WorldWideScience

Sample records for broadband diffuse optical

  1. Solution processable broadband transparent mixed metal oxide nanofilm optical coatings via substrate diffusion doping.

    Science.gov (United States)

    Glynn, Colm; Aureau, Damien; Collins, Gillian; O'Hanlon, Sally; Etcheberry, Arnaud; O'Dwyer, Colm

    2015-12-21

    Devices composed of transparent materials, particularly those utilizing metal oxides, are of significant interest due to increased demand from industry for higher fidelity transparent thin film transistors, photovoltaics and a myriad of other optoelectronic devices and optics that require more cost-effective and simplified processing techniques for functional oxides and coatings. Here, we report a facile solution processed technique for the formation of a transparent thin film through an inter-diffusion process involving substrate dopant species at a range of low annealing temperatures compatible with processing conditions required by many state-of-the-art devices. The inter-diffusion process facilitates the movement of Si, Na and O species from the substrate into the as-deposited vanadium oxide thin film forming a composite fully transparent V0.0352O0.547Si0.4078Na0.01. Thin film X-ray diffraction and Raman scattering spectroscopy show the crystalline component of the structure to be α-NaVO3 within a glassy matrix. This optical coating exhibits high broadband transparency, exceeding 90-97% absolute transmission across the UV-to-NIR spectral range, while having low roughness and free of surface defects and pinholes. The production of transparent films for advanced optoelectronic devices, optical coatings, and low- or high-k oxides is important for planar or complex shaped optics or surfaces. It provides opportunities for doping metal oxides to ternary, quaternary or other mixed metal oxides on glass, encapsulants or other substrates that facilitate diffusional movement of dopant species. PMID:26575987

  2. Broadband optical isolator in fibre optics

    OpenAIRE

    Berent, Michal; Rangelov, Andon A.; Vitanov, Nikolay V.

    2013-01-01

    We propose a broadband optical diode, which is composed of one achromatic reciprocal quarter-wave plate and one non-reciprocal quarter-wave plate, both placed between two crossed polarizers. The presented design of achromatic wave plates relies on an adiabatic evolution of the Stokes vector, thus, the scheme is robust and efficient. The possible simple implementation using fiber optics is suggested.

  3. Incoherent broadband optical pulse generation using an optical gate

    Institute of Scientific and Technical Information of China (English)

    Biao Chen; Qiong Jiang

    2008-01-01

    In two-dimensional (2D) time-spreading/wavelength-hopping optical code division multiple access (OCDMA) systems, employing less coherent broadband optical pulse sources allows lower electrical operating rate and better system performance. An optical gate based scheme for generating weakly coherent(approximately incoherent) broadband optical pulses was proposed and experimentally demonstrated. Inthis scheme, the terahertz optical asymmetric demultiplexer, together with a coherent narrowband controlpulse source, turns an incoherent broadband continuous-wave (CW) light source into the required pulse source.

  4. Broadband phase-preserved optical elevator

    OpenAIRE

    Luo, Yuan; Han, Tiancheng; Zhang, Baile; Qiu, Cheng-Wei; Barbastathis, George

    2011-01-01

    Phase-preserved optical elevator is an optical device to lift up an entire plane virtually without distortion in light path or phase. Using transformation optics, we have predicted and observed the realization of such a broadband phase-preserved optical elevator, made of a natural homogeneous birefringent crystal without resorting to absorptive and narrowband metamaterials involving time-consuming nano-fabrication. In our demonstration, the optical elevator is designed to lift a sheet upwards...

  5. BROADBAND TRAVELLING WAVE SEMICONDUCTOR OPTICAL AMPLIFIER

    DEFF Research Database (Denmark)

    2010-01-01

    Broadband travelling wave semiconductor optical amplifier (100, 200, 300, 400, 800) for amplification of light, wherein the amplifier (100, 200, 300, 400, 800) comprises a waveguide region (101, 201, 301, 401, 801) for providing confinement of the light in transverse directions and adapted...

  6. Broadband phase-preserved optical elevator

    CERN Document Server

    Luo, Yuan; Zhang, Baile; Qiu, Cheng-Wei; Barbastathis, George

    2011-01-01

    Phase-preserved optical elevator is an optical device to lift up an entire plane virtually without distortion in light path or phase. Using transformation optics, we have predicted and observed the realization of such a broadband phase-preserved optical elevator, made of a natural homogeneous birefringent crystal without resorting to absorptive and narrowband metamaterials involving time-consuming nano-fabrication. In our demonstration, the optical elevator is designed to lift a sheet upwards, and the phase is verified to be preserved always. The camouflage capability is also demonstrated in the presence of adjacent objects of the same scale at will. The elevating device functions in different surrounding media over the wavelength range of 400-700 nm. Our work opens up prospects for studies of light trapping, solar energy, illusion optics, communication, and imaging.

  7. A graphene-based broadband optical modulator

    Science.gov (United States)

    Liu, Ming; Yin, Xiaobo; Ulin-Avila, Erick; Geng, Baisong; Zentgraf, Thomas; Ju, Long; Wang, Feng; Zhang, Xiang

    2011-06-01

    Integrated optical modulators with high modulation speed, small footprint and large optical bandwidth are poised to be the enabling devices for on-chip optical interconnects. Semiconductor modulators have therefore been heavily researched over the past few years. However, the device footprint of silicon-based modulators is of the order of millimetres, owing to its weak electro-optical properties. Germanium and compound semiconductors, on the other hand, face the major challenge of integration with existing silicon electronics and photonics platforms. Integrating silicon modulators with high-quality-factor optical resonators increases the modulation strength, but these devices suffer from intrinsic narrow bandwidth and require sophisticated optical design; they also have stringent fabrication requirements and limited temperature tolerances. Finding a complementary metal-oxide-semiconductor (CMOS)-compatible material with adequate modulation speed and strength has therefore become a task of not only scientific interest, but also industrial importance. Here we experimentally demonstrate a broadband, high-speed, waveguide-integrated electroabsorption modulator based on monolayer graphene. By electrically tuning the Fermi level of the graphene sheet, we demonstrate modulation of the guided light at frequencies over 1GHz, together with a broad operation spectrum that ranges from 1.35 to 1.6µm under ambient conditions. The high modulation efficiency of graphene results in an active device area of merely 25µm2, which is among the smallest to date. This graphene-based optical modulation mechanism, with combined advantages of compact footprint, low operation voltage and ultrafast modulation speed across a broad range of wavelengths, can enable novel architectures for on-chip optical communications.

  8. Twisted optical metamaterials for planarized ultrathin broadband circular polarizers.

    Science.gov (United States)

    Zhao, Y; Belkin, M A; Alù, A

    2012-05-29

    Optical metamaterials are usually based on planarized, complex-shaped, resonant nano-inclusions. Three-dimensional geometries may provide a wider set of functionalities, including broadband chirality to manipulate circular polarization at the nanoscale, but their fabrication becomes challenging as their dimensions get smaller. Here we introduce a new paradigm for the realization of optical metamaterials, showing that three-dimensional effects may be obtained without complicated inclusions, but instead by tailoring the relative orientation within the lattice. We apply this concept to realize planarized, broadband bianisotropic metamaterials as stacked nanorod arrays with a tailored rotational twist. Because of the coupling among closely spaced twisted plasmonic metasurfaces, metamaterials realized with conventional lithography may effectively operate as three-dimensional helical structures with broadband bianisotropic optical response. The proposed concept is also shown to relax alignment requirements common in three-dimensional metamaterial designs. The realized sample constitutes an ultrathin, broadband circular polarizer that may be directly integrated within nanophotonic systems.

  9. Broadband Optical Access Technologies to Converge towards a Broadband Society in Europe

    Science.gov (United States)

    Coudreuse, Jean-Pierre; Pautonnier, Sophie; Lavillonnière, Eric; Didierjean, Sylvain; Hilt, Benoît; Kida, Toshimichi; Oshima, Kazuyoshi

    This paper provides insights on the status of broadband optical access market and technologies in Europe and on the expected trends for the next generation optical access networks. The final target for most operators, cities or any other player is of course FTTH (Fibre To The Home) deployment although we can expect intermediate steps with copper or wireless technologies. Among the two candidate architectures for FTTH, PON (Passive Optical Network) is by far the most attractive and cost effective solution. We also demonstrate that Ethernet based optical access network is very adequate to all-IP networks without any incidence on the level of quality of service. Finally, we provide feedback from a FTTH pilot network in Colmar (France) based on Gigabit Ethernet PON technology. The interest of this pilot lies on the level of functionality required for broadband optical access networks but also on the development of new home network configurations.

  10. Fiber Optic Broadband Ultrasonic Probe for Virtual Biopsy: Technological Solutions

    OpenAIRE

    Biagi, E.; Cerbai, S.; Masotti, L.; L. Belsito; A. RONCAGLIA; Masetti, G.; N. Speciale

    2010-01-01

    An ultrasonic probe was developed by using, in conjunction, optoacoustic and acousto-optic devices based on fiber optic technology. The intrinsic high frequency and wide bandwidth associated both to the opto-acoustic source and to the acousto-optic receiving element could open a way towards a “virtual biopsy” of biological tissue. A Micro-Opto-Mechanical-System (MOMS) approach is proposed to realize the broadband ultrasonic probe on micromachined silicon frames suited to be mounted on the tip...

  11. Acousto-Optics Tunable Filter Based on a Hollow Optical Fiber for Broadband Polarization Switch Application

    Institute of Scientific and Technical Information of China (English)

    Jaewon; Lee; Jaewang; Yu; Sangsoo; Choi; Kyunghwan; Oh; Dong; Il; Yum; Byoung; Yoon; Kim

    2003-01-01

    A novel acousto-optic tunable filter (AOTF) using a hollow optical fiber (HOF) is proposed. Its broadband rejection over 100nm was observed and high polarization dependence as a polarization switch is discussed.

  12. Coherent broadband light source for parallel optical coherence tomography

    NARCIS (Netherlands)

    Rivier, S.; Laversenne, L.; Bourquin, S.; Salathé, R.P.; Pollnau, M.; Grivas, C.; Shepherd, D.P.; Eason, R.W.; Flury, M.; Philipoussis, I.; Herzig, H.P.

    2004-01-01

    A Ti:sapphire planar waveguide is rib structured by Ar ion milling to provide parallel channel waveguides. By coupling high-power pump light through a microlens array into the waveguides, a novel broadband luminescent parallel emitter is demonstrated as a light source for parallel optical coherence

  13. Broadband optical characterization of material properties

    DEFF Research Database (Denmark)

    Nielsen, Otto Højager Attermann

    Optical inspection of material properties is of great interest to industry because it can perform objective and non-invasive characterisation of large sample quantities. This may be used in various ways to lower production costs and improve product quality. In this thesis the objective has been...

  14. Secure communication in fiber optic systems via transmission of broad-band optical noise.

    Science.gov (United States)

    Buskila, O; Eyal, A; Shtaif, M

    2008-03-01

    We propose a new scheme for data encryption in the physical layer. Our scheme is based on the distribution of a broadband optical noise-like signal between Alice and Bob. The broadband signal is used for the establishment of a secret key that can be used for the secure transmission of information by using the one-time-pad method. We characterize the proposed scheme and study its applicability to the existing fiber-optics communications infrastructure.

  15. Broadband Wireline Provider Service: Optical Carrier - Fiber to the End User; BBRI_fiber12

    Data.gov (United States)

    University of Rhode Island Geospatial Extension Program — This dataset represents the availability of wireline broadband Internet access in Rhode Island via "Optical Carrier - Fiber to the End User" technology. Broadband...

  16. The supply side of innovation diffusion - A UK SME broadband adoption perspective

    OpenAIRE

    O Oni; Papazafeiropoulou, A

    2011-01-01

    Recent research suggests that the majority of the Small and medium sized enterprises (SMEs) e-business research focusses primarily on studying innovation diffusion within the SMEs themselves with limited research into the supply-side of innovation diffusion This study examines the supply side of innovation diffusion to SMEs in south east United Kingdom (UK). It aims to examine and provide an indepth view of the broadband diffusion process to SMEs in UK by exploring the views and activities of...

  17. Potential roles of optical interconnections within broadband switching modules

    Science.gov (United States)

    Lalk, Gail R.; Habiby, Sarry F.; Hartman, Davis H.; Krchnavek, Robert R.; Wilson, Donald K.; Young, Kenneth C., Jr.

    1991-04-01

    An investigation of potential physical design bottlenecks in future broadband telecommunication switches has led to the identification of several areas where optical interconnections may play a role in the practical realization of required system performance. In the model used the speed and interconnection densities as well as requirements for ease-of-access and efficient power utilization challenge conventional partitioning and packaging strategies. Potential areas where optical interconnections may relieve some of the physical design bottlenecks include fiber management at the customer interface to the switch routing and distribution of high-density interconnections within the fabric of the switch and backplane interconnections to increase system throughput.

  18. Spectral diffraction efficiency characterization of broadband diffractive optical elements.

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Junoh; Cruz-Cabrera, Alvaro Augusto; Tanbakuchi, Anthony

    2013-03-01

    Diffractive optical elements, with their thin profile and unique dispersion properties, have been studied and utilized in a number of optical systems, often yielding smaller and lighter systems. Despite the interest in and study of diffractive elements, the application has been limited to narrow spectral bands. This is due to the etch depths, which are optimized for optical path differences of only a single wavelength, consequently leading to rapid decline in efficiency as the working wavelength shifts away from the design wavelength. Various broadband diffractive design methodologies have recently been developed that improve spectral diffraction efficiency and expand the working bandwidth of diffractive elements. We have developed diffraction efficiency models and utilized the models to design, fabricate, and test two such extended bandwidth diffractive designs.

  19. Broadband continuum generation in an irregularly multicore microstructured optical fiber

    Institute of Scientific and Technical Information of China (English)

    Peiguang Yan; Qinlin Guo; Guiyao Zhou; Lantian Hou; Yaqing Jia; Hongxin Su; Yigang Li; Lei Ding; Wei Zhang; Kecheng Lü; Tiequn Zhang; Xiaonong Zhu

    2005-01-01

    @@ A broadband continuum generation is reported in a novel multicore microstructured optical fiber (MOF) where irregular air holes are randomly distributed in cladding. By launching ultrashort light pulses from a Ti:sapphire laser into a 190-mm-long fiber of this type, we have observed a group of continua generated from different cores, each with distinct color. 20-dB bandwidth of the broadest continuum is 1260 nm with an average power of 143 mW. The result confirms that the multicore MOF can be fabricated, with different dispersion profiles tailored for specific supercontinuum (SC) generation towards practical applications.

  20. A socio-technical approach to broadband diffusion by SMEs

    OpenAIRE

    O Oni; Papazafeiropoulou, A

    2008-01-01

    Technological deterministic theories such as Diffusion of Innovations (DOIs) theory provide a useful view of the diffusion process of new technologies. However, the view provided is limited, as it mainly looks at the supply side of the diffusion process hence, the need for the ability to examine various sides that influence the diffusion of new technologies. The Social Construction of Technology (SCOT) provides an avenue to examine such views. In this paper, we examine the adoption of broadba...

  1. Broadband diffuse terahertz wave scattering by flexible metasurface with randomized phase distribution

    OpenAIRE

    Yin Zhang; Lanju Liang; Jing Yang; Yijun Feng; Bo Zhu; Junming Zhao; Tian Jiang; Biaobing Jin; Weiwei Liu

    2016-01-01

    Suppressing specular electromagnetic wave reflection or backward radar cross section is important and of broad interests in practical electromagnetic engineering. Here, we present a scheme to achieve broadband backward scattering reduction through diffuse terahertz wave reflection by a flexible metasurface. The diffuse scattering of terahertz wave is caused by the randomized reflection phase distribution on the metasurface, which consists of meta-particles of differently sized metallic patche...

  2. Broadband hitless silicon electro-optic switch for on-chip optical networks.

    Science.gov (United States)

    Lira, Hugo L R; Manipatruni, Sasikanth; Lipson, Michal

    2009-12-01

    We report on the demonstration of a broadband (60 GHz), spectrally hitless, compact (20 microm x 40 microm), fast (7 ns) electro-optical switch. The device is composed of two coupled resonant cavities, each with an independently addressable PIN diode. This topology enables operation of the switch without perturbing adjacent channels in a wavelength division multiplexing (WDM) system. PMID:20052150

  3. Synchronously pumped femtosecond optical parametric oscillator with broadband chirped mirrors

    Science.gov (United States)

    Stankevičiūte, Karolina; Melnikas, Simas; Kičas, Simonas; Trišauskas, Lukas; Vengelis, Julius; Grigonis, Rimantas; Vengris, Mikas; Sirutkaitis, Valdas

    2015-05-01

    We present results obtained during investigation of synchronously pumped optical parametric oscillator (SPOPO) with broadband complementary chirped mirror pairs (CMP). The SPOPO based on β-BBO nonlinear crystal is pumped by second harmonic of femtosecond Yb:KGW laser and provides signal pulses tunable over spectral range from 625 to 980 nm. More than 500 mW are generated in the signal beam, giving up to 27 % pump power to signal power conversion efficiency. The plane SPOPO cavity mirror pairs were specially designed to provide 99 % reflection in broad spectral range corresponding to signal wavelength tuning (630-1030 nm) and to suppress group delay dispersion (GDD) oscillations down to +/-10 fs2. Dispersion properties of designed mirrors were tested with white light interferometer (WLI) and attributed to the SPOPO tuning behaviour.

  4. Broadband passive optical network media access control protocols

    Science.gov (United States)

    Quayle, Alan

    1996-11-01

    Most telecommunication operators are currently deciding on how to respond to customers' needs stimulated by the synergy between compression coding of multimedia and the emergence of broadband digital networks. This paper describes a range of broadband access architectures under consideration in the full services access network initiative. All architectures have a common requirement for a broadband ATM PON. A common broadband PON applicable to many operators increases the world-wide market for the product. With greater production volumes manufacturers' costs reduce because of the experience curve effect making broadband access systems economic.

  5. Optical diffusers based on silicone emulsions

    Science.gov (United States)

    Wang, Jui-Hao; Lien, Shui-Yang; Ho, Jeng-Rong; Shih, Teng-Kai; Chen, Chia-Fu; Chen, Chien-Chung; Whang, Wha-Tzong

    2009-12-01

    The present study provides an experimental approach for fabricating optical diffuser films based on silicone emulsions. The silicone emulsion consisting of silicone polymer (Sylgard 184) and NaCl aq. solution was used as the optical material of diffusers, wherein NaCl aq. solution was severed as surfactant to stabilize the emulsions. After stirring mechanically, microscaled water drop with various sizes distributed randomly in silicone polymer, wherein water drop was used as scattering diffusion particles. To modulate the volume of NaCl aq. solution, the diffusing performance of diffusers could be change by different amount drop particles. Thereafter, an optical examination was carried out to characterize optical properties, transmittance, and light diffusivity of volumetric diffuser films.

  6. Optical depth retrievals from Delta-T SPN1 measurements of broadband solar irradiance at ground

    Science.gov (United States)

    Estelles, Victor; Serrano, David; Segura, Sara; Wood, John; Webb, Nick

    2016-04-01

    The SPN1 radiometer, manufactured by Delta-T Devices Ltd., is an instrument designed for the measurement of global solar irradiance and its components (diffuse, direct) at ground level. In the present study, the direct irradiance component has been used to retrieve an effective total optical depth, by applying the Beer-Lambert law to the broadband measurements. The results have been compared with spectral total optical depths derived from two Cimel CE318 and Prede POM01 sun-sky radiometers, located at the Burjassot site in Valencia (Spain), during years 2013 - 2015. The SPN1 is an inexpensive and versatile instrument for the measurement of the three components of the solar radiation without any mobile part and without any need to azimuthally align the instrument to track the sun (http://www.delta-t.co.uk). The three components of the solar radiation are estimated from a combination of measurements performed by 7 different miniature thermopiles. In turn, the Beer-Lambert law has been applied to the broadband direct solar component to obtain an effective total optical depth, representative of the total extinction in the atmosphere. For the assessment of the total optical depth values retrieved with the SPN1, two different sun-sky radiometers (Cimel CE318 and Prede POM01L) have been employed. Both instruments belong to the international networks AERONET and SKYNET. The modified SUNRAD package has been applied in both Cimel and Prede instruments. Cloud affected data has been removed by applying the Smirnov cloud-screening procedure in the SUNRAD algorithm. The broadband SPN1 total optical depth has been analysed by comparison with the spectral total optical depth from the sun-sky radiometer measurements at wavelengths 440, 500, 675, 870 and 1020 nm. The slopes and intercepts have been estimated to be 0.47 - 0.98 and 0.055 - 0.16 with increasing wavelength. The average correlation coefficients and RMSD were 0.80 - 0.83 and 0.034 - 0.036 for all the channels. The

  7. Broadband diffusion metasurface based on a single anisotropic element and optimized by the Simulated Annealing algorithm

    Science.gov (United States)

    Zhao, Yi; Cao, Xiangyu; Gao, Jun; Sun, Yu; Yang, Huanhuan; Liu, Xiao; Zhou, Yulong; Han, Tong; Chen, Wei

    2016-04-01

    We propose a new strategy to design broadband and wide angle diffusion metasurfaces. An anisotropic structure which has opposite phases under x- and y-polarized incidence is employed as the “0” and “1” elements base on the concept of coding metamaterial. To obtain a uniform backward scattering under normal incidence, Simulated Annealing algorithm is utilized in this paper to calculate the optimal layout. The proposed method provides an efficient way to design diffusion metasurface with a simple structure, which has been proved by both simulations and measurements.

  8. Broadband diffusion metasurface based on a single anisotropic element and optimized by the Simulated Annealing algorithm.

    Science.gov (United States)

    Zhao, Yi; Cao, Xiangyu; Gao, Jun; Sun, Yu; Yang, Huanhuan; Liu, Xiao; Zhou, Yulong; Han, Tong; Chen, Wei

    2016-01-01

    We propose a new strategy to design broadband and wide angle diffusion metasurfaces. An anisotropic structure which has opposite phases under x- and y-polarized incidence is employed as the "0" and "1" elements base on the concept of coding metamaterial. To obtain a uniform backward scattering under normal incidence, Simulated Annealing algorithm is utilized in this paper to calculate the optimal layout. The proposed method provides an efficient way to design diffusion metasurface with a simple structure, which has been proved by both simulations and measurements. PMID:27034110

  9. Structure Design of Polymer Electro-Optic Modulator with Ultra- Broadband

    Institute of Scientific and Technical Information of China (English)

    Haibo Peng; Boyu Wu; Qiong Song; Fei Lu; Shuyun Luo

    2003-01-01

    Using finite element method, lots of calculating focusing on polymer electro-optic modulators with ultra-broadband were done, a few structures were analyzed. Coplanar waveguide electrode system was advanced, a few real examples was given.

  10. Generation of linearized optical single sideband signal for broadband radio over fiber systems

    Institute of Scientific and Technical Information of China (English)

    Tao Wang; Qingjiang Chang; Yikai Su

    2009-01-01

    We propose a new scheme to generate broadband linearized optical single-sideband (OSSB) signal for radio over fiber systems. By using an unbalanced dual parallel Mach-zehnder modulator (DPMZM) followed by optical filtering, a linearized OSSB signal is obtained. With coherent detection, radio frequency (RF) signal can be recovered with simultaneously suppressed second-order distortion and third-order intermodulation. This scheme can be used to realize broadband systems with wide dynamic range.

  11. Fiber optics speckle interferometer for diffusivity measurements

    OpenAIRE

    Paoletti, D.; Schirripa Spagnolo, G.

    1993-01-01

    A digital speckle pattern interferometer with optical fibers is proposed for the real time measurement of the diffusion coefficient of liquid binary mixtures. Some examples of application of the technique are reported.

  12. Broadband angle- and permittivity-insensitive nondispersive optical activity based on chiral metamaterials

    CERN Document Server

    Song, Kun; Su, Zhaoxian; Ding, Changlin; Liu, Yahong; Luo, Chunrong; Zhao, Xiaopeng; Bhattarai, Khagendra; Zhou, Jiangfeng

    2016-01-01

    Because of the strong inherent resonances, the giant optical activity obtained via chiral metamaterials generally suffers from high dispersion, which has been a big stumbling block to broadband applications. In this paper, we propose a type of chiral metamaterial consisting of interconnected metal helix structures with four-fold symmetry, which exhibits nonresonant Drude-like response and can therefore avoid the highly dispersive optical activity resulting from resonances. It shows that the well-designed chiral metamaterial can achieve nondispersive and pure optical activity with high transmittance in a broadband frequency range. And the optical activity of multi-layer chiral metamaterials is proportional to the layer numbers of single-layer chiral metamaterial. Most remarkably, the broadband behaviors of nondispersive optical activity and high transmission are insensitive to the incident angles of electromagnetic waves and permittivity of dielectric substrate, thereby enabling more flexibility in polarizatio...

  13. Broadband local service offerings using free-space optical links: a network business perspective

    Science.gov (United States)

    Britz, David M.; Dodley, J. P.; Barnickel, D. J.

    2001-02-01

    12 This paper describes a promising optical wireless broadband technology that will provide low cost broadband services to the local access `last mile' market. This paper examines the application, advantages and limitations of utilizing Free Space Optical Communications (FSOC) systems for broadband access markets. The service markets that would fully utilize FSOC technologies include metropolitan areas, BLECs (multi- tenant dwellings/business apartments), campuses, industrial parks and `pole-to-hole' neighborhood deployments. This paper will identify weather dependent link availability as being the primary consideration in defining and selecting suitable locations for FSOC-based systems. Link availability in turn determines link range, type of service, and the need for transmission diversity. This paper will describe the implications of telecom `five nines' last-mile access availability and its effect on the transparent integration of FSOC technologies into the existing fiber optic networks. This paper will also describe propagation losses and link budget requirements for broadband FSOC-based local service. During adverse weather conditions, stand-alone, FSOC-based optical wireless links typically offer path lengths of less than 200 meters while still meeting the `five nines' availability criteria. This paper will also consider `availability limited' services. These services may prove to be attractive to customers who are willing to accept broadband service on an `as available basis'. The use of availability-enhancing transmission diversity and the use of intelligent `roof-top' routing and optical wireless cross connects between buildings will also be discussed.

  14. Multichannel fiber optic broadband video communication system for monitoring CT/MR examinations

    Science.gov (United States)

    Huang, H. K.; Kangarloo, Hooshang; Tecotzky, Raymond H.; Cheng, Xin; Vanderweit, Don

    1991-05-01

    The Department of Radiological Sciences, UCLA operates five MR and four CT scanners located in three different buildings and two mobile sites. We have designed and implemented a multi-channel fiber optic broadband video communication system connecting these scanners together. This system consists of baseband fiber optic transmitters and receivers, a multiplexing headend, and broadband fiber optic transmitters and receivers. It can serve up to 5 km. The video signal from each scanner is sent through a baseband fiber optic link to the headend, where it is frequency modulated and distributed over broadband fiber optic links. A receiver, consisting of a demodulator, a TV monitor, and a channel selector, is placed at fourteen strategic locations including the fiber optic hub rooms, chest, neuroradiology, abdomen, bone, gastrointestinal, genitourinary, and pediatric reading rooms as well as scheduling rooms. A radiologist can use any of these fourteen receivers to view a patient''s CT/MR image in real time by selecting the proper channel assigned to the scanner, and use the telephone to communicate with the technologist to monitor the examination. This fiber optic broadband video communication system has been integrated into daily clinical use.

  15. Ultra-broadband and ultra-fast optical signal processing

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo

    2015-01-01

    We have recently seen that nanowires can provide unparalleled optical signal processing (OSP) bandwidth and provide ultra-fast operation as well. Utilising the ultra-broad OSP bandwidth for e.g. optical time lenses allows for energy-efficient optical switching. © 2015 OSA.......We have recently seen that nanowires can provide unparalleled optical signal processing (OSP) bandwidth and provide ultra-fast operation as well. Utilising the ultra-broad OSP bandwidth for e.g. optical time lenses allows for energy-efficient optical switching. © 2015 OSA....

  16. Service Class Resource Management For Green Wireless-Optical Broadband Access NetworksWOBAN

    Directory of Open Access Journals (Sweden)

    SRUTHY.S

    2015-08-01

    Full Text Available Abstract-Broadband access networks have become an essential part of worldwide communication systems because of the exponential growth of broadband services such as video on demand high definition TV internet protocol TV and video conferencing. Exponential growth in the volume of wireless data boosted by the growing popularity of mobile devices such as smartphone and tablets has forced the telecommunication industries to rethink the way networks are currently designed and to focus on the development of high-capacity mobile broadband networks. In response to this challenge researchers have been working toward the development of an integrated wireless optical broadband access network. Two major candidate technologies which are currently known for their high capacity as well as quality of service QoS for multimedia traffic are passive optical networks PON and fourth generation 4G wireless networks. PON is a wired access technology well known for its cost efficiency and high capacity whereas 4G is a wireless broadband access technology which has achieved broad market acceptance because of its ease of deployment ability to offer mobility and its cost efficiency. Integration of PON and 4G technologies in the form of wireless-optical broadband access networks offers advantages such as extension of networks in rural areas support for mobile broadband services and quick deployment of broadband networks. These two technologies however have different design architectures for handling broadband services that require quality of service. For example 4G networks use traffic classification for supporting different QoS demands whereas the PON architecture has no such mechanism to differentiate between types of traffic. These two technologies also differ in their power saving mechanisms. Propose a service class mapping for the integrated PON-4G network which is based on the MG1 queuing model and class-based power saving mechanism which significantly improves the

  17. Broadband diffuse terahertz wave scattering by flexible metasurface with randomized phase distribution

    Science.gov (United States)

    Zhang, Yin; Liang, Lanju; Yang, Jing; Feng, Yijun; Zhu, Bo; Zhao, Junming; Jiang, Tian; Jin, Biaobing; Liu, Weiwei

    2016-05-01

    Suppressing specular electromagnetic wave reflection or backward radar cross section is important and of broad interests in practical electromagnetic engineering. Here, we present a scheme to achieve broadband backward scattering reduction through diffuse terahertz wave reflection by a flexible metasurface. The diffuse scattering of terahertz wave is caused by the randomized reflection phase distribution on the metasurface, which consists of meta-particles of differently sized metallic patches arranged on top of a grounded polyimide substrate simply through a certain computer generated pseudorandom sequence. Both numerical simulations and experimental results demonstrate the ultralow specular reflection over a broad frequency band and wide angle of incidence due to the re-distribution of the incident energy into various directions. The diffuse scattering property is also polarization insensitive and can be well preserved when the flexible metasurface is conformably wrapped on a curved reflective object. The proposed design opens up a new route for specular reflection suppression, and may be applicable in stealth and other technology in the terahertz spectrum.

  18. Optically controlled reconfigurable antenna for 5G future broadband cellular communication networks

    DEFF Research Database (Denmark)

    da Costa, Igor; Cerqueira Sodre Jr., Arismar; Gustavo da Silva, Luis;

    to higher frequency solutions, such as E-and W-band solutions. We present two key elements for the project: a broadband horn antenna for millimetre-wave and an optically controlled reconfigurable antenna, which can adapt its frequency response and radiation pattern by using photonics technology...

  19. Optical nanostructures in 2D for wide-diameter and broadband beam collimation.

    Science.gov (United States)

    Clark, James; Anguita, José V; Chen, Ying; Silva, S Ravi P

    2016-01-01

    Eliminating curved refracting lensing components used in conventional projection, imaging and sensing optical assemblies, is critical to enable compactness and miniaturisation of optical devices. A suitable means is replacing refracting lenses with two-dimensional optical media in flat-slab form, to achieve an equivalent optical result. One approach, which has been the focus of intense research, uses a Veselago lens which features a negative-index metamaterial. However, practical implementations rely on resonance techniques, thus broadband operation at optical frequencies imposes significant technical challenges that have been difficult to overcome. Here, we demonstrate a highly-collimated, broadband, wide-diameter beam from a compact source in flat-slab form, based on light collimation using nanomaterials ordered in patterns and embedded into flexible polymers. These provide a highly anisotropic absorption coefficient due to patterns created by vertical carbon nanotube structures grown on glass, and the anisotropic electrical conductivity of the nanotubes. We show this nanostructure strongly absorbs unwanted off-axis light rays, whilst transmitting the desired on-axis rays, to achieve the required optical effect over broadband, from visible to short-infrared, thus circumventing some technical limitations of negative-index metamaterials. We further show a low substrate-temperature system for nanotube growth, allowing direct implementation into heat-sensitive large-area devices. PMID:26732851

  20. Radio over fiber transceiver employing phase modulation of an optical broadband source.

    Science.gov (United States)

    Grassi, Fulvio; Mora, José; Ortega, Beatriz; Capmany, José

    2010-10-11

    This paper proposes a low-cost RoF transceiver for multichannel SCM/WDM signal distribution suitable for future broadband access networks. The transceiver is based on the phase modulation of an optical broadband source centered at third transmission window. Prior to phase modulation the optical broadband source output signal is launched into a Mach-Zehnder interferometer structure, as key device enabling radio signals propagation over the optical link. Furthermore, an optical CWDM is employed to create a multichannel scenario by performing the spectral slicing of the modulated optical signal into a number of channels each one conveying the information from the central office to different base stations. The operation range is up to 20 GHz with a modulation bandwidth around of 500 MHz. Experimental results of the transmission of SCM QPSK and 64-QAM data through 20 Km of SMF exhibit good EVM results in the operative range determined by the phase-to-intensity conversion process. The proposed approach shows a great suitability for WDM networks based on RoF signal transport and also represents a cost-effective solution for passive optical networks. PMID:20941075

  1. Optical nanostructures in 2D for wide-diameter and broadband beam collimation

    Science.gov (United States)

    Clark, James; Anguita, José V.; Chen, Ying; Silva, S. Ravi P.

    2016-01-01

    Eliminating curved refracting lensing components used in conventional projection, imaging and sensing optical assemblies, is critical to enable compactness and miniaturisation of optical devices. A suitable means is replacing refracting lenses with two-dimensional optical media in flat-slab form, to achieve an equivalent optical result. One approach, which has been the focus of intense research, uses a Veselago lens which features a negative-index metamaterial. However, practical implementations rely on resonance techniques, thus broadband operation at optical frequencies imposes significant technical challenges that have been difficult to overcome. Here, we demonstrate a highly-collimated, broadband, wide-diameter beam from a compact source in flat-slab form, based on light collimation using nanomaterials ordered in patterns and embedded into flexible polymers. These provide a highly anisotropic absorption coefficient due to patterns created by vertical carbon nanotube structures grown on glass, and the anisotropic electrical conductivity of the nanotubes. We show this nanostructure strongly absorbs unwanted off-axis light rays, whilst transmitting the desired on-axis rays, to achieve the required optical effect over broadband, from visible to short-infrared, thus circumventing some technical limitations of negative-index metamaterials. We further show a low substrate-temperature system for nanotube growth, allowing direct implementation into heat-sensitive large-area devices.

  2. Effects of chirp of pump pulses on broadband terahertz pulse spectra generated by optical rectification

    Science.gov (United States)

    Hamazaki, Junichi; Furusawa, Kentaro; Sekine, Norihiko; Kasamatsu, Akifumi; Hosako, Iwao

    2016-11-01

    The effects of the chirp of the pump pulse in broadband terahertz (THz) pulse generation by optical rectification (OR) in GaP were systematically investigated. It was found that the pre-compensation for the dispersion of GaP is important for obtaining smooth and single-peaked THz spectra as well as high power-conversion efficiency. It was also found that an excessive amount of chirp leads to distortions in THz spectra, which can be quantitatively analyzed by using a simple model. Our results highlight the importance of accurate control over the chirp of the pump pulse for generating broadband THz pulses by OR.

  3. Parallel broadband fluorescent light source for optical coherence tomography

    NARCIS (Netherlands)

    Bourquin, S; Laversenne, L.; Rivier, S; Lasser, T.; Salathé, R.P.; Pollnau, M.; Grivas, C.; Shepherd, D.P.; Eason, R.W.; Tuchin, V.V.; Izatt, J.J.; Fugimoto, J.G.

    2005-01-01

    We present a new light source for parallel Optical Coherence Tomography (OCT) based on multiple waveguides written in Ti:sapphire. Each channel can generate a spectrum of 174 nm bandwidth centered at 772 nm, with an optical power on sample of 30 uW. A system depth resolution of 1.9 um is obtained, w

  4. High gain broadband amplification of ultraviolet pulses in optical parametric chirped pulse amplifier.

    Science.gov (United States)

    Wnuk, Paweł; Stepanenko, Yuriy; Radzewicz, Czesław

    2010-04-12

    We report on a high gain amplification of broadband ultraviolet femtosecond pulses in an optical parametric chirped pulse amplifier. Broadband ultraviolet seed pulses were obtained by an achromatic frequency doubling of the output from a femtosecond Ti:Sapphire oscillator. Stretched seed pulses were amplified in a multipass parametric amplifier with a single BBO crystal pumped by a ns frequency quadrupled Nd:YAG laser. A noncollinear configuration was used for a broadband amplification. The total (after compression) amplification of 2.510(5) was achieved, with compressed pulse energy of 30 microJ and pulse duration of 24 fs. We found that the measured gain was limited by thermal effects induced by the absorption of the pump laser by color centers created in the BBO crystal.

