandgap are measured using photothermal deflection spectroscopy. Bandgap as a function of size is extracted taking into account the polydispersity of the samples. A systematic blue shift inabsorption edge due to quantum confinement in the SiNPs is observed with increasing flow of SF6. Photoluminescence (PL) spectra show a similar blue shift with size. However, a ~300 meV difference in energy between emission and absorption for all sizes suggests that PL emission involves a defect related process. While PL may allow size-induced shifts in the bandgap of SiNPs to be monitored, it cannot be relied on to give an accurate value for the bandgap as a function of size.

  2. Extremely small bandgaps, engineered by controlled multi-scale ordering in InAsSb

    Science.gov (United States)

    Sarney, W. L.; Svensson, S. P.; Lin, Y.; Donetsky, D.; Shterengas, L.; Kipshidze, G.; Belenky, G.

    2016-06-01

    The relationship between the effective bandgap and the crystalline structure in ordered InAsSb material has been studied. Modulation of the As/Sb ratio was induced along the growth direction during molecular beam epitaxy, producing a strained layer superlattice. To enable the use of concentration ratios near unity in both layers in the period, the structures were grown with negligible net strain on a virtual substrate with a lattice constant considerably larger than that of GaSb. The bandgap line-up of InAsSb layers with different compositions is such that a type II superlattice is formed, which exhibits smaller bandgaps than either of the two constituents. It can also be smaller than the possible minimum direct-bandgap of the alloy. From observations of CuPt ordering in bulk layers with small amounts of strain of both signs, we postulate that strain is the main driving force for atomic ordering in InAsSb. Because the modulated structures exhibit small but opposing amounts of strain, both layers in the period exhibit ordering at the atomic scale throughout the structure. Since the strain can be controlled, the ordering can be controlled and sustained for arbitrary thick layers, unlike the situation in uniform bulk layers where the residual strain eventually leads to dislocation formation. This offers a unique way of using ordering at two different scales to engineer the band-structure.

  3. Narrow Bandgap in beta-BaZn2As2 and Its Chemical Origins

    CERN Document Server

    Xiao, Zewen; Ueda, Shigenori; Toda, Yoshitake; Ran, Fan-Yong; Guo, Jiangang; Lei, Hechang; Matsuishi, Satoru; Hosono, Hideo; Kamiya, Toshio

    2015-01-01

    Beta-BaZn2As2 is known to be a p-type semiconductor with the layered crystal structure similar to that of LaZnAsO, leading to the expectation that beta-BaZn2As2 and LaZnAsO have similar bandgaps; however, the bandgap of beta-BaZn2As2 (previously-reported value ~0.2 eV) is one order of magnitude smaller than that of LaZnAsO (1.5 eV). In this paper, the reliable bandgap value of beta-BaZn2As2 is determined to be 0.23 eV from the intrinsic region of the tem-perature dependence of electrical conductivity. The origins of this narrow bandgap are discussed based on the chemi-cal bonding nature probed by 6 keV hard X-ray photoemission spectroscopy, hybrid density functional calculations, and the ligand theory. One origin is the direct As-As hybridization between adjacent [ZnAs] layers, which leads to a secondary splitting of As 4p levels and raises the valence band maximum. The other is that the non-bonding Ba 5dx2-y2 orbitals form unexpectedly deep conduction band minimum (CBM) in beta-BaZn2As2 although the CBM of L...

  4. Physical ageing in the above-bandgap photoexposured glassy arsenic selenides

    Energy Technology Data Exchange (ETDEWEB)

    Kozdras, A [Faculty of Physics of Opole University of Technology, 75, Ozimska str., Opole, PL-45370 (Poland); Golovchak, R [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 202, Stryjska str., Lviv, UA-79031 (Ukraine); Shpotyuk, O [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 202, Stryjska str., Lviv, UA-79031 (Ukraine)

    2007-08-15

    Physical ageing induced by above-bandgap light illumination is studied in glassy As-Se using differential scanning calorimetry. It is shown that measurable effect like to known short-term physical ageing is observed only in Se-rich glasses. The kinetics of this effect is compared with that caused by natural storage in a dark.