  5. High gain broadband amplification of ultraviolet pulses in optical parametric chirped pulse amplifier.

    Science.gov (United States)

    Wnuk, Paweł; Stepanenko, Yuriy; Radzewicz, Czesław

    2010-04-12

    We report on a high gain amplification of broadband ultraviolet femtosecond pulses in an optical parametric chirped pulse amplifier. Broadband ultraviolet seed pulses were obtained by an achromatic frequency doubling of the output from a femtosecond Ti:Sapphire oscillator. Stretched seed pulses were amplified in a multipass parametric amplifier with a single BBO crystal pumped by a ns frequency quadrupled Nd:YAG laser. A noncollinear configuration was used for a broadband amplification. The total (after compression) amplification of 2.510(5) was achieved, with compressed pulse energy of 30 microJ and pulse duration of 24 fs. We found that the measured gain was limited by thermal effects induced by the absorption of the pump laser by color centers created in the BBO crystal. PMID:20588633

  6. Computational adaptive optics for broadband interferometric tomography of tissues and cells

    Science.gov (United States)

    Adie, Steven G.; Mulligan, Jeffrey A.

    2016-03-01

    Adaptive optics (AO) can shape aberrated optical wavefronts to physically restore the constructive interference needed for high-resolution imaging. With access to the complex optical field, however, many functions of optical hardware can be achieved computationally, including focusing and the compensation of optical aberrations to restore the constructive interference required for diffraction-limited imaging performance. Holography, which employs interferometric detection of the complex optical field, was developed based on this connection between hardware and computational image formation, although this link has only recently been exploited for 3D tomographic imaging in scattering biological tissues. This talk will present the underlying imaging science behind computational image formation with optical coherence tomography (OCT) -- a beam-scanned version of broadband digital holography. Analogous to hardware AO (HAO), we demonstrate computational adaptive optics (CAO) and optimization of the computed pupil correction in 'sensorless mode' (Zernike polynomial corrections with feedback from image metrics) or with the use of 'guide-stars' in the sample. We discuss the concept of an 'isotomic volume' as the volumetric extension of the 'isoplanatic patch' introduced in astronomical AO. Recent CAO results and ongoing work is highlighted to point to the potential biomedical impact of computed broadband interferometric tomography. We also discuss the advantages and disadvantages of HAO vs. CAO for the effective shaping of optical wavefronts, and highlight opportunities for hybrid approaches that synergistically combine the unique advantages of hardware and computational methods for rapid volumetric tomography with cellular resolution.

  7. Determination of the broadband optical properties of biomass burning aerosol

    Science.gov (United States)

    Bluvshtein, Nir; Flores, J. Michel; Segev, Lior; Lin, Peng; Laskin, Alexander; Rudich, Yinon

    2016-04-01

    The direct and semi-direct effects of atmospheric aerosol on the Earth's energy balance are still the two of the largest uncertainties in our understanding of anthropogenic radiative forcing. In this study we developed a new approach for determining high sensitivity broadband UV-Vis spectrum (300-650 nm) of extinction, scattering and absorption coefficients, single scattering albedo and the complex refractive index for continuous, spectral and time dependent, monitoring of polydisperse aerosols population. This new approach was applied in a study of biomass burning aerosol. Extinction, scattering and absorption coefficients (αext, αsca, αabs, respectively) were continually monitored using photoacoustic spectrometer coupled to a cavity ring down spectrometer (PA-CRD-AS) at 404 nm, a dual-channel Broadband cavity-enhanced spectrometer (BBCES) at 315-345 nm and 390-420 nm and a three channel integrating nephelometer (IN) centered at 457, 525 and 637 nm. During the biomass burning event, the measured aerosol number concentration increased by more than an order of magnitude relative to other week nights and the mode of the aerosols size distribution increased from 40-50 nm to 110nm diameter. αext and αsca increased by a factor of about 5.5 and 4.5, respectively. The αabs increased by a factor over 20, indicating a significant change in the aerosol overall chemical composition. The imaginary part of the complex RI at 404nm increased from its background level at about 0.02 to a peak of about 0.08 and the SSA decreased from 0.9 to about 0.6. Significant change of the absorption spectral dependence indicates formation of visible-light absorbing compounds. The mass absorption cross section of the water soluble organic aerosol (MACWSOA) reached up to about 12% of the corresponding value for black carbon (BC) at 450 nm and up to 30% at 300 nm. These results demonstrate the importance of biomass burning in understanding global and regional radiative forcing.

  8. Ultrafast defect dynamics: A new approach to all optical broadband switching employing amorphous selenium thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Rituraj; Adarsh, K. V., E-mail: drabold@ohio.edu, E-mail: adarsh@iiserb.ac.in [Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066 (India); Prasai, Kiran; Drabold, D. A., E-mail: drabold@ohio.edu, E-mail: adarsh@iiserb.ac.in [Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States)

    2015-07-15

    Optical switches offer higher switching speeds than electronics, however, in most cases utilizing the interband transitions of the active medium for switching. As a result, the signal suffers heavy losses. In this article, we demonstrate a simple and yet efficient ultrafast broadband all-optical switching on ps timescale in the sub-bandgap region of the a-Se thin film, where the intrinsic absorption is very weak. The optical switching is attributed to short-lived transient defects that form localized states in the bandgap and possess a large electron-phonon coupling. We model these processes through first principles simulation that are in agreement with the experiments.

  9. Ultrafast defect dynamics: A new approach to all optical broadband switching employing amorphous selenium thin films

    Directory of Open Access Journals (Sweden)

    Rituraj Sharma

    2015-07-01

    Full Text Available Optical switches offer higher switching speeds than electronics, however, in most cases utilizing the interband transitions of the active medium for switching. As a result, the signal suffers heavy losses. In this article, we demonstrate a simple and yet efficient ultrafast broadband all-optical switching on ps timescale in the sub-bandgap region of the a-Se thin film, where the intrinsic absorption is very weak. The optical switching is attributed to short-lived transient defects that form localized states in the bandgap and possess a large electron-phonon coupling. We model these processes through first principles simulation that are in agreement with the experiments.

  10. Photoinduced Birefringence and Broadband All-Optical Photonic Switch in a Bacteriorhodopsin/Polymer Composite Film

    Institute of Scientific and Technical Information of China (English)

    WEI Lai; TENG Xue-Lei; Lu Ming; ZHAO You-Yuan; MA De-Wang; DING Jian-Dong

    2007-01-01

    Photoinduced birefringence with large optical nonlinearity in a bacteriorhodopsin/polymer composite film is observed.A high refractive index change of 8.5×10-5 photoinduced by 476nm pumping beam is reached at the low intensity of 6.5mW/cm2.Based on it,a broadband all-optical photonic switch is realized with an optical controlling switch system.Because of controlling beam's selectivity in switching,the transporting beams of different wavelengths with different intensities and shapes can be modulated by adjusting the wavelength and intensity of the controlling beam.

  11. Lanthanide-Activated Fiber Materials for Broadband Optical Amplifiers

    Institute of Scientific and Technical Information of China (English)

    Yong Gyu Choi; Bong Je Park; Doo Hee Cho; Hong Seok Seo; Myung Hyun Lee; Kyong Hon Kim

    2003-01-01

    Some intra-4 f-configurational transitions of lanthanide, of which radiative emissions cover in wavelengths the optical communication window of the currently available OH-free silica-based line fibers, are discussed in terms of relationship between their emission properties and host fiber materials.

  12. Optical frequency comb technology for ultra-broadband radio-frequency photonics

    CERN Document Server

    Torres-Company, Victor

    2014-01-01

    The outstanding phase-noise performance of optical frequency combs has led to a revolution in optical synthesis and metrology, covering a myriad of applications, from molecular spectroscopy to laser ranging and optical communications. However, the ideal characteristics of an optical frequency comb are application dependent. In this review, the different techniques for the generation and processing of high-repetition-rate (>10 GHz) optical frequency combs with technologies compatible with optical communication equipment are covered. Particular emphasis is put on the benefits and prospects of this technology in the general field of radio-frequency photonics, including applications in high-performance microwave photonic filtering, ultra-broadband coherent communications, and radio-frequency arbitrary waveform generation.

  13. Adoption of Broadband Services

    DEFF Research Database (Denmark)

    Falch, Morten

    2008-01-01

    Broadband is seen as a key infrastructure for developing the information society. For this reason many Governments are actively engaged in stimulating investments in broadband infrastructures and use of broadband services. This chapter compares a wide range of broadband strategies in the most suc....... Many countries have provided active support for stimulating diffusion of broadband and national variants of this type of policies in different countries are important for an explanation of national differences in adoption of broadband....

  14. Erratum to “Ultra-Broadband Photonic Harmonic Mixer Based on Optical Comb Generation”

    DEFF Research Database (Denmark)

    Zhao, Ying; Pang, Xiaodan; Deng, Lei;

    2012-01-01

    We propose a novel photonic harmonic mixer operating at frequencies up to the millimeter-wave (MMW) band. By combining a broadband fiber-wireless signal with highorder harmonics of a fundamental local oscillator in an optical frequency comb generator, frequency down-conversion can be implemented...... without using costly ultra-broadband photodiode. It is theoretically shown that the down-conversion efficiency and the bandwidth of the mixer is highly dependent on the optical modulation indices and the fundamental frequency of comb lines. Down-conversion of a W-band (75-110GHz) fiberwireless signal...... is experimentally demonstrated. Moreover, the error vector magnitude (EVM) performance of a multi-gigabit quadrature phase shift keying (QPSK) signal at 62.5, 82.5 and 102.5GHz carrier frequencies is studied to evaluate the downconversion efficiency. The proposed photonic harmonic mixer can be a candidate...

  15. Fiber-integrated single photon source of high efficiency based on a concept of ultra-broadband optical horn antenna

    OpenAIRE

    Grosjean, T.; Mivelle, M.; Burr, G. W.; Baida, F.I.

    2016-01-01

    We theoretically demonstrate a fiber-integrated single photon source of unprecedented efficiency. This fiber single photon source is achieved by coupling optically a single quantum emitter to a monomode optical fiber with a new concept of ultra-broadband optical antenna. Such an optical antenna concept is the result of the transposition to optical frequencies of the well-known low-frequency horn antenna The optical horn antenna is here shown to be capable of directing the radiation from the e...

  16. A fiber-optic broadband CT/MR video communication system.

    Science.gov (United States)

    Huang, H K; Tecotzky, R H; Bazzill, T

    1992-02-01

    Our department operates three magnetic resonance (MR) and three computed tomography (CT) scanners that are located in three different buildings up to 2 km apart. We have designed and implemented a multichannel, fiber-optic broadband video communication system as a remote scanner monitoring network. This system consists of baseband and broadband fiberoptic transmitters, receivers, and multiplexers. The structure of the video network is supported by two strategically located headends (distributors) connecting local/remote scanners and monitoring stations. The system is capable of serving up to 5 km from each headend. The video signal from each scanner is sent through a baseband fiber-optic link to a headend, where it is frequency modulated, multiplexed with other scanner video signals, and distributed over broadband fiber-optic links to monitoring stations. Each receiver consists of a demodulator, a channel selectable tuner, and a video monitor. The current design provides up to 16 scanner channels and 16 remote monitoring station connections. Monitoring stations are placed in 14 clinical locations including the following reading rooms: thoracic, neuro, abdomen, musculoskeletal, gastrointestinal, genitourinary, and pediatric radiology. A radiologist can use any of these 14 monitoring stations to view a patient's CT/MR images in real-time as they appear on any of the six scanner consoles. By selecting the proper channel assigned to a patient's scanner, the radiologist may monitor the examination while using the telephone to communicate with the technologist at the scanner site. This fiber-optic broadband video communication system has been integrated into daily clinical use for over 6 months. PMID:1554755

  17. Microwave photonic filter with multiple independently tunable passbands based on a broadband optical source.

    Science.gov (United States)

    Huang, Long; Chen, Dalei; Zhang, Fangzheng; Xiang, Peng; Zhang, Tingting; Wang, Peng; Lu, Linlin; Pu, Tao; Chen, Xiangfei

    2015-10-01

    In this paper, a novel microwave photonic filter (MPF) with multiple independently tunable passbands is proposed. A broadband optical source (BOS) is employed and split by a 1:N coupler into several branches. One branch is directed to a phase modulator which is modulated by a radio frequency signal and the other branches are delayed by optical delay lines (ODLs), respectively. All of these branches are combined by another 1:N coupler and sent to a dispersion compensation fiber which is used to introduce group delay dispersion to the optical signal. At a photodetector, each time-delayed broadband lightwave beating with the sidebands produced by the phase modulator forms a passband of the MPF. By tuning the delay of each broadband lightwave, the center frequency of the passband can be independently tuned. An MPF with two independently tunable passbands is experimentally demonstrated. The two passbands can be tuned from DC to 30 GHz with a 3-dB bandwidth of about 250 MHz. The stability and dynamic range of the MPF are also evaluated. By employing more branches delayed by ODLs, more passbands can be generated. PMID:26480071

  18. Assessing PDT response with diffuse optical spectroscopies

    Science.gov (United States)

    Rohrbach, Daniel J.

    Photodynamic therapy (PDT) is used to treat a variety of conditions including cancer. Effective PDT requires three components: a photosensitizer (PS), light of a specific wavelength to activate the PS and oxygen. When all three are present in a lesion it leads to cell death and vascular destruction. Optical techniques such as diffuse reflectance spectroscopy (DRS), diffuse fluorescence spectroscopy (DFS) and diffuse correlation spectroscopy (DCS) can be used to quantify vascular parameters and photosensitizer content before and after PDT, providing valuable information for assessing response. For the quantification of vascular parameters, a probe-specific empirical light transport model was developed. A look-up-table was constructed using tissue simulating phantoms made of Intralipid to control the scattering, India Ink to control the absorption and water. The empirical model allowed the quantification of optical properties as well as the vascular parameters blood volume fraction (BVf) and blood oxygen saturation (SO2) with DRS. Blood flow was measured using DCS. For the quantification of PS content two techniques were used. DRS was used to fit the absorption of the PS and DFS measured the fluorescence of the PS. For quantification of PS content from measured fluorescence, a correction factor was developed using Monte Carlo simulations to account for the optical properties at the excitation and emission wavelengths. The three techniques were used to assess PDT response in pre-clinical and clinical studies. For the preclinical study, mice were treated with HPPH-PDT and blood flow was measured continuously with DCS. Blood flow variables were compared to STAT3 crosslinking (a molecular marker for PDT photoreaction) and CD31 staining (to visualize intact endothelial cells after PDT). For the clinical study, patients in a clinical trial for HPPH-PDT were measured with DRS, DFS and DCS before and after treatment. Multiple parameters were compared to the clinical response

  19. Noise analysis in photonic true time delay systems based on broadband optical source and dispersion components.

    Science.gov (United States)

    Xue, Xiaoxiao; Wen, He; Zheng, Xiaoping; Zhang, Hanyi; Guo, Yili; Zhou, Bingkun

    2009-02-01

    The noise in photonic true time delay systems based on broadband optical source and dispersion components is investigated. It is found that the beat noise induced by the optical source begins to dominate and grows far larger than other noise terms quickly, as long as the detected optical power is above some certain value P(thr). When the system dispersion is nonzero, the output carrier-to-noise ratio (CNR) will change periodically with the optical bandwidth due to the noise power increment and the dispersion induced radio frequency signal power degradation. The maximum CNR is the peak value of the first period. For a set of specified system conditions, the P(thr) is calculated to be -21 dBm, and the optimal optical bandwidth is 0.8 nm, at which the maximum CNR is 93.3 dB by considering the noise in a 1 Hz bandwidth. The results are verified experimentally.

  20. Complementary chiral metasurface with strong broadband optical activity and enhanced transmission

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Yan-Peng [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, No. 29 Zhongguancun East Road, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100190 (China); Zhang, Yong-Liang; Dong, Xian-Zi, E-mail: dongxianzi@mail.ipc.ac.cn, E-mail: xmduan@mail.ipc.ac.cn; Zheng, Mei-Ling; Li, Jing; Liu, Jie; Zhao, Zhen-Sheng [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, No. 29 Zhongguancun East Road, Beijing 100190 (China); Duan, Xuan-Ming, E-mail: dongxianzi@mail.ipc.ac.cn, E-mail: xmduan@mail.ipc.ac.cn [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, No. 29 Zhongguancun East Road, Beijing 100190 (China); Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, No. 266 Fangzheng Ave, Shuitu Technology Development Zone, Beibei District, Chongqing 400714 (China)

    2014-01-06

    We present the design and realization of ultra-thin chiral metasurfaces with giant broadband optical activity in the infrared wavelength. The chiral metasurfaces consisting of periodic hole arrays of complementary asymmetric split ring resonators are fabricated by femtosecond laser two-photon polymerization. Enhanced transmission with strong polarization conversion up to 97% is observed owing to the chiral surface plasmons resulting from mirror symmetry broken. The dependence of optical activity on the degree of structural asymmetry is investigated. This simple planar metasurface is expected to be useful for designing ultra-thin active devices and tailoring the polarization behavior of complex metallic nanostructures.

  1. Chaos-assisted, broadband trapping of light in optical resonators

    CERN Document Server

    Liu, C; Molinari, D; Khan, Y; Ooi, B S; Krauss, T F; Fratalocchi, A

    2012-01-01

    Chaos is a phenomenon that occurs in many aspects of contemporary science. In classical dynamics, chaos is defined as a hypersensitivity to initial conditions. The presence of chaos is often unwanted, as it introduces unpredictability, which makes it difficult to predict or explain experimental results. Conversely, we demonstrate here how chaos can be used to enhance the ability of an optical resonator to store energy. We combine analytic theory with ab-initio simulations and experiments in photonic crystal resonators to show that a chaotic resonator can store six times more energy than its classical counterpart of the same volume. We explain the observed increase with the equipartition of energy among all degrees of freedom of the chaotic resonator, i.e. the cavity modes, which is evident from the convergence of their lifetime towards a single value. A compelling illustration of the theory is provided by demonstrating enhanced absorption in deformed polystyrene microspheres.

  2. Design of Optical Metamaterial Mirror with Metallic Nanoparticles for Broadband Light Absorption in Graphene Optoelectronic Devices

    CERN Document Server

    Lee, Seungwoo

    2015-01-01

    A general metallic mirror (i.e., a flat metallic surface) has been a popular optical component that can contribute broadband light absorption to thin-film optoelectronic devices; nonetheless, such electric mirror with a reversal of reflection phase inevitably causes the problem of minimized electric field near at the mirror surface (maximized electric field at one quarter of wavelength from mirror). This problem becomes more elucidated, when the deep-subwavelength-scaled two-dimensional (2D) material (e.g., graphene and molybdenum disulfide) is implemented into optoelectronic device as an active channel layer. The purpose of this work was to conceive the idea for using a charge storage layer (spherical Au nanoparticles (AuNPs), embedded into dielectric matrix) of the floating-gate graphene photodetector as a magnetic mirror, which allows the device to harness the increase in broadband light absorption. In particular, we systematically examined whether the versatile assembly of spherical AuNP monolayer within ...

  3. Broadband semiconductor optical amplifiers of the spectral range 750 – 1100 nm

    International Nuclear Information System (INIS)

    A line of travelling-wave semiconductor optical amplifiers (SOAs) based on heterostructures used for production of broadband superluminescent diodes is developed. The pure small-signal gains of the developed SOA modules are about 25 dB, while the gain bandwidths at a level of –10 dB reach 50 – 100 nm. As a whole, the SOA modules cover the IR spectral range from 750 to 1100 nm. The SOAs demonstrate a high reliability at a single-mode fibre-coupled cw output power up to 50 mW. Examples of application of two of the developed SOA modules as active elements of broadband fast-tunable lasers are presented. (lasers)

  4. Diffuse Optical Tomography for Brain Imaging: Theory

    Science.gov (United States)

    Yuan, Zhen; Jiang, Huabei

    Diffuse optical tomography (DOT) is a noninvasive, nonionizing, and inexpensive imaging technique that uses near-infrared light to probe tissue optical properties. Regional variations in oxy- and deoxy-hemoglobin concentrations as well as blood flow and oxygen consumption can be imaged by monitoring spatiotemporal variations in the absorption spectra. For brain imaging, this provides DOT unique abilities to directly measure the hemodynamic, metabolic, and neuronal responses to cells (neurons), and tissue and organ activations with high temporal resolution and good tissue penetration. DOT can be used as a stand-alone modality or can be integrated with other imaging modalities such as fMRI/MRI, PET/CT, and EEG/MEG in studying neurophysiology and pathology. This book chapter serves as an introduction to the basic theory and principles of DOT for neuroimaging. It covers the major aspects of advances in neural optical imaging including mathematics, physics, chemistry, reconstruction algorithm, instrumentation, image-guided spectroscopy, neurovascular and neurometabolic coupling, and clinical applications.

  5. Field Studies of Broadband Aerosol Optical Extinction in the Ultraviolet Spectral Region

    Science.gov (United States)

    Washenfelder, R. A.; Attwood, A.; Brock, C. A.; Brown, S. S.

    2013-12-01

    Aerosols influence the Earth's radiative budget by scattering and absorbing incoming solar radiation. The optical properties of aerosols vary as a function of wavelength, but few measurements have reported the wavelength dependence of aerosol extinction cross sections and complex refractive indices. In the case of brown carbon, its wavelength-dependent absorption in the ultraviolet spectral region has been suggested as an important component of aerosol radiative forcing. We describe a new field instrument to measure aerosol optical extinction as a function of wavelength, using cavity enhanced spectroscopy with a broadband light source. The instrument consists of two broadband channels which span the 360-390 and 385-420 nm spectral regions using two light emitting diodes (LED) and a grating spectrometer with charge-coupled device (CCD) detector. We deployed this instrument during the Fire Lab at Missoula Experiment during Fall 2012 to measure biomass burning aerosol, and again during the Southern Oxidant and Aerosol Study in summer 2013 to measure organic aerosol in the Southeastern U.S. In both field experiments, we determined aerosol optical extinction as a function of wavelength and can interpret this together with size distribution and composition measurements to characterize the aerosol optical properties and radiative forcing.

  6. Inverse design of an ultra-compact broadband optical diode based on asymmetric spatial mode conversion.

    Science.gov (United States)

    Callewaert, Francois; Butun, Serkan; Li, Zhongyang; Aydin, Koray

    2016-01-01

    The objective-first inverse-design algorithm is used to design an ultra-compact optical diode. Based on silicon and air only, this optical diode relies on asymmetric spatial mode conversion between the left and right ports. The first even mode incident from the left port is transmitted to the right port after being converted into an odd mode. On the other hand, same mode incident from the right port is reflected back by the optical diode dielectric structure. The convergence and performance of the algorithm are studied, along with a transform method that converts continuous permittivity medium into a binary material design. The optimal device is studied with full-wave electromagnetic simulations to compare its behavior under right and left incidences, in 2D and 3D settings as well. A parametric study is designed to understand the impact of the design space size and initial conditions on the optimized devices performance. A broadband optical diode behavior is observed after optimization, with a large rejection ratio between the two transmission directions. This illustrates the potential of the objective-first inverse-design method to design ultra-compact broadband photonic devices. PMID:27586852

  7. Offline Effects of Online Connecting: The Impact of Broadband Diffusion on Teen Fertility Decisions

    OpenAIRE

    Guldi, Melanie; Chris M. Herbst

    2015-01-01

    Broadband (high-speed) internet access expanded rapidly from 1999 to 2007. This expansion is associated with higher economic growth and labor market activity. In this paper, we examine whether the rollout also affected the social connections teens make. Specifically, we look at the relationship between increased broadband access and teen fertility. We hypothesize that increasing access to high-speed internet can influence fertility decisions by changing the size of the market as well as incre...

  8. 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.

  9. Colloidal superlattices for unnaturally high-index metamaterials at broadband optical frequencies

    CERN Document Server

    Lee, Seungwoo

    2015-01-01

    The recent advance in the assembly of metallic nanoparticles (NPs) has enabled sophisticated engineering of unprecedented light-matter interaction at the optical domain. In this work, I expand the design flexibility of NP optical metamaterial to push the upper limit of accessible refractive index to the unnaturally high regime. The precise control over the geometrical parameters of NP superlattice monolayer conferred the dramatic increase in electric resonance and related effective permittivity far beyond the naturally accessible regime. Simultaneously, effective permeability, another key factor to achieving high refractive index, was effectively suppressed by reducing the thickness of NPs. By establishing this design rule, I have achieved unnaturally high refractive index (15.7 at the electric resonance and 7.3 at the quasi-static limit) at broadband optical frequencies (100 THz ~ 300 THz). I also combined this NP metamaterial with graphene to electrically control the high refractive index over the broad opt...

  10. Ultra-broadband Photonic Harmonic Mixer Based on Optical Comb Generation

    DEFF Research Database (Denmark)

    Zhao, Ying; Pang, Xiaodan; Deng, Lei;

    2012-01-01

    We propose a novel photonic harmonic mixer operating at frequencies up to the millimeter-wave (MMW) band. By combining a broadband fiber-wireless signal with highorder harmonics of a fundamental local oscillator in an optical frequency comb generator, frequency down-conversion can be implemented...... is experimentally demonstrated. Moreover, the error vector magnitude (EVM) performance of a multi-gigabit quadrature phase shift keying (QPSK) signal at 62.5, 82.5 and 102.5GHz carrier frequencies is studied to evaluate the downconversion efficiency. The proposed photonic harmonic mixer can be a candidate...... for applications in high capacity fiber-wireless communication systems....

  11. Focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces.

    Science.gov (United States)

    Zhong, Qiuhang; Veerasubramanian, Venkat; Wang, Yun; Shi, Wei; Patel, David; Ghosh, Samir; Samani, Alireza; Chrostowski, Lukas; Bojko, Richard; Plant, David V

    2014-07-28

    We report on the design and characterization of focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces. With implementation of waveguide dispersion engineered subwavelength structures, an ultra-wide 1-dB bandwidth of over 100 nm (largest reported to date) near 1550 nm is experimentally achieved for transverse-electric polarized light. By tapering the subwavelength structures, back reflection is effectively suppressed and grating coupling efficiency is increased to -4.7 dB. A compact device footprint of 40 µm × 20 µm is realized by curving the gratings in a focusing scheme. PMID:25089441

  12. Tunable microwave photonic notch filter based on sliced broadband optical source.

    Science.gov (United States)

    Yu, Yang; Li, Shangyuan; Zheng, Xiaoping; Zhang, Hanyi; Zhou, Bingkun

    2015-09-21

    A microwave photonic filter is demonstrated with both tunable center frequency and bandwidth. This filter is switchable from all-pass, bandpass to notch filter, and the notch filter is a result of the subtraction of a bandpass filter from an all-pass filter based on a balanced photodetector. The all-pass filter is achieved based on a single wavelength radio over fiber link, and the bandpass one is acquired by using the spectrum-sliced broadband optical source. Theoretical analysis and experimental results show that both the center frequency and the bandwidth of the notch filter can be widely tuned. PMID:26406636

  13. α-bandlimited diffuser in fractional Fourier optics

    Science.gov (United States)

    Patiño-Vanegas, Alberto; Durand, Pierre-Emmanuel; Torres, Rafael; Pellat-Finet, Pierre

    2016-04-01

    We propose a method for calculating appropriate α-band limited diffusers using the fractional Fourier transform. In order to do this, we implement a method for performing a numerical interpolation in the fractional Fourier domain. Such diffusers with compact support in the Fresnel regime may be used in fractional Fourier optical systems where the use of diffusers produce speckles, e.g. digital holography or optical encryption. Numerical simulations are presented.

  14. Propagation characteristics of a high-power broadband laser beam passing through a nonlinear optical medium with defects

    Institute of Scientific and Technical Information of China (English)

    Xueqiong; Chen; Xiaoyan; Li; Ziyang; Chen; Jixiong; Pu; Guowen; Zhang; Jianqiang; Zhu

    2013-01-01

    The intensity distributions of a high-power broadband laser beam passing through a nonlinear optical medium with defects and then propagating in free space are investigated based on the general nonlinear Schr¨odinger equation and the split-step Fourier numerical method. The influences of the bandwidth of the laser beam, the thickness of the medium,and the defects on the light intensity distribution are revealed. We find that the nonlinear optical effect can be suppressed and that the uniformity of the beam can be improved for a high-power broadband laser beam with appropriate wide bandwidth. It is also found that, under the same incident light intensity, a thicker medium will lead to a stronger self-focusing intensity, and that the influence of defects in the optical elements on the intensity is stronger for a narrowband beam than for a broadband beam.

  15. New Insight into the Angle Insensitivity of Ultrathin Planar Optical Absorbers for Broadband Solar Energy Harvesting

    Science.gov (United States)

    Liu, Dong; Yu, Haitong; Duan, Yuanyuan; Li, Qiang; Xuan, Yimin

    2016-09-01

    Two challenging problems still remain for optical absorbers consisting of an ultrathin planar semiconductor film on top of an opaque metallic substrate. One is the angle-insensitive mechanism and the other is the system design needed for broadband solar energy harvesting. Here, first we theoretically demonstrates that the high refractive index, instead of the ultrathin feature as reported in previous studies, is the physical origin of the angle insensitivity for ultrathin planar optical absorbers. They exhibit omnidirectional resonance for TE polarization due to the high complex refractive index difference between the semiconductor and the air, while for TM polarization the angle insensitivity persists up to an incident angle related to the semiconductor refractive index. These findings were validated by fabricating and characterizing an 18 nm Ge/Ag absorber sample (representative of small band gap semiconductors for photovoltaic applications) and a 22 nm hematite/Ag sample (representative of large band gap semiconductors for photoelectrochemical applications). Then, we took advantage of angle insensitivity and designed a spectrum splitting configuration for broadband solar energy harvesting. The cascaded solar cell and unassisted solar water splitting systems have photovoltaic and photoelectrochemical cells that are also spectrum splitters, so an external spectrum splitting element is not needed.

  16. Broadband optical transparency in plasmonic nanocomposite polymer films via exciton-plasmon energy transfer.

    Science.gov (United States)

    Dhama, R; Rashed, A R; Caligiuri, V; El Kabbash, M; Strangi, G; De Luca, A

    2016-06-27

    Inherent absorptive losses affect the performance of all plasmonic devices, limiting their fascinating applications in the visible range. Here, we report on the enhanced optical transparency obtained as a result of the broadband mitigation of optical losses in nanocomposite polymeric films, embedding core-shell quantum dots (CdSe@ZnS QDs) and gold nanoparticles (Au-NPs). Exciton-plasmon coupling enables non-radiative energy transfer processes from QDs to metal NPs, resulting in gain induced transparency of the hybrid flexible systems. Experimental evidences, such as fluorescence quenching and modifications of fluorescence lifetimes confirm the presence of this strong coupling between plexcitonic elements. Measures performed by means of an ultra-fast broadband pump-probe setup demonstrate loss compensation of gold NPs dispersed in plastic network in presence of gain. Furthermore, we compare two films containing different concentrations of gold NPs and same amount of QDs, to investigate the role of acceptor concentration (Au-NPs) in order to promote an effective and efficient energy transfer mechanism. Gain induced transparency in bulk systems represents a promising path towards the realization of loss compensated plasmonic devices. PMID:27410615

  17. New Insight into the Angle Insensitivity of Ultrathin Planar Optical Absorbers for Broadband Solar Energy Harvesting.

    Science.gov (United States)

    Liu, Dong; Yu, Haitong; Duan, Yuanyuan; Li, Qiang; Xuan, Yimin

    2016-01-01

    Two challenging problems still remain for optical absorbers consisting of an ultrathin planar semiconductor film on top of an opaque metallic substrate. One is the angle-insensitive mechanism and the other is the system design needed for broadband solar energy harvesting. Here, first we theoretically demonstrates that the high refractive index, instead of the ultrathin feature as reported in previous studies, is the physical origin of the angle insensitivity for ultrathin planar optical absorbers. They exhibit omnidirectional resonance for TE polarization due to the high complex refractive index difference between the semiconductor and the air, while for TM polarization the angle insensitivity persists up to an incident angle related to the semiconductor refractive index. These findings were validated by fabricating and characterizing an 18 nm Ge/Ag absorber sample (representative of small band gap semiconductors for photovoltaic applications) and a 22 nm hematite/Ag sample (representative of large band gap semiconductors for photoelectrochemical applications). Then, we took advantage of angle insensitivity and designed a spectrum splitting configuration for broadband solar energy harvesting. The cascaded solar cell and unassisted solar water splitting systems have photovoltaic and photoelectrochemical cells that are also spectrum splitters, so an external spectrum splitting element is not needed.

  18. Ultraviolet broadband light scattering for optically-trapped submicron-sized aerosol particles.

    Science.gov (United States)

    David, Grégory; Esat, Kıvanç; Ritsch, Irina; Signorell, Ruth

    2016-02-21

    We describe a broadband light scattering setup for the characterization of size and refractive index of single submicron-to-micron sized aerosol particles. Individual particles are isolated in air by a quadruple Bessel beam optical trap or a counter-propagating optical tweezer. The use of very broadband radiation in the wavelength range from 320 to 700 nm covering the ultraviolet region allows to size submicron particles. We show that a broad wavelength range is required to determine the particle radius and the refractive index with an uncertainty of several nanometers and ∼ 0.01, respectively. The smallest particle radius that can be accurately determined lies around 300 nm. Wavelength-dependent refractive index data over a broad range are obtained, including the ultraviolet region where corresponding data are rare. Four different applications are discussed: (1) the sizing of submicron polystyrene latex spheres, (2) the evaporation of binary glycerol water droplets, (3) hydration/dehydration cycling of aqueous potassium carbonate droplets, and (4) photochemical reactions of oleic acid droplets. PMID:26863396

  19. New Insight into the Angle Insensitivity of Ultrathin Planar Optical Absorbers for Broadband Solar Energy Harvesting.

    Science.gov (United States)

    Liu, Dong; Yu, Haitong; Duan, Yuanyuan; Li, Qiang; Xuan, Yimin

    2016-01-01

    Two challenging problems still remain for optical absorbers consisting of an ultrathin planar semiconductor film on top of an opaque metallic substrate. One is the angle-insensitive mechanism and the other is the system design needed for broadband solar energy harvesting. Here, first we theoretically demonstrates that the high refractive index, instead of the ultrathin feature as reported in previous studies, is the physical origin of the angle insensitivity for ultrathin planar optical absorbers. They exhibit omnidirectional resonance for TE polarization due to the high complex refractive index difference between the semiconductor and the air, while for TM polarization the angle insensitivity persists up to an incident angle related to the semiconductor refractive index. These findings were validated by fabricating and characterizing an 18 nm Ge/Ag absorber sample (representative of small band gap semiconductors for photovoltaic applications) and a 22 nm hematite/Ag sample (representative of large band gap semiconductors for photoelectrochemical applications). Then, we took advantage of angle insensitivity and designed a spectrum splitting configuration for broadband solar energy harvesting. The cascaded solar cell and unassisted solar water splitting systems have photovoltaic and photoelectrochemical cells that are also spectrum splitters, so an external spectrum splitting element is not needed. PMID:27582317

  20. Functionally graded poly(dimethylsiloxane)/silver nanocomposites with tailored broadband optical absorption

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaou, P.; Mina, C.; Constantinou, M.; Koutsokeras, L.E.; Constantinides, G. [Research Unit for Nanostructured Materials Systems, Department of Mechanical Engineering and Materials Science and Engineering, PO Box 50329, 3603 Limassol (Cyprus); Lidorikis, E.; Avgeropoulos, A. [Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina (Greece); Kelires, P.C. [Research Unit for Nanostructured Materials Systems, Department of Mechanical Engineering and Materials Science and Engineering, PO Box 50329, 3603 Limassol (Cyprus); Patsalas, P., E-mail: ppats@physics.auth.gr [Physics Department, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)

    2015-04-30

    In this work, we produce functionally graded nanocomposites consisting of silver (Ag) plasmonic nanoparticles (PNPs) supported in a poly(dimethylsiloxane) (PDMS) matrix. PDMS was selected due to its high optical transparency, nontoxicity and ease of use. The Ag PNPs were formed by annealing sputtered Ag ultra-thin films and were subsequently capped by a spin-coated PDMS layer. We investigate the factors that affect their plasmonic behavior, such as the PNP size, the annealing conditions and the surrounding environment. In order to achieve broadband absorption, we developed PDMS/Ag(PNPs) multilayers with graded PNP size. Thus, we demonstrate the significance of the stacking sequence of various plasmonic layers sandwiched between PDMS layers and its potential for tailoring the plasmonic response of multilayer structure. As a demonstration of this approach, we deposited a specially designed multilayer structure, whose optical extinction resembles the solar emission spectrum. - Highlights: • Elastomers are combined with plasmonic nanoparticles. • The plasmonic effects in stratified media are identified. • Broadband absorption similar to solar emission is achieved.