  5. Analysis of band-gap formation in squashed arm-chair CNT

    CERN Document Server

    Mehrer, H; Anantram, M P; Elstner, M; Frauenheim, T

    2005-01-01

    The electronic properties of squashed arm-chair carbon nanotubes are modeled using constraint free density functional tight binding molecular dynamics simulations. Independent from CNT diameter, squashing path can be divided into {\\it three} regimes. In the first regime, the nanotube deforms with negligible force. In the second one, there is significantly more resistance to squashing with the force being $\\sim 40-100$ nN/per CNT unit cell. In the last regime, the CNT looses its hexagonal structure resulting in force drop-off followed by substantial force enhancement upon squashing. We compute the change in band-gap as a function of squashing and our main results are: (i) A band-gap initially opens due to interaction between atoms at the top and bottom sides of CNT. The $\\pi-$orbital approximation is successful in modeling the band-gap opening at this stage. (ii) In the second regime of squashing, large $\\pi-\\sigma$ interaction at the edges becomes important, which can lead to band-gap oscillation. (iii) Contr...

  6. Bandgap measurement of thin dielectric films using monochromated STEM-EELS

    International Nuclear Information System (INIS)

    High-resolution electron energy-loss spectroscopy (HR-EELS), achieved by attaching electron monochromators to transmission electron microscopes (TEM), has proved to be a powerful tool for measuring bandgaps. However, the method itself is still uncertain, due to Cerenkov loss and surface effects that can potentially influence the quality of EELS data. In the present study, we achieved an energy resolution of about 0.13 eV at 0.1 s, with a spatial resolution of a few nanometers, using a monochromated STEM-EELS technique. We also assessed various methods of bandgap measurement for a-SiNx and SiO2 thin dielectric films. It was found that the linear fit method was more reliable than the onset reading method in avoiding the effects of Cerenkov loss and specimen thickness. The bandgap of the SiO2 was estimated to be 8.95 eV, and those of a-SiNx with N/Si ratios of 1.46, 1.20 and 0.92 were measured as 5.3, 4.1 and 2.9 eV, respectively. These bandgap-measurement results using monochromated STEM-EELS were compared with those using Auger electron spectroscopy (AES)-reflective EELS (REELS).

  7. Bandgap determination of P(VDF–TrFE) copolymer film by electron energy loss spectroscopy

    Indian Academy of Sciences (India)

    Dipankar Mandal; K Henkel; K Müller; D Schmeißer

    2010-08-01

    The ferroelectric of poly(vinylidene fluoride trifluoroethylene), P(VDF–TrFE) is confirmed for 100 nm thickness spin coated copolymer film. The homogeneous coverage of the copolymer film is investigated by the help of X-ray photoelectron spectroscopy (XPS). Most importantly, the existing bandgap in the crystalline phase of the copolymer is determined directly from the electron energy loss spectroscopy (EELS).

  8. Ultrathin Fe3O4 epitaxial films on wide bandgap GaN

    NARCIS (Netherlands)

    Wong, P.K.J.; Zhang, W.; Cui, X.G.; Wu, J.; Xu, Y.B.; Tao, Z.K.; Li, X.; Xie, Z.L.; Zhang, R.; Van de Laan, G.

    2010-01-01

    Ultrathin films of magnetite Fe3O4 have been grown epitaxially on wurtzite wide bandgap semiconductor GaN0001 surfaces using molecular-beam epitaxy. Reflection high-energy electron-diffraction patterns show a 111 orientation of the Fe3O4 films and in-plane epitaxial relationship of 11¯0Fe3O4 112¯0G

  9. 10 Gbit/s transmission over air-guiding photonic bandgap fibre at 1550 nm

    DEFF Research Database (Denmark)

    Peucheret, Christophe; Zsigri, Beata; Hansen, T.P.;

    2005-01-01

    The first data transmission over air-guiding photonic bandgap (PBG) fibre is demonstrated. A 10 Gbit/s signal was successfully transmitted at 1550 nm over 150 m of singlemode PBG fibre, thus demonstrating their applicability to optical communications. Furthermore, the impact of the polarisation...

  10. Thermally activated emission from direct bandgap-like silicon quantum dots

    NARCIS (Netherlands)

    K. Dohnalova; S. Saeed; A. N. Poddubny; A.A. Prokofiev; T. Gregorkiewicz

    2013-01-01

    Due to the covalent character of silicon-carbon (Si-C) bond, C-linked molecules on the silicon quantum dot (SiQD) surface lead to dramatic changes in wavefunctions of the excited electron-hole pairs. Some of the optical transitions are strongly modified and attain direct bandgap-like character, givi

  11. Radiation effects in optoelectronic devices

    International Nuclear Information System (INIS)

    Purpose of this report is to provide not only a summary of radiation damage studies at Sandia National Laboratories, but also of those in the literature on the components of optoelectronic systems: light emitting diodes (LEDs), laser diodes, photodetectors, optical fibers, and optical isolators. This review of radiation damage in optoelectronic components is structured according to device type. In each section, a brief discussion of those device properties relevant to radiation effects is given

  12. Low-temperature-grown InGaAs quantum wells for optical device applications

    Science.gov (United States)

    Juodawlkis, Paul William

    1999-11-01

    The large optical absorption and carrier-induced nonlinearities of semiconductor materials are useful for optical signal processing applications. For absorptive devices operating at ultrafast data rates (>100 Gb/s) or high optical intensities, it is necessary to reduce the intrinsic photo-excited carrier removal time. One method of achieving this reduction is to increase the nonradiative recombination rate through the controlled introduction of defects. In this thesis, we explore the use of low-temperature molecular-beam epitaxy (MBE) to introduce nonradiative recombination centers into InGaAs-based quantum-wells (QWs). The objectives of the thesis are: (i)to improve the understanding of the optoelectronic properties of low-temperature-grown (LTG) InGaAs/InAlAs QWs, and (ii)to assess the feasibility of using these materials for optical device applications in the 1.5-μm wavelength region. Time-resolved differential transmission measurements reveal that the nonlinear absorption recovery time in InGaAs/InAlAs QWs can be reduced from >100 ps to 0.6 ps through the combination of low-temperature growth (~250°C) and beryllium (Be) doping. The bandedge absorption slope and the nonlinear absorption cross- section are only diminished by factors of 2 to 3 relative to QWs grown at standard temperature (~500°C). The Be doping dependence of the recovery time and the residual electron density in the LTG-QWs can be mainly attributed to impurity-related compensation. Be doping also maintains the ultrafast recovery following thermal anneal. The recovery response results from fast electron- trapping followed by slow (>100 ps) trapped- electron/free-hole recombination. Detailed simulations of the nonlinear absorption saturation and recovery processes agree quantitatively with measured data and substantiate the importance of the photo-excitation wavelength on the observed recovery response. The absorption saturation model includes the competition between band-filling and band-gap

  13. A phase mask fiber grating and sensing applications

    Directory of Open Access Journals (Sweden)

    Preecha P. Yupapin

    2003-09-01

    Full Text Available This paper presents an investigation of a fabricated fiber grating device characteristics and its applications, using a phase mask writing technique. The use of a most common UV phase laser (KrF eximer laser, with high intensity light source was focussed to the phase mask for writing on a fiber optic sample. The device (i.e. grating characteristic especially, in sensing application, was investigated. The possibility of using such device for temperature and strain sensors is discussed.

  14. Electrical Properties of Macro-Fiber Composite Actuators and Sensors

    OpenAIRE

    Lloyd, Justin Michael

    2004-01-01

    Piezoceramic fiber composite (PFC) actuators and sensors offer many advantages over conventional monolithic piezoceramic devices. Conformable, durable and, when equipped with interdigitated electrodes (IDEs), more responsive than regular monolithic devices, PFCs promise to revolutionize the application of piezoelectric materials. Developed by the NASA-Langley Research Center, the Macro-Fiber Composite (MFC) actuator and sensor is the most sophisticated PFC device yet invented. With superio...

  15. Monolithic, High-Speed Fiber-Optic Switching Array for Lidar Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed optical device is a fiber-based multi-channel switch to quickly switch a fiber-coupled laser among many possible output channels to create a...

  16. Band-gap shrinkage calculations and analytic model for strained bulk InGaAsP

    Science.gov (United States)

    Connelly, Michael J.