  1. New Insight into the Angle Insensitivity of Ultrathin Planar Optical Absorbers for Broadband Solar Energy Harvesting

    Science.gov (United States)

    Liu, Dong; Yu, Haitong; Duan, Yuanyuan; Li, Qiang; Xuan, Yimin

    2016-01-01

    Two challenging problems still remain for optical absorbers consisting of an ultrathin planar semiconductor film on top of an opaque metallic substrate. One is the angle-insensitive mechanism and the other is the system design needed for broadband solar energy harvesting. Here, first we theoretically demonstrates that the high refractive index, instead of the ultrathin feature as reported in previous studies, is the physical origin of the angle insensitivity for ultrathin planar optical absorbers. They exhibit omnidirectional resonance for TE polarization due to the high complex refractive index difference between the semiconductor and the air, while for TM polarization the angle insensitivity persists up to an incident angle related to the semiconductor refractive index. These findings were validated by fabricating and characterizing an 18 nm Ge/Ag absorber sample (representative of small band gap semiconductors for photovoltaic applications) and a 22 nm hematite/Ag sample (representative of large band gap semiconductors for photoelectrochemical applications). Then, we took advantage of angle insensitivity and designed a spectrum splitting configuration for broadband solar energy harvesting. The cascaded solar cell and unassisted solar water splitting systems have photovoltaic and photoelectrochemical cells that are also spectrum splitters, so an external spectrum splitting element is not needed. PMID:27582317

  2. Time domain diffuse optical spectroscopy: In vivo quantification of collagen in breast tissue

    Science.gov (United States)

    Taroni, Paola; Pifferi, Antonio; Quarto, Giovanna; Farina, Andrea; Ieva, Francesca; Paganoni, Anna Maria; Abbate, Francesca; Cassano, Enrico; Cubeddu, Rinaldo

    2015-05-01

    Time-resolved diffuse optical spectroscopy provides non-invasively the optical characterization of highly diffusive media, such as biological tissues. Light pulses are injected into the tissue and the effects of light propagation on re-emitted pulses are interpreted with the diffusion theory to assess simultaneously tissue absorption and reduced scattering coefficients. Performing spectral measurements, information on tissue composition and structure is derived applying the Beer law to the measured absorption and an empiric approximation to Mie theory to the reduced scattering. The absorption properties of collagen powder were preliminarily measured in the range of 600-1100 nm using a laboratory set-up for broadband time-resolved diffuse optical spectroscopy. Optical projection images were subsequently acquired in compressed breast geometry on 218 subjects, either healthy or bearing breast lesions, using a portable instrument for optical mammography that operates at 7 wavelengths selected in the range 635-1060 nm. For all subjects, tissue composition was estimated in terms of oxy- and deoxy-hemoglobin, water, lipids, and collagen. Information on tissue microscopic structure was also derived. Good correlation was obtained between mammographic breast density (a strong risk factor for breast cancer) and an optical index based on collagen content and scattering power (that accounts mostly for tissue collagen). Logistic regression applied to all optically derived parameters showed that subjects at high risk for developing breast cancer for their high breast density can effectively be identified based on collagen content and scattering parameters. Tissue composition assessed in breast lesions with a perturbative approach indicated that collagen and hemoglobin content are significantly higher in malignant lesions than in benign ones.

  3. Broadband optical limiter based on nonlinear photoinduced anisotropy in bacteriorhodopsin film

    Science.gov (United States)

    Huang, Yuhua; Siganakis, Georgios; Moharam, M. G.; Wu, Shin-Tson

    2004-11-01

    Nonlinear photoinduced anisotropy in a bacteriorhodopsin film was theoretically and experimentally investigated and a broadband active optical limiter was demonstrated in the visible spectral range. A diode-pumped second harmonic yttrium aluminum garnet laser was used as a pumping beam and three different wavelengths at λ =442, 532, and 655nm from different lasers were used as probing beams. The pump and probe beams overlap at the sample. When the pumping beam is absent, the probing beam cannot transmit the crossed polarizers. With the presence of the pumping beam, a portion of the probing light is detected owing to the photoinduced anisotropy. Due to the optical nonlinearity, the transmitted probing beam intensity is clamped at a certain value, which depends on the wavelength, when the pumping beam intensity exceeds 5mW/mm2. Good agreement between theory and experiment is found.

  4. Broadband Continuous-Wave Multi-Harmonic Optical Comb Based on a Frequency Division-by-Three Optical Parametric Oscillator

    Directory of Open Access Journals (Sweden)

    Yen-Yin Lin

    2014-11-01

    Full Text Available We report a multi-watt broadband continuous-wave multi-harmonic optical comb based on a frequency division-by-three singly-resonant optical parametric oscillator. This cw optical comb is frequency-stabilized with the help of a beat signal derived from the signal and frequency-doubled idler waves. The measured frequency fluctuation in one standard deviation is ~437 kHz. This is comparable to the linewidth of the pump laser which is a master-oscillator seeded Yb:doped fiber amplifier at ~1064 nm. The measured powers of the fundamental wave and the harmonic waves up to the 6th harmonic wave are 1.64 W, 0.77 W, 3.9 W, 0.78 W, 0.17 W, and 0.11 W, respectively. The total spectral width covered by this multi-harmonic comb is ~470 THz. When properly phased, this multi-harmonic optical comb can be expected to produce by Fourier synthesis a light source consisting of periodic optical field waveforms that have an envelope full-width at half-maximum of 1.59 fs in each period.

  5. Broadband energy-efficient optical modulation by hybrid integration of silicon nanophotonics and organic electro-optic polymer

    CERN Document Server

    Zhang, Xingyu; Subbaraman, Harish; Luo, Jingdong; Jen, Alex K -Y; Chung, Chi-jui; Yan, Hai; Pan, Zeyu; Nelson, Robert L; Chen, Ray T

    2015-01-01

    Silicon-organic hybrid integrated devices have emerging applications ranging from high-speed optical interconnects to photonic electromagnetic-field sensors. Silicon slot photonic crystal waveguides (PCWs) filled with electro-optic (EO) polymers combine the slow-light effect in PCWs with the high polarizability of EO polymers, which promises the realization of high-performance optical modulators. In this paper, a broadband, power-efficient, low-dispersion, and compact optical modulator based on an EO polymer filled silicon slot PCW is presented. A small voltage-length product of V{\\pi}*L=0.282Vmm is achieved, corresponding to an unprecedented record-high effective in-device EO coefficient (r33) of 1230pm/V. Assisted by a backside gate voltage, the modulation response up to 50GHz is observed, with a 3-dB bandwidth of 15GHz, and the estimated energy consumption is 94.4fJ/bit at 10Gbit/s. Furthermore, lattice-shifted PCWs are utilized to enhance the optical bandwidth by a factor of ~10X over other modulators bas...

  6. Fabrication of fiber-optic broadband ultrasound emitters by micro-opto-mechanical technology

    Science.gov (United States)

    Belsito, L.; Vannacci, E.; Mancarella, F.; Ferri, M.; Veronese, G. P.; Biagi, E.; Roncaglia, A.

    2014-08-01

    A micro-opto-mechanical system (MOMS) technology for the fabrication of fiber-optic optoacoustic emitters is presented. The described devices are based on the thermoelastic generation of ultrasonic waves from patterned carbon films obtained by the controlled pyrolysis of photoresist layers and fabricated on miniaturized single-crystal silicon frames used to mount the emitters on the tip of an optical fiber. Thanks to the micromachining process adopted, high miniaturization levels are reached in the fabrication of the emitters, and self-standing devices on optical fiber with diameter around 350 µm are demonstrated, potentially suited to minimally invasive medical applications. The functional testing of fiber-optic emitter prototypes in water performed by using a 1064 nm Q-switched Nd-YAG excitation laser source is also presented, yielding broadband emission spectra extended from low frequencies up to more than 40 MHz, and focused emission fields with a maximum peak-to-peak pressure level of about 1.2 MPa at a distance of 1 mm from the devices.

  7. Fabrication of fiber-optic broadband ultrasound emitters by micro-opto-mechanical technology

    International Nuclear Information System (INIS)

    A micro-opto-mechanical system (MOMS) technology for the fabrication of fiber-optic optoacoustic emitters is presented. The described devices are based on the thermoelastic generation of ultrasonic waves from patterned carbon films obtained by the controlled pyrolysis of photoresist layers and fabricated on miniaturized single-crystal silicon frames used to mount the emitters on the tip of an optical fiber. Thanks to the micromachining process adopted, high miniaturization levels are reached in the fabrication of the emitters, and self-standing devices on optical fiber with diameter around 350 µm are demonstrated, potentially suited to minimally invasive medical applications. The functional testing of fiber-optic emitter prototypes in water performed by using a 1064 nm Q-switched Nd-YAG excitation laser source is also presented, yielding broadband emission spectra extended from low frequencies up to more than 40 MHz, and focused emission fields with a maximum peak-to-peak pressure level of about 1.2 MPa at a distance of 1 mm from the devices. (paper)

  8. Broadband Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS – applicability and corrections

    Directory of Open Access Journals (Sweden)

    D. Pöhler

    2009-11-01

    Full Text Available Atmospheric trace gas measurements by cavity assisted long-path absorption spectroscopy are an emerging technology. An interesting approach is the combination of CEAS with broadband light sources, the broadband CEAS (BB-CEAS. BB-CEAS lends itself to the application of the DOAS technique to analyse the derived absorption spectra. While the DOAS approach has enormous advantages in terms of sensitivity and specificity of the measurement, an important implication is the reduction of the light path by the trace gas absorption, since cavity losses due to absorption by gases reduce the quality (Q of the cavity. In fact, at wavelength, where the quality of the BB-CEAS cavity is dominated by the trace gas absorption (especially at very high mirror reflectivity, the average light path will vary nearly inversely with the trace gas concentration and the strength of the band will become only weakly dependent on the trace gas concentration c in the cavity, (the differential optical density being proportional to the logarithm of the trace gas concentration. Only in the limiting case where the mirror reflectivity determines Q at all wavelength, the strength of the band as seen by the CE-DOAS instrument becomes directly proportional to the concentration c. We investigate these relationships in detail and present methods to correct for the cases between the two above extremes, which are of course the important ones in practice.

  9. Ultra-broadband optical parametric generation and simultaneous RGB generation in periodically poled lithium niobate.

    Science.gov (United States)

    Lim, Hwan-Hong; Prakash, Om; Kim, Byeong-Joo; Pandiyan, Krishnamoorthy; Cha, Myoungsik; Rhee, Bum Ku

    2007-12-24

    We report on efficient collinear optical parametric generation (OPG) with gain band ranging from 1400 to 2600 nm in a 2 cm-long periodically poled lithium niobate (PPLN) crystal. Such an ultra-broad gain band was obtained by choosing the pump wavelength at 933 nm, at which the group-velocities of the signal and the idler match near the degeneracy point. High OPG efficiency was obtained by quasi-phase matching (QPM). The ultra-broadband OPG led to efficient collinear RGB generation from a single PPLN crystal at a fixed pump wavelength. The green and red beams were found to be originating from high-order QPM sum-frequency generation between the pump and selected frequencies in the OPG band, while the blue beam was high-order QPM second-harmonic generation of the pump.

  10. Broadband, Polarization-insensitive and Wide-angle Optical Absorber based on Fractal Plasmonics

    CERN Document Server

    Eshaghian, Ali; Chizari, Ata; Mehrany, Khashayar

    2016-01-01

    In this paper, a plasmonic absorber consisting of a metal-dielectric-metal stack with a top layer of Sierpinski nanocarpet is theoretically investigated. Such compact absorber depicts broadband angle-independent behavior over a wide optical wavelength range ($400-700$ nm) and a broad range of angles of light incidence ($0-80^{\\circ}$). Including several feature sizes, such fractal-like structure shows widely strong extinction ($85-99$\\%) response for either transverse electric or magnetic polarization states under normal incidence. Underlying mechanisms of absorbance due to excited surface plasmon modes as well as electric/magnetic dipole resonances are well revealed by investigating electric field, magnetic field and current distributions. The proposed absorber opens a path to realize high-performance ultrathin light trapping devices.

  11. Tuning characteristics of femtosecond optical parametric oscillator with broadband chirped mirrors

    Science.gov (United States)

    Stankevičiūtė, Karolina; Vengris, Mikas; Melnikas, Simas; Kičas, Simonas; Grigonis, Rimantas; Sirutkaitis, Valdas

    2015-12-01

    We present the investigation of a synchronously pumped optical parametric oscillator (SPOPO) based on beta barium borate (BBO) nonlinear crystal with broadband complementary chirped mirror pairs (CMPs). Three SPOPO cavity configurations with slightly different intracavity dispersion were explored. Dispersion properties of cavity mirrors were characterized using a white light interferometer and found to be the key factor determining the gap-free tuning range as well as simultaneous multiwavelength generation. The SPOPO is pumped by the second harmonic of a Yb:KGW oscillator and provides signal pulses tunable over a spectral range from 625 to 980 nm. Signal pulse duration ranges from 102 to 268 fs in various intracavity dispersion regimes. In addition, signal beam power in excess of 500 mW is demonstrated, corresponding to 27% conversion efficiency from pump to signal wave.

  12. Broadband optical absorbance spectroscopy using a whispering gallery mode microsphere resonator

    Science.gov (United States)

    Westcott, Sarah L.; Zhang, Jiangquan; Shelton, Robert K.; Bruce, Nellie M. K.; Gupta, Sachin; Keen, Steven L.; Tillman, Jeremy W.; Wald, Lara B.; Strecker, Brian N.; Rosenberger, A. T.; Davidson, Roy R.; Chen, Wei; Donovan, Kevin G.; Hryniewicz, John V.

    2008-03-01

    We demonstrate the ability to excite and monitor many whispering gallery modes (WGMs) of a microsphere resonator simultaneously in order to make broadband optical absorbance measurements. The 340μm diameter microsphere is placed in a microfluidic channel. A hemispherical prism is used for coupling the WGMs into and out of the microsphere. The flat surface of the prism seals the microfluidic channel. The slight nonsphericity in the microsphere results in coupling to precessed modes whose emission is spatially separated from the reflected excitation light. The evanescent fields of the light trapped in WGMs interact with the surrounding environment. The change in transmission observed in the precessed modes is used to determine the absorbance of the surrounding environment. In contrast to our broadband optical absorbance measurements, previous WGM sensors have used only a single narrow mode to measure properties such as refractive index. With the microfluidic cell, we have measured the absorbance of solutions of dyes (lissamine green B, sunset yellow, orange G, and methylene blue), aromatic molecules (benzylamine and benzoic acid), and biological molecules (tryptophan, phenylalanine, tyrosine, and o-phospho-L-tyrosine) at visible and ultraviolet wavelengths. The microsphere surface was reacted with organosilane molecules to attach octadecyl groups, amino groups, and fluorogroups to the surface. Both electrostatic and hydrophobic interactions were observed between the analytes and the microsphere surface, as indicated by changes in the measured effective pathlength with different organosilanes. For a given analyte and coated microsphere, the pathlength measurement was repeatable within a few percent. Methylene blue dye had a very strong interaction with the surface and pathlengths of several centimeters were measured. Choosing an appropriate surface coating to interact with a specific analyte should result in the highest sensitivity detection.

  13. Efficient and broadband optical parametric four wave mixing in chalcogenide-PMMA hybrid microwires

    CERN Document Server

    Ahmad, Raja

    2012-01-01

    The recent development of devices based on novel nonlinear materials like chalcogenides (ChGs), silicon (Si) and other semi-conductors has revolutionized the field of nonlinear photonics [1,2,3]. Among the nonlinear effects observed in these materials, four-wave mixing (FWM) is the process that finds the most applications including wavelength conversion [4], optical regeneration [5,6], optical delay [7], time-domain demultiplexing[8], temporal cloaking[9] and negative refraction[10]. Although FWM has been observed in several media including chalcogenides [11,12,13,14], silicon[15, 16], bismuth [17] and silica [18,19], there is a continued quest for devices that realize efficient and broadband FWM while offering compactness, low-power consumption and compatibility with optical fibers. Here, we demonstrate the fabrication of 10 cm long polymer cladded chalcogenide (As2Se3) microwires to realize FWM-led sub watt threshold (70-370 mW) wavelength conversion with a 12 dB bandwidth as broad as 190 nm, and conversion...

  14. A linear coherent integrated receiver based on a broadband optical phase-locked loop

    Science.gov (United States)

    Ramaswamy, Anand

    Optical Phase-Locked Loops (OPLL) have diverse applications in future communication systems. They can be used in high sensitivity homodyne phase-shift keying receivers for phase noise reduction, provided sufficient loop bandwidth is maintained. Alternative phase-locked loop applications include coherent synchronization of laser arrays and frequency synthesis by offset locking. In this work, a broadband OPLL based coherent receiver is used for linear phase demodulation. Phase modulated (PM) analog optical links have the potential to outperform conventional direct detection links. However, their progress has been stymied by the lack of a linear phase demodulator. We describe how feedback can be used to suppress non-linearities arising from the phase demodulation process. The receiver concept is demonstrated at low frequencies and is found to improve the Spurious Free Dynamic Range (SFDR) of an experimental analog link by over 20dB. In order to extend the operation of the receiver to microwave frequencies, latencies arising from physical delays in the feedback path need to be dramatically reduced. To facilitate this, monolithic and hybrid versions of the receiver based on compact integration of InP photonic integrated circuits (PIC) with InP and SiGe electronic integrated circuits (EIC) have been developed at UCSB. In this work, we develop novel measurement techniques to characterize the linearity of the individual components of the PIC, namely, the semiconductor photodiodes and optical phase modulators. We then demonstrate the operation of the receiver in a high power analog link. The OPLL based receiver has a bandwidth of 1.5GHz. The link gain and shot-noise limited SFDR at 300MHz are -2dB and 125dB-Hz2/3, respectively. Further, optical sampling downconversion is demonstrated as a viable technique to increase the operating frequency of the receiver beyond the baseband range.

  15. Ultra-broadband light source for optical coherence tomography by fiber matching

    Science.gov (United States)

    Wang, Zhaoying; Zhang, Lei

    2009-11-01

    In this paper, an ultra-broadband all fiber light source for optical coherence tomography was obtained. This light source was obtained by supercontinuum (SC) generated in matched fibers with different characteristics. It was showed that the spectrum quality was affected by dispersion and nonlinear characteristics of the fiber pumped firstly. SC spectrum flatness on the short wavelength side of pumping wavelength was affected by characteristic of the fiber pumped secondly. Dispersion shifted fiber (DSF) was connected after highly nonlinear fiber (HNLF) to optimize spectral shape. Widely broadened SC spectrum was generated in the combination of 120m HNLF+4.5km DSF+2km single mode fiber (SMF) with 55 mW average pump power. 140.6nm 3 dB bandwidth spectrum on the short wavelength was obtained. About 4.1 μm longitudinal resolution could be obtained theoretically around ~1300nm by using this SC spectrum as the light source of optical coherence tomography system. A Fourier-domain OCT (FD-OCT) system was set up by using this light source. Dielectric film plane mirror, a three-layer microscope cover glass with 160 μm thick and onion scarfskin were used as test sample and their depth signal at one point was obtained respectively.

  16. Inexpensive diffuse reflectance spectroscopy system for measuring changes in tissue optical properties

    Science.gov (United States)

    Glennie, Diana L.; Hayward, Joseph E.; McKee, Daniel E.; Farrell, Thomas J.

    2014-10-01

    The measurement of changes in blood volume in tissue is important for monitoring the effects of a wide range of therapeutic interventions, from radiation therapy to skin-flap transplants. Many systems available for purchase are either expensive or difficult to use, limiting their utility in the clinical setting. A low-cost system, capable of measuring changes in tissue blood volume via diffuse reflectance spectroscopy is presented. The system consists of an integrating sphere coupled via optical fibers to a broadband light source and a spectrometer. Validation data are presented to illustrate the accuracy and reproducibility of the system. The validity and utility of this in vivo system were demonstrated in a skin blanching/reddening experiment using epinephrine and lidocaine, and in a study measuring the severity of radiation-induced erythema during radiation therapy.

  17. Image reconstruction in diffuse optical tomography using the coupled radiative transport-diffusion model

    International Nuclear Information System (INIS)

    The coupled radiative transport-diffusion model can be used as light transport model in situations in which the diffusion equation is not a valid approximation everywhere in the domain. In the coupled model, light propagation is modelled with the radiative transport equation in sub-domains in which the approximations of the diffusion equation are not valid, such as within low-scattering regions, and the diffusion approximation is used elsewhere in the domain. In this paper, an image reconstruction method for diffuse optical tomography based on using the coupled radiative transport-diffusion model is developed. In the approach, absorption and scattering distributions are estimated by minimising a regularised least-squares error between the measured data and solution of the coupled model. The approach is tested with simulations. Reconstructions from different cases including domains with low-scattering regions are shown. The results show that the coupled radiative transport-diffusion model can be utilised in image reconstruction problem of diffuse optical tomography and that it produces as good quality reconstructions as the full radiative transport equation also in the presence of low-scattering regions.

  18. Fiber-bundle microendoscopy with sub-diffuse reflectance spectroscopy and intensity mapping for multimodal optical biopsy of stratified epithelium.

    Science.gov (United States)

    Greening, Gage J; James, Haley M; Powless, Amy J; Hutcheson, Joshua A; Dierks, Mary K; Rajaram, Narasimhan; Muldoon, Timothy J

    2015-12-01

    Early detection of structural or functional changes in dysplastic epithelia may be crucial for improving long-term patient care. Recent work has explored myriad non-invasive or minimally invasive "optical biopsy" techniques for diagnosing early dysplasia, such as high-resolution microendoscopy, a method to resolve sub-cellular features of apical epithelia, as well as broadband sub-diffuse reflectance spectroscopy, a method that evaluates bulk health of a small volume of tissue. We present a multimodal fiber-based microendoscopy technique that combines high-resolution microendoscopy, broadband (450-750 nm) sub-diffuse reflectance spectroscopy (sDRS) at two discrete source-detector separations (374 and 730 μm), and sub-diffuse reflectance intensity mapping (sDRIM) using a 635 nm laser. Spatial resolution, magnification, field-of-view, and sampling frequency were determined. Additionally, the ability of the sDRS modality to extract optical properties over a range of depths is reported. Following this, proof-of-concept experiments were performed on tissue-simulating phantoms made with poly(dimethysiloxane) as a substrate material with cultured MDA-MB-468 cells. Then, all modalities were demonstrated on a human melanocytic nevus from a healthy volunteer and on resected colonic tissue from a murine model. Qualitative in vivo image data is correlated with reduced scattering and absorption coefficients.

  19. 3-D Model of Broadband Emission from Supernova Remnants Undergoing Non-linear Diffusive Shock Acceleration

    CERN Document Server

    Lee, Shiu-Hang; Ellison, Donald C

    2008-01-01

    We present a 3-dimensional model of supernova remnants (SNRs) where the hydrodynamical evolution of the remnant is modeled consistently with nonlinear diffusive shock acceleration occuring at the outer blast wave. The model includes particle escape and diffusion outside of the forward shock, and particle interactions with arbitrary distributions of external ambient material, such as molecular clouds. We include synchrotron emission and cooling, bremsstrahlung radiation, neutral pion production, inverse-Compton (IC), and Coulomb energy-loss. Boardband spectra have been calculated for typical parameters including dense regions of gas external to a 1000 year old SNR. In this paper, we describe the details of our model but do not attempt a detailed fit to any specific remnant. We also do not include magnetic field amplification (MFA), even though this effect may be important in some young remnants. In this first presentation of the model we don't attempt a detailed fit to any specific remnant. Our aim is to devel...

  20. Spectral Properties of Erbium-Doped Oxyfluoride Silicate Glasses for Broadband Optical Amplifiers

    Institute of Scientific and Technical Information of China (English)

    徐时清; 杨中民; 戴世勋; 杨建虎; 温磊; 胡丽丽; 姜中宏

    2003-01-01

    The new oxyfluoride silicate glasses of Er3+-doped 50SiO2-(50-x)PbO-xPbF2 were prepared. With increasing PbF2 content in the glass composition, the fluorescence full width at half maximum and lifetimes of the 4I13/2level of Er3+ increase, while the refractive indices and densities decrease. Er3+-doped 50SiO2-50PbF2 glass showed broad fluorescence spectra of 1.55μm with a large stimulated emission cross-section and long lifetimes of 4I13/2level of Er3+. Compared with other glass hosts, the gain bandwidth properties of Er3+-doped 50SiO2-50PbF2glass are close to those of tellurite and bismuth glasses, and have advantages over those of silicate, phosphate and germante glasses. The broad and flat 4I13/2 → 4I15/2 emission of Er3+ around 1.55μm can be used as host material for potential broadband optical amplifier in wavelength-division-multiplexing network system.

  1. Toward a Broadband Astro-comb: Effects of Nonlinear Spectral Broadening in Optical Fibers

    CERN Document Server

    Chang, Guoqing; Phillips, David F; Walsworth, Ronald L; Kärtner, Franz X

    2010-01-01

    We propose and analyze a new approach to generate a broadband astro-comb by spectral broadening of a narrowband astro-comb inside a highly nonlinear optical fiber. Numerical modeling shows that cascaded four-wave-mixing dramatically degrades the input comb's side-mode suppression and causes side-mode amplitude asymmetry. These two detrimental effects can systematically shift the center-of-gravity of astro-comb spectral lines as measured by an astrophysical spectrograph with resolution \\approx100,000; and thus lead to wavelength calibration inaccuracy and instability. Our simulations indicate that this performance penalty, as a result of nonlinear spectral broadening, can be compensated by using a filtering cavity configured for double-pass. As an explicit example, we present a design based on an Yb-fiber source comb (with 1 GHz repetition rate) that is filtered by double-passing through a low finesse cavity (finesse = 208), and subsequent spectrally broadened in a 2-cm, SF6-glass photonic crystal fiber. Spann...

  2. Compact dual-crystal optical parametric amplification for broadband IR pulse generation using a collinear geometry.

    Science.gov (United States)

    Hong, Zuofei; Zhang, Qingbin; Lu, Peixiang

    2013-04-22

    A novel compact dual-crystal optical parametric amplification (DOPA) scheme, collinearly pumped by a Ti:sapphire laser (0.8 μm), is theoretically investigated for efficiently generating broadband IR pulses at non-degenerate wavelengths (1.2 μm~1.4 μm and 1.8 μm~2.1 μm). By inserting a pair of barium fluoride (BaF(2)) wedges between two thin β-barium borate (BBO) crystals, the group velocity mismatch (GVM) between the three interacting pulses can be compensated simultaneously. In this case, the obtained signal spectrum centered at 1.3 μm is nearly 20% broader and the conversion efficiency is increased, but also the pulse contrast and beam quality are improved due to the better temporal overlap. Furthermore, sub-two-cycle idler pulses with carrier-envelope phase (CEP) fluctuation of sub-100-mrad root mean square (RMS) can be generated. Because a tunable few-cycle IR pulse with millijoule energy is attainable in this scheme, it will contribute to ultrafast community and be particularly useful as a driving or controlling field for the generation of ultrafast coherent x-ray supercontinuum.

  3. Compact dual-crystal optical parametric amplification for broadband IR pulse generation using a collinear geometry.

    Science.gov (United States)

    Hong, Zuofei; Zhang, Qingbin; Lu, Peixiang

    2013-04-22

    A novel compact dual-crystal optical parametric amplification (DOPA) scheme, collinearly pumped by a Ti:sapphire laser (0.8 μm), is theoretically investigated for efficiently generating broadband IR pulses at non-degenerate wavelengths (1.2 μm~1.4 μm and 1.8 μm~2.1 μm). By inserting a pair of barium fluoride (BaF(2)) wedges between two thin β-barium borate (BBO) crystals, the group velocity mismatch (GVM) between the three interacting pulses can be compensated simultaneously. In this case, the obtained signal spectrum centered at 1.3 μm is nearly 20% broader and the conversion efficiency is increased, but also the pulse contrast and beam quality are improved due to the better temporal overlap. Furthermore, sub-two-cycle idler pulses with carrier-envelope phase (CEP) fluctuation of sub-100-mrad root mean square (RMS) can be generated. Because a tunable few-cycle IR pulse with millijoule energy is attainable in this scheme, it will contribute to ultrafast community and be particularly useful as a driving or controlling field for the generation of ultrafast coherent x-ray supercontinuum. PMID:23609660

  4. Continuous Vernier filtering of an optical frequency comb for broadband cavity-enhanced molecular spectroscopy

    CERN Document Server

    Rutkowski, Lucile

    2016-01-01

    We have recently introduced the Vernier-based Direct Frequency Comb Cavity-Enhanced Spectroscopy technique and we present the corresponding formalism for quantitative broadband spectroscopy. We achieve high sensitivity and broadband performance by acquiring spectra covering more than 2000 cm$^{-1}$ around 12600 cm$^{-1}$ (800 nm), resolving the 3$\

  5. Characterization of Fresnel lens optical performances using an opal diffuser

    Energy Technology Data Exchange (ETDEWEB)

    Chemisana, Daniel [University of Lleida, c/ Pere de Cabrera s/n, 25001 Lleida (Spain); Vossier, Alexis; Pujol, Loic; Perona, Arnaud; Dollet, Alain [PROMES CNRS, Avenue Felix Trombe, 66120 Odeillo (France)

    2011-01-15

    An experimental procedure based on the use of a Lambertian diffuser is described, which allows the characterization of Fresnel lenses in the field or the laboratory, whatever their characteristics. Lambertian reflectors have already been successfully used in combination with CCD cameras for the optical characterization of solar concentrators (mainly reflective mirrors). The procedure used in this work for characterizing Fresnel lenses is based on the use of a CCD camera taking pictures of the light intensity profile through an opal diffuser which operates like a Lambertian source placed at the focus of the optical concentrator; it also requires power and light spectrum measurements. Key optical characteristics such as optical efficiency, lens transmittance spectrum and concentration ratio profile in the focal area have been obtained for a linear and a point-focus Fresnel lens. (author)

  6. Highly Linear, Broadband Optical Modulator Based on Electro-optic Polymer

    CERN Document Server

    Zhang, Xingyu; Lin, Che-yun; Wang, Alan X; Hosseini, Amir; Chen, Ray T

    2014-01-01

    In this paper, we present the design, fabrication and characterization of a traveling wave directional coupler modulator based on electro-optic polymer, which is able to provide both high linearity and broad bandwidth. The high linearity is realized by introducing domain-inversion technique in the two-domain directional coupler. A travelling wave electrode is designed to function with bandwidth-length product of 302GHz cm, by achieving low microwave loss, excellent impedance matching and velocity matching, as well as smooth electric field profile transformation. The 3-dB bandwidth of the device is measured to be 10GHz. The spurious free dynamic range of about 110dB Hz^(2/3) is measured over the modulation frequency range 2-8GHz. To the best of our knowledge, such high linearity is first measured at the frequency up to 8GHz. In addition, a 1-to-2 multi-mode interference 3dB-splitter, a photobleached refractive index taper and a quasi-vertical taper are used to reduce the optical insertion loss of the device.

  7. Numerical modelling and image reconstruction in diffuse optical tomography

    OpenAIRE

    Dehghani, Hamid; Srinivasan, Subhadra; Pogue, Brian W.; Gibson, Adam

    2009-01-01

    The development of diffuse optical tomography as a functional imaging modality has relied largely on the use of model-based image reconstruction. The recovery of optical parameters from boundary measurements of light propagation within tissue is inherently a difficult one, because the problem is nonlinear, ill-posed and ill-conditioned. Additionally, although the measured near-infrared signals of light transmission through tissue provide high imaging contrast, the reconstructed images suffer ...

  8. In Vivo Diffuse Optical Tomography and Fluorescence Molecular Tomography

    Directory of Open Access Journals (Sweden)

    Mingze Li

    2010-01-01

    Full Text Available Diffuse optical tomography (DOT and fluorescence molecular tomography (FMT are two attractive imaging techniques for in vivo physiological and psychological research. They have distinct advantages such as non-invasiveness, non-ionizing radiation, high sensitivity and longitudinal monitoring. This paper reviews the key components of DOT and FMT. Light propagation model, mathematical reconstruction algorithm, imaging instrumentation and medical applications are included. Future challenges and perspective on optical tomography are discussed.

  9. Broadband optical parametric amplifier formed by two pairs of adjacent four-wave mixing sidebands in a tellurite microstructured optical fibre

    Science.gov (United States)

    Zhang, Lei; Tuan, Tong-Hoang; Kawamura, Harutaka; Nagasaka, Kenshiro; Suzuki, Takenobu; Ohishi, Yasutake

    2016-05-01

    A broadband fibre-optical parametric amplifier (FOPA) operating at a novel wavelength region that is far from the pump wavelength has been demonstrated by exploiting two pairs of adjacent four-wave mixing (FWM) sidebands generated simultaneously in a tellurite microstructured optical fibre (TMOF). Owing to the large nonlinearity of the TMOF and the high pump peak power provided by a picosecond laser, a maximal average gain of 65.1 dB has been obtained. When the FOPA is operated in a saturated state, a flat-gain amplification from 1424 nm to 1459 nm can be achieved. This broadband and high-gain FOPA operating at new wavelength regions far from the pump offers the prospect of all-optical signal processing.

  10. Integrated diffuse optical tomography and photoacoustic tomography: phantom validations

    OpenAIRE

    Li, Xiaoqi; Xi, Lei; Jiang, Ruixin; Yao, Lei; Jiang, Huabei

    2011-01-01

    We designed, fabricated and tested a novel imaging system that fuses diffuse optical tomography (DOT) and photoacoustic tomography (PAT) in a single platform. This platform takes advantages of both DOT and PAT, and can potentially provide dual-modality two dimensional functional and cellular images of the breast quantitatively. Here we describe this integrated platform along with initial tissue phantom validations.

  11. Light scattering and optical diffusion from willemite spherulites

    Science.gov (United States)

    Knowles, Kevin M.; Butt, Haider; Batal, Afif; Sabouri, Aydin; Anthony, Carl J.

    2016-02-01

    Willemite is a zinc silicate mineral used in modern day pottery as a decorative feature within glazes. It is produced by controlled heat treatment of zinc oxide-containing ceramic glazes. The heat-treated glazes devitrify, producing thin nanoscale needle-like willemite crystals growing in spherulitic morphologies through branching of the needles. We show here that this resulting morphology of willemite crystals in an inorganic glass matrix has a previously unreported strong interaction with light, displaying remarkable optical diffraction patterns. Thin sections of such spherulites act as optical diffusers, enabling light beams to be spread up to 160° in width. Analysis of the interaction between the willemite spherulites and light suggests that the high density of willemite crystals in the spherulites and the length scales associated with both the thickness of the needles and the spacings between branches are together responsible for this optical diffusion behaviour.

  12. Novel alkaline-free Er3+-doped fluorophosphate glasses for broadband optical fiber lasers and amplifiers

    International Nuclear Information System (INIS)

    Two sets of Er3+-doped alkaline-free glass systems, MgF2-BaF2-Ba(PO3)2-Al(PO3)3 (MBBA) and Bi(PO3)3-Ba(PO3)2-BaF2-MgF2 (BBBM), have been prepared and investigated with the aim of using them as active media. Radiative lifetimes (τrad) and branching ratios (β) have been obtained for the excited states of Er3+. The absorption spectra were recorded to obtain the intensity parameters (Ωt) which are found to be Ω2 = 4.47 x 10-20 cm2, Ω4 = 1.31 x 10-20 cm2, Ω6 = 0.81 x 10-20 cm2 for the MBBA system and Ω2 = 4.03 x 10-20 cm2, Ω4 = 1.34 x 10-20 cm2, Ω6 = 0.53 x 10-20 for the BBBM system, respectively. The emission cross-section for the 4I13/2 → 4I15/2 transition is determined by the Fuchtbauer-Ladenburg method and found to be 2.35 x 10-20 cm2 and 3.54 x 10-20 cm2 for the MBBA and BBBM system, respectively. Comparison of the measured values to those of Er3+ transitions in other glass hosts suggests that our new glass systems are good candidates for broadband compact optical fiber and waveguide amplifier applications

  13. Service Class Resource Management For Green Wireless-Optical Broadband Access NetworksWOBAN

    OpenAIRE

    Sruthy, S.; SUMI CHITRA K.A

    2015-01-01

    Abstract-Broadband access networks have become an essential part of worldwide communication systems because of the exponential growth of broadband services such as video on demand high definition TV internet protocol TV and video conferencing. Exponential growth in the volume of wireless data boosted by the growing popularity of mobile devices such as smartphone and tablets has forced the telecommunication industries to rethink the way networks are currently designed and to focus on the devel...

  14. Broadband Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) – applicability and corrections

    OpenAIRE

    U. Platt; J. Meinen; D. Pöhler; T. Leisner

    2008-01-01

    Atmospheric trace gas measurements by cavity assisted long-path absorption spectroscopy are an emerging technology. An interesting approach is the combination of CEAS with broadband light sources, the broadband CEAS (BB-CEAS). BB-CEAS lends itself to the application of the DOAS technique to analyse the derived absorption spectra. While the DOAS approach has enormous advantages in terms of sensitivity and specificity of the measurement, an important implication is the reduction of the light pa...

  15. Broadband and tunable optical parametric generator for remote detection of gas molecules in the short and mid-infrared.

    Science.gov (United States)

    Lambert-Girard, Simon; Allard, Martin; Piché, Michel; Babin, François

    2015-04-01

    The development of a novel broadband and tunable optical parametric generator (OPG) is presented. The OPG properties are studied numerically and experimentally in order to optimize the generator's use in a broadband spectroscopic LIDAR operating in the short and mid-infrared. This paper discusses trade-offs to be made on the properties of the pump, crystal, and seeding signal in order to optimize the pulse spectral density and divergence while enabling energy scaling. A seed with a large spectral bandwidth is shown to enhance the pulse-to-pulse stability and optimize the pulse spectral density. A numerical model shows excellent agreement with output power measurements; the model predicts that a pump having a large number of longitudinal modes improves conversion efficiency and pulse stability. PMID:25967164

  16. Broadband and tunable optical parametric generator for remote detection of gas molecules in the short and mid-infrared.

    Science.gov (United States)

    Lambert-Girard, Simon; Allard, Martin; Piché, Michel; Babin, François

    2015-04-01

    The development of a novel broadband and tunable optical parametric generator (OPG) is presented. The OPG properties are studied numerically and experimentally in order to optimize the generator's use in a broadband spectroscopic LIDAR operating in the short and mid-infrared. This paper discusses trade-offs to be made on the properties of the pump, crystal, and seeding signal in order to optimize the pulse spectral density and divergence while enabling energy scaling. A seed with a large spectral bandwidth is shown to enhance the pulse-to-pulse stability and optimize the pulse spectral density. A numerical model shows excellent agreement with output power measurements; the model predicts that a pump having a large number of longitudinal modes improves conversion efficiency and pulse stability.

  17. Diffusion MR Imaging of Postoperative Bilateral Acute Ischemic Optic Neuropathy

    Energy Technology Data Exchange (ETDEWEB)

    Kannan, Anusha; Srinivasan, Sivasubramanian [Khoo Teck Puat Hospital, Singapore (Singapore)

    2012-09-15

    We read with great interest, the case report on ischemic optic neuropathy (1). We would like to add a few points concerning the blood supply of the optic nerve and the correlation with the development of post-operative ischemic neuropathy. Actually, the perioperative or post-operative vision loss (postoperative ischemic neuropathy) is most likely due to ischemic optic neuropathy. Ischemic optic neuropathy (2) is classified as an anterior ischemic optic neuropathy (AION) and posterior ischemic optic neuropathy (PION). This classification is based on the fact that blood supply (2) to the anterior segment of the optic nerve (part of the optic nerve in the scleral canal and the optic disc) is supplied by short posterior ciliary vessels or anastamotic ring branches around the optic nerve. The posterior part of the optic canal is relatively less perfused, and is supplied by ophthalmic artery and central fibres are perfused by a central retinal artery. So, in the post-operative period, the posterior part of the optic nerve is more vulnerable for ischemia, especially, after major surgeries (3), one of the theories being hypotension or anaemia (2) and resultant decreased perfusion. The onset of PION is slower than the anterior ischemic optic neuropathy. AION on the other hand, is usually spontaneous (idiopathic) or due to arteritis, and is usually sudden in its onset. The reported case is most likely a case of PION. The role of imaging, especially the diffusion weighted magnetic resonance imaging, is very important because the ophthalmoscopic findings in early stages of PION is normal, and it may delay the diagnosis. On the other hand, edema of the disc is usually seen in the early stages of AION.

  18. Femtosecond writing of near-surface waveguides in lithium niobate for low-loss electro-optical modulators of broadband emission

    Science.gov (United States)

    Bukharin, Mikhail A.; Skryabin, Nikolay N.; Khudyakov, Dmitriy V.; Vartapetov, Sergey K.

    2016-05-01

    In the investigation we demonstrated technique of direct femtosecond laser writing of tracks with induced refractive index at record low depth under surface of lithium niobate (3-15 μm). It was shown that with the help of proposed technique one can be written claddings of near surface optical waveguides that plays a key role in fabrication of fast electro-optical modulators with low operating voltage. Fundamental problem resolved in the investigation consists in suppression of negative factors impeding femtosecond inscription of waveguides at low depths. To prevent optical breakdown of crystal surface we used high numerical aperture objectives for focusing of light. It was shown, that advanced heat accumulation regime of femtosecond inscription is inapplicable for writing of near-surface waveguides, and near the surface waveguides should be written in non-thermal regime in contrast to widespread femtosecond writing at depths of tens micrometers. Inscribed waveguides were examined for optical losses and polarization properties. It was experimentally shown, that femtosecond written near surface waveguides have such advantages over widely used proton exchanged and Ti-diffusion waveguides as lower optical losses (down to 0.3 dB/cm) and maintaining of all polarization states of propagation light, which is crucial for development of electro-optical modulators for broadband and ultrashort laser emission. Novelty of the results consists in technique of femtosecond inscription of waveguides at record low depths under the surface of crystals. As compared to previous investigations in the field (structures at depths near 50 um with buried electrodes), the obtained waveguides could be used with simple closely adjacent on-surface electrodes.

  19. Narrow linewidth broadband tunable semiconductor laser at 840 nm with dual acousto-optic tunable configuration for OCT applications

    Science.gov (United States)

    Chamorovskiy, Alexander; Shramenko, Mikhail V.; Lobintsov, Andrei A.; Yakubovich, Sergei D.

    2016-03-01

    We demonstrate a tunable narrow linewidth semiconductor laser for the 840 nm spectral range. The laser has a linear cavity comprised of polarization maintaining (PM) fiber. A broadband semiconductor optical amplifier (SOA) in in-line fiber-coupled configuration acts as a gain element. It is based on InGaAs quantum-well (QW) active layer. SOA allows for tuning bandwidth exceeding 25 nm around 840 nm. Small-signal fiber-to-fiber gain of SOA is around 30 dB. A pair of acousto-optic tunable filters (AOTF) with a quasi-collinear interaction of optical and acoustic waves are utilized as spectrally selective elements. AOTF technology benefits in continuous tuning, broadband operation, excellent reproducibility and stability of the signal, as well as a high accuracy of wavelength selectivity due to the absence of mechanically moving components. A single AOTF configuration has typical linewidth in 0.05-0.15 nm range due to a frequency shift obtained during each roundtrip. A sequential AOTF arrangement enables instantaneous linewidth generation of power is in the range of 1 mW. While the majority of commercial tunable sources operate in 1060-1550 nm spectral ranges, the 840 nm spectral range is beneficial for optical coherence tomography (OCT). The developed narrow linewidth laser can be relevant for OCT with extended imaging depth, as well as spectroscopy, non-destructive testing and other applications.

  20. Broadband optical mammography instrument for depth-resolved imaging and local dynamic measurements

    Science.gov (United States)

    Krishnamurthy, Nishanth; Kainerstorfer, Jana M.; Sassaroli, Angelo; Anderson, Pamela G.; Fantini, Sergio

    2016-02-01

    We present a continuous-wave instrument for non-invasive diffuse optical imaging of the breast in a parallel-plate transmission geometry. The instrument measures continuous spectra in the wavelength range 650-1000 nm, with an intensity noise level <1.5% and a spatial sampling rate of 5 points/cm in the x- and y-directions. We collect the optical transmission at four locations, one collinear and three offset with respect to the illumination optical fiber, to recover the depth of optical inhomogeneities in the tissue. We imaged a tissue-like, breast shaped, silicone phantom (6 cm thick) with two embedded absorbing structures: a black circle (1.7 cm in diameter) and a black stripe (3 mm wide), designed to mimic a tumor and a blood vessel, respectively. The use of a spatially multiplexed detection scheme allows for the generation of on-axis and off-axis projection images simultaneously, as opposed to requiring multiple scans, thus decreasing scan-time and motion artifacts. This technique localizes detected inhomogeneities in 3D and accurately assigns their depth to within 1 mm in the ideal conditions of otherwise homogeneous tissue-like phantoms. We also measured induced hemodynamic changes in the breast of a healthy human subject at a selected location (no scanning). We applied a cyclic, arterial blood pressure perturbation by alternating inflation (to a pressure of 200 mmHg) and deflation of a pneumatic cuff around the subject's thigh at a frequency of 0.05 Hz, and measured oscillations with amplitudes up to 1 μM and 0.2 μM in the tissue concentrations of oxyhemoglobin and deoxyhemoglobin, respectively. These hemodynamic oscillations provide information about the vascular structure and functional integrity in tissue, and may be used to assess healthy or abnormal perfusion in a clinical setting.

  1. Ex vivo laser lipolysis assisted with radially diffusing optical applicator

    Science.gov (United States)

    Hwang, Jieun; Hau, Nguyen Trung; Park, Sung Yeon; Rhee, Yun-Hee; Ahn, Jin-Chul; Kang, Hyun Wook

    2016-05-01

    Laser-assisted lipolysis has been implemented to reduce body fat in light of thermal interactions with adipose tissue. However, using a flat fiber with high irradiance often needs rapid cannula movements and even undesirable thermal injury due to direct tissue contact. The aim of the current study was to explore the feasibility of a radially diffusing optical applicator to liquefy the adipose tissue for effective laser lipolysis. The proposed diffuser was evaluated with a flat fiber in terms of temperature elevation and tissue liquefaction after laser lipolysis with a 980-nm wavelength. Given the same power (20 W), the diffusing applicator generated a 30% slower temperature increase with a 25% lower maximum temperature (84±3.2°C in 1 min ptissue, compared with the flat fiber. Under the equivalent temperature development, the diffuser induced up to fivefold larger area of the adipose liquefaction due to radial light emission than the flat fiber. Ex vivo tissue tests for 5-min irradiation demonstrated that the diffuser (1.24±0.15 g) liquefied 66% more adipose tissue than the flat fiber (0.75±0.05 g). The proposed diffusing applicator can be a feasible therapeutic device for laser lipolysis due to low temperature development and wide coverage of thermal treatment.

  2. Fiber-integrated single photon source of high efficiency based on a concept of ultra-broadband optical antenna

    CERN Document Server

    Grosjean, T; Burr, G W; Baida, F I

    2016-01-01

    We theoretically demonstrate a fiber-integrated single photon source of unprecedented efficiency. This fiber single photon source is achieved by coupling optically a single quantum emitter to a monomode optical fiber with a new concept of ultra-broadband optical antenna. Such an optical antenna concept is the result of the transposition to optical frequencies of the well-known low-frequency horn antenna The optical horn antenna is here shown to be capable of directing the radiation from the emitter toward the optical fiber and efficiently phase-matching the photon emission with the fiber mode. Numerical results show that an optical horn antenna can funnel up to 85% of the radiation from a dipolar source within an emission cone semi-angle as small as 7 degrees (antenna directivity of 300). It is also shown that 50% of the emitted power from the dipolar source can be collected and coupled to an SMF-28 fiber mode over spectral ranges larger than 1000 nm, with a maximum energy transfer reaching 70 %. This approac...

  3. Anatomical Atlas-Guided Diffuse Optical Tomography of Brain Activation

    OpenAIRE

    Custo, Anna; Boas, David A.; Tsuzuki, Daisuke; Dan, Ippeita; Mesquita, Rickson; Fischl, Bruce; Grimson, W. Eric L.; Wells, Williams

    2009-01-01

    We describe a neuro imaging protocol that utilizes an anatomical atlas of the human head to guide Diffuse optical tomography of human brain activation. The protocol is demonstrated by imaging the hemodynamic response to median nerve stimulation in three healthy subjects, and comparing the images obtained using a head atlas with the images obtained using the subject-specific head anatomy. The results indicate that using the head atlas anatomy it is possible to reconstruct the location of the b...

  4. Nonquadratic penalization improves near-infrared diffuse optical tomography

    OpenAIRE

    Jagannath, Ravi Prasad K; Yalavarthy, Phaneendra K

    2013-01-01

    A new approach that can easily incorporate any generic penalty function into the diffuse optical tomographic image reconstruction is introduced to show the utility of nonquadratic penalty functions. The penalty functions that were used include quadratic (l(2)), absolute (l(1)), Cauchy, and Geman-McClure. The regularization parameter in each of these cases was obtained automatically by using the generalized cross-validation method. The reconstruction results were systematically compared with e...

  5. Dynamic diffuse optical tomography imaging of peripheral arterial disease

    OpenAIRE

    Khalil, Michael A.; Kim, Hyun K.; Kim, In-Kyong; Flexman, Molly; Dayal, Rajeev; Shrikhande, Gautam; Hielscher, Andreas H.

    2012-01-01

    Peripheral arterial disease (PAD) is the narrowing of arteries due to plaque accumulation in the vascular walls. This leads to insufficient blood supply to the extremities and can ultimately cause cell death. Currently available methods are ineffective in diagnosing PAD in patients with calcified arteries, such as those with diabetes. In this paper we investigate the potential of dynamic diffuse optical tomography (DDOT) as an alternative way to assess PAD in the lower extremities. DDOT is a ...

  6. Time-domain diffuse optics: towards next generation devices

    Science.gov (United States)

    Contini, Davide; Dalla Mora, Alberto; Arridge, Simon; Martelli, Fabrizio; Tosi, Alberto; Boso, Gianluca; Farina, Andrea; Durduran, Turgut; Martinenghi, Edoardo; Torricelli, Alessandro; Pifferi, Antonio

    2015-07-01

    Diffuse optics is a powerful tool for clinical applications ranging from oncology to neurology, but also for molecular imaging, and quality assessment of food, wood and pharmaceuticals. We show that ideally time-domain diffuse optics can give higher contrast and a higher penetration depth with respect to standard technology. In order to completely exploit the advantages of a time-domain system a distribution of sources and detectors with fast gating capabilities covering all the sample surface is needed. Here, we present the building block to build up such system. This basic component is made of a miniaturised source-detector pair embedded into the probe based on pulsed Vertical-Cavity Surface-Emitting Lasers (VCSEL) as sources and Single-Photon Avalanche Diodes (SPAD) or Silicon Photomultipliers (SiPM) as detectors. The possibility to miniaturized and dramatically increase the number of source detectors pairs open the way to an advancement of diffuse optics in terms of improvement of performances and exploration of new applications. Furthermore, availability of compact devices with reduction in size and cost can boost the application of this technique.

  7. Experimental demonstration of broadband femtosecond optical parametric amplification based on YCOB crystal at near critical wavelength degeneracy

    Science.gov (United States)

    Guo, Xiaoyang; Leng, Yuxin; Li, Yanyan; Li, Wenkai; Lu, Xiaoming; Xu, Yi; Li, Ruxin

    2016-07-01

    Broadband optical parametric amplification (OPA) in the near-infrared region (1.3-1.8 μm) is demonstrated in YCOB crystal pumped by 1 kHz Ti:sapphire based femtosecond laser at near critical wavelength degeneracy phase matching condition at first time. The gain bandwidth is closed to BIBO or BBO crystal OPA gain bandwidth. The energy obtained with 3.5 mm-thick YCOB reached 20 μJ with RMS 1.9%. After second harmonic generation, 17.6 fs pulse is obtained, and the pulse compressibility is demonstrated.

  8. Calcium barium niobate as a functional material for broadband optical frequency conversion.

    Science.gov (United States)

    Sheng, Yan; Chen, Xin; Lukasiewicz, Tadeusz; Swirkowicz, Marek; Koynov, Kaloian; Krolikowski, Wieslaw

    2014-03-15

    We demonstrate the application of as-grown calcium barium niobate (CBN) crystal with random-sized ferroelectric domains as a broadband frequency converter. The frequency conversion process is similar to broadband harmonic generation in commonly used strontium barium niobate (SBN) crystal, but results in higher conversion efficiency reflecting a larger effective nonlinear coefficient of the CBN crystal. We also analyzed the polarization properties of the emitted radiation and determined the ratio of d32 and d33 components of the second-order susceptibility tensor of the CBN crystal. PMID:24690779

  9. BROADBAND COMMUNICATIONS FOR AERONAUTICAL NETWORKS: THE ATENAA OUTER OPTICAL LINK VALIDATION

    OpenAIRE

    Fuchs, Christian; Henniger, Hennes; Epple, Bernhard; Giggenbach, Dirk; Amirfeiz, Massimiliano; Jentile, Massimo; Di Nepi, Giorgia; Mazzi, Francesco; Martini, Gianluca

    2007-01-01

    The ATENAA-Project[4] aims on the development and validation of several technologies that are able to offer broadband communication services to civil aircraft passengers. The proposed Mobile-Ad-Hoc-Network (MANET) in conjunction with broadband data links would allow high data rate services, like In-Flight-Entertainment such as Video-On- Demand or High-Speed Internet Connections. Besides that, flight-relevant information with high amounts of data, e.g. high-resolution weather maps, could be ma...

  10. A simple parameterization of the short-wave aerosol optical properties for surface direct and diffuse irradiances assessment in a numerical weather model

    Directory of Open Access Journals (Sweden)

    J. A. Ruiz-Arias

    2014-01-01

    Full Text Available Broadband short-wave (SW surface direct and diffuse irradiances are not typically within the set of output variables produced by numerical weather prediction (NWP models. However, they are being more and more demanded in solar energy applications. A detailed representation of the aerosol optical properties is important to achieve an accurate assessment of these direct and diffuse irradiances. Nonetheless, NWP models typically oversimplify its representation or even neglect its effect. In this work, a flexible method to account for the SW aerosol optical properties in the computation of broadband SW surface direct and diffuse irradiances is presented. It only requires aerosol optical depth at 0.55 μm and the type of predominant aerosol. The rest of parameters needed to consider spectral aerosol extinction, namely, Angström exponent, aerosol single-scattering albedo and aerosol asymmetry factor, are parameterized. The parameterization has been tested in the RRTMG SW scheme of the Weather Research and Forecasting (WRF NWP model. However, it can be adapted to any other SW radiative transfer band model. It has been verified against a control experiment along five radiometric stations in the contiguous US. The control experiment consisted of a clear-sky evaluation of the RRTMG solar radiation estimates obtained in WRF when RRTMG is driven with ground-observed aerosol optical properties. Overall, the verification has shown very satisfactory results for both broadband SW surface direct and diffuse irradiances. It has proven effective to significantly reduce the prediction error and constraint the seasonal bias in clear-sky conditions to within the typical observational error in well-maintained radiometers.

  11. Enhanced broadband upconversion emission and 23 dB optical gain at 780 nm in Tm3+/Nd3+ codoped optical fiber

    International Nuclear Information System (INIS)

    Maximum gain of 23 dB at 780 nm and a broadband optical gain with full width at half maximum (FWHM) of 88 nm (761–849 nm) were obtained from the Tm3+/Nd3+ codoped fiber upon pumping at 1550 nm. The enhancement of the upconversion emission stretching from 730 to 970 nm was observed in the Tm3+/Nd3+ codoped fiber due to the energy transfer from Tm3+ to Nd3+ ions. - Highlights: • We fabricated the Tm3+/Nd3+ codoped silica based fiber. • The broadband upconversion emission was observed with 1550 nm pumping. • Maximum gain of 23 dB was observed at 780 nm from the Tm3+/Nd3+ codoped fiber. • The gain bandwidth of the upconversion emission was largely increased due to energy transfer process

  12. Broadband conformal phased array with optical beam forming for airborne satellite communication

    NARCIS (Netherlands)

    Schippers, H.; Verpoorte, J.; Jorna, P.; Hulzinga, A.; Meijerink, A.; Roeloffzen, C.G.H.; Zhuang, L.; Marpaung, D.A.I.; Etten, van W.; Heideman, R.G.; Leinse, A.; Borreman, A.; Hoekman, M.; Wintels, M.

    2008-01-01

    For enhanced communication on board an aircraft, novel antenna systems with broadband satellite based capabilities are required. The technology will enhance airline operations by providing in-flight connectivity for flight crew information and will bring live TV and high speed Internet connectivity

  13. Broadband behavior of transmission volume holographic optical elements for solar concentration.

    Science.gov (United States)

    Bañares-Palacios, Paula; Álvarez-Álvarez, Samuel; Marín-Sáez, Julia; Collados, María-Victoria; Chemisana, Daniel; Atencia, Jesús

    2015-06-01

    A ray tracing algorithm is developed to analyze the energy performance of transmission and phase volume holographic lenses that operate with broadband illumination. The agreement between the experimental data and the theoretical treatment has been tested. The model has been applied to analyze the optimum recording geometry for solar concentration applications.

  14. High-resolution and nondestructive profile measurement by spectral-domain optical coherence tomography with a visible broadband light source for optical-device fabrication

    Science.gov (United States)

    Nishi, Tsuyoshi; Ozaki, Nobuhiko; Oikawa, Yoichi; Miyaji, Kunio; Ohsato, Hirotaka; Watanabe, Eiichiro; Ikeda, Naoki; Sugimoto, Yoshimasa

    2016-08-01

    We developed a spectral-domain optical coherence tomography (OCT) using a visible broadband light source (vis-OCT) for application to high-resolution and nondestructive profile measurement and imaging in semiconductor optical-device fabrication. By using visible broadband light centered at 625 nm and with spectral bandwidth of 260 nm, an axial resolution of 0.69 µm in air was obtained. This was effective for inspection of a transparent photoresist film with thickness of 1–2 µm coated on a semiconductor wafer; the interface between the photoresist film and its substrate and the interface between the photoresist and air were resolved, and the film thickness was measured. In addition, the interface between an opaque epitaxially grown semiconductor layer (Al0.35Ga0.65As) and a GaAs substrate was also detected by vis-OCT. Here we propose a thickness-measurement technique that combines finite-difference time-domain simulation with vis-OCT. This method enables us to determine the thickness of even an optically absorbent epitaxial layer and offers a profile-measurement method that is particularly suitable for the fabrication of semiconductor optical devices.

  15. Few-cycle, Broadband, Mid-infrared Optical Parametric Oscillator Pumped by a 20-fs Ti:sapphire Laser

    CERN Document Server

    Kumar, Suddapalli Chaitanya; Ideguchi, Takuro; Yan, Ming; Holzner, Simon; Hänsch, Theodor W; Picqué, Nathalie; Ebrahim-Zadeh, Majid

    2014-01-01

    We report a few-cycle, broadband, singly-resonant optical parametric oscillator (OPO) for the mid-infrared based on MgO-doped periodically-poled LiNbO3 (MgO:PPLN), synchronously pumped by a 20-fs Ti:sapphire laser. By using crystal interaction lengths as short as 250 um, and careful dispersion management of input pump pulses and the OPO resonator, near-transform-limited, few-cycle idler pulses tunable across the mid-infrared have been generated, with as few as 3.7 optical cycles at 2682 nm. The OPO can be continuously tuned over 2179-3732 nm by cavity delay tuning, providing up to 33 mW of output power at 3723 nm. The idler spectra exhibit stable broadband profiles with bandwidths spaning over 422 nm (FWHM) recorded at 3732 nm. We investigate the effect of crystal length on spectral bandwidth and pulse duration at a fixed wavelength, confirming near-transform-limited idler pulses for all grating interaction lengths. By locking the repetition frequency of the pump laser to a radio-frequency reference, and with...

  16. Research progress of cholesteric liquid crystals with broadband reflection characteristics in application of intelligent optical modulation materials

    Science.gov (United States)

    Zhang, Lan-Ying; Gao, Yan-Zi; Song, Ping; Wu, Xiao-Juan; Yuan, Xiao; He, Bao-Feng; Chen, Xing-Wu; Hu, Wang; Guo, Ren-Wei; Ding, Hang-Jun; Xiao, Jiu-Mei; Yang, Huai

    2016-09-01

    Cholesteric liquid crystals (CLCs) have recently sparked an enormous amount of interest in the development of soft matter materials due to their unique ability to self-organize into a helical supra-molecular architecture and their excellent selective reflection of light based on the Bragg relationship. Nowadays, by the virtue of building the self-organized nanostructures with pitch gradient or non-uniform pitch distribution, extensive work has already been performed to obtain CLC films with a broad reflection band. Based on authors’ many years’ research experience, this critical review systematically summarizes the physical and optical background of the CLCs with broadband reflection characteristics, methods to obtain broadband reflection of CLCs, as well as the application in the field of intelligent optical modulation materials. Combined with the research status and the advantages in the field, the important basic and applied scientific problems in the research direction are also introduced. Project supported by the National Natural Science Foundation of China (Grant Nos. 51573006, 51573003, 51203003, 51303008, 51302006, 51402006, 51272026, and 51273022), the Major Project of Beijing Science and Technology Program, China (Grant Nos. Z151100003315023 and Z141100003814011), and the Fok Ying Tung Education Foundation, China (Grant No. 142009).

  17. Monitoring tumor therapeutic response with diffuse optical spectroscopies

    Science.gov (United States)

    Sunar, Ulas

    The diffuse optical technique using Near-Infrared (NIR) light provides a promising means for non-invasive imaging and clinical diagnosis of deep tissues. During the last few years, we have developed a multi-modal diffuse optical technique combining two qualitatively different methodologies: Diffuse Reflectance Spectroscopy (DRS) and Diffuse Correlation Spectroscopy (DCS). This approach permits real-time, non-invasive and simultaneous quantification of tissue hemoglobin concentration, blood oxygen saturation and blood flow. The instrumentation is portable and rapid, and it has enabled us to study tissue responses in a variety of physiological contexts from cancer treatment monitoring to functional imaging of brain. In this thesis I focus on monitoring of tumor responses to therapies in preclinical and clinical contexts. In preclinical applications, I investigate an antivascular therapy in animal models. The effects of an antivascular drug, Combretastatin, were monitored continuously and were found to induce substantial reduction of blood flow and tissue oxygen. The observations of blood flow and oxygenation were then correlated with power Doppler Ultrasound and EF5 (hypoxia biomarker) techniques, respectively. In another animal model application, the chemotherapy drug, Onconase (Onc), was tested. Onc enhances the therapeutic effects of the drug Cisplatin, which is currently used as a chemotherapeutic agent for head and neck patients during chemoradiation therapy. Our observations demonstrated that Onc increased both tissue blood flow and tissue blood oxygenation; we also compared our results with those from MRI/MRS measurements. The diffuse optical technique was then translated to the clinic, i.e. head and neck patients during chemo-radiation therapy. Our pilot study with eight patients revealed significant early changes in hemodynamic parameters suggesting that daily optics-based therapy monitoring during the first two weeks of chemo-radiation therapy may have

  18. Broadband optical mammography instrument for depth-resolved imaging and local dynamic measurements

    Science.gov (United States)

    Krishnamurthy, Nishanth; Kainerstorfer, Jana M.; Sassaroli, Angelo; Anderson, Pamela G.; Fantini, Sergio

    2016-02-01

    We present a continuous-wave instrument for non-invasive diffuse optical imaging of the breast in a parallel-plate transmission geometry. The instrument measures continuous spectra in the wavelength range 650-1000 nm, with an intensity noise level blood vessel, respectively. The use of a spatially multiplexed detection scheme allows for the generation of on-axis and off-axis projection images simultaneously, as opposed to requiring multiple scans, thus decreasing scan-time and motion artifacts. This technique localizes detected inhomogeneities in 3D and accurately assigns their depth to within 1 mm in the ideal conditions of otherwise homogeneous tissue-like phantoms. We also measured induced hemodynamic changes in the breast of a healthy human subject at a selected location (no scanning). We applied a cyclic, arterial blood pressure perturbation by alternating inflation (to a pressure of 200 mmHg) and deflation of a pneumatic cuff around the subject's thigh at a frequency of 0.05 Hz, and measured oscillations with amplitudes up to 1 μM and 0.2 μM in the tissue concentrations of oxyhemoglobin and deoxyhemoglobin, respectively. These hemodynamic oscillations provide information about the vascular structure and functional integrity in tissue, and may be used to assess healthy or abnormal perfusion in a clinical setting.

  19. A flexible experimental setup for femtosecond time-resolved broad-band ellipsometry and magneto-optics

    Energy Technology Data Exchange (ETDEWEB)

    Boschini, F.; Hedayat, H.; Piovera, C.; Dallera, C. [Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano (Italy); Gupta, A. [Department of Chemistry, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Carpene, E., E-mail: ettore.carpene@polimi.it [CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano (Italy)

    2015-01-15

    A versatile experimental setup for femtosecond time-resolved ellipsometry and magneto-optical Kerr effect measurements in the visible light range is described. The apparatus is based on the pump-probe technique and combines a broad-band probing beam with an intense near-infrared pump. According to Fresnel scattering matrix formalism, the analysis of the reflected beam at different polarization states of the incident probe light allows one to determine the diagonal and the off-diagonal elements of the dielectric tensor in the investigated sample. Moreover, the pump-probe method permits to study the dynamics of the dielectric response after a short and intense optical excitation. The performance of the experimental apparatus is tested on CrO{sub 2} single crystals as a benchmark.

  20. Narrow linewidth broadband tunable semiconductor laser at 840 nm with dual acousto-optic tunable configuration for OCT applications

    Science.gov (United States)

    Chamorovskiy, Alexander; Shramenko, Mikhail V.; Lobintsov, Andrei A.; Yakubovich, Sergei D.

    2016-03-01

    We demonstrate a tunable narrow linewidth semiconductor laser for the 840 nm spectral range. The laser has a linear cavity comprised of polarization maintaining (PM) fiber. A broadband semiconductor optical amplifier (SOA) in in-line fiber-coupled configuration acts as a gain element. It is based on InGaAs quantum-well (QW) active layer. SOA allows for tuning bandwidth exceeding 25 nm around 840 nm. Small-signal fiber-to-fiber gain of SOA is around 30 dB. A pair of acousto-optic tunable filters (AOTF) with a quasi-collinear interaction of optical and acoustic waves are utilized as spectrally selective elements. AOTF technology benefits in continuous tuning, broadband operation, excellent reproducibility and stability of the signal, as well as a high accuracy of wavelength selectivity due to the absence of mechanically moving components. A single AOTF configuration has typical linewidth in 0.05-0.15 nm range due to a frequency shift obtained during each roundtrip. A sequential AOTF arrangement enables instantaneous linewidth generation of <0.01 nm by compensating for this shift. Linewidth as narrow as 0.0036 nm is observed at 846 nm wavelength using a scanning Fabry-Perot interferometer with 50 MHz spectral resolution. Output power is in the range of 1 mW. While the majority of commercial tunable sources operate in 1060-1550 nm spectral ranges, the 840 nm spectral range is beneficial for optical coherence tomography (OCT). The developed narrow linewidth laser can be relevant for OCT with extended imaging depth, as well as spectroscopy, non-destructive testing and other applications.

  1. Suppressing Spectral Diffusion of the Emitted Photons with Optical Pulses

    CERN Document Server

    Fotso, H F; Awschalom, D D; Dobrovitski, V V

    2016-01-01

    In many quantum architectures the solid-state qubits, such as quantum dots or color centers, are interfaced via emitted photons. However, the frequency of photons emitted by solid-state systems exhibits slow uncontrollable fluctuations over time (spectral diffusion), creating a serious problem for implementation of the photon-mediated protocols. Here we show that a sequence of optical pulses applied to the solid-state emitter can stabilize the emission line at the desired frequency. We demonstrate efficiency, robustness, and feasibility of the method analytically and numerically. Taking nitrogen-vacancy (NV) center in diamond as an example, we show that only several pulses, with the width of 1 ns, separated by few ns (which is not difficult to achieve) can suppress spectral diffusion. Our method provides a simple and robust way to greatly improve the efficiency of photon-mediated entanglement and/or coupling to photonic cavities for solid-state qubits.

  2. Powerful 170-attosecond XUV pulses generated with few-cycle laser pulses and broadband multilayer optics

    Energy Technology Data Exchange (ETDEWEB)

    Schultze, M [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermannstrasse 1, D-85748 Garching (Germany); Goulielmakis, E [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermannstrasse 1, D-85748 Garching (Germany); Uiberacker, M [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Hofstetter, M [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Kim, J [Laser Science Laboratory, Department of Physics, POSTECH, Pohang, Kyungbuk 790-784 (Korea, Republic of); Kim, D [Laser Science Laboratory, Department of Physics, POSTECH, Pohang, Kyungbuk 790-784 (Korea, Republic of); Krausz, F [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermannstrasse 1, D-85748 Garching (Germany); Kleineberg, U [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany)

    2007-07-15

    Single 170-as extreme ultraviolet (XUV) pulses delivering more than 10{sup 6} photons/pulse at {approx}100 eV at a repetition rate of 3 kHz are produced by ionizing neon with waveform-controlled sub-5 fs near-infrared (NIR) laser pulses and spectrally filtering the emerging near-cutoff high-harmonic continuum with a broadband, chirped multilayer molybdenum-silicon (Mo/Si) mirror.

  3. Transmission of a broadband light through a fiber optic loop: effect of nonlinear refractive index

    OpenAIRE

    Zakhidov, Erkin; KOKHKHAROV, ABDUMUTALLIB; MIRTADJIEV, Farrukh

    2014-01-01

    The results of studies of broadband light transmission through a fiber loop and a double loop under the effect of nonlinear refractive index are presented in this paper. Fiber loop and double loop transmission/reflection vs. a coupler splitting ratio at various powers of the light with a spectral width of approximately 35 nm are studied and high efficient nonlinear light switching is demonstrated. It is shown that a double loop formed by consecutive connecting 2 fiber loops allows us to...

  4. Efficient optical pumping and high optical depth in a hollow-core photonic-crystal fibre for a broadband quantum memory

    Science.gov (United States)

    Sprague, Michael R.; England, Duncan G.; Abdolvand, Amir; Nunn, Joshua; Jin, Xian-Min; Kolthammer, W. Steven; Barbieri, Marco; Rigal, Bruno; Michelberger, Patrick S.; Champion, Tessa F. M.; Russell, Philip St. J.; Walmsley, Ian A.

    2013-05-01

    The generation of large multiphoton quantum states—for applications in computing, metrology and simulation—requires a network of high-efficiency quantum memories capable of storing broadband pulses. Integrating these memories into a fibre offers a number of advantages towards realizing this goal: strong light-matter coupling at low powers, simplified alignment and compatibility with existing photonic architectures. Here, we introduce a large-core kagome-structured hollow-core fibre as a suitable platform for an integrated fibre-based quantum memory with a warm atomic vapour. We demonstrate, for the first time, efficient optical pumping in such a system, where 90 ± 1% of atoms are prepared in the ground state. We measure high optical depths (3 × 104) and narrow homogeneous linewidths (6 ± 2 MHz) that do not exhibit significant transit-time broadening, showing that we can prepare a Λ-level system in a pure state. Our results establish that kagome fibres are suitable for implementing a broadband, room-temperature quantum memory, as well as a range of nonlinear optical effects.

  5. New frontiers in time-domain diffuse optics, a review.

    Science.gov (United States)

    Pifferi, Antonio; Contini, Davide; Mora, Alberto Dalla; Farina, Andrea; Spinelli, Lorenzo; Torricelli, Alessandro

    2016-09-01

    The recent developments in time-domain diffuse optics that rely on physical concepts (e.g., time-gating and null distance) and advanced photonic components (e.g., vertical cavity source-emitting laser as light sources, single photon avalanche diode, and silicon photomultipliers as detectors, fast-gating circuits, and time-to-digital converters for acquisition) are focused. This study shows how these tools could lead on one hand to compact and wearable time-domain devices for point-of-care diagnostics down to the consumer level and on the other hand to powerful systems with exceptional depth penetration and sensitivity. PMID:27311627

  6. Diffused holographic information storage and retrieval using photorefractive optical materials

    Science.gov (United States)

    McMillen, Deanna Kay

    Holography offers a tremendous opportunity for dense information storage, theoretically one bit per cubic wavelength of material volume, with rapid retrieval, of up to thousands of pages of information simultaneously. However, many factors prevent the theoretical storage limit from being reached, including dynamic range problems and imperfections in recording materials. This research explores new ways of moving closer to practical holographic information storage and retrieval by altering the recording materials, in this case, photorefractive crystals, and by increasing the current storage capacity while improving the information retrieved. As an experimental example of the techniques developed, the information retrieved is the correlation peak from an optical recognition architecture, but the materials and methods developed are applicable to many other holographic information storage systems. Optical correlators can potentially solve any signal or image recognition problem. Military surveillance, fingerprint identification for law enforcement or employee identification, and video games are but a few examples of applications. A major obstacle keeping optical correlators from being universally accepted is the lack of a high quality, thick (high capacity) holographic recording material that operates with red or infrared wavelengths which are available from inexpensive diode lasers. This research addresses the problems from two positions: find a better material for use with diode lasers, and reduce the requirements placed on the material while maintaining an efficient and effective system. This research found that the solutions are new dopants introduced into photorefractive lithium niobate to improve wavelength sensitivities and the use of a novel inexpensive diffuser that reduces the dynamic range and optical element quality requirements (which reduces the cost) while improving performance. A uniquely doped set of 12 lithium niobate crystals was specified and

  7. Glaucoma severity affects diffusion tensor imaging (DTI) parameters of the optic nerve and optic radiation

    International Nuclear Information System (INIS)

    Objectives: To evaluate whether MR diffusion tensor imaging (DTI) of the optic nerve and optic radiation in glaucoma patients provides parameters to discriminate between mild and severe glaucoma and to determine whether DTI derived indices correlate with retinal nerve fibre layer (RNFL) thickness. Methods: 3-Tesla DTI was performed on 90 subjects (30 normal, 30 mild glaucoma and 30 severe glaucoma subjects) and the FA and MD of the optic nerve and optic radiation were measured. The categorisation into mild and severe glaucoma was done using the Hodapp–Parrish–Anderson (HPA) classification. RNFL thickness was also assessed on all subjects using OCT. Receiver operating characteristic (ROC) analysis and Spearman's correlation coefficient was carried out. Results: FA and MD values in the optic nerve and optic radiation decreased and increased respectively as the disease progressed. FA at the optic nerve had the highest sensitivity (87%) and specificity (80%). FA values displayed the strongest correlation with RNFL thickness in the optic nerve (r = 0.684, p ≤ 0.001) while MD at the optic radiation showed the weakest correlation with RNFL thickness (r = −0.360, p ≤ 0.001). Conclusions: The high sensitivity and specificity of DTI-derived FA values in the optic nerve and the strong correlation between DTI-FA and RNFL thickness suggest that these parameters could serve as indicators of disease severity

  8. Glaucoma severity affects diffusion tensor imaging (DTI) parameters of the optic nerve and optic radiation

    Energy Technology Data Exchange (ETDEWEB)

    Sidek, S. [Department of Biomedical Imaging, University Malaya, Research Imaging Centre, Faculty of Medicine, University Malaya (Malaysia); Medical Imaging Unit, Faculty of Medicine, Universiti Teknologi MARA, Selangor (Malaysia); Ramli, N. [Department of Biomedical Imaging, University Malaya, Research Imaging Centre, Faculty of Medicine, University Malaya (Malaysia); Rahmat, K., E-mail: katt_xr2000@yahoo.com [Department of Biomedical Imaging, University Malaya, Research Imaging Centre, Faculty of Medicine, University Malaya (Malaysia); Ramli, N.M.; Abdulrahman, F. [Department of Ophthalmology, Faculty of Medicine, University Malaya, Kuala Lumpur (Malaysia); Tan, L.K. [Department of Biomedical Imaging, University Malaya, Research Imaging Centre, Faculty of Medicine, University Malaya (Malaysia)

    2014-08-15

    Objectives: To evaluate whether MR diffusion tensor imaging (DTI) of the optic nerve and optic radiation in glaucoma patients provides parameters to discriminate between mild and severe glaucoma and to determine whether DTI derived indices correlate with retinal nerve fibre layer (RNFL) thickness. Methods: 3-Tesla DTI was performed on 90 subjects (30 normal, 30 mild glaucoma and 30 severe glaucoma subjects) and the FA and MD of the optic nerve and optic radiation were measured. The categorisation into mild and severe glaucoma was done using the Hodapp–Parrish–Anderson (HPA) classification. RNFL thickness was also assessed on all subjects using OCT. Receiver operating characteristic (ROC) analysis and Spearman's correlation coefficient was carried out. Results: FA and MD values in the optic nerve and optic radiation decreased and increased respectively as the disease progressed. FA at the optic nerve had the highest sensitivity (87%) and specificity (80%). FA values displayed the strongest correlation with RNFL thickness in the optic nerve (r = 0.684, p ≤ 0.001) while MD at the optic radiation showed the weakest correlation with RNFL thickness (r = −0.360, p ≤ 0.001). Conclusions: The high sensitivity and specificity of DTI-derived FA values in the optic nerve and the strong correlation between DTI-FA and RNFL thickness suggest that these parameters could serve as indicators of disease severity.

  9. Developing High-Density Diffuse Optical Tomography for Neuroimaging

    Science.gov (United States)

    White, Brian Richard

    Clinicians who care for brain-injured patients and premature infants desire a bedside monitor of brain function. A decade ago, there was hope that optical imaging would be able to fill this role, as it combined fMRI's ability to construct cortical maps with EEG's portable, cap-based systems. However, early optical systems had poor imaging performance, and the momentum for the technique slowed. In our lab, we develop diffuse optical tomography (DOT), which is a more advanced method of performing optical imaging. My research has been to pioneer the in vivo use of DOT for advanced neuroimaging by (1) quantifying the advantages of DOT through both in silico simulation and in vivo performance metrics, (2) restoring confidence in the technique with the first retinotopic mapping of the visual cortex (a benchmark for fMRI and PET), and (3) creating concepts and methods for the clinical translation of DOT. Hospitalized patients are unable to perform complicated neurological tasks, which has motivated us to develop the first DOT methods for resting-state brain mapping with functional connectivity. Finally, in collaboration with neonatologists, I have extended these methods with proof-of-principle imaging of brain-injured premature infants. This work establishes DOT's improvements in imaging performance and readies it for multiple clinical and research roles.

  10. Broadband and enhanced nonlinear optical response of MoS2/graphene nanocomposites for ultrafast photonics applications

    Science.gov (United States)

    Jiang, Yaqin; Miao, Lili; Jiang, Guobao; Chen, Yu; Qi, Xiang; Jiang, Xiao-Fang; Zhang, Han; Wen, Shuangchun

    2015-11-01

    Due to their relatively high compatibility with specific photonic structures, strong light-matter interactions and unique nonlinear optical response, two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides, are attractive for ultrafast photonics applications. Here, we fabricate MoS2/graphene nanocomposites by a typical hydrothermal method. In addition, we systematically investigate their nonlinear optical responses. Our experiments indicate that the combined advantages of ultrafast relaxation, a broadband response from graphene, and the strong light-matter interaction from MoS2, can be integrated together by composition. The optical properties in terms of carrier relaxation dynamics, saturation intensity and modulation depth suggest great potential for the MoS2/graphene nanocomposites in photonics applications. We have further fabricated 2D nanocomposites based optical saturable absorbers and integrated them into a 1.5 μm Erbium-doped fiber laser to demonstrate Q-switched and mode-locked pulse generation. The fabrication of 2D nanocomposites assembled from different types of 2D materials, via this simple and scalable growth approach, paves the way for the formation and tuning of new 2D materials with desirable photonic properties and applications.

  11. Threaded molecular wires as building blocks for advanced polymer blends: WPLEDs, ultra-broadband optical amplifiers, multi color lasers

    Science.gov (United States)

    Brovelli, Sergio; Mroz, Marta; Sforazzini, Giuseppe; Virgili, Tersilla; Meinardi, Franco; Paleari, Alberto; Anderson, Harry L.; Lanzani, Guglielmo; Cacialli, Franco

    2011-03-01

    The ability to produce semiconducting polymer blends with white emission spectra, large emission cross sections and broad optical gain is critical to their application in white PLEDs, lasers and broadband amplifiers. Cyclodextrin-encapsulation is an effective means of suppressing detrimental intermolecular interactions, and energy transfer (ET) channels in polymer blends, thus enabling fabrication of white-PLEDs. We show that all such properties combine into a high impact photonic application: ultra-broad optical gain and two-color lasing in a binary polyrotaxane blend. We study the ultrafast photophysics of a blend of a conventional and an encapsulated polyfluorene. The morphology is investigated by microRaman imaging, AFM, and fluorescence lifetime microscopy. We ascribe the ultra-broad optical gain (>850 meV), and the simultaneous ASE for both constituents, to the dual effect of reduced polaron formation and suppressed ET. Our results demonstrate that polyrotaxanes could realistically represent the building blocks for advanced polymer blends with highly controlled optical properties, for applications in solid state lightning, lasers and photovoltaic technologies.

  12. Thermal diffusivity determination by the photodeflection method. The influence of wave optical effects

    OpenAIRE

    Walther, H.-G.; Muratikov, K.; A. Glazov

    1994-01-01

    Possible approaches to thermal wave based measurement of thermal diffusivity are considered. The calculation of the transverse photodeflection signal in the framework of wave optics prove to be a more accurate approach compared to that of geometrical optics. The influence of the account of wave optical effects on the accuracy of the thermal diffusivity determination is theoretically analyzed under various conditions.

  13. Region-of-interest diffuse optical tomography system

    Science.gov (United States)

    Saikia, Manob Jyoti; Kanhirodan, Rajan

    2016-01-01

    Diffuse optical tomography (DOT) using near-infrared light is a promising tool for non-invasive imaging of deep tissue. This technique is capable of quantitative reconstruction of absorption (μa) and scattering coefficient (μs) inhomogeneities in the tissue. The rationale for reconstructing the optical property map is that the absorption coefficient variation provides diagnostic information about metabolic and disease states of the tissue. The aim of DOT is to reconstruct the internal tissue cross section with good spatial resolution and contrast from noisy measurements non-invasively. We develop a region-of-interest scanning system based on DOT principles. Modulated light is injected into the phantom/tissue through one of the four light emitting diode sources. The light traversing through the tissue gets partially absorbed and scattered multiple times. The intensity and phase of the exiting light are measured using a set of photodetectors. The light transport through a tissue is diffusive in nature and is modeled using radiative transfer equation. However, a simplified model based on diffusion equation (DE) can be used if the system satisfies following conditions: (a) the optical parameter of the inhomogeneity is close to the optical property of the background, and (b) μs of the medium is much greater than μa (μs > > μa). The light transport through a highly scattering tissue satisfies both of these conditions. A discrete version of DE based on finite element method is used for solving the inverse problem. The depth of probing light inside the tissue depends on the wavelength of light, absorption, and scattering coefficients of the medium and the separation between the source and detector locations. Extensive simulation studies have been carried out and the results are validated using two sets of experimental measurements. The utility of the system can be further improved by using multiple wavelength light sources. In such a scheme, the spectroscopic

  14. Region-of-interest diffuse optical tomography system

    Energy Technology Data Exchange (ETDEWEB)

    Saikia, Manob Jyoti; Kanhirodan, Rajan, E-mail: rajan@physics.iisc.ernet.in [Department of Physics, Indian Institute of Science, Bangalore 560012 (India)

    2016-01-15

    Diffuse optical tomography (DOT) using near-infrared light is a promising tool for non-invasive imaging of deep tissue. This technique is capable of quantitative reconstruction of absorption (μ{sub a}) and scattering coefficient (μ{sub s}) inhomogeneities in the tissue. The rationale for reconstructing the optical property map is that the absorption coefficient variation provides diagnostic information about metabolic and disease states of the tissue. The aim of DOT is to reconstruct the internal tissue cross section with good spatial resolution and contrast from noisy measurements non-invasively. We develop a region-of-interest scanning system based on DOT principles. Modulated light is injected into the phantom/tissue through one of the four light emitting diode sources. The light traversing through the tissue gets partially absorbed and scattered multiple times. The intensity and phase of the exiting light are measured using a set of photodetectors. The light transport through a tissue is diffusive in nature and is modeled using radiative transfer equation. However, a simplified model based on diffusion equation (DE) can be used if the system satisfies following conditions: (a) the optical parameter of the inhomogeneity is close to the optical property of the background, and (b) μ{sub s} of the medium is much greater than μ{sub a} (μ{sub s} > > μ{sub a}). The light transport through a highly scattering tissue satisfies both of these conditions. A discrete version of DE based on finite element method is used for solving the inverse problem. The depth of probing light inside the tissue depends on the wavelength of light, absorption, and scattering coefficients of the medium and the separation between the source and detector locations. Extensive simulation studies have been carried out and the results are validated using two sets of experimental measurements. The utility of the system can be further improved by using multiple wavelength light sources. In such

  15. Simulation experiments to generate broadband chaos using dual-wavelength optically injected Fabry-Perot laser

    Science.gov (United States)

    Obaid, Hafiz Muhammad; Khawar Islam, Muhammad; Obaid Ullah, Muhammad

    2016-08-01

    Broadband chaos can be generated by beating two wavelengths in a hybrid arrangement of Fabry-Perot (FP) Laser and Fiber ring cavity by injecting dual wavelengths. The bandwidth of generated chaos can be controlled by detuning different modes of FP Laser for beating. The bandwidth of generated chaos increased to many folds depending upon the injected strength and wavelength spacing matched to FP laser modes. The bandwidth enhancement in different simulation experiments conducted is optimized by varying different parameters of FP laser and cavity. The waveforms are analyzed and Lyapunov exponents are calculated in order to validate the existence of high bandwidth non-pulsating chaos.

  16. Efficient optical pumping and high optical depth in a hollow-core photonic-crystal fibre for a broadband quantum memory

    CERN Document Server

    Sprague, Michael R; Abdolvand, Amir; Nunn, Joshua; Jin, Xian-Min; Kolthammer, W Steven; Barbieri, Marco; Rigal, Bruno; Michelberger, Patrick S; Champion, Tessa F M; Russell, Philip St J; Walmsley, Ian A

    2012-01-01

    The generation of large multiphoton quantum states - for applications in computing, metrology, and simulation - requires a network of high-efficiency quantum memories capable of storing broadband pulses. Integrating these memories into a fibre offers a number of advantages towards realising this goal: strong light-matter coupling at low powers, simplified alignment, and compatibility with existing photonic architectures. Here, we introduce a large-core kagome-structured hollow-core fibre as a suitable platform for an integrated fibre-based quantum memory with a warm atomic vapour. We demonstrate, for the first time, efficient optical pumping in a hollow-core photonic-crystal fibre with a warm atomic vapour, where (90 $\\pm$ 1)% of atoms are prepared in the ground state. We measure high optical depths (3$\\times 10^{4}$) and, also, narrow homogeneous linewidths that do not exhibit significant transit-time broadening. Our results establish that kagome fibres are suitable for implementing a broadband, room-tempera...

  17. Broadband multilayer mirror and diffractive optics for attosecond pulse shaping in the 280-500 eV photon energy range

    Directory of Open Access Journals (Sweden)

    Schmidt J.

    2013-03-01

    Full Text Available Chirped broadband multilayer mirrors are key components to shape attosecond pulses in the XUV range. Compressing high harmonic pulses to their Fourier limit is the major goal for attosecond physics utilizing short pulse pump-probe experiments. Here, we report about the first implementation of multilayers and diffractive optics fulfilling these requirements in the “water-window” spectral range.

  18. A Versatile Setup for Ultrafast Broadband Optical Spectroscopy of Coherent Collective Modes in Strongly Correlated Quantum Systems

    CERN Document Server

    Baldini, Edoardo; Borroni, Simone; Arrell, Christopher; van Mourik, Frank; Carbone, Fabrizio

    2016-01-01

    A femtosecond pump-probe setup is described that is optimised for broadband transient reflectivity experiments on solid samples over a wide range of temperatures. By combining a temporal resolution of 45 fs and a broad detection range between 1.75 and 2.85 eV, this apparatus can provide insightful information on the interplay between coherent collective modes and high-energy electronic excitations, which is one of the distinctive characteristics of strongly interacting and correlated quantum systems. The use of a single-shot readout CMOS array detector at frame rates up to 10 kHz allows to resolve coherent oscillations with amplitudes below 10$^{-4}$ in $\\Delta$R/R. We demonstrate the operation of this setup on the prototypical charge-transfer insulator La$_2$CuO$_4$, revealing the presence of coherent optical phonons with frequencies as high as 13 THz.

  19. Broadband millimeter-wave electro-optic modulator using multi-patch antennas for pico-cell radar networks

    Science.gov (United States)

    Wijayanto, Yusuf Nur; Kanno, Atsushi; Kawanishi, Tetsuya

    2015-01-01

    An electro-optic (EO) modulator using multi patch antennas is proposed for broadband millimeter-wave bands in pico-cell radar networks. The proposed device is composed of multi patch antennas with a gap fabricated on a LiNbO3 crystal bonded with a low-k dielectric material. Multiple millimeter-wave operational frequencies can be received by the multi patch antennas and converting directly to lightwave signals through the Pockel effects of the LiNbO3 crystal. By adjusting the metal patch size for receiving with relatively close millimeter-wave frequencies, the bandwidth of the EO modulator can be enlarged. Based on that, bandwidth of over 30% in millimeter-wave bands can be achieved using the proposed device.

  20. Development of multilayer optics for X-ray broadband spectrometry of plasma emission

    International Nuclear Information System (INIS)

    Within the framework of the research on inertial confinement fusion, the 'Commissariat a l'energie atomique et aux energies alternatives' has studied and implemented an absolute calibrated time-Resolved broadband soft x-Ray spectrometer, called 'Diagnostic de Mesure du rayonnement X'. This diagnostic, composed of 20 measurement channels, measures the emitted radiant power from a laser created plasma in the range from 50 eV to 20 keV. We have developed additional measurement channels to obtain redundancy and an improvement in measurement accuracy. The principle of these new channels is based on an original concept to obtain spectral bounded flat-Responses. Two channels have been developed for the 2 - 4 keV and 4 - 6 keV spectral ranges, using aperiodic multilayer mirrors made at the 'Laboratoire Charles Fabry' with Cr/Sc and Ni/W/SiC/W layers respectively. These mirrors were characterized at synchrotron radiation facilities and integrated into the spectrometer. The two new channels were used during laser-Plasma experimental campaigns at the OMEGA laser facility in Rochester (USA). This allowed us to determine directly the radiant power with only one measurement within a certain spectral band, and with a better precision when compared with using standard channels. The results, in good agreement with the standard measurement channels, allowed us to validate the use of aperiodic multilayer mirrors for X-Ray broadband spectrometry. (author)

  1. Broadband optical gain in the normally dispersive region of a high-birefringence photonic crystal fiber

    International Nuclear Information System (INIS)

    Based on a designed high-birefringence photonic crystal fiber (HB-PCF) with two zero-dispersion wavelengths (ZDWs), the effect of pump parameters and Raman scattering on the modulation instability (MI) gain is comprehensively analyzed in this paper. An interesting result is found, in that only when the pump wavelength lies within an approximately 10 nm range of the zero-dispersion points in the normal dispersion region of the HB-PCF does a broadband gain characteristic appear. The Raman effect results in a combination of the gain spectra from the Stokes and anti-Stokes band, which finally promotes the formation of broadband amplification. Moreover, there exist an optimal pump wavelength and a suitable pump power along the fast axis or the slow axis of the fiber. With these optimal pump parameters, the total MI gain bandwidth finally reaches 159 nm for the fiber fast axis and 162 nm for the fiber slow axis. (paper)

  2. Transmission RF diffuse optical tomography instrument for human breast imaging

    Science.gov (United States)

    Lee, Kijoon; Konecky, Soren D.; Choe, Regine; Ban, Han Y.; Corlu, Alper; Durduran, Turgut; Yodh, Arjun G.

    2007-07-01

    In this paper, we describe a novel clinical breast diffuse optical tomography (DOT) instrument for CW and RF data acquisition in transmission geometry. It is designed to be able to acquire a massive amount of data in a short amount of time available for patient measurement by using a 209-channel galvo-based fast optical switch and a fast electron-multiplying CCD. In addition to CW measurements, RF measurements were made by using an electro-optic modulator for source modulation and a gain-modulated image intensifier for detection. The patient bed has many clinically-oriented features as well as improved data acquisition rate and transmission RF measurement capability. A series of preliminary results will be shown, including a heterodyne RF experiment for bulk property measurement and a CW experiment for 3D imaging. In order to deal with large data size, a linear reconstruction algorithm that exploits separability of the inverse problem in Fourier domain is used for fast and memory-load-free reconstruction.

  3. CT guided diffuse optical tomography for breast cancer imaging

    Science.gov (United States)

    Baikejiang, Reheman; Zhang, Wei; Zhu, Dianwen; Li, Changqing

    2016-03-01

    Diffuse optical tomography (DOT) has attracted attentions in the last two decades due to its intrinsic sensitivity in imaging chromophores of tissues such as blood, water, and lipid. However, DOT has not been clinically accepted yet due to its low spatial resolution caused by strong optical scattering in tissues. Structural guidance provided by an anatomical imaging modality enhances the DOT imaging substantially. Here, we propose a computed tomography (CT) guided multispectral DOT imaging system for breast cancer detection. To validate its feasibility, we have built a prototype DOT imaging system which consists of a laser at wavelengths of 650 and an electron multiplying charge coupled device (EMCCD) camera. We have validated the CT guided DOT reconstruction algorithms with numerical simulations and phantom experiments, in which different imaging setup parameters, such as projection number of measurements, the width of measurement patch, have been investigated. Our results indicate that an EMCCD camera with air cooling is good enough for the transmission mode DOT imaging. We have also found that measurements at six projections are sufficient for DOT to reconstruct the optical targets with 4 times absorption contrast when the CT guidance is applied. Finally, we report our effort and progress on the integration of the multispectral DOT imaging system into a breast CT scanner.

  4. Simultaneous characterization of rotational and translational diffusion of optically anisotropic particles by optical microscopy

    Science.gov (United States)

    Giavazzi, Fabio; Haro-Pérez, Catalina; Cerbino, Roberto

    2016-05-01

    We probe the roto-translational Brownian motion of optically anisotropic particles suspended in water with a simple and straightforward optical microscopy experiment that does not require positional or rotational particle tracking. We acquire a movie of the suspension placed between two polarizing elements and we extract the translational diffusion coefficient D T and the rotational diffusion coefficient D R from the analysis of the temporal correlation properties of the spatial Fourier modes of the intensity fluctuations in the movie. Our method is successfully tested with a dilute suspension of birefringent spherical colloidal particles obtained by polymerizing an emulsion of droplets of liquid crystal in a nematic phase, whose roto-translational dynamics is found to be well described by theory. The simplicity of our approach makes our method a viable alternative to particle tracking and depolarized dynamic light scattering.

  5. Control of broadband optically generated ultrasound pulses using binary amplitude holograms.

    Science.gov (United States)

    Brown, Michael D; Jaros, Jiri; Cox, Ben T; Treeby, Bradley E

    2016-04-01

    In this work, the use of binary amplitude holography is investigated as a mechanism to focus broadband acoustic pulses generated by high peak-power pulsed lasers. Two algorithms are described for the calculation of the binary holograms; one using ray-tracing, and one using an optimization based on direct binary search. It is shown using numerical simulations that when a binary amplitude hologram is excited by a train of laser pulses at its design frequency, the acoustic field can be focused at a pre-determined distribution of points, including single and multiple focal points, and line and square foci. The numerical results are validated by acoustic field measurements from binary amplitude holograms, excited by a high peak-power laser. PMID:27106311

  6. Fast Bayesian inference of optical trap stiffness and particle diffusion

    CERN Document Server

    Bera, Sudipta; Singh, Rajesh; Ghosh, Dipanjan; Kundu, Avijit; Banerjee, Ayan; Adhikari, R

    2016-01-01

    Bayesian inference provides a principled way of estimating the parameters of a stochastic process that is observed discretely in time. The overdamped Brownian motion of a particle confined in an optical trap is generally modelled by the Ornstein-Uhlenbeck process and can be observed directly in experiment. Here we present Bayesian methods for inferring the parameters of this process, the trap stiffness and the particle diffusion coefficient, that use exact likelihoods and sufficient statistics to arrive at simple expressions for the maximum a posteriori estimates. This obviates the need for Monte Carlo sampling and yields methods that are both fast and accurate. We apply these to experimental data and demonstrate their advantage over commonly used non-Bayesian fitting methods.

  7. Low-cost diffuse optical tomography for the classroom

    Science.gov (United States)

    Minagawa, Taisuke; Zirak, Peyman; Weigel, Udo M.; Kristoffersen, Anna K.; Mateos, Nicolas; Valencia, Alejandra; Durduran, Turgut

    2012-10-01

    Diffuse optical tomography (DOT) is an emerging imaging modality with potential applications in oncology, neurology, and other clinical areas. It allows the non-invasive probing of the tissue function using relatively inexpensive and safe instrumentation. An educational laboratory setup of a DOT system could be used to demonstrate how photons propagate through tissues, basics of medical tomography, and the concepts of multiple scattering and absorption. Here, we report a DOT setup that could be introduced to the advanced undergraduate or early graduate curriculum using inexpensive and readily available tools. The basis of the system is the LEGO Mindstorms NXT platform which controls the light sources, the detectors (photo-diodes), a mechanical 2D scanning platform, and the data acquisition. A basic tomographic reconstruction is implemented in standard numerical software, and 3D images are reconstructed. The concept was tested and developed in an educational environment that involved a high-school student and a group of post-doctoral fellows.

  8. Nonquadratic penalization improves near-infrared diffuse optical tomography.

    Science.gov (United States)

    Jagannath, Ravi Prasad K; Yalavarthy, Phaneendra K

    2013-08-01

    A new approach that can easily incorporate any generic penalty function into the diffuse optical tomographic image reconstruction is introduced to show the utility of nonquadratic penalty functions. The penalty functions that were used include quadratic (ℓ2), absolute (ℓ1), Cauchy, and Geman-McClure. The regularization parameter in each of these cases was obtained automatically by using the generalized cross-validation method. The reconstruction results were systematically compared with each other via utilization of quantitative metrics, such as relative error and Pearson correlation. The reconstruction results indicate that, while the quadratic penalty may be able to provide better separation between two closely spaced targets, its contrast recovery capability is limited, and the sparseness promoting penalties, such as ℓ1, Cauchy, and Geman-McClure have better utility in reconstructing high-contrast and complex-shaped targets, with the Geman-McClure penalty being the most optimal one. PMID:24323209

  9. Ultrafast broadband tuning of resonant optical nanostructures using phase change materials

    CERN Document Server

    Rudé, Miquel; Cetin, Arif E; Miller, Timothy A; Carrilero, Albert; Wall, Simon; de Abajo, F Javier García; Altug, Hatice; Pruneri, Valerio

    2015-01-01

    The phenomenon of extraordinary optical transmission {EOT} through arrays of nanoholes patterned in a metallic film has emerged as a promising tool for a wide range of applications, including photovoltaics, nonlinear optics, and sensing. Designs and methods enabling the dynamic tuning of the optical resonances of these structures are essential to build efficient optical devices, including modulators, switches, filters, and biosensors. However, the efficient combination of EOT and dynamic tuning remains a challenge, mainly because of the lack of materials that can induce modulation over a broad spectral range at high speeds. Here, we demonstrate tuneable resonance wavelength shifts as large as 385 nm - an order of magnitude higher than previously reported - through the combination of phase change materials {PCMs}, which exhibit dramatic variations in optical properties upon transitions between amorphous and crystalline phases, with properly designed subwavelength nanohole metallic arrays. We further find throu...

  10. Towards next generation time-domain diffuse optics devices

    Science.gov (United States)

    Dalla Mora, Alberto; Contini, Davide; Arridge, Simon R.; Martelli, Fabrizio; Tosi, Alberto; Boso, Gianluca; Farina, Andrea; Durduran, Turgut; Martinenghi, Edoardo; Torricelli, Alessandro; Pifferi, Antonio

    2015-03-01

    Diffuse Optics is growing in terms of applications ranging from e.g. oximetry, to mammography, molecular imaging, quality assessment of food and pharmaceuticals, wood optics, physics of random media. Time-domain (TD) approaches, although appealing in terms of quantitation and depth sensibility, are presently limited to large fiber-based systems, with limited number of source-detector pairs. We present a miniaturized TD source-detector probe embedding integrated laser sources and single-photon detectors. Some electronics are still external (e.g. power supply, pulse generators, timing electronics), yet full integration on-board using already proven technologies is feasible. The novel devices were successfully validated on heterogeneous phantoms showing performances comparable to large state-of-the-art TD rack-based systems. With an investigation based on simulations we provide numerical evidence that the possibility to stack many TD compact source-detector pairs in a dense, null source-detector distance arrangement could yield on the brain cortex about 1 decade higher contrast as compared to a continuous wave (CW) approach. Further, a 3-fold increase in the maximum depth (down to 6 cm) is estimated, opening accessibility to new organs such as the lung or the heart. Finally, these new technologies show the way towards compact and wearable TD probes with orders of magnitude reduction in size and cost, for a widespread use of TD devices in real life.

  11. Broadband miniature optical ultrasound probe for high resolution vascular tissue imaging.

    OpenAIRE

    Colchester, R. J.; Zhang, E. Z.; Mosse, C. A.; Beard, P.C.; Papakonstantinou, I.; Desjardins, A. E.

    2015-01-01

    An all-optical ultrasound probe for vascular tissue imaging was developed. Ultrasound was generated by pulsed laser illumination of a functionalized carbon nanotube composite coating on the end face of an optical fiber. Ultrasound was detected with a Fabry-Pérot (FP) cavity on the end face of an adjacent optical fiber. The probe diameter was < 0.84 mm and had an ultrasound bandwidth of ~20 MHz. The probe was translated across the tissue sample to create a virtual linear array of ultrasound tr...

  12. Scalable and reconfigurable generation of flat optical comb for WDM-based next-generation broadband optical access networks

    Science.gov (United States)

    Chen, Chen; Zhang, Chongfu; Zhang, Wei; Jin, Wei; Qiu, Kun

    2014-06-01

    A tunable comb generator (TCG) by cascading a single phase modulator (PM) with two identical intensity modulators (IMs) is proposed for the scalable and reconfigurable generation of flat optical comb. Detailed theoretical analysis is performed to find out the optimized condition for flat optical comb generation using the proposed TCG and the scalability of the generated optical comb is also analyzed under the optimized condition. An experiment is conducted to verify the feasibility of the TCG and the experimental results agree well with the theoretical prediction. The reconfigurability and stability of the obtained optical comb are discussed as well in the experiment. After that, the obtained optical comb is utilized as the optical source for a wavelength-division multiplexed radio-over-fiber (WDM-RoF) system and a hybrid WDM orthogonal frequency-division multiple access passive optical network (WDM-OFDMA-PON). Two corresponding experimental demonstrations are presented to verify the feasibility of employing the obtained flat optical comb as the WDM optical source, respectively. In the WDM-RoF system, 17 WDM channels each carrying 16×5 Gb/s non-return-to-zero (NRZ) data have been up-converted to 10 GHz simultaneously. In the hybrid WDM-OFDMA-PON, 17-channel OFDM-WDM double-sideband (DSB) signal achieving 10.85 Gb/s traffic per channel is successfully transmitted for both wired baseband OFDM access and wireless 10 GHz OFDM access.

  13. Detailed optical and near-infrared polarimetry, spectroscopy and broadband photometry of the afterglow of GRB 091018: Polarisation evolution

    CERN Document Server

    Wiersema, K; Kruehler, T; Melandri, A; Rol, E; Starling, R L C; Tanvir, N R; van der Horst, A J; Covino, S; Fynbo, J P U; Goldoni, P; Gorosabel, J; Hjorth, J; Klose, S; Mundell, C G; O'Brien, P T; Palazzi, E; Wijers, R A M J; D'Elia, V; Evans, P A; Filgas, R; Gomboc, A; Greiner, J; Guidorzi, C; Kaper, L; Kobayashi, S; Kouveliotou, C; Levan, A J; Rossi, A; Rowlinson, A; Steele, I A; Postigo, A de Ugarte; Vergani, S D

    2012-01-01

    [Abridged] A number of phenomena have been observed in GRB afterglows that defy explanation by simple versions of the standard fireball model, leading to a variety of new models. Polarimetry can be a major independent diagnostic of afterglow physics, probing the magnetic field properties and internal structure of the GRB jets. In this paper we present the first high quality multi-night polarimetric light curve of a Swift GRB afterglow, aimed at providing a well calibrated dataset of a typical afterglow to serve as a benchmark system for modelling afterglow polarisation behaviour. In particular, our dataset of the afterglow of GRB 091018 (at redshift z=0.971) comprises optical linear polarimetry (R band, 0.13 - 2.3 days after burst); circular polarimetry (R band) and near-infrared linear polarimetry (Ks band). We add to that high quality optical and near-infrared broadband light curves and spectral energy distributions as well as afterglow spectroscopy. The linear polarisation varies between 0 and 3%, with bot...

  14. Radio-frequency transparent demodulation for broadband hybrid wireless-optical links

    DEFF Research Database (Denmark)

    Zibar, Darko; Sambaraju, Rakesh; Alemany, Ruben;

    2010-01-01

    A novel demodulation technique which is transparent to radio-frequency (RF) carrier frequency is presented and experimentally demonstrated for multigigabit wireless signals. The presented demodulation technique employs optical single-sideband filtering, coherent detection, and baseband digital...

  15. Broadband Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS – applicability and corrections

    Directory of Open Access Journals (Sweden)

    D. Pöhler

    2008-12-01

    Full Text Available Atmospheric trace gas measurements by cavity assisted long-path absorption spectroscopy are an emerging technology. An interesting approach is the combination of CEAS with broad band light sources, the broad-band CEAS (BB-CEAS. BB-CEAS lends itself to the application of the DOAS technique to analyse the derived absorption spectra. While the DOAS approach has enormous advantages in terms of sensitivity and specificity of the measurement, an important implication is the reduction of the light path by the trace gas absorption, since cavity losses due to absorption by gases reduce the quality (Q of the cavity. In fact, at wavelength, where the quality of the BB-CEAS cavity is dominated by the trace gas absorption (esp. at very high mirror reflectivity, the light path will vary inversely with the trace gas concentration and the strength of the band will become nearly independent of the trace gas concentration c in the cavity, rendering the CEAS Method useless for trace gas measurements. Only in the limiting case where the mirror reflectivity determines Q at all wavelength, the strength of the band as seen by the BB-CEAS instrument becomes proportional to the concentration c. We investigate these relationships in detail and present methods to correct for the cases between the two above extremes, which are of course the important ones in practice.

  16. Full Spectrum Diffused and Beamed Solar Energy Application Using Optical Fibre

    OpenAIRE

    Majumdar, M. R. Dutta; Das, Debasish

    2007-01-01

    Existing solar energy application systems use small fraction of full spectrum of solar energy. So attempts are made to show how full spectrum solar energy can be used for diffused and beamed form of incident solar energy. Luminescent Solar Concentrator (LSC) principle with optical fibre in diffused sun light and dielectric mirror separation technique with optical fibre in beamed form are discussed. Comparison of both the cases are done. Keywords: full spectrum, solar photonics, diffused solar...

  17. System for diffusing light from an optical fiber or light guide

    Science.gov (United States)

    Maitland, Duncan J [Pleasant Hill, CA; Wilson, Thomas S [San Leandro, CA; Benett, William J [Livermore, CA; Small, IV, Ward [

    2008-06-10

    A system for diffusing light from an optical fiber wherein the optical fiber is coupled to a light source, comprising forming a polymer element adapted to be connected to the optical fiber and incorporating a scattering element with the polymer element wherein the scattering element diffuses the light from the polymer element. The apparatus of the present invention comprises a polymer element operatively connected to the optical fiber and a scattering element operatively connected with the shape polymer element that diffuses the light from the polymer element.

  18. Broadband single-mode operation of standard optical fibers by using a sub-wavelength optical wire filter

    OpenAIRE

    Jung, Yongmin; Brambilla, Gilberto; Richardson, David J

    2008-01-01

    We report the use of a sub-wavelength optical wire (SOW) with a specifically designed transition region as an efficient tool to filter higher order modes in multimode waveguides. Higher-order modes are effectively suppressed by controlling the transition taper profile and the diameter of the sub-wavelength optical wire. As a practical example, single-mode operation of a standard telecom optical fiber over a broad spectral window (400~1700 nm) was demonstrated with a 1?m SOW. The ability to ob...

  19. Experimental verification of a broadband planar focusing antenna based on transformation optics

    Science.gov (United States)

    Lei Mei, Zhong; Bai, Jing; Cui, Tie Jun

    2011-06-01

    It is experimentally verified that a two-dimensional planar focusing antenna based on gradient-index metamaterials has a similar performance as that of its parabolic counterpart. The antenna is designed using quasi-conformal transformation optics, and is realized with non-resonant I-shaped metamaterial unit cells. It is shown that the antenna has a broad bandwidth and very low loss. Near-field distributions of the antenna are measured and far-field radiation patterns are calculated from the measured data, which have good agreement with the full-wave simulations. Using all-dielectric metamaterials, the design can be scaled down to find applications at optical frequencies.

  20. Experimental verification of a broadband planar focusing antenna based on transformation optics

    Energy Technology Data Exchange (ETDEWEB)

    Mei Zhonglei; Bai Jing [School of Information Science and Engineering, Lanzhou University, Lanzhou 730000 (China); Cui Tiejun, E-mail: meizl@lzu.edu.cn, E-mail: tjcui@seu.edu.cn [State Key Laboratory of Millimeter Waves, Department of Radio Engineering, Southeast University, Nanjing 210096 (China)

    2011-06-15

    It is experimentally verified that a two-dimensional planar focusing antenna based on gradient-index metamaterials has a similar performance as that of its parabolic counterpart. The antenna is designed using quasi-conformal transformation optics, and is realized with non-resonant I-shaped metamaterial unit cells. It is shown that the antenna has a broad bandwidth and very low loss. Near-field distributions of the antenna are measured and far-field radiation patterns are calculated from the measured data, which have good agreement with the full-wave simulations. Using all-dielectric metamaterials, the design can be scaled down to find applications at optical frequencies.

  1. Design and optimization of broadband wide-angle antireflection structures for binary diffractive optics.

    Science.gov (United States)

    Chang, Chih-Hao; Waller, Laura; Barbastathis, George

    2010-04-01

    We propose a class of antireflecting structures that can effectively suppress reflections for binary diffractive optics. In this structure, multiple periodic thin films with gradually varying refractive indices are used to shift all reflected diffraction to the transmitted orders. The structure is optimized to operate over broad bands and wide angles using rigorous coupled-wave analysis and genetic algorithms. We validated the structure numerically using finite-difference time-domain methods. The proposed structure may lead to more efficient diffractive devices for applications in thin-film photovoltaic, waveguide coupler, and holographic optical elements.

  2. Broadband optical properties of large-area monolayer CVD molybdenum disulfide

    Science.gov (United States)

    Li, Wei; Birdwell, A. Glen; Amani, Matin; Burke, Robert A.; Ling, Xi; Lee, Yi-Hsien; Liang, Xuelei; Peng, Lianmao; Richter, Curt A.; Kong, Jing; Gundlach, David J.; Nguyen, N. V.

    2014-11-01

    Recently emerging large-area single-layer MoS2 grown by chemical vapor deposition has triggered great interest due to its exciting potential for applications in advanced electronic and optoelectronic devices. Unlike gapless graphene, MoS2 has an intrinsic band gap in the visible which crosses over from an indirect to a direct gap when reduced to a single atomic layer. In this paper, we report a comprehensive study of fundamental optical properties of MoS2 revealed by optical spectroscopy of Raman, photoluminescence, and vacuum ultraviolet spectroscopic ellipsometry. A band gap of 1.42 eV is determined by the absorption threshold of bulk MoS2 that shifts to 1.83 eV in monolayer MoS2. We extracted the high precision dielectric function up to 9.0 eV, which leads to the identification of many unique interband transitions at high symmetry points in the MoS2 momentum space. The positions of the so-called A and B excitons in single layers are found to shift upwards in energy compared with those of the bulk form and have smaller separation because of the decreased interactions between the layers. A very strong optical critical point predicted to correspond to a quasiparticle gap is observed at 2.86 eV, which is attributed to optical transitions along the parallel bands between the M and Γ points in the reduced Brillouin zone. The absence of the bulk MoS2 spin-orbit interaction peak at ˜3.0 eV in monolayer MoS2 is, as predicted, the consequence of the coalescence of nearby excitons. A higher energy optical transition at 3.98 eV, commonly occurring in bulk semiconductors, is associated with a combination of several critical points. Additionally, extending into the vacuum ultraviolet energy spectrum are a series of newly observed oscillations representing optical transitions from valence bands to higher conduction bands of the monolayer MoS2 complex band structure. These optical transitions herein reported enhance our understanding of monolayer MoS2 as well as of two

  3. Coherent detection passive optical access network enabling converged delivery of broadcast and dedicated broadband services

    DEFF Research Database (Denmark)

    Osadchiy, Alexey Vladimirovich; Prince, Kamau; Guerrero Gonzalez, Neil;

    2011-01-01

    We propose a passive optical network architecture based on coherent detection for converged delivery of broadcast services from a dedicated remote broadcast server and user-specific services from a local central office. We experimentally demonstrate this architecture with mixed traffic types...

  4. A Bottom-Up Engineered Broadband Optical Nanoabsorber for Radiometry and Energy Harnessing Applications

    Science.gov (United States)

    Kaul, Anupama B.; Coles, James B.; Megerian, Krikor G.; Eastwood, Michael; Green, Robert O.; Bandaru, Prabhakar R.

    2013-01-01

    Optical absorbers based on vertically aligned multi-walled carbon nanotubes (MWCNTs), synthesized using electric-field assisted growth, are described here that show an ultra-low reflectance, 100X lower compared to Au-black from wavelength lamba approximately 350 nm - 2.5 micron. A bi-metallic Co/Ti layer was shown to catalyze a high site density of MWCNTs on metallic substrates and the optical properties of the absorbers were engineered by controlling the bottom-up synthesis conditions using dc plasma-enhanced chemical vapor deposition (PECVD). Reflectance measurements on the MWCNT absorbers after heating them in air to 400deg showed negligible changes in reflectance which was still low, approximately 0.022 % at lamba approximately 2 micron. In contrast, the percolated structure of the reference Au-black samples collapsed completely after heating, causing the optical response to degrade at temperatures as low as 200deg. The high optical absorption efficiency of the MWCNT absorbers, synthesized on metallic substrates, over a broad spectral range, coupled with their thermal ruggedness, suggests they have promise in solar energy harnessing applications, as well as thermal detectors for radiometry.

  5. Spectral Domain Optical Coherence Tomography in Diffuse Unilateral Subacute Neuroretinitis

    Directory of Open Access Journals (Sweden)

    Carlos Alexandre de A. Garcia Filho

    2011-01-01

    Full Text Available Purpose. To describe the SD-OCT findings in patients with diffuse unilateral subacute neuroretinitis (DUSN and evaluate CRT and RNFL thickness. Methods. Patients with clinical diagnosis of DUSN who were submitted to SD-OCT were included in the study. Complete ophthalmologic examination and SD-OCT were performed. Cirrus scan strategy protocols used were macular cube, optic nerve head cube, and HD-5 line raster. Results. Eight patients with DUSN were included. Mean RNFL thickness was 80.25 μm and 104.75 μm for affected and normal eyes, respectively. Late stage had mean RNFL thickness of 74.83 μm compared to 96.5 μm in early stage. Mean CMT was 205.5 μm for affected eyes and 255.13 μm for normal fellow eyes. Conclusion. RNFL and CMT were thinner in DUSN eyes compared to normal eyes. Late-stage disease had more pronounced thinning compared to early-stage patients. This thinning in RNFL and CMT may reflect the low visual acuity in patients with DUSN.

  6. Flux density calibration in diffuse optical tomographic systems.

    Science.gov (United States)

    Biswas, Samir Kumar; Rajan, Kanhirodan; Vasu, Ram M

    2013-02-01

    The solution of the forward equation that models the transport of light through a highly scattering tissue material in diffuse optical tomography (DOT) using the finite element method gives flux density (Φ) at the nodal points of the mesh. The experimentally measured flux (Umeasured) on the boundary over a finite surface area in a DOT system has to be corrected to account for the system transfer functions (R) of various building blocks of the measurement system. We present two methods to compensate for the perturbations caused by R and estimate true flux density (Φ) from Umeasuredcal. In the first approach, the measurement data with a homogeneous phantom (Umeasuredhomo) is used to calibrate the measurement system. The second scheme estimates the homogeneous phantom measurement using only the measurement from a heterogeneous phantom, thereby eliminating the necessity of a homogeneous phantom. This is done by statistically averaging the data (Umeasuredhetero) and redistributing it to the corresponding detector positions. The experiments carried out on tissue mimicking phantom with single and multiple inhomogeneities, human hand, and a pork tissue phantom demonstrate the robustness of the approach.

  7. Broadband radiometry for photodynamic therapy

    Science.gov (United States)

    Folgosi-Correa, M. S.; Caly, J. P.; Nogueira, G. E. C.

    2010-04-01

    The effective irradiance is a useful measure to compare performances of different broadband light sources and to more precisely predict the outcome of a topical photodynamic therapy. The effective irradiance (or effective fluence rate) and the exposition time of the optical radiation usually determine the light dose. The effective irradiance (Eeff) takes into account the spectral irradiance of the source as well as the action spectrum, where the wavelength dependence of both optical diffusion through tissue and photosensitizer are considered. In practice there are no standard action spectra for the currently used photosensitizers. As a consequence, measured values of effective irradiance using different action spectra can not be compared. In order to solve this problem, the basis of the calibration theory developed for the broadband ultraviolet radiometry can be applied, where an experimental radiometer is compared with a standard radiometer. Here is presented a simple set of linear relations in the form Eeff = k . E, where E is the source irradiance and k a real positive value, here denoted as a characteristic of the radiometer, as valuable tools for correction of effective irradiances measured according to different action spectra. As a result, for two effective radiometers with different characteristics k1 and k2, measured values are Eeff and Qeff respectively, and it is easily shown that the value Eeff = Qeff • k1/k2 .

  8. Optic nerve diffusion tensor imaging after acute optic neuritis predicts axonal and visual outcomes.

    Directory of Open Access Journals (Sweden)

    Anneke van der Walt

    Full Text Available BACKGROUND: Early markers of axonal and clinical outcomes are required for early phase testing of putative neuroprotective therapies for multiple sclerosis (MS. OBJECTIVES: To assess whether early measurement of diffusion tensor imaging (DTI parameters (axial and radial diffusivity within the optic nerve during and after acute demyelinating optic neuritis (ON could predict axonal (retinal nerve fibre layer thinning and multi-focal visual evoked potential amplitude reduction or clinical (visual acuity and visual field loss outcomes at 6 or 12 months. METHODS: Thirty-seven patients presenting with acute, unilateral ON were studied at baseline, one, three, six and 12 months using optic nerve DTI, clinical and paraclinical markers of axonal injury and clinical visual dysfunction. RESULTS: Affected nerve axial diffusivity (AD was reduced at baseline, 1 and 3 months. Reduced 1-month AD correlated with retinal nerve fibre layer (RNFL thinning at 6 (R=0.38, p=0.04 and 12 months (R=0.437, p=0.008 and VEP amplitude loss at 6 (R=0.414, p=0.019 and 12 months (R=0.484, p=0.003. AD reduction at three months correlated with high contrast visual acuity at 6 (ρ = -0.519, p = 0.001 and 12 months (ρ = -0.414, p=0.011. The time-course for AD reduction for each patient was modelled using a quadratic regression. AD normalised after a median of 18 weeks and longer normalisation times were associated with more pronounced RNFL thinning and mfVEP amplitude loss at 12 months. Affected nerve radial diffusivity (RD was unchanged until three months, after which time it remained elevated. CONCLUSIONS: These results demonstrate that AD reduces during acute ON. One month AD reduction correlates with the extent of axonal loss and persistent AD reduction at 3 months predicts poorer visual outcomes. This suggests that acute ON therapies that normalise optic nerve AD by 3 months could also promote axon survival and improve visual outcomes.

  9. Nonlinear optics with broad-band lasers: Progress report, July 15, 1987-April 14, 1988

    International Nuclear Information System (INIS)

    During this reporting period several important results were obtained on the fluctuation dynamics of both continuous-wave (cw) and pulsed dye lasers, as well as their effects in certain nonlinear optical processes: (1) A new method discovered for producing optical pulses with broad bandwidths (5 GHz) and smooth, slowly varying amplitude. The bandwidth is determined purely by phase fluctuations. (2) A theoretical treatment of pulsed dye lasers was developed to explain intensity autocorrelation measurements. (3) The effects of laser bandwidth on the resonance fluorescence spectrum of a two-level atom were calculated. (4) The source of mode intensity fluctuations in a multimode, cw dye laser were shown, both experimentally and theoretically, to be caused by deterministic chaos, rather than quantum noise as had been previously assumed in the literature

  10. Broadband Fourier domain mode-locked laser for optical coherence tomography at 1060 nm

    DEFF Research Database (Denmark)

    Marschall, Sebastian; Klein, Thomas; Wieser, Wolfgang;

    2012-01-01

    Optical coherence tomography (OCT) in the 1060nm range is interesting for in vivo imaging of the human posterior eye segment (retina, choroid, sclera) due to low absorption in water and deep penetration into the tissue. Rapidly tunable light sources, such as Fourier domain mode-locked (FDML) lasers......, enable acquisition of densely sampled three-dimensional datasets covering a wide field of view. However, semiconductor optical amplifiers (SOAs)-the typical laser gain media for swept sources-for the 1060nm band could until recently only provide relatively low output power and bandwidth. We have...... implemented an FDML laser using a new SOA featuring broad gain bandwidth and high output power. The output spectrum coincides with the wavelength range of minimal water absorption, making the light source ideal for OCT imaging of the posterior eye segment. With a moderate SOA current (270 mA) we achieve up...

  11. High-dynamic-range hybrid analog-digital control broadband optical spectral processor using micromirror and acousto-optic devices.

    Science.gov (United States)

    Riza, Nabeel A; Reza, Syed Azer

    2008-06-01

    For the first time, to the best of our knowledge, the design and demonstration of a programmable spectral filtering processor is presented that simultaneously engages the power of an analog-mode optical device such as an acousto-optic tunable filter and a digital-mode optical device such as the digital micromirror device. The demonstrated processor allows a high 50 dB attenuation dynamic range across the chosen 1530-1565 nm (~C band). The hybrid analog-digital spectral control mechanism enables the processor to operate with greater versatility when compared to analog- or digital-only processor designs. Such a processor can be useful both as a test instrument in biomedical applications and as an equalizer in fiber communication networks.

  12. Self-assembly of cadmium metasilicate nanowires as a broadband optical limiter

    Science.gov (United States)

    Zheng, Chan; Dai, Chongchong; Huang, Li; Li, Wei; Chen, Wenzhe

    2016-04-01

    Cadmium metasilicate nanowires (CdSiO3 NWs) have been synthesized through a facile, eco-friendly, low-cost water-ethanol mixed-solution hydrothermal route. The transmission electron microscopy measurements of as-prepared samples indicate that the CdSiO3 NWs with diameters in the range of 10-60 nm and lengths of more than 1 μm were constructed by self-assembly of 5-10-nm CdSiO3 nanoparticles with good crystallinity. The monoclinic phase formation of the sample is studied in detail by X-ray diffraction, Fourier-transform infrared spectroscopy, and thermo gravimetric analysis. The results indicate that a pure monoclinic phase of CdSiO3 can be obtained by a hydrothermal route without further calcinations and SiO4 tetrahedra were the main constituents of the CdSiO3 NWs. The nanosecond optical limiting (OL) effects were characterized by using an open-aperture (OA) Z-scan technique with 4-ns laser pulses at both 532 and 1064 nm. Theses CdSiO3 NWs displayed an excellent OL performance at 532 and 1064 nm, which was better than carbon nanotubes, a benchmark optical limiter. Input-fluence dependent scattering measurements suggested than nonlinear scattering played an important role in the observed optical limiting behavior in CdSiO3 NWs at 532 and 1064 nm. More significantly, the NLO performance in CdSiO3 NWs incorporated solid silica gel glass has been improved in comparison to those dispersed in water. The unique structure and excellent OL property render these CdSiO3 NWs competitors in the realms of optical limiting applications.

  13. A broadband Ytterbium-doped tunable fiber laser for 3He optical pumping at 1083 nm

    OpenAIRE

    Tastevin, Geneviève; Grot, Sébastien; Courtade, Emmanuel; Bordais, Sylvain; Nacher, Pierre-Jean

    2004-01-01

    Submitted: July 2003, Published online: December 2003, Published: Appl. Phys. B 78 (2004) 145-156. Copyright : Springer-Verlag 2003 (http://www.springerlink.com). V3: symbols corrected in Figs 10-11; minor final changes included. Large amounts of hyperpolarized 3He gas with high nuclear polarization rates are required for use in neutron spin filters or nuclear magnetic resonance imaging of human lung. Very high efficiency can be obtained by metastability exchange optical pumping using mult...

  14. Method to improve the performance of reflectance diffuse optical imaging based on polygonal optical fibers arrangement

    Institute of Scientific and Technical Information of China (English)

    Weitao Li; Zhiyu Qian; Ting Li

    2009-01-01

    In order to improve the performance of reflectance diffuse optical imaging(rDOI),a novel polynomial geometry(PG)of optical fibers arrangement is proposed.Polynomial geometry is based on the hexagonal geometry(HG)and multicentered double-density(MD)mode.The overlapping sensitivity matrix,area ratio(AR),reconstruction image,two-absorber model,arid contrast-to-noise ratio(CNR)in different depths are used to evaluate the performance of PG.The other three geometries including HG,rectangular geometry(RG),and MD mode are also compared with PG.The deformation of the reconstruction images is evaluted by circular ratio(CR).The results prove that the proposed PG has high performance and minimum deformation in quality of reconstruction image in rDOI.

  15. Broadband Supercontinuum Spectrum Generated Highly Nonlinear Photonic Crystal Fiber Applicable to Medical and Optical Communication Systems

    Science.gov (United States)

    Begum, Feroza; Namihira, Yoshinori; Kaijage, Shubi F.; Kinjo, Tatsuya

    2011-09-01

    Optical-fiber-based supercontinuum (SC) light sources have attracted much research attention in recent years. High-quality nonlinear optical fibers allow us to readily implement stable and practical SC sources. In this work, we present a highly nonlinear photonic crystal fiber (HN-PCF) in optical coherence tomography (OCT) and telecommunication windows that can generate SC spectra. The finite difference method with an anisotropic perfectly matched layer boundary condition is used to calculate different properties of the proposed HN-PCF. From numerical simulation results, it is found that the HN-PCF nonlinear coefficients are more than 108.0, 74.0, and 53.0 (W·km)-1 at 1.06, 1.31, and 1.55 µm, respectively. The flattened chromatic dispersion is 0 to -4.0 ps/(nm·km) in the wavelength range of 1.06 to 1.7 µm (640 nm bandwidth), and the confinement loss is lower than 10-2 dB/km in the entire wavelength range. The generated supercontinuum bandwidths are 295.0, 408.0, and 590.0 nm at 1.06, 1.31, and 1.55 µm, respectively. The calculated longitudinal resolutions for biomedical imaging are 1.2, 1.2, and 1.1 µm at 1.06, 1.31, and 1.55 µm, respectively.

  16. Optical coupling devices to a broadband low level laser therapy set

    Science.gov (United States)

    Gryko, L.; Zajac, A.

    2011-10-01

    Precise knowledge of the spatial distributions of optical radiation in the biological medium is required in all cases of medical laser procedures, but for the low-energy interactions influencing the course of photochemical processes (biostimulation treatments) has not yet been precisely controlled. The variety of procedures and results of the trials will mobilize to look for unequivocal parameters of laser radiation, which both in vitro and in vivo will result in acceleration of cell proliferation and the expected therapeutic efficacy. There is a need to conduct objective diagnostic tests of tissues during treatment using a laser measuring system analyzing the status of the tissue (its optical properties) during therapeutic exposition. It is necessary to build an illuminator providing homogeneous distribution of spectral power density and spatial power density on the surface of the test. An illumination set is composed of a collection of over a dozen diodes LED emitting in therapeutic window of biological tissue (range 600-1000 nm). In this paper are presented the optical couplers enable the implementation of this purpose - conical coupler and MM planar fiber.

  17. Ultra-compact, broadband tunable optical bandstop filters based on a multimode one-dimensional photonic crystal waveguide.

    Science.gov (United States)

    Huang, Qingzhong; Jie, Kun; Liu, Qiang; Huang, Ying; Wang, Yi; Xia, Jinsong

    2016-09-01

    In this paper, ultra-compact, broadband tunable optical bandstop filters (OBSFs) based on a multimode one-dimensional photonic crystal waveguide (PhCW) are proposed and systematically investigated. For the wavelengths in the mini-stopband, the input mode is coupled to a contra-propagating higher order mode by the PhCW and then radiates in a taper, resulting in a stopband at the output with low backreflection at the input. Three-dimensional finite-difference time-domain method is employed to study the OBSFs. The influence of main structural parameters is analyzed, and the design is optimized to reduce the back-reflection and band sidelobes. Using localized heating, we can shift the stopband and tune the bandwidth continuously by cascading the proposed structures. Due to the strong grating strength, our device provides a more compact footprint (40 μm × 1 μm) and much broader stopband (bandwidth of up to 84 nm), compared to the counterparts based on microrings, long-period waveguide gratings, and multimode two-dimensional PhCWs. PMID:27607658

  18. General Strategy for Broadband Coherent Perfect Absorption and Multi-wavelength All-optical Switching Based on Epsilon-Near-Zero Multilayer Films

    Science.gov (United States)

    Kim, Tae Young; Badsha, Md. Alamgir; Yoon, Junho; Lee, Seon Young; Jun, Young Chul; Hwangbo, Chang Kwon

    2016-03-01

    We propose a general, easy-to-implement scheme for broadband coherent perfect absorption (CPA) using epsilon-near-zero (ENZ) multilayer films. Specifically, we employ indium tin oxide (ITO) as a tunable ENZ material, and theoretically investigate CPA in the near-infrared region. We first derive general CPA conditions using the scattering matrix and the admittance matching methods. Then, by combining these two methods, we extract analytic expressions for all relevant parameters for CPA. Based on this theoretical framework, we proceed to study ENZ CPA in a single layer ITO film and apply it to all-optical switching. Finally, using an ITO multilayer of different ENZ wavelengths, we implement broadband ENZ CPA structures and investigate multi-wavelength all-optical switching in the technologically important telecommunication window. In our design, the admittance matching diagram was employed to graphically extract not only the structural parameters (the film thicknesses and incident angles), but also the input beam parameters (the irradiance ratio and phase difference between two input beams). We find that the multi-wavelength all-optical switching in our broadband ENZ CPA system can be fully controlled by the phase difference between two input beams. The simple but general design principles and analyses in this work can be widely used in various thin-film devices.

  19. Full Spectrum Diffused and Beamed Solar Energy Application Using Optical Fibre

    CERN Document Server

    Dutta Majumdar, M R

    2007-01-01

    Existing solar energy application systems use small fraction of full spectrum of solar energy. So attempts are made to show how full spectrum solar energy can be used for diffused and beamed form of incident solar energy. Luminescent Solar Concentrator (LSC) principle with optical fibre in diffused sun light and dielectric mirror separation technique with optical fibre in beamed form are discussed. Comparison of both the cases are done. Keywords: full spectrum, solar photonics, diffused solar energy, beamed solar energy, LSC, dielectric mirror, optical fibre, Photo-Voltaic

  20. Switchable semiconductor optical fiber laser incorporating AWG and broadband FBG with high SMSR

    International Nuclear Information System (INIS)

    In this paper we propose and demonstrate a switchable wavelength fiber laser (SWFL) using a semiconductor optical amplifier (SOA) together with an arrayed waveguide grating (AWG). The proposed SOA-based SWFL is capable of generating up to 14 lasing channels from 1530.1 nm to 1534.9 nm at a channel spacing of 0.8 nm (100 GHz) and a bandwidth of 11.8 and 10.2 nm respectively. The EDFA-based SWFL has a higher peak power at –5 dBm, while to SOA-based SWFL has a peak power of only –10 dBm. However, the SOA-based SWFL exhibits a much better SMSR of between 10 to 20 dB as compared to the SMSR of the EDFA-based SWFL due to the inhomogeneous broadening properties of the SOA

  1. Light transport and rotational diffusion in optically anisotropic colloidal suspensions

    OpenAIRE

    Sandomirski, Kirill

    2006-01-01

    We have investigated for the first time the influence of magnetic field on rotational diffusion in anisotropic colloidal suspensions by the method of diffusing wave spectroscopy. It has been established that the change of static properties of the sample in magnetic field exceeds the influence of rotational Brawnian motion of colloidal particles.The main dependencies of magnitude and direction of a magnetic field B on anisotropic diffusion of light has been established. It has been shown that...

  2. Er–Yb codoped phosphate glasses with improved gain characteristics for an efficient 1.55 µm broadband optical amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Langar, Aroua; Bouzidi, Chaker [Laboratoire des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, Technopole de Borj-Cedria - B.P. 95 Hammam-Lif, 2050 (Tunisia); Elhouichet, Habib, E-mail: habib.elhouichet@fst.rnu.tn [Laboratoire des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, Technopole de Borj-Cedria - B.P. 95 Hammam-Lif, 2050 (Tunisia); Département de Physique, Faculté des Sciences de Tunis, Université de Tunis-ElManar, ElManar 2092 (Tunisia); Férid, Mokhtar [Laboratoire des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, Technopole de Borj-Cedria - B.P. 95 Hammam-Lif, 2050 (Tunisia)

    2014-04-15

    Broadband and high absorption and emission cross-sections for the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition. • This Er–Yb codoped phosphate glass is a promising gain media for developing the solid-state 1.55 µm optical amplifiers.

  3. Optical investigation of diffusion of levofloxacin mesylate in agarose hydrogel

    Science.gov (United States)

    Tan, Shuaixia; Dai, Hongjun; Wu, Juejie; Zhao, Ning; Zhang, Xiaoli; Xu, Jian

    2009-09-01

    Real-time electronic speckle pattern interferometry method has been applied to study the diffusion behavior of levofloxacin mesylate (MSALVFX) in agarose hydrogel. The results show that the diffusivity of solute decreases with the increase of concentration of agarose and adapts to Kohlrausch's law. Furthermore, Amsden's model, based on the retardance effect associated with polymer chain flexibility, was employed to simulate the diffusion behavior. The consistent results suggest that the retardance effect dominates the diffusion process of MSALFVX in hydrogel; moreover, polymer chain flexibility greatly affects drug transport within the polymer matrix.

  4. OFDM-based broadband underwater wireless optical communication system using a compact blue LED

    Science.gov (United States)

    Xu, Jing; Kong, Meiwei; Lin, Aobo; Song, Yuhang; Yu, Xiangyu; Qu, Fengzhong; Han, Jun; Deng, Ning

    2016-06-01

    We propose and experimentally demonstrate an IM/DD-OFDM-based underwater wireless optical communication system. We investigate the dependence of its BER performance on the training symbol number as well as LED's bias voltage and driving voltage. With single compact blue LED and a low-cost PIN photodiode, we achieve net bit rates of 225.90 Mb/s at a BER of 1.54×10-3 using 16-QAM and 231.95 Mb/s at a BER of 3.28×10-3 using 32-QAM, respectively, over a 2-m air channel. Over a 2-m underwater channel, we achieve net bit rates of 161.36 Mb/s using 16-QAM, 156.31 Mb/s using 32-QAM, and 127.07 Mb/s using 64-QAM, respectively. The corresponding BERs are 2.5×10-3, 7.42×10-4, and 3.17×10-3, respectively, which are all below the FEC threshold.

  5. 3D printed broadband transformation optics based all-dielectric microwave lenses

    Science.gov (United States)

    Yi, Jianjia; Nawaz Burokur, Shah; Piau, Gérard-Pascal; de Lustrac, André

    2016-04-01

    Quasi-conformal transformation optics is applied to design electromagnetic devices for focusing and collimating applications at microwave frequencies. Two devices are studied and conceived by solving Laplace’s equation that describes the deformation of a medium in a space transformation. As validation examples, material parameters of two different lenses are derived from the analytical solutions of Laplace’s equation. The first lens is applied to produce an overall directive in-phase emission from an array of sources conformed on a cylindrical structure. The second lens allows deflecting a directive beam to an off-normal direction. Full-wave simulations are performed to verify the functionality of the calculated lenses. Prototypes presenting a graded refractive index are fabricated through three-dimensional polyjet printing using solely dielectric materials. Experimental measurements carried out show very good agreement with numerical simulations, thereby validating the proposed lenses. Such easily realizable designs open the way to low-cost all-dielectric microwave lenses for beam forming and collimation.

  6. Slow and fast light via SBS in optical fibers for short pulses and broadband pump

    Science.gov (United States)

    Kalosha, V. P.; Chen, Liang; Bao, Xiaoyi

    2006-12-01

    Slow-light effect via stimulated Brillouin scattering (SBS) in single-mode optical fibers was considered for short probe pulses of nanosecond duration relevant to Gb/s data streams. Unlike recent estimations of delay versus pump based on steady-state small-signal approximation we have used numerical solution of three-wave equations describing SBS for a realistic fiber length. Both regimes of small signal and pump depletion (gain saturation) were considered. The physical origin of Stokes pulse distortion is revealed which is related to excitation of long-living acoustic field behind the pulse and prevents effective delay control by pump power increase at cw pumping. We have shown different slope of the gain-dependent delay for different pulse durations. Spectrally broadened pumping by multiple cw components, frequency-modulated pump and pulse train were studied for short pulses which allow to obtain large delay and suppress pulse distortion. In the pump-depletion regime of pumping by pulse train, both pulse delay and distortion decrease with increasing pump, and the pulse achieves advancement.

  7. Slow and fast light via SBS in optical fibers for short pulses and broadband pump.

    Science.gov (United States)

    Kalosha, V P; Chen, Liang; Bao, Xiaoyi

    2006-12-25

    Slow-light effect via stimulated Brillouin scattering (SBS) in single-mode optical fibers was considered for short probe pulses of nanosecond duration relevant to Gb/s data streams. Unlike recent estimations of delay versus pump based on steady-state small-signal approximation we have used numerical solution of three-wave equations describing SBS for a realistic fiber length. Both regimes of small signal and pump depletion (gain saturation) were considered. The physical origin of Stokes pulse distortion is revealed which is related to excitation of long-living acoustic field behind the pulse and prevents effective delay control by pump power increase at cw pumping. We have shown different slope of the gain-dependent delay for different pulse durations. Spectrally broadened pumping by multiple cw components, frequency-modulated pump and pulse train were studied for short pulses which allow to obtain large delay and suppress pulse distortion. In the pump-depletion regime of pumping by pulse train, both pulse delay and distortion decrease with increasing pump, and the pulse achieves advancement. PMID:19532161

  8. Predicting response to breast cancer neoadjuvant chemotherapy using diffuse optical spectroscopy

    OpenAIRE

    Cerussi, Albert; Hsiang, David; Shah, Natasha; Mehta, Rita; Durkin, Amanda; Butler, John; Tromberg, Bruce J.

    2007-01-01

    Diffuse optical spectroscopy (DOS) and imaging are emerging diagnostic techniques that quantitatively measure the concentration of deoxy-hemoglobin (ctHHb), oxy-hemoglobin (ctO2Hb), water (ctH2O), and lipid in cm-thick tissues. In early-stage clinical studies, diffuse optical imaging and DOS have been used to characterize breast tumor biochemical composition and monitor therapeutic response in stage II/III neoadjuvant chemotherapy patients. We investigated whether DOS measurements obtained be...

  9. Analogies between optical propagation and heat diffusion: Applications to micro-cavities, gratings and cloaks

    CERN Document Server

    Amra, Claude; Zerrad, Myriam; Guenneau, Sébastien; Soriano, Gabriel; Gralak, Boris; Bellieud, Michel; Veynante, Denis; Rolland, Nathalie

    2015-01-01

    A new analogy between optical propagation and heat diffusion in heterogeneous anisotropic media has been proposed recently [S. Guenneau, C. Amra, and D. Veynante, Optics Express Vol. 20, 8207-8218 (2012)]. A detailed derivation of this unconventional correspondence is presented and developed. In time harmonic regime, all thermal parameters are related to optical ones in artificial metallic media, thus making possible to use numerical codes developed for optics. Then the optical admittance formalism is extended to heat conduction in multilayered structures. The concepts of planar micro-cavities, diffraction gratings, and planar transformation optics for heat conduction are addressed. Results and limitations of the analogy are emphasized.

  10. OPTICAL METHOD AND SET-UP FOR THE THERMAL DIFFUSIVITY MEASURMENT OF SOLID STATE MATERIALS

    OpenAIRE

    I. G. Kisialiou; E. V. Ivakin

    2013-01-01

    Application of light-induced thermal transient gratings for measurement of thermal diffusivity of solid state materials including thin films is presented. Laser-optical set-up, which allows non-contact measurement of thermal diffusivity by transient gratings′ method is described. The set-up was designed in B.I. Stepanov Institute of Physics of NAS of Belarus.

  11. Space Telescope and Optical Reverberation Mapping Project. III. Optical Continuum Emission and Broad-Band Time Delays in NGC 5548

    CERN Document Server

    Fausnaugh, M M; Barth, A J; Bentz, M C; Bottorff, M C; Carini, M T; Croxall, K V; De Rosa, G; Goad, M R; Horne, Keith; Joner, M D; Kaspi, S; Kim, M; Klimanov, S A; Kochanek, C S; Leonard, D C; Netzer, H; Peterson, B M; Schnulle, K; Sergeev, S G; Vestergaard, M; Zheng, W -K; Anderson, M D; Arevalo, P; Bazhaw, C; Borman, G A; Boroson, T A; Brandt, W N; Breeveld, A A; Brewer, B J; Cackett, E M; Crenshaw, D M; Bonta, E Dalla; De Lorenzo-Caceres, A; Dietrich, M; Edelson, R; Efimova, N V; Ely, J; Evans, P A; Filippenko, A V; Flatland, K; Gehrels, N; Geier, S; Gelbord, J M; Gonzalez, L; Gorjian, V; Grier, C J; Grupe, D; Hall, P B; Hicks, S; Horenstein, D; Hutchison, T; Im, M; Jensen, J J; Jones, J; Kaastra, J; Kelly, B C; Kennea, J A; Kim, S C; Korista, K T; Kriss, G A; Larionov, V M; Lee, J C; Lira, P; MacInnis, F; Manne-Nicholas, E R; Mathur, S; McHardy, I M; Montouri, C; Musso, R; Nazarov, S V; Norris, R P; Nousek, J A; Okhmat, D N; Pancoast, A; Papadakis, I; Parks, J R; Pei, L; Pogge, R W; Pott, J -U; Rafter, S E; Rix, H -W; Saylor, D A; Schimoia, J S; Siegel, M; Spencer, M; Starkey, D; Sung, H -I; Teems, K G; Treu, T; Turner, C S; Uttley, P; Villforth, C; Weiss, Y; Woo, J -H; Yan, H; Young, S; Zu, Y

    2015-01-01

    We present ground-based optical photometric monitoring data for NGC 5548, part of an extended multi-wavelength reverberation mapping campaign. The light curves have nearly daily cadence from 2014 January to July in nine filters ($BVRI$ and $ugriz$). Combined with UV data from the $Hubble$ $Space$ $Telescope$ and $Swift$, we confirm significant time delays between the continuum bands as a function of wavelength, extending the wavelength coverage from $1158\\,{\\rm \\AA}$ to the $z$-band ($\\sim\\! 9160\\,{\\rm \\AA}$). We find that the lags at wavelengths longer than the $V$ band are equal to or greater than the lags of high ionization-state emission lines (such as HeII$\\lambda 1640$ and $\\lambda 4686$), suggesting that the continuum emitting source is of a physical size comparable to the inner broad line region. The trend of lag with wavelength is broadly consistent with the prediction for continuum reprocessing by an accretion disk with $\\tau \\propto \\lambda^{4/3}$. However, the lags also imply a disk radius that is...

  12. Diffuse Reflectance Spectroscopy of Human Skin Using a Commercial Fiber Optic Spectrometer

    International Nuclear Information System (INIS)

    Diffuse reflectance spectroscopy is a reliable and easy to implement technique in human tissue characterization. In this work we evaluate the performance of the commercial USB4000 miniature fiber optic spectrometer in the in-vivo measurement of the diffuse reflectance spectra of different healthy skin sites and lesions in a population of 54 volunteers. Results show, that this spectrometer reproduces well the typical signatures of skin spectra over the 400-1000 nm region. Remarkable spectral differences exist between lesions and normal surrounding skin. A diffusion-based model was used to simulate reflectance spectra collected by the optical probe of the system

  13. Modeling and tissue parameter extraction challenges for free space broadband fNIR brain imaging systems

    Science.gov (United States)

    Sultan, E.; Manseta, K.; Khwaja, A.; Najafizadeh, L.; Gandjbakhche, A.; Pourrezaei, K.; Daryoush, A. S.

    2011-02-01

    Fiber based functional near infra-red (fNIR) spectroscopy has been considered as a cost effective imaging modality. To achieve a better spatial resolution and greater accuracy in extraction of the optical parameters (i.e., μa and μ's), broadband frequency modulated systems covering multi-octave frequencies of 10-1000MHz is considered. A helmet mounted broadband free space fNIR system is considered as significant improvement over bulky commercial fiber fNIR realizations that are inherently uncomfortable and dispersive for broadband operation. Accurate measurements of amplitude and phase of the frequency modulated NIR signals (670nm, 795nm, and 850nm) is reported here using free space optical transmitters and receivers realized in a small size and low cost modules. The tri-wavelength optical transmitter is based on vertical cavity semiconductor lasers (VCSEL), whereas the sensitive optical receiver is based on either PIN or APD photodiodes combined with transimpedance amplifiers. This paper also has considered brain phantoms to perform optical parameter extraction experiments using broadband modulated light for separations of up to 5cm. Analytical models for predicting forward (transmittance) and backward (reflectance) scattering of modulated photons in diffused media has been modeled using Diffusion Equation (DE). The robustness of the DE modeling and parameter extraction algorithm was studied by experimental verification of multi-layer diffused media phantoms. In particular, comparison between analytical and experimental models for narrow band and broadband has been performed to analyze the advantages of our broadband fNIR system.

  14. Optical properties change in Te diffused As50Se50 chalcogenide thin film

    Science.gov (United States)

    Naik, Ramakanta; Behera, M.; Panda, R.; Mishra, N. C.

    2016-05-01

    In the present report, we present the effect of Te diffusion into As50Se50 thin film which changes the optical properties. The Te/As50Se50 film was irradiated by a laser beam of 532 nm to study the diffusion mechanism due to photo induced effect. The As50Se50, Te/As50Se50 films show a completely amorphous nature from X-ray diffraction study. A non direct transition was found for these films on the basis of optical transmission data carried out by Fourier Transform infrared Spectroscopy. The optical bandgap is found to be decreased with Te deposition and photo darkening phenomena is observed for the diffused film. The change in the optical constants are well supported by the corresponding change in different types of bonds which are being studied by X-ray photoelectron spectroscopy.

  15. Fast diffusion and broadening use: A research on residential adoption and usage of broadband internet in the Netherlands between 2001 and 2005

    NARCIS (Netherlands)

    Vermaas, K.

    2007-01-01

    The Netherlands has the second-highest broadband penetration at 22.5 subscribers per 100 inhabitants (OECD, 2005). This rapid adoption process makes the Netherlands an interesting case for other countries. The main goal of this research is to gain insight in the adoption and the use of broadband int

  16. Power losses in diffuse ultraviolet optical communications channels.

    Science.gov (United States)

    Raptis, Nikos; Pikasis, Evangelos; Syvridis, Dimitris

    2016-09-15

    One of the most critical parameters in free-space optical communications systems operating in a non-line-of-sight regime are the optical losses. In this Letter, we numerically calculate these losses taking into account the scattering effects using the Monte Carlo simulation technique. The obtained results are compared with experimentally obtained data at 265 nm (solar-blind UV regime). A large set of measurements at distances up to 20 m, for different elevation angles of the transmitter (UV-LEDs) and receiver (photomultiplier tube) and for different atmospheric conditions has been taken for the characterization of the optical communications channel in terms of its loss properties. PMID:27628413

  17. Recovery of optical properties using interstitial cylindrical diffusers as source and detector fibers

    Science.gov (United States)

    Baran, Timothy M.

    2016-07-01

    We demonstrate recovery of optical properties using arrays of interstitial cylindrical diffusing fibers as sources and detectors. A single 1-cm diffuser delivered laser illumination at 665 nm, while seven 1- and 2-cm diffusers at 1-cm grid spacing acted as detectors. Extraction of optical properties from these measurements was based upon a diffusion model of emission and detection distributions for these diffuser fibers, informed by previous measurements of heterogeneous axial detection. Verification of the technique was performed in 15 liquid tissue-simulating phantoms consisting of deionized water, India ink as absorber, and Intralipid 20% as scatterer. For the range of optical properties tested, mean errors were 4.4% for effective attenuation coefficient, 12.6% for absorption coefficient, and 7.6% for reduced scattering coefficient. Error in recovery tended to increase with decreasing transport albedo. For therapeutic techniques involving the delivery of light to locations deep within the body, such as interstitial photodynamic and photothermal therapies, the methods described here would allow the treatment diffuser fibers also to be used as sources and detectors for recovery of optical properties. This would eliminate the need for separately inserted fibers for spectroscopy, reducing clinical complexity and improving the accuracy of treatment planning.

  18. Ti:sapphire rib waveguides as single-transverse-mode broadband fluorescence sources for optical coherence tomography applications

    NARCIS (Netherlands)

    Grivas, C.; Shepherd, D.P.; May-Smith, T.C.; Eason, R.W.; Pollnau, M.; Crunteanu, A.; Jelinek, M.

    2003-01-01

    Ar+-beam-milled rib waveguides in pulsed-laser-deposited Ti:sapphire layers show broadband single transverse mode fluorescence emission at output powers up to 300 μW and propagation losses comparable to those in unstructured planar waveguide counterparts.

  19. Combined zero-quantum and spin-diffusion mixing for efficient homonuclear correlation spectroscopy under fast MAS: broadband recoupling and detection of long-range correlations

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Xingyu, E-mail: luxingyu@udel.edu; Guo, Changmiao, E-mail: cmguo@udel.edu; Hou, Guangjin, E-mail: hou@udel.edu; Polenova, Tatyana, E-mail: tpolenov@udel.edu [University of Delaware, Department of Chemistry and Biochemistry (United States)

    2015-01-15

    Fast magic angle spinning (MAS) NMR spectroscopy is emerging as an essential analytical and structural biology technique. Large resolution and sensitivity enhancements observed under fast MAS conditions enable structural and dynamics analysis of challenging systems, such as large macromolecular assemblies and isotopically dilute samples, using only a fraction of material required for conventional experiments. Homonuclear dipolar-based correlation spectroscopy constitutes a centerpiece in the MAS NMR methodological toolbox, and is used essentially in every biological and organic system for deriving resonance assignments and distance restraints information necessary for structural analysis. Under fast MAS conditions (rotation frequencies above 35–40 kHz), dipolar-based techniques that yield multi-bond correlations and non-trivial distance information are ineffective and suffer from low polarization transfer efficiency. To overcome this limitation, we have developed a family of experiments, CORD–RFDR. These experiments exploit the advantages of both zero-quantum RFDR and spin-diffusion based CORD methods, and exhibit highly efficient and broadband dipolar recoupling across the entire spectrum, for both short-range and long-range correlations. We have verified the performance of the CORD–RFDR sequences experimentally on a U-{sup 13}C,{sup 15}N-MLF tripeptide and by numerical simulations. We demonstrate applications of 2D CORD–RFDR correlation spectroscopy in dynein light chain LC8 and HIV-1 CA tubular assemblies. In the CORD–RFDR spectra of LC8 acquired at the MAS frequency of 40 kHz, many new intra- and inter-residue correlations are detected, which were not observed with conventional dipolar recoupling sequences. At a moderate MAS frequency of 14 kHz, the CORD–RFDR experiment exhibits excellent performance as well, as demonstrated in the HIV-1 CA tubular assemblies. Taken together, the results indicate that CORD–RFDR experiment is beneficial in a

  20. Thermal Diffusion Process Estimation for Fabrication of Graded Plastic Optical Fibre

    Institute of Scientific and Technical Information of China (English)

    M. S. Kovacevic; A. Djordjevich

    2008-01-01

    Thermal diffusion of dopants is investigated in the process of generating the graded-index profile of plastic optical fibres. Because the diffusion coefficient in high polymers has been shown to depend strongly on dopant concentration, it is allowed in this work to vary with the radial coordinate of the multistep-core fibre. A novel multi-layer model is presented for solving the diffusion equation with the variable diffusion coefficient. It is solved by the finite difference method. The solution determines the dopant diffusion profile in the fibre. It is verified against a solution from the literature and two cases of fibres with diffused profiles. The application is demonstrated on two examples of graded-index plastic optical fibres, one originally with a two-step and the other with four-step core. The results indicate that closer to the core-cladding interface, the computed diffused profile with variable diffusion coefficient D is closer to target profile than the profile obtained with constant D for the same time of thermal process.

  1. Noninvasive optical cytochrome c oxidase redox state measurements using diffuse optical spectroscopy

    Science.gov (United States)

    Lee, Jangwoen; Kim, Jae G.; Mahon, Sari B.; Mukai, David; Yoon, David; Boss, Gerry R.; Patterson, Steven E.; Rockwood, Gary; Isom, Gary; Brenner, Matthew

    2014-05-01

    A major need exists for methods to assess organ oxidative metabolic states in vivo. By contrasting the responses to cyanide (CN) poisoning versus hemorrhage in animal models, we demonstrate that diffuse optical spectroscopy (DOS) can detect cytochrome c oxidase (CcO) redox states. Intermittent decreases in inspired O2 from 100% to 21% were applied before, during, and after CN poisoning, hemorrhage, and resuscitation in rabbits. Continuous DOS measurements of total hemoglobin, oxyhemoglobin, deoxyhemoglobin, and oxidized and reduced CcO from muscle were obtained. Rabbit hemorrhage was accomplished with stepwise removal of blood, followed by blood resuscitation. CN treated rabbits received 0.166 mg/min NaCN infusion. During hemorrhage, CcO redox state became reduced concurrently with decreases in oxyhemoglobin, resulting from reduced tissue oxygen delivery and hypoxia. In contrast, during CN infusion, CcO redox state decreased while oxyhemoglobin concentration increased due to CN binding and reduction of CcO with resultant inhibition of the electron transport chain. Spectral absorption similarities between hemoglobin and CcO make noninvasive spectroscopic distinction of CcO redox states difficult. By contrasting physiological perturbations of CN poisoning versus hemorrhage, we demonstrate that DOS measured CcO redox state changes are decoupled from hemoglobin concentration measurement changes.

  2. Simultaneous measurement of thermal diffusivity and optical absorption coefficient using photothermal radiometry. II Multilayered solids

    Science.gov (United States)

    Salazar, Agustín; Fuente, Raquel; Apiñaniz, Estibaliz; Mendioroz, Arantza; Celorrio, R.

    2011-08-01

    The aim of this work is to analyze the ability of modulated photothermal radiometry to retrieve the thermal diffusivity and the optical absorption coefficient of layered materials simultaneously. First, we extend the thermal quadrupole method to calculate the surface temperature of semitransparent multilayered materials. Then, this matrix method is used to evaluate the influence of heat losses by convection and radiation, the influence of the use of thin paint layers on the accuracy of thermal diffusivity measurements, and the effect of lateral heat diffusion due to the use of Gaussian laser beams. Finally, we apply the quadrupole method to retrieve (a) the thermal contact resistance in glass stacks and (b) the thermal diffusivity and optical absorption coefficient depth profiles in heterogeneous materials with continuously varying physical properties, as is the case of functionally graded materials and partially cured dental resins.

  3. Functional imaging and assessment of the glucose diffusion rate in epithelial tissues in optical coherence tomography

    International Nuclear Information System (INIS)

    Functional imaging, monitoring and quantitative description of glucose diffusion in epithelial and underlying stromal tissues in vivo and controlling of the optical properties of tissues are extremely important for many biomedical applications including the development of noninvasive or minimally invasive glucose sensors as well as for therapy and diagnostics of various diseases, such as cancer, diabetic retinopathy, and glaucoma. Recent progress in the development of a noninvasive molecular diffusion biosensor based on optical coherence tomography (OCT) is described. The diffusion of glucose was studied in several epithelial tissues both in vitro and in vivo. Because OCT provides depth-resolved imaging of tissues with high in-depth resolution, the glucose diffusion is described not only as a function of time but also as a function of depth. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)

  4. An electrically-activated dynamic tissue-equivalent phantom for assessment of diffuse optical imaging systems

    Energy Technology Data Exchange (ETDEWEB)

    Hebden, Jeremy C; Brunker, Joanna; Correia, Teresa; Price, Ben D; Gibson, Adam P; Everdell, N L [Department of Medical Physics and Bioengineering, University College London, Gower Street, London WC1E 6BT (United Kingdom)

    2008-01-21

    A novel design of solid dynamic phantom with tissue-like optical properties is presented, which contains variable regions of contrast which are activated electrically. Reversible changes in absorption are produced by localized heating of targets impregnated with thermochromic pigment. A portable, battery-operated prototype has been constructed, and its optical and temporal characteristics have been investigated. The phantom has been developed as a means of assessing the performance of diffuse optical imaging systems, such as those used to monitor haemodynamic changes in the brain and other tissues. Images of the phantom have been reconstructed using data acquired with a continuous wave optical topography system.

  5. An electrically-activated dynamic tissue-equivalent phantom for assessment of diffuse optical imaging systems

    Science.gov (United States)

    Hebden, Jeremy C.; Brunker, Joanna; Correia, Teresa; Price, Ben D.; Gibson, Adam P.; Everdell, N. L.

    2008-01-01

    A novel design of solid dynamic phantom with tissue-like optical properties is presented, which contains variable regions of contrast which are activated electrically. Reversible changes in absorption are produced by localized heating of targets impregnated with thermochromic pigment. A portable, battery-operated prototype has been constructed, and its optical and temporal characteristics have been investigated. The phantom has been developed as a means of assessing the performance of diffuse optical imaging systems, such as those used to monitor haemodynamic changes in the brain and other tissues. Images of the phantom have been reconstructed using data acquired with a continuous wave optical topography system.

  6. Determination of Optical Properties of Turbid Media from Spatially Resolved Diffuse Reflectance by Neural Network

    Institute of Scientific and Technical Information of China (English)

    REN Hongwu; FANG Zujie

    2000-01-01

    A backpropagation (BP) network is applied to the inversion of spatially resolved diffuse reflectance from turbid media and then to determine its optical properties. A standard BP network may be trapped to the local minimum. A BP network with variable momentum and variable leaning rate can reduce this effect. After being trained, this network will produce reduced scattering coefficients and absorption coefficients when the spatially resolved diffuse reflectance are fed to its input.

  7. Diffuse optical correlation tomography of cerebral blood flow during cortical spreading depression in rat brain

    Science.gov (United States)

    Zhou, Chao; Yu, Guoqiang; Furuya, Daisuke; Greenberg, Joel; Yodh, Arjun; Durduran, Turgut

    2006-02-01

    Diffuse optical correlation methods were adapted for three-dimensional (3D) tomography of cerebral blood flow (CBF) in small animal models. The image reconstruction was optimized using a noise model for diffuse correlation tomography which enabled better data selection and regularization. The tomographic approach was demonstrated with simulated data and during in-vivo cortical spreading depression (CSD) in rat brain. Three-dimensional images of CBF were obtained through intact skull in tissues(~4mm) deep below the cortex.

  8. Diffuse optical monitoring of hemodynamic changes in piglet brain with closed head injury

    Science.gov (United States)

    Zhou, Chao; Eucker, Stephanie A.; Durduran, Turgut; Yu, Guoqiang; Ralston, Jill; Friess, Stuart H.; Ichord, Rebecca N.; Margulies, Susan S.; Yodh, Arjun G.

    2009-05-01

    We used a nonimpact inertial rotational model of a closed head injury in neonatal piglets to simulate the conditions following traumatic brain injury in infants. Diffuse optical techniques, including diffuse reflectance spectroscopy and diffuse correlation spectroscopy (DCS), were used to measure cerebral blood oxygenation and blood flow continuously and noninvasively before injury and up to 6 h after the injury. The DCS measurements of relative cerebral blood flow were validated against the fluorescent microsphere method. A strong linear correlation was observed between the two techniques (R=0.89, p<0.00001). Injury-induced cerebral hemodynamic changes were quantified, and significant changes were found in oxy- and deoxy-hemoglobin concentrations, total hemoglobin concentration, blood oxygen saturation, and cerebral blood flow after the injury. The diffuse optical measurements were robust and also correlated well with recordings of vital physiological parameters over the 6-h monitoring period, such as mean arterial blood pressure, arterial oxygen saturation, and heart rate. Finally, the diffuse optical techniques demonstrated sensitivity to dynamic physiological events, such as apnea, cardiac arrest, and hypertonic saline infusion. In total, the investigation corraborates potential of the optical methods for bedside monitoring of pediatric and adult human patients in the neurointensive care unit.

  9. Light-Induced Agglomeration and Diffusion of Different Particles with Optical Tweezers

    Institute of Scientific and Technical Information of China (English)

    LI Xue-Cong; SUN Xiu-Dong; LIU Hong-Peng; ZHANG Jian-Long

    2010-01-01

    @@ The dynamic process of light-induced agglomeration of carbon nanotubes(CNTs),C60 and Escherichia coli(E.coli)in aqueous solutions is demonstrated using an optical tweezers system.Based on the results,the diameter of the agglomerated region and the agglomeration rate increase with the increasing laser power.After the saturation-stable period,CNTs diffuse completely,C60 dusters only diffuse partially,and E.coli never diffuses in the agglomeration region.Theoretical analyses show that the molecular polarization and thermal diffusion of particles play crucial roles in the diffusion process.The results indicate the possibility of using light to aggregate and sort nanoparticles.

  10. Broadband photonic single sideband frequency up-converter based on the cross polarization modulation effect in a semiconductor optical amplifier for radio-over-fiber systems.

    Science.gov (United States)

    Lee, Seung-Hun; Kim, Hyoung-Jun; Song, Jong-In

    2014-01-13

    A broadband photonic single sideband (SSB) frequency up-converter based on the cross polarization modulation (XPolM) effect in a semiconductor optical amplifier (SOA) is proposed and experimentally demonstrated. An optical radio frequency (RF) signal in the form of an optical single sideband (OSSB) is generated by the photonic SSB frequency up-converter to solve the power fading problem caused by fiber chromatic dispersion. The generated OSSB RF signal has almost identical optical carrier power and optical sideband power. This SSB frequency up-conversion scheme shows an almost flat electrical RF power response as a function of the RF frequency in a range from 31 GHz to 75 GHz after 40 km single mode fiber (SMF) transmission. The photonic SSB frequency up-conversion technique shows negligible phase noise degradation. The phase noise of the up-converted RF signal at 49 GHz for an offset of 10 kHz is -93.17 dBc/Hz. Linearity analysis shows that the photonic SSB frequency up-converter has a spurious free dynamic range (SFDR) value of 79.51 dB · Hz(2/3). PMID:24514980

  11. Noninvasive Evaluation of Nuclear Morphometry in Breast Lesions Using Multispectral Diffuse Optical Tomography

    OpenAIRE

    Mohammad Reza Hajihashemi; Grobmyer, Stephen R.; Al-Quran, Samer Z.; Huabei Jiang

    2012-01-01

    Breast cancer is the most prevalent cancer and the main cause of cancer-related death in women worldwide. There are limitations associated with the existing clinical tools for breast cancer detection and alternative modalities for early detection and classification of breast cancer are urgently needed. Here we describe an optical imaging technique, called multispectral diffuse optical tomography (DOT), and demonstrate its ability of non-invasively evaluating nuclear morphometry for differenti...

  12. Effect of probe geometry and optical properties on the sampling depth for diffuse reflectance spectroscopy.

    Science.gov (United States)

    Hennessy, Ricky; Goth, Will; Sharma, Manu; Markey, Mia K; Tunnell, James W

    2014-01-01

    The sampling depth of light for diffuse reflectance spectroscopy is analyzed both experimentally and computationally. A Monte Carlo (MC) model was used to investigate the effect of optical properties and probe geometry on sampling depth. MC model estimates of sampling depth show an excellent agreement with experimental measurements over a wide range of optical properties and probe geometries. The MC data are used to define a mathematical expression for sampling depth that is expressed in terms of optical properties and probe geometry parameters. PMID:25349033

  13. Selective coupling of optical energy into the fundamental diffusion mode of a scattering medium

    CERN Document Server

    Ojambati, Oluwafemi S; Lagendijk, Ad; Mosk, Allard P; Vos, Willem L

    2015-01-01

    We demonstrate experimentally that optical wavefront shaping selectively couples light into the fundamental diffusion mode of a scattering medium. The total energy density inside a scattering medium of zinc oxide (ZnO) nanoparticles was probed by measuring the emitted fluorescent power of spheres that were randomly positioned inside the medium. The fluorescent power of an optimized incident wave front is observed to be enhanced compared to a non-optimized incident front. The observed enhancement increases with sample thickness. Based on diffusion theory, we derive a model wherein the distribution of energy density of wavefront-shaped light is described by the fundamental diffusion mode. The agreement between our model and the data is striking not in the least since there are no adjustable parameters. Enhanced total energy density is crucial to increase the efficiency of white LEDs, solar cells, and of random lasers, as well as to realize controlled illumination in biomedical optics.

  14. Calibration of diffuse correlation spectroscopy blood flow index with venous-occlusion diffuse optical spectroscopy in skeletal muscle

    Science.gov (United States)

    Li, Zhe; Baker, Wesley B.; Parthasarathy, Ashwin B.; Ko, Tiffany S.; Wang, Detian; Schenkel, Steven; Durduran, Turgut; Li, Gang; Yodh, Arjun G.

    2015-12-01

    We investigate and assess the utility of a simple scheme for continuous absolute blood flow monitoring based on diffuse correlation spectroscopy (DCS). The scheme calibrates DCS using venous-occlusion diffuse optical spectroscopy (VO-DOS) measurements of arm muscle tissue at a single time-point. A calibration coefficient (γ) for the arm is determined, permitting conversion of DCS blood flow indices to absolute blood flow units, and a study of healthy adults (N=10) is carried out to ascertain the variability of γ. The average DCS calibration coefficient for the right (i.e., dominant) arm was γ=(1.24±0.15)×108 (mL·100 mL-1·min-1)/(cm2/s). However, variability can be significant and is apparent in our site-to-site and day-to-day repeated measurements. The peak hyperemic blood flow overshoot relative to baseline resting flow was also studied following arm-cuff ischemia; excellent agreement between VO-DOS and DCS was found (R2=0.95, slope=0.94±0.07, mean difference=-0.10±0.45). Finally, we show that incorporation of subject-specific absolute optical properties significantly improves blood flow calibration accuracy.

  15. No Evidence of Intrinsic Optical/Near-Infrared Linear Polarization for V404 Cygni During its Bright Outburst in 2015: Broadband Modeling and Constraint on Jet Parameters

    CERN Document Server

    Tanaka, Y T; Uemura, M; Inoue, Y; Cheung, C C; Watanabe, M; Kawabata, K S; Fukazawa, Y; Yatsu, Y; Yoshii, T; Tachibana, Y; Fujiwara, T; Saito, Y; Kawai, N; Kimura, M; Isogai, K; Kato, T; Akitaya, M; Kawabata, M; Nakaoka, T; Shiki, K; Takaki, K; Yoshida, M; Imai, M; Gouda, S; Gouda, Y; Akimoto, H; Honda, S; Hosoya, K; Ikebe, A; Morihana, K; Ohshima, T; Takagi, Y; Takahashi, J; Watanabe, K; Kuroda, D; Morokuma, T; Murata, K; Nagayama, T; Nogami, D; Oasa, Y; Sekiguchi, K

    2016-01-01

    We present simultaneous optical and near-infrared (NIR) polarimetric results for the black hole binary V404 Cygni spanning the duration of its 7-day long optically-brightest phase of its 2015 June outburst. The simultaneous R and Ks-band light curves showed almost the same temporal variation except for the isolated (~30 min duration) orphan Ks-band flare observed at MJD 57193.54. We did not find any significant temporal variation of polarization degree (PD) and position angle (PA) in both R and Ks bands throughout our observations, including the duration of the orphan NIR flare. We show that the observed PD and PA are predominantly interstellar in origin by comparing the V404 Cyg polarimetric results with those of the surrounding sources within the 7'x7' field-of-view. The low intrinsic PD (less than a few percent) implies that the optical and NIR emissions are dominated by either disk or optically-thick synchrotron emission, or both. We also present the broadband spectra of V404 Cyg during the orphan NIR fla...

  16. Significance of background optical properties, time-resolved information and optode arrangement in diffuse optical imaging of term neonates

    International Nuclear Information System (INIS)

    The significance of accurate knowledge of background optical properties and time-resolved information in reconstructing images of hemodynamic changes in the neonatal brain from diffuse optical imaging data was studied using Monte Carlo (MC) simulation. A segmented anatomical magnetic resonance (MR) image and literature-derived optical properties for each tissue type were used to create a voxel-based anatomical model. Small absorbing perturbations were introduced into the anatomical model to simulate localized hemodynamic responses related to brain activation. Perturbation MC (pMC) was used as the primary method of image reconstruction. For comparison, reconstructions were also performed using the finite element method (FEM) to solve the diffusion approximation (DA) to the radiative transfer equation (RTE). The effect of optode layout was investigated using three different grids. Of the factors studied, the density of the optode grid was found to have the greatest effect on image quality. The use of time-resolved information significantly improved the spatial accuracy with all optode grids. Adequate knowledge and modeling of the optical properties of the background was found to significantly improve the spatial accuracy of the reconstructed images and make the recovery of contrast of absorption changes more consistent over simplified modeling. Localization accuracy of small perturbations was found to be 2-3 mm with accurate a priori knowledge of the background optical properties, when a grid with high optode density (>1 optode cm-2) was used.

  17. Broadband terahertz spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Wenhui Fan

    2011-01-01

    1.Introduction Spanning the frequency range between the infrared (IR) radiation and microwaves,terahertz (THz) waves are,also known as T-rays,T-lux,or simply called THz,assigned to cover the electromagnetic spectrum typically from 100 GHz (1011 Hz) to 10 THz (1013 Hz),namely,from 3 mm to 30 μm in wavelength,although slightly different definitions have been quoted by different authors.For a very long time,THz region is an almost unexplored field due to its rather unique location in the electromagnetic spectrum.Well-known techniques in optical or microwave region can not be directly employed in the THz range because optical wavelengths are too short and microwave wavelengths are too long compared to THz wavelengths.%An overview of the major techniques to generate and detect THz radiation so far, especially the major approaches to generate and detect coherent ultra-short THz pulses using ultra-short pulsed laser, has been presented. And also, this paper, in particularly, focuses on broadband THz spectroscopy and addresses on a number of issues relevant to generation and detection of broadband pulsed THz radiation as well as broadband time-domain THz spectroscopy (THz-TDS) with the help of ultra-short pulsed laser. The time-domain waveforms of coherent ultra-short THz pulses from photoconductive antenna excited by femtosecond laser with different pulse durations and their corresponding Fourier-transformed spectra have been obtained via the numerical simulation of ultrafast dynamics between femtosecond laser pulse and photoconductive material. The origins of fringes modulated on the top of broadband amplitude spectrum, which is measured by electric-optic detector based on thin nonlinear crystal and extracted by fast Fourier transformation, have been analyzed and the major solutions to get rid of these fringes are discussed.

  18. Brownian motion in a speckle light field: tunable anomalous diffusion and selective optical manipulation.

    Science.gov (United States)

    Volpe, Giorgio; Volpe, Giovanni; Gigan, Sylvain

    2014-01-01

    The motion of particles in random potentials occurs in several natural phenomena ranging from the mobility of organelles within a biological cell to the diffusion of stars within a galaxy. A Brownian particle moving in the random optical potential associated to a speckle pattern, i.e., a complex interference pattern generated by the scattering of coherent light by a random medium, provides an ideal model system to study such phenomena. Here, we derive a theory for the motion of a Brownian particle in a speckle field and, in particular, we identify its universal characteristic timescale. Based on this theoretical insight, we show how speckle light fields can be used to control the anomalous diffusion of a Brownian particle and to perform some basic optical manipulation tasks such as guiding and sorting. Our results might broaden the perspectives of optical manipulation for real-life applications. PMID:24496461

  19. Application of novel optical diffuser for urethral stricture treatment (Conference Presentation)

    Science.gov (United States)

    Nguyen, Trung Hau; Rhee, Yun-Hee; Ahn, Jin-Chul; Kang, Hyun Wook

    2016-02-01

    Optical fibers have frequently been used for photothermal laser therapy due to its efficiency to deliver laser energy directly to tissue. The aim of the current study was to develop a diffusing optical fiber to achieve radially uniform light irradiation for endoscopically treating urethral stricture. The optical diffuser was fabricated by micro-machining helical patterns on the fiber surface using CO2 laser light at 5 W. Visible light emission (632 nm) and spatial emissions (including polar, azimuthal, and longitudinal emissions) of the fiber tip were evaluated to validate the performance of the fabricated diffuser. Prior to tissue tests, numerical simulation on heat distribution was developed to estimate the degree of tissue coagulation depth during interstitial coagulation. Due to a high absorption coefficient by tissue water, 1470 nm laser was used for photothermal therapy treatment of urethral stricture to obtain a more precise depth profile. For in vitro tissue tests, porcine liver tissue was irradiated with three different power levels (3, 6, and 9 W) at various irradiation times. Porcine urethral tissue was also tested with the diffuser for 10 sec at 6 W to validate the feasibility of circumferential photothermal treatment. The treated tissue was stained with hematoxylin and eosin (H and E) and then imaged with an optical transmission microscope. The spatial emission characteristics of the diffusing optical fiber presented an almost uniform power distribution along the diffuser tip (less than 10% deviation) and around its circumference (less than 5% deviation). The peak temperature in simulation model at the tissue interface between the glass-cap and the tissue was 373 K that was higher than that at the distal end. The tissue tests showed that higher power levels resulted in lower coagulation thresholds (e.g., 1 sec at 9 W vs 8 sec at 3 W). Furthermore, the coagulation depth was approximately 20% thinner than the simulation results (p<0.001). The extent of

  20. Frequency-resolved measurement of the orbital angular momentum spectrum of femtosecond ultra-broadband optical-vortex pulses based on field reconstruction

    International Nuclear Information System (INIS)

    We propose a high-precision method for measuring the orbital angular momentum (OAM) spectrum of ultra-broadband optical-vortex (OV) pulses from fork-like interferograms between OV pulses and a reference plane-wave pulse. It is based on spatial reconstruction of the electric fields of the pulses to be measured from the frequency-resolved interference pattern. Our method is demonstrated experimentally by obtaining the OAM spectra for different spectral components of the OV pulses, enabling us to characterize the frequency dispersion of the topological charge of the OAM spectrum by a simple experimental setup. Retrieval is carried out in quasi-real time, allowing us to investigate OAM spectra dynamically. Furthermore, we determine the relative phases (including the sign) of the topological-charge-resolved electric-field amplitudes, which are significant for evaluating OVs or OV pulses with arbitrarily superposed modes. (paper)

  1. On-chip broadband ultra-compact optical couplers and polarization splitters based on off-centered and non-symmetric slotted Si-wire waveguides

    Science.gov (United States)

    Haldar, Raktim; Mishra, V.; Dutt, Avik; Varshney, Shailendra K.

    2016-10-01

    In this work, we propose novel schemes to design on-chip ultra-compact optical directional couplers (DC) and broadband polarization beam splitters (PBS) based on off-centered and asymmetric dielectric slot waveguides, respectively. Slot dimensions and positions are optimized to achieve maximum coupling coefficients between two symmetric and non-symmetric slotted Si wire waveguides through overlap integral method. We observe >88% of enhancement in the coupling coefficients when the size-optimized slots are placed in optimal positions, with respect to the same waveguides with no slot. When the waveguides are parallel, in that case, a coupling length as short as 1.73 μm is accomplished for TM mode with the off-centered and optimized slots. This scheme enables us to design optical DC with very small footprint, L c ∼ 0.9 μm in the presence of S-bends. We also report a compact (L c ∼ 1.1 μm) on-chip broadband PBS with hybrid slots. Extinction ratios of 13 dB and 22.3 dB are realized with very low insertion loss (0.055 dB and 0.008 dB) for TM and TE modes at 1.55 μm, respectively. The designed PBS exhibits a bandwidth of 78 nm for the TM mode (C-and partial L-bands) and >100 nm for the TE mode (S + C + L wavelength bands). Such on-chip devices can be used to design compact photonic interconnects and quantum information processing units efficiently. We have also investigated the fabrication tolerances of the proposed devices and described the fabrication steps to realize such hybrid devices. Our results are in good agreement with 3D FDTD simulations.

  2. Non-invasive measurements of tissue hemodynamics with hybrid diffuse optical methods

    Science.gov (United States)

    Durduran, Turgut

    Diffuse optical techniques were used to measure hemodynamics of tissues non-invasively. Spectroscopy and tomography of the brain, muscle and implanted tumors were carried out in animal models and humans. Two qualitatively different methods, diffuse optical tomography and diffuse correlation tomography, were hybridized permitting simultaneous measurement of total hemoglobin concentration, blood oxygen saturation and blood flow. This combination of information was processed further to derive estimates of oxygen metabolism (e.g. CMRO 2) in tissue. The diffuse correlation measurements of blood flow were demonstrated in human tissues, for the first time, demonstrating continous, non-invasive imaging of oxygen metabolism in large tissue volumes several centimeters below the tissue surface. The bulk of these investigations focussed on cerebral hemodynamics. Extensive validation of this methodology was carried out in in vivo rat brain models. Three dimensional images of deep tissue hemodynamics in middle cerebral artery occlusion and cortical spreading depression (CSD) were obtained. CSD hemodynamics were found to depend strongly on partial pressure of carbon dioxide. The technique was then adapted for measurement of human brain. All optical spectroscopic measurements of CMRO2 during functional activation were obtained through intact human skull non-invasively. Finally, a high spatio-temporal resolution measurement of cerebral blood flow due to somatosensory cortex activation following electrical forepaw stimulation in rats was carried out with laser speckle flowmetry. New analysis methods were introduced for laser speckle flowmetry. In other organs, deep tissue hemodynamics were measured on human calf muscle during exercise and cuff-ischemia and were shown to have some clinical utility for peripheral vascular disease. In mice tumor models, the measured hemodynamics were shown to be predictive of photodynamic therapy efficacy, again suggesting promise of clinical utility

  3. Linear optical studies of metal surfaces: Diffusion, growth, and surface dynamics

    Science.gov (United States)

    Nabighian, Edward Ara

    Through the use of laser-induced thermal desorption, a monolayer density grating is produced on a Ni(111) substrate. Using linear optical diffraction from this grating we monitor surface diffusion. By varying the angular direction of the grating we also monitor the azimuthal dependence of diffusion over 360° rotation. For hydrogen on Ni(111) we measured the diffusion rates from 65 K to 240 K, yielding diffusion rates which vary from 2 × 10 -15 cm2/sec to 2 × 10-7 cm2/sec. The results reveal energies of diffusion in both the classical overbarrier hopping and phonon-assisted quantum regimes. For xenon on Ni(111) we measured the diffusion rates from 30 K to 60 K, yielding diffusion rates which vary from 1.3 × 10-10 cm2/sec to 1 × 10-9 cm2/sec. In the case of xenon diffusion, the results also reveal an unusually low diffusivity. In addition, growth measurements of xenon on Ni(111) were studied from 35 K to 60 K using an optical reflectance difference technique. The growth of xenon was found to change mechanisms as temperature varied. At 35 K xenon grows in 3-dimensional islands (Volmer-Weber growth), at 40 K xenon grows as 2-dimensional islands (Frank van der Merwe growth), and above 60 K xenon grows to a thickness of only one monolayer. We can not only monitor the growth mechanism, but the growth rate as well. Finally we use optical reflectance difference to monitor sputtering and annealing on the Ni(111) substrate. The competing surface roughening of sputtering and surface reordering of annealing was found to follow an Arrhenius form with an activation energy of Ea = 1.1 eV/atom given by direct atom evaporation from step edges. By monitoring the formation of islands and pits on the surface during sputtering at various temperatures we are able to determine that above 823 K the annealing process reorders the surface faster than sputtering can create surface roughness. As temperature decreases we see an increase in island and pit formation due to the lessened

  4. A broadband chip-scale optical frequency synthesizer at 2.7 × 10−16 relative uncertainty

    OpenAIRE

    Huang, Shu-Wei; Yang, Jinghui; Yu, Mingbin; McGuyer, Bart H.; Kwong, Dim-Lee; Zelevinsky, Tanya; Wong, Chee Wei

    2016-01-01

    Optical frequency combs—coherent light sources that connect optical frequencies with microwave oscillations—have become the enabling tool for precision spectroscopy, optical clockwork, and attosecond physics over the past decades. Current benchmark systems are self-referenced femtosecond mode-locked lasers, but Kerr nonlinear dynamics in high-Q solid-state microresonators has recently demonstrated promising features as alternative platforms. The advance not only fosters studies of chip-scale ...

  5. A hybrid algorithm for reengineering the refractive index profile of inhomogeneous coatings from optical in-situ broadband monitoring data

    Institute of Scientific and Technical Information of China (English)

    S.Wilbrandt; O.Stenzel; D.G(a¨)bler; N.Kaiser

    2005-01-01

    Reengineering the refractive index profile of inhomogeneous coatings is a troublesome task. Multiplicity of solutions may significantly reduced by providing additional information. For this reason an in-situ broadband monitoring system was developed to measure the transmittance of the growing film directly at the rotating substrate. For characterization of these coatings, a new model was developed, which significantly reduces the number of parameters. The refractive index profile may be described by a proper number of equally spaced volume fraction values using the Bruggeman effective media approach. A good initial approximation of the refractive index profile can be generated based on deposition rates for both materials recorded with quartz crystal monitor during manufacturing. During the optimization process, a second order minimization algorithm was used to vary the refractive index profile of the whole coating and film thickness of the intermediate stages. Finally, a significantly improved accuracy of the modelled transmittance was achieved.

  6. Algorithm for localized adaptive diffuse optical tomography and its application in bioluminescence tomography

    Science.gov (United States)

    Naser, Mohamed A.; Patterson, Michael S.; Wong, John W.

    2014-04-01

    A reconstruction algorithm for diffuse optical tomography based on diffusion theory and finite element method is described. The algorithm reconstructs the optical properties in a permissible domain or region-of-interest to reduce the number of unknowns. The algorithm can be used to reconstruct optical properties for a segmented object (where a CT-scan or MRI is available) or a non-segmented object. For the latter, an adaptive segmentation algorithm merges contiguous regions with similar optical properties thereby reducing the number of unknowns. In calculating the Jacobian matrix the algorithm uses an efficient direct method so the required time is comparable to that needed for a single forward calculation. The reconstructed optical properties using segmented, non-segmented, and adaptively segmented 3D mouse anatomy (MOBY) are used to perform bioluminescence tomography (BLT) for two simulated internal sources. The BLT results suggest that the accuracy of reconstruction of total source power obtained without the segmentation provided by an auxiliary imaging method such as x-ray CT is comparable to that obtained when using perfect segmentation.

  7. Algorithm for localized adaptive diffuse optical tomography and its application in bioluminescence tomography

    International Nuclear Information System (INIS)

    A reconstruction algorithm for diffuse optical tomography based on diffusion theory and finite element method is described. The algorithm reconstructs the optical properties in a permissible domain or region-of-interest to reduce the number of unknowns. The algorithm can be used to reconstruct optical properties for a segmented object (where a CT-scan or MRI is available) or a non-segmented object. For the latter, an adaptive segmentation algorithm merges contiguous regions with similar optical properties thereby reducing the number of unknowns. In calculating the Jacobian matrix the algorithm uses an efficient direct method so the required time is comparable to that needed for a single forward calculation. The reconstructed optical properties using segmented, non-segmented, and adaptively segmented 3D mouse anatomy (MOBY) are used to perform bioluminescence tomography (BLT) for two simulated internal sources. The BLT results suggest that the accuracy of reconstruction of total source power obtained without the segmentation provided by an auxiliary imaging method such as x-ray CT is comparable to that obtained when using perfect segmentation. (paper)

  8. Development of a noncontact diffuse optical spectroscopy probe for measuring tissue optical properties.

    Science.gov (United States)

    Bish, Sheldon F; Rajaram, Narasimhan; Nichols, Brandon; Tunnell, James W

    2011-12-01

    Optical reflectance probes are often used as tools to obtain optical spectra from superficial tissues and subsequently determine optical and physiological properties associated with early stage cancer. These probes, when placed directly on the tissue, are known to cause significant pressure-dependent changes in local optical properties. To address this, we fit the probe with an optical device that images the illumination and collection fibers onto the tissue surface, eliminating the influence of contact probe pressure on the sampling area. The noncontact probe addition addresses new optical conditions that may affect its performance such as tissue surface contour, and specular reflections by implementing an autofocusing mechanism and cross polarization. Extracted optical properties of tissue simulating phantoms yield errors of 3.46% in reduced scattering and 8.62% in absorbance. Autofocusing has extended the depth of field from 4 mm to throughout the 12 mm range of autofocus travel, while cross polarization has removed the incidence angle dependent specular reflection component from the collected signal. PMID:22191909

  9. Broadband microwave phase shifter based on high speed cross gain modulation in quantum dot semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2009-01-01

    We present a scheme to achieve tunable ~180 degrees microwave phase shifts at frequencies exceeding 100 GHz based on high speed cross gain modulation in quantum dot semiconductor optical amplifiers.......We present a scheme to achieve tunable ~180 degrees microwave phase shifts at frequencies exceeding 100 GHz based on high speed cross gain modulation in quantum dot semiconductor optical amplifiers....

  10. Towards optical attosecond pulses: broadband phase coherence between an ultrafast laser and OPO using lock-tozero CEO stabilization

    Science.gov (United States)

    McCracken, R. A.; Sun, J.; Leburn, C. G.; Reid, D. T.

    2013-03-01

    The carrier-envelope-offset frequencies of the pump, signal, idler and related sum-frequency mixing pulses have been locked to 0 Hz in a 20-fs-Ti:sapphire-pumped optical parametric oscillator, satisfying a critical prerequisite for optical attosecond pulse synthesis.

  11. Imaging hemodynamic changes in preterm infant brains with two-dimensional diffuse optical tomography

    Science.gov (United States)

    Gao, Feng; Ma, Yiwen; Yang, Fang; Zhao, Huijuan; Jiang, Jingying; Kusaka, Takashi; Ueno, Masanori; Yamada, Yukio

    2008-02-01

    We present our preliminary results on two-dimensional (2-D) optical tomographic imaging of hemodynamic changes of two preterm infant brains in different ventilation settings conditions. The investigations use the established two-wavelength, 16-channel time-correlated single photon counting system for the detection, and the generalized pulse spectrum technique based algorithm for the image reconstruction. The experiments demonstrate that two-dimensional diffuse optical tomography may be a potent and relatively simple way of investigating the functions and neural development of infant brains in the perinatal period.

  12. Phase-contrast diffuse optical tomography for in vivo breast imaging: a two-step method

    International Nuclear Information System (INIS)

    We present a two-step reconstruction method that can qualitatively and quantitatively improve the reconstruction of tissue refractive index (RI) distribution by phase-contrast diffuse optical tomography (PCDOT). In this two-step method, we first recover the distribution of tissue absorption and scattering coefficients by conventional diffuse optical tomography to obtain the geometrical information of lesions, allowing the incorporation of geometrical information as a priori in the PCDOT reconstruction using a locally refined mesh. The method is validated by a series of phantom experiments and evaluated using in vivo data from 42 human subjects. The results demonstrate clear contrast of RI between the lesion and the surroundings, making the image interpretation straightforward. The sensitivity and specificity from these 42 cases are both 81% when RI is used as an imaging parameter for distinguishing between malignant and benign lesions.

  13. Theoretical limit of spatial resolution in diffuse optical tomography using a perturbation model

    Energy Technology Data Exchange (ETDEWEB)

    Konovalov, A B; Vlasov, V V [E.I. Zababakhin All-Russian Scientific-Research Institute of Technical Physics, Russian Federal Nuclear Centre, Snezhinsk, Chelyabinsk region (Russian Federation)

    2014-03-28

    We have assessed the limit of spatial resolution of timedomain diffuse optical tomography (DOT) based on a perturbation reconstruction model. From the viewpoint of the structure reconstruction accuracy, three different approaches to solving the inverse DOT problem are compared. The first approach involves reconstruction of diffuse tomograms from straight lines, the second – from average curvilinear trajectories of photons and the third – from total banana-shaped distributions of photon trajectories. In order to obtain estimates of resolution, we have derived analytical expressions for the point spread function and modulation transfer function, as well as have performed a numerical experiment on reconstruction of rectangular scattering objects with circular absorbing inhomogeneities. It is shown that in passing from reconstruction from straight lines to reconstruction using distributions of photon trajectories we can improve resolution by almost an order of magnitude and exceed the accuracy of reconstruction of multi-step algorithms used in DOT. (optical tomography)

  14. Decoding diffusivity in multiple sclerosis: analysis of optic radiation lesional and non-lesional white matter.

    Directory of Open Access Journals (Sweden)

    Alexander Klistorner

    Full Text Available Diffusion tensor imaging (DTI has been suggested as a new promising tool in MS that may provide greater pathological specificity than conventional MRI, helping, therefore, to elucidate disease pathogenesis and monitor therapeutic efficacy. However, the pathological substrates that underpin alterations in brain tissue diffusivity are not yet fully delineated. Tract-specific DTI analysis has previously been proposed in an attempt to alleviate this problem. Here, we extended this approach by segmenting a single tract into areas bound by seemingly similar pathological processes, which may better delineate the potential association between DTI metrics and underlying tissue damage.Several compartments were segmented in optic radiation (OR of 50 relapsing-remitting MS patients including T2 lesions, proximal and distal parts of fibers transected by lesion and fibers with no discernable pathology throughout the entire length of the OR.Asymmetry analysis between lesional and non-lesional fibers demonstrated a marked increase in Radial Diffusivity (RD, which was topographically limited to focal T2 lesions and potentially relates to the lesional myelin loss. A relative elevation of Axial Diffusivity (AD in the distal part of the lesional fibers was observed in a distribution consistent with Wallerian degeneration, while diffusivity in the proximal portion of transected axons remained normal. A moderate, but significant elevation of RD in OR non-lesional fibers was strongly associated with the global (but not local T2 lesion burden and is probably related to microscopic demyelination undetected by conventional MRI.This study highlights the utility of the compartmentalization approach in elucidating the pathological substrates of diffusivity and demonstrates the presence of tissue-specific patterns of altered diffusivity in MS, providing further evidence that DTI is a sensitive marker of tissue damage in both lesions and NAWM. Our results suggest that, at

  15. Brownian Motion in a Speckle Light Field: Tunable Anomalous Diffusion and Selective Optical Manipulation

    OpenAIRE

    Volpe, Giorgio; Volpe, Giovanni; Gigan, Sylvain

    2014-01-01

    The motion of particles in random potentials occurs in several natural phenomena ranging from the mobility of organelles within a biological cell to the diffusion of stars within a galaxy. A Brownian particle moving in the random optical potential associated to a speckle, i.e., a complex interference pattern generated by the scattering of coherent light by a random medium, provides an ideal mesoscopic model system to study such phenomena. Here, we derive a theory for the motion of a Brownian ...

  16. Optical properties of Mg[sub 2]NiH[sub 4] and hydrogen diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Lupu, D. (Inst. of Isotopic and Molecular Technology, Cluj-Napoca (Romania)); Grecu, R. (Inst. of Chemistry, Cluj-Napoca (Romania)); Farcas, S.I. (Inst. of Isotopic and Molecular Technology, Cluj-Napoca (Romania))

    1993-01-01

    Optical absorption of the polarons in Mg[sub 2]NiH[sub 4] has been evidenced at 1.85-1.90 eV. This leads to a polaron hopping energy in excellent agreement with the activation energy of hydrogen diffusion. A model is proposed for intrinsic defect states implied in the correlated motion of the proton and a localized electron. (orig.)

  17. A diffusion approximation theorem for a nonlinear PDE with application to random birefringent optical fibers

    CERN Document Server

    Gazeau, Maxime

    2011-01-01

    In this article, we propose a generalization of the theory of diffusion approximation for random ODE to a nonlinear system of random Schr\\"odinger equations. This system arises in the study of pulse propagation in randomly birefringent optical fibers. We first show existence and uniqueness of solutions for the random PDE and the limiting equation. We follow the work of Garnier-Marty, where a linear electric field is considered, and we get an asymptotic dynamic for the nonlinear electric field.

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

    OpenAIRE

    Amir Reza Sadrolhosseini; Suraya Abdul Rashid; Noor, A. S. M.; Alireza Kharazmi; Lim, H. N.; Mohd Adzir Mahdi

    2016-01-01

    A polypyrrole-nanoparticles reduced graphene oxide nanocomposite layer was prepared using electrochemical method. The prepared samples were characterized using Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and UV-visible spectroscopy. The band gap of nanocomposite layers was calculated from UV-visible spectra and the thermal diffusivity of layers was measured using a photoacoustic technique. As experimental results, the optical band gap was in the range...

  19. High-Speed GPU-Based Fully Three-Dimensional Diffuse Optical Tomographic System

    OpenAIRE

    2014-01-01

    We have developed a graphics processor unit (GPU-) based high-speed fully 3D system for diffuse optical tomography (DOT). The reduction in execution time of 3D DOT algorithm, a severely ill-posed problem, is made possible through the use of (1) an algorithmic improvement that uses Broyden approach for updating the Jacobian matrix and thereby updating the parameter matrix and (2) the multinode multithreaded GPU and CUDA (Compute Unified Device Architecture) software a...

  20. Comparing analytical and Monte Carlo optical diffusion models in phosphor-based X-ray detectors

    Science.gov (United States)

    Kalyvas, N.; Liaparinos, P.

    2014-03-01

    Luminescent materials are employed as radiation to light converters in detectors of medical imaging systems, often referred to as phosphor screens. Several processes affect the light transfer properties of phosphors. Amongst the most important is the interaction of light. Light attenuation (absorption and scattering) can be described either through "diffusion" theory in theoretical models or "quantum" theory in Monte Carlo methods. Although analytical methods, based on photon diffusion equations, have been preferentially employed to investigate optical diffusion in the past, Monte Carlo simulation models can overcome several of the analytical modelling assumptions. The present study aimed to compare both methodologies and investigate the dependence of the analytical model optical parameters as a function of particle size. It was found that the optical photon attenuation coefficients calculated by analytical modeling are decreased with respect to the particle size (in the region 1- 12 μm). In addition, for particles sizes smaller than 6μm there is no simultaneous agreement between the theoretical modulation transfer function and light escape values with respect to the Monte Carlo data.

  1. Yb- and Er-doped fiber laser Q-switched with an optically uniform, broadband WS2 saturable absorber

    OpenAIRE

    Zhang, M; Guohua Hu; Guoqing Hu; Howe, R. C. T.; Chen, L.; Zheng, Z.; Hasan, T.

    2015-01-01

    We demonstrate a ytterbium (Yb) and an erbium (Er)-doped fiber laser Q-switched by a solution processed, optically uniform, few-layer tungsten disulfide saturable absorber (WS?-SA). Nonlinear optical absorption of the WS?-SA in the sub-bandgap region, attributed to the edge-induced states, is characterized by 3.1% and 4.9% modulation depths with 1.38 and 3.83?MW/cm? saturation intensities at 1030 and 1558?nm, respectively. By integrating the optically uniform WS?-SA in the Yb- and Er-doped la...

  2. A broadband chip-scale optical frequency synthesizer at 2.7 × 10(-16) relative uncertainty.

    Science.gov (United States)

    Huang, Shu-Wei; Yang, Jinghui; Yu, Mingbin; McGuyer, Bart H; Kwong, Dim-Lee; Zelevinsky, Tanya; Wong, Chee Wei

    2016-04-01

    Optical frequency combs-coherent light sources that connect optical frequencies with microwave oscillations-have become the enabling tool for precision spectroscopy, optical clockwork, and attosecond physics over the past decades. Current benchmark systems are self-referenced femtosecond mode-locked lasers, but Kerr nonlinear dynamics in high-Q solid-state microresonators has recently demonstrated promising features as alternative platforms. The advance not only fosters studies of chip-scale frequency metrology but also extends the realm of optical frequency combs. We report the full stabilization of chip-scale optical frequency combs. The microcomb's two degrees of freedom, one of the comb lines and the native 18-GHz comb spacing, are simultaneously phase-locked to known optical and microwave references. Active comb spacing stabilization improves long-term stability by six orders of magnitude, reaching a record instrument-limited residual instability of [Formula: see text]. Comparing 46 nitride frequency comb lines with a fiber laser frequency comb, we demonstrate the unprecedented microcomb tooth-to-tooth relative frequency uncertainty down to 50 mHz and 2.7 × 10(-16), heralding novel solid-state applications in precision spectroscopy, coherent communications, and astronomical spectrography.

  3. Covalent Modification of MoS2 with Poly(N-vinylcarbazole) for Solid-State Broadband Optical Limiters.

    Science.gov (United States)

    Cheng, Hongxia; Dong, Ningning; Bai, Ting; Song, Yi; Wang, Jun; Qin, Yuanhao; Zhang, Bin; Chen, Yu

    2016-03-18

    New soluble MoS2 nanosheets covalently functionalized with poly(N-vinylcarbazole) (MoS2-PVK) were in situ synthesized for the first time. In contrast to MoS2 and MoS2 /PVK blends, both the solution of MoS2 -PVK in DMF and MoS2-PVK/poly(methyl methacrylate) (PMMA) film show superior nonlinear optical and optical limiting responses. The MoS2-PVK/PMMA film shows the largest nonlinear coefficients (βeff) of about 917 cm GW(-1) at λ=532 nm (cf. 100.69 cm GW(-1) for MoS2/PMMA and 125.12 cm GW(-1) for MoS2/PVK/PMMA) and about 461 cm GW(-1) at λ=1064 nm (cf. -48.92 cm GW(-1) for MoS2/PMMA and 147.56 cm GW(-1) for MoS2/PVK/PMMA). A larger optical limiting effect, with thresholds of about 0.3 GW cm(-2) at λ=532 nm and about 0.5 GW cm(-2) at λ=1064 nm, was also achieved from the MoS2-PVK/PMMA film. These values are among the highest reported for MoS2-based nonlinear optical materials. These results show that covalent functionalization of MoS2 with polymers is an effective way to improve nonlinear optical responses for efficient optical limiting devices.

  4. A broadband chip-scale optical frequency synthesizer at 2.7 × 10(-16) relative uncertainty.

    Science.gov (United States)

    Huang, Shu-Wei; Yang, Jinghui; Yu, Mingbin; McGuyer, Bart H; Kwong, Dim-Lee; Zelevinsky, Tanya; Wong, Chee Wei

    2016-04-01

    Optical frequency combs-coherent light sources that connect optical frequencies with microwave oscillations-have become the enabling tool for precision spectroscopy, optical clockwork, and attosecond physics over the past decades. Current benchmark systems are self-referenced femtosecond mode-locked lasers, but Kerr nonlinear dynamics in high-Q solid-state microresonators has recently demonstrated promising features as alternative platforms. The advance not only fosters studies of chip-scale frequency metrology but also extends the realm of optical frequency combs. We report the full stabilization of chip-scale optical frequency combs. The microcomb's two degrees of freedom, one of the comb lines and the native 18-GHz comb spacing, are simultaneously phase-locked to known optical and microwave references. Active comb spacing stabilization improves long-term stability by six orders of magnitude, reaching a record instrument-limited residual instability of [Formula: see text]. Comparing 46 nitride frequency comb lines with a fiber laser frequency comb, we demonstrate the unprecedented microcomb tooth-to-tooth relative frequency uncertainty down to 50 mHz and 2.7 × 10(-16), heralding novel solid-state applications in precision spectroscopy, coherent communications, and astronomical spectrography. PMID:27152341

  5. Covalent Modification of MoS2 with Poly(N-vinylcarbazole) for Solid-State Broadband Optical Limiters.

    Science.gov (United States)

    Cheng, Hongxia; Dong, Ningning; Bai, Ting; Song, Yi; Wang, Jun; Qin, Yuanhao; Zhang, Bin; Chen, Yu

    2016-03-18

    New soluble MoS2 nanosheets covalently functionalized with poly(N-vinylcarbazole) (MoS2-PVK) were in situ synthesized for the first time. In contrast to MoS2 and MoS2 /PVK blends, both the solution of MoS2 -PVK in DMF and MoS2-PVK/poly(methyl methacrylate) (PMMA) film show superior nonlinear optical and optical limiting responses. The MoS2-PVK/PMMA film shows the largest nonlinear coefficients (βeff) of about 917 cm GW(-1) at λ=532 nm (cf. 100.69 cm GW(-1) for MoS2/PMMA and 125.12 cm GW(-1) for MoS2/PVK/PMMA) and about 461 cm GW(-1) at λ=1064 nm (cf. -48.92 cm GW(-1) for MoS2/PMMA and 147.56 cm GW(-1) for MoS2/PVK/PMMA). A larger optical limiting effect, with thresholds of about 0.3 GW cm(-2) at λ=532 nm and about 0.5 GW cm(-2) at λ=1064 nm, was also achieved from the MoS2-PVK/PMMA film. These values are among the highest reported for MoS2-based nonlinear optical materials. These results show that covalent functionalization of MoS2 with polymers is an effective way to improve nonlinear optical responses for efficient optical limiting devices. PMID:26891470

  6. A broadband chip-scale optical frequency synthesizer at 2.7 × 10−16 relative uncertainty

    Science.gov (United States)

    Huang, Shu-Wei; Yang, Jinghui; Yu, Mingbin; McGuyer, Bart H.; Kwong, Dim-Lee; Zelevinsky, Tanya; Wong, Chee Wei

    2016-01-01

    Optical frequency combs—coherent light sources that connect optical frequencies with microwave oscillations—have become the enabling tool for precision spectroscopy, optical clockwork, and attosecond physics over the past decades. Current benchmark systems are self-referenced femtosecond mode-locked lasers, but Kerr nonlinear dynamics in high-Q solid-state microresonators has recently demonstrated promising features as alternative platforms. The advance not only fosters studies of chip-scale frequency metrology but also extends the realm of optical frequency combs. We report the full stabilization of chip-scale optical frequency combs. The microcomb’s two degrees of freedom, one of the comb lines and the native 18-GHz comb spacing, are simultaneously phase-locked to known optical and microwave references. Active comb spacing stabilization improves long-term stability by six orders of magnitude, reaching a record instrument-limited residual instability of 3.6mHz/τ. Comparing 46 nitride frequency comb lines with a fiber laser frequency comb, we demonstrate the unprecedented microcomb tooth-to-tooth relative frequency uncertainty down to 50 mHz and 2.7 × 10−16, heralding novel solid-state applications in precision spectroscopy, coherent communications, and astronomical spectrography. PMID:27152341

  7. Broadband frequency conversion

    DEFF Research Database (Denmark)

    Sanders, Nicolai; Jensen, Ole Bjarlin; Tidemand-Lichtenberg, Peter;

    We present a simple, passive and static setup for broadband frequency conversion. By using simple optical components like lenses, mirrors and gratings, we obtain the spectral angular dispersion to match the second harmonic generation phasematching angles in a nonlinear BiBO crystal. We are able to...... frequency double a single-frequency diode laser, tunable in the 1020-1090 nm range, with almost equal efficiency for all wavelengths. In the experimental setup, the width of the phasematch was increased with a factor of 50. The method can easily be extended to other wavelength ranges and nonlinear crystals...

  8. Assessment of Optic Nerve Impairment in Patients with Neuromyelitis Optica by MR Diffusion Tensor Imaging.

    Directory of Open Access Journals (Sweden)

    Zhiye Chen

    Full Text Available Diffusion tensor imaging (DTI has been used for the evaluation of the white matter integrity. In this study, we evaluated optic nerve impairment in patients with neuromyelitis optica (NMO using DTI.Optic nerve DTI were performed on 28 NMO patients and 38 normal controls. Fractional anisotropy (FA values were measured in the anterior, middle, and posterior parts of the intraorbital optic nerve segment. For the posterior intraorbital optic nerve, FA values of BI (0.20±0.07, MI (0.24±0.16, and NA (0.25±0.14 decreased significantly compared with that of NC (0.43±0.07 (P<0.05, and ROC analysis demonstrated that the area under the curve (AUC measurements for BI vs. NC, MI vs. NC, NA vs. NC, and NMO (including BI, MI, and NA vs. NC were 0.99, 0.93, 0.88, and 0.96, respectively. The corresponding diagnostic sensitivities of ROC analysis were 100%, 80%, 80%, and 91%; and the specificities were 93%, 97%, 91%, and 93%.Decreased FA value in the intraorbital optic nerve, especially in the posterior part of the nerve, was demonstrated as a characteristic MR feature for NMO-related optic nerve impairment.

  9. Magnetic resonance diffusion tensor imaging (MRDTI) of the optic nerve and optic radiations at 3T in children with neurofibromatosis type I (NF-1)

    Energy Technology Data Exchange (ETDEWEB)

    Filippi, Christopher G.; Nickerson, Joshua P. [University of Vermont School of Medicine-FAHC, Department of Radiology, Burlington, VT (United States); Bos, Aaron [University of Vermont School of Medicine, Burlington, VT (United States); Salmela, Michael B. [University of Minnesota School of Medicine, Department of Radiology, Minneapolis, MN (United States); Koski, Chris J. [James Madison University, Department of Political Sciences, Harrisonburg, VA (United States); Cauley, Keith A. [University of Massachusetts Memorial Medical Center, Department of Radiology, Worcester, MA (United States)

    2012-02-15

    Optic pathway glioma (OPG) is a characteristic hallmark of neurofibromatosis type I (NF-I). To evaluate the feasibility of magnetic resonance diffusion tensor imaging (MRDTI) at 3T to detect abnormalities of the optic nerves and optic radiations in children with NF-I. 3-T MRDTI was prospectively performed in 9 children with NF-I (7 boys, 2 girls, average age 7.8 years, range 3-17 years) and 44 controls (25 boys, 19 girls, average age 8.1 years, range 3-17 years). Fractional anisotropy (FA) and mean diffusivity were determined by region-of-interest analysis for the optic nerves and radiations. Statistical analysis compared controls to NF-I patients. Two NF-I patients had bilateral optic nerve gliomas, three had chiasmatic gliomas and four had unidentified neurofibromatosis objects (UNOs) along the optic nerve pathways. All NF-I patients had statistically significant decreases in FA and elevations in mean diffusivity in the optic nerves and radiations compared to age-matched controls. MRDTI can evaluate the optic pathways in children with NF-I. Statistically significant abnormalities were detected in the diffusion tensor metrics of the optic nerves and radiations in children with NF-I compared to age-matched controls. (orig.)

  10. Broadband emission at NIR in double-core optical fiber co-doped with Nd3+/Yb3+ ions

    Science.gov (United States)

    Bykowski, Kamil; Bruszewski, Artur; Cimaszewski, Dominik; Ragin, Tomasz; Zmojda, Jacek; Kochanowicz, Marcin; Miluski, Piotr; Dorosz, Dominik

    2015-09-01

    In the paper spectroscopic properties of aluminosilicate glasses co-doped with Nd3+/Yb3+ were investigated. Strong and wide emission in the 1μm region obtained by optimization of Nd3+ --> Yb3+ energy transfer corresponding to the superposition of optical transitions Nd3+:4F3/2 --> 4I11/2 and Yb3+:2F5/2 --> 2F7/2 (Yb3+) was observed. The construction of double-core, double-clad optical fiber with cores manufactured from the aluminosilicate glass (co-doped with 1st core- 0.15Nd2O3, 2nd core - 0.15Nd2O3/0.45Yb2O3 mol%) was developed. Comparative analysis of shape of luminescence (λp=808 nm) obtained in bulk glass (0.15Nd2O3/0.45Yb2O3) and ASE in double-core optical fiber clearly shows significant differences in luminescent properties. Mechanisms influencing differences in the shape of luminescence of fabricated glass and optical fiber were also discussed.

  11. Fast silicon photomultiplier improves signal harvesting and reduces complexity in time-domain diffuse optics.

    Science.gov (United States)

    Mora, Alberto Dalla; Martinenghi, Edoardo; Contini, Davide; Tosi, Alberto; Boso, Gianluca; Durduran, Turgut; Arridge, Simon; Martelli, Fabrizio; Farina, Andrea; Torricelli, Alessandro; Pifferi, Antonio

    2015-06-01

    We present a proof of concept prototype of a time-domain diffuse optics probe exploiting a fast Silicon PhotoMultiplier (SiPM), featuring a timing resolution better than 80 ps, a fast tail with just 90 ps decay time-constant and a wide active area of 1 mm2. The detector is hosted into the probe and used in direct contact with the sample under investigation, thus providing high harvesting efficiency by exploiting the whole SiPM numerical aperture and also reducing complexity by avoiding the use of cumbersome fiber bundles. Our tests also demonstrate high accuracy and linearity in retrieving the optical properties and suitable contrast and depth sensitivity for detecting localized inhomogeneities. In addition to a strong improvement in both instrumentation cost and size with respect to legacy solutions, the setup performances are comparable to those of state-of-the-art time-domain instrumentation, thus opening a new way to compact, low-cost and high-performance time-resolved devices for diffuse optical imaging and spectroscopy. PMID:26072763

  12. Study of continuous-wave domain fluorescence diffuse optical tomography for quality control on agricultural produce

    Energy Technology Data Exchange (ETDEWEB)

    Nadhira, Vebi, E-mail: vebi@tf.itb.ac.id; Kurniadi, Deddy, E-mail: vebi@tf.itb.ac.id; Juliastuti, E., E-mail: vebi@tf.itb.ac.id; Sutiswan, Adeline, E-mail: vebi@tf.itb.ac.id [Instrumentation and Control Research Group, Faculty of Industrial Technology, Institute Technology of Bandung, Ganesha 10 40132 Bandung (Indonesia)

    2014-03-24

    The importance of monitoring the quality of vegetables and fruits is prosperity by giving a competitive advantage for producer and providing a more healthy food for consumer. Diffuse Optical Tomography (DOT) is offering the possibility to detect the internal defects of the agricultural produce quality. Fluorescence diffuse optical tomography (FDOT) is the development of DOT, offering the possibilities to improve spatial resolution and to contrast image. The purpose of this research is to compare FDOT and DOT in forward analysis with continuous wave approach. The scattering and absorbing parameters of potatoes are used to represent the real condition. The object was illuminated by the NIR source from some positions on the boundary of object. A set of NIR detector are placed on the peripheral position of the object to measure the intensity of propagated or emitted light. In the simulation, we varied a condition of object then we analyzed the sensitivity of forward problem. The result of this study shows that FDOT has a better sensitivity than DOT and a better potential to monitor internal defects of agricultural produce because of the contrast value between optical and fluorescence properties of agricultural produce normal tissue and defects.

  13. Study of continuous-wave domain fluorescence diffuse optical tomography for quality control on agricultural produce

    International Nuclear Information System (INIS)

    The importance of monitoring the quality of vegetables and fruits is prosperity by giving a competitive advantage for producer and providing a more healthy food for consumer. Diffuse Optical Tomography (DOT) is offering the possibility to detect the internal defects of the agricultural produce quality. Fluorescence diffuse optical tomography (FDOT) is the development of DOT, offering the possibilities to improve spatial resolution and to contrast image. The purpose of this research is to compare FDOT and DOT in forward analysis with continuous wave approach. The scattering and absorbing parameters of potatoes are used to represent the real condition. The object was illuminated by the NIR source from some positions on the boundary of object. A set of NIR detector are placed on the peripheral position of the object to measure the intensity of propagated or emitted light. In the simulation, we varied a condition of object then we analyzed the sensitivity of forward problem. The result of this study shows that FDOT has a better sensitivity than DOT and a better potential to monitor internal defects of agricultural produce because of the contrast value between optical and fluorescence properties of agricultural produce normal tissue and defects

  14. Hybrid diffuse optical techniques for continuous hemodynamic measurement in gastrocnemius during plantar flexion exercise

    Science.gov (United States)

    Henry, Brad; Zhao, Mingjun; Shang, Yu; Uhl, Timothy; Thomas, D. Travis; Xenos, Eleftherios S.; Saha, Sibu P.; Yu, Guoqiang

    2015-12-01

    Occlusion calibrations and gating techniques have been recently applied by our laboratory for continuous and absolute diffuse optical measurements of forearm muscle hemodynamics during handgrip exercises. The translation of these techniques from the forearm to the lower limb is the goal of this study as various diseases preferentially affect muscles in the lower extremity. This study adapted a hybrid near-infrared spectroscopy and diffuse correlation spectroscopy system with a gating algorithm to continuously quantify hemodynamic responses of medial gastrocnemius during plantar flexion exercises in 10 healthy subjects. The outcomes from optical measurement include oxy-, deoxy-, and total hemoglobin concentrations, blood oxygen saturation, and relative changes in blood flow (rBF) and oxygen consumption rate (rV˙O2). We calibrated rBF and rV˙O2 profiles with absolute baseline values of BF and V˙O2 obtained by venous and arterial occlusions, respectively. Results from this investigation were comparable to values from similar studies. Additionally, significant correlation was observed between resting local muscle BF measured by the optical technique and whole limb BF measured concurrently by a strain gauge venous plethysmography. The extensive hemodynamic and metabolic profiles during exercise will allow for future comparison studies to investigate the diagnostic value of hybrid technologies in muscles affected by disease.

  15. Dynamics of an optically confined nanoparticle diffusing normal to a surface

    Science.gov (United States)

    Schein, Perry; O'Dell, Dakota; Erickson, David

    2016-06-01

    Here we measure the hindered diffusion of an optically confined nanoparticle in the direction normal to a surface, and we use this to determine the particle-surface interaction profile in terms of the absolute height. These studies are performed using the evanescent field of an optically excited single-mode silicon nitride waveguide, where the particle is confined in a height-dependent potential energy well generated from the balance of optical gradient and surface forces. Using a high-speed cmos camera, we demonstrate the ability to capture the short time-scale diffusion dominated motion for 800-nm-diam polystyrene particles, with measurement times of only a few seconds per particle. Using established theory, we show how this information can be used to estimate the equilibrium separation of the particle from the surface. As this measurement can be made simultaneously with equilibrium statistical mechanical measurements of the particle-surface interaction energy landscape, we demonstrate the ability to determine these in terms of the absolute rather than relative separation height. This enables the comparison of potential energy landscapes of particle-surface interactions measured under different experimental conditions, enhancing the utility of this technique.

  16. Diffusion, thermalization and optical pumping of YbF molecules in a cold buffer gas cell

    CERN Document Server

    Skoff, S M; Sinclair, C D J; Hudson, J J; Segal, D M; Sauer, B E; Hinds, E A; Tarbutt, M R

    2010-01-01

    We produce YbF molecules with a density of 10^18 m^-3 using laser ablation inside a cryogenically-cooled cell filled with a helium buffer gas. Using absorption imaging and absorption spectroscopy we study the formation, diffusion, thermalization and optical pumping of the molecules. The absorption images show an initial rapid expansion of molecules away from the ablation target followed by a much slower diffusion to the cell walls. We study how the time constant for diffusion depends on the helium density and temperature, and obtain values for the YbF-He diffusion cross-section at two different temperatures. We measure the translational and rotational temperatures of the molecules as a function of time since formation, obtain the characteristic time constant for the molecules to thermalize with the cell walls, and elucidate the process responsible for limiting this thermalization rate. Finally, we make a detailed study of how the absorption of the probe laser saturates as its intensity increases, showing that...

  17. Broadband absorption engineering of hyperbolic metafilm patterns

    Science.gov (United States)

    Ji, Dengxin; Song, Haomin; Zeng, Xie; Hu, Haifeng; Liu, Kai; Zhang, Nan; Gan, Qiaoqiang

    2014-03-01

    Perfect absorbers are important optical/thermal components required by a variety of applications, including photon/thermal-harvesting, thermal energy recycling, and vacuum heat liberation. While there is great interest in achieving highly absorptive materials exhibiting large broadband absorption using optically thick, micro-structured materials, it is still challenging to realize ultra-compact subwavelength absorber for on-chip optical/thermal energy applications. Here we report the experimental realization of an on-chip broadband super absorber structure based on hyperbolic metamaterial waveguide taper array with strong and tunable absorption profile from near-infrared to mid-infrared spectral region. The ability to efficiently produce broadband, highly confined and localized optical fields on a chip is expected to create new regimes of optical/thermal physics, which holds promise for impacting a broad range of energy technologies ranging from photovoltaics, to thin-film thermal absorbers/emitters, to optical-chemical energy harvesting.

  18. Optical coherence photoacoustic microscopy (OC-PAM) with an intensity-modulated continuous-wave broadband light source

    Science.gov (United States)

    Liu, Xiaojing; Wen, Rong; Li, Yiwen; Jiao, Shuliang

    2016-06-01

    We developed an optical coherence photoacoustic microscopy system using an intensity-modulated continuous-wave superluminescent diode with a center wavelength of 840 nm. The system can accomplish optical coherence tomography (OCT) and photoacoustic microscopy (PAM) simultaneously. Compared to the system with a pulsed light source, this system is able to achieve OCT imaging with quality as high as conventional spectral-domain OCT. Since both of the OCT and PAM images are generated from the same group of photons, they are intrinsically registered in the lateral directions. The system was tested for multimodal imaging the vasculature of mouse ear in vivo by using gold nanorods as contrast agent for PAM, as well as excised porcine eyes ex vivo. The OCT and PAM images showed complimentary information of the sample.

  19. Effect of fiber dispersion on broadband chaos communications implemented by electro-optic nonlinear delay phase dynamics

    OpenAIRE

    Nguimdo, Romain Modeste; Lavrov, R.; Colet, Pere; Jacquot, M.; Chembo Kouomou, Yanne; Larger, Laurent

    2010-01-01

    We investigate theoretically and experimentally the detrimental e ect of ber dispersion on the synchroniza- tion of an optoelectronic phase chaos cryptosystem. We evaluate the root-mean square synchronization error and the cancellation spectra between the emitter and the re- ceiver in order to characterize the quality of the optical ber communication link. These two indicators explicitly show in temporal and spectral domain how ber dispersion does negatively a ect t...

  20. Optical Spectroscopy of Galactic Cirrus Clouds Extended Red Emission in the Diffuse Interstellar Medium

    CERN Document Server

    Szomoru, A; Szomoru, Arpad; Guhathakurta, Puragra

    1997-01-01

    We present initial results from the first optical spectroscopic survey of high latitude Galactic cirrus clouds. The observed shape of the cirrus spectrum does not agree with that of scattered ambient Galactic starlight. This mismatch can be explained by the presence of Extended Red Emission (ERE) in the diffuse interstellar medium, as found in many other astronomical objects, probably caused by photoluminescence of hydrocarbons. The integrated ERE intensity, I_ERE \\approx 1.2 x 10^{-5} erg s^{-1} cm^{-2} sr^{-1}, is roughly a third of the scattered light intensity, consistent with recent color measurements of diffuse Galactic light. The peak of the cirrus ERE (lambda_{0} \\sim 6000 AA) is shifted towards short (bluer) wavelengths compared to the ERE in sources excited by intense ultraviolet radiation, such as HII regions (lambda_{0} sim 8000 AA); such a trend is seen in laboratory experiments on hydrogenated amorphous carbon films.

  1. Adaptive anisotropic diffusion for noise reduction of phase images in Fourier domain Doppler optical coherence tomography.

    Science.gov (United States)

    Xia, Shaoyan; Huang, Yong; Peng, Shizhao; Wu, Yanfeng; Tan, Xiaodi

    2016-08-01

    Phase image in Fourier domain Doppler optical coherence tomography offers additional flow information of investigated samples, which provides valuable evidence towards accurate medical diagnosis. High quality phase images are thus desirable. We propose a noise reduction method for phase images by combining a synthetic noise estimation criteria based on local noise estimator (LNE) and distance median value (DMV) with anisotropic diffusion model. By identifying noise and signal pixels accurately and diffusing them with different coefficients respectively and adaptive iteration steps, we demonstrated the effectiveness of our proposed method in both phantom and mouse artery images. Comparison with other methods such as filtering method (mean, median filtering), wavelet method, probabilistic method and partial differential equation based methods in terms of peak signal-to-noise ratio (PSNR), equivalent number of looks (ENL) and contrast-to-noise ratio (CNR) showed the advantages of our method in reserving image energy and removing noise. PMID:27570687

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

    Directory of Open Access Journals (Sweden)

    Amir Reza Sadrolhosseini

    2016-01-01

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

  3. Generation of high beam quality, high-energy and broadband tunable mid-infrared pulse from a KTA optical parametric amplifier

    Science.gov (United States)

    Chen, Yun; Li, Yanyan; Li, Wenkai; Guo, Xiaoyang; Leng, Yuxin

    2016-04-01

    We have demonstrated efficient generation of high beam quality, high-energy and broadband tunable femtosecond mid-infrared pulses using a three-stage collinear optical parametric amplifier (OPA). The white-light continuum (WLC) seeded OPA setup, based on KTA crystal in three stages and pumped by a femtosecond laser pulse at 800 nm, is capable of producing idler wavelength ranging from 2.4 μm to 4.0 μm with energy up to 82 μJ at 3.27 μm, which corresponds to signal energy of 350 μJ at 1060 nm. The output pulse has excellent intensity distribution with measured beam quality factor M2~1.1 for signal and M2~1.7 for idler. To our knowledge, this is the best beam quality reported in 3-5 μm femtosecond OPA until now. The achieved mid-infrared pulse also has a good energy stability with a fluctuation of 1.01% rms over half an hour.

  4. Optimization for high-energy and high-efficiency broadband optical parametric chirped-pulse amplification in LBO near 800  nm.

    Science.gov (United States)

    Yu, Lianghong; Liang, Xiaoyan; Xu, Lu; Li, Wenqi; Peng, Chun; Hu, Zhanggui; Wang, Cheng; Lu, Xiaoming; Chu, Yuxi; Gan, Zebiao; Liu, Xiaodi; Liu, Yanqi; Wang, Xinliang; Lu, Haihe; Yin, Dingjun; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan

    2015-07-15

    In this Letter, we present a study of high-energy and high-conversion-efficiency broadband optical parametric chirped-pulse amplification (OPCPA) system with a 100  mm×100  mm×17  mm LBO crystal near 800 nm. The results showed that the back-conversion was sensitively affected by the pump intensity and the injected signal intensity. It occurred when the injected signal was above 0.82 J with a pump energy of 170 J, and this effect also reshaped the amplified spectrum. After optimization, an amplified energy of 45.3 J was achieved with a conversion efficiency of 26.3% by the OPCPA. The peak power of the hybrid CPA-OPCPA laser system reached 1.02 PW with a compressed duration of 32 fs, which is the first reported OPCPA peak power higher than 1 PW, to the best of our knowledge. PMID:26176482

  5. Modelling the variable broad-band optical/UV/X-ray spectrum of PG1211+143: Implications for the ionized outflow

    CERN Document Server

    Papadakis, I E; Panagiotou, C

    2016-01-01

    We present the results from a detailed analysis of the 2007 Swift monitoring campaign of the quasar PG1211+143. We constructed broad-band, optical/UV/X-ray spectral energy distributions over three X-ray flux intervals. We fitted them with a model which accounts for the disc and the X-ray coronal emission and the warm absorber (well established in this source). The three flux spectra are well fitted by the model we considered. The disc inner temperature remains constant at ~2 eV, while X-rays are variable both in spectral slope and normalization. The absorber covers almost 90% of the central source. It is outflowing with a velocity less than 2.3*10^4 km/s (3sigma upper limit), and has a column density of ~10^23.2. Its ionization parameter varies by a factor of 1.6, and it is in photo-ionizing equilibrium with the ionizing flux. It is located at a distance of less than 0.35 pc from the central source and its relative thickness, DR/R is less than 0.1. The absorber' s ionization parameter variations can explain t...

  6. Broadband surface plasmon jets: direct observation of plasmon propagation for application to sensors and optical communications in microscale and nanoscale circuitry

    Science.gov (United States)

    Bouhelier, Alexandre; Wiederrecht, Gary P.

    2008-02-19

    A system and method for generating and using broadband surface plasmons in a metal film for characterization of analyte on or near the metal film. The surface plasmons interact with the analyte and generate leakage radiation