    2015-02-01

    Band-gap shrinkage is an important effect in semiconductor lasers and optical amplifiers. In the former it leads to an increase in the lasing wavelength and in the latter an increase in the gain peak wavelength as the bias current is increased. The most common model used for carrier-density dependent band-gap shrinkage is a cube root dependency on carrier density, which is strictly only true for high carrier densities and low temperatures. This simple model, involves a material constant which is treated as a fitting parameter. Strained InGaAsP material is commonly used to fabricate polarization insensitive semiconductor optical amplifiers (SOAs). Most mathematical models for SOAs use the cube root bandgap shrinkage model. However, because SOAs are often operated over a wide range of drive currents and input optical powers leading to large variations in carrier density along the amplifier length, for improved model accuracy it is preferable to use band-gap shrinkage calculated from knowledge of the material bandstructure. In this letter the carrier density dependent band-gap shrinkage for strained InGaAsP is calculated by using detailed non-parabolic conduction and valence band models. The shrinkage dependency on temperature and both tensile and compressive strain is investigated and compared to the cube root model, for which it shows significant deviation. A simple power model, showing an almost square-root dependency, is derived for carrier densities in the range usually encountered in InGaAsP laser diodes and SOAs.

  17. Band-gap shrinkage calculations and analytic model for strained bulk InGaAsP

    International Nuclear Information System (INIS)

    Band-gap shrinkage is an important effect in semiconductor lasers and optical amplifiers. In the former it leads to an increase in the lasing wavelength and in the latter an increase in the gain peak wavelength as the bias current is increased. The most common model used for carrier-density dependent band-gap shrinkage is a cube root dependency on carrier density, which is strictly only true for high carrier densities and low temperatures. This simple model, involves a material constant which is treated as a fitting parameter. Strained InGaAsP material is commonly used to fabricate polarization insensitive semiconductor optical amplifiers (SOAs). Most mathematical models for SOAs use the cube root bandgap shrinkage model. However, because SOAs are often operated over a wide range of drive currents and input optical powers leading to large variations in carrier density along the amplifier length, for improved model accuracy it is preferable to use band-gap shrinkage calculated from knowledge of the material bandstructure. In this letter the carrier density dependent band-gap shrinkage for strained InGaAsP is calculated by using detailed non-parabolic conduction and valence band models. The shrinkage dependency on temperature and both tensile and compressive strain is investigated and compared to the cube root model, for which it shows significant deviation. A simple power model, showing an almost square-root dependency, is derived for carrier densities in the range usually encountered in InGaAsP laser diodes and SOAs. (paper)

  18. Fiber fuse light-induced continuous breakdown of silica glass optical fiber

    CERN Document Server

    Todoroki, Shin-ichi

    2014-01-01

    This book describes the fiber fuse phenomenon that causes a serious problem for the present optical communication systems. High-power light often brings about catastrophic damage to optical devices. Silica glass optical fibers with ultralow transmission loss are not the exception. A fiber fuse appears in a heated region of the fiber cable delivering a few watts of light and runs toward the light source destroying its core region. Understanding this phenomenon is a necessary first step in the development of future optical communication systems. This book provides supplementary videos and photog

  19. Carbon based prosthetic devices

    Energy Technology Data Exchange (ETDEWEB)

    Devlin, D.J.; Carroll, D.W.; Barbero, R.S.; Archuleta, T. [Los Alamos National Lab., NM (US); Klawitter, J.J.; Ogilvie, W.; Strzepa, P. [Ascension Orthopedics (US); Cook, S.D. [Tulane Univ., New Orleans, LA (US). School of Medicine

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project objective was to evaluate the use of carbon/carbon-fiber-reinforced composites for use in endoprosthetic devices. The application of these materials for the metacarpophalangeal (MP) joints of the hand was investigated. Issues concerning mechanical properties, bone fixation, biocompatibility, and wear are discussed. A system consisting of fiber reinforced materials with a pyrolytic carbon matrix and diamond-like, carbon-coated wear surfaces was developed. Processes were developed for the chemical vapor infiltration (CVI) of pyrolytic carbon into porous fiber preforms with the ability to tailor the outer porosity of the device to provide a surface for bone in-growth. A method for coating diamond-like carbon (DLC) on the articulating surface by plasma-assisted chemical vapor deposition (CVD) was developed. Preliminary results on mechanical properties of the composite system are discussed and initial biocompatibility studies were performed.

  20. Nonlinear multimodal interference and saturable absorption using a short graded-index multimode optical fiber

    OpenAIRE

    Nazemosadat, Elham; Mafi, Arash

    2013-01-01

    A detailed investigation of the nonlinear multimodal interference in a short graded-index multimode optical fiber is presented. The analysis is performed for a specific device geometry, where the light is coupled in and out of the multimode fiber via single-mode fibers. The same device geometry was recently used to obtain ultra-low-loss coupling between two single-mode optical fibers with very different mode-field diameters. Our results indicate the potential application of this simple geomet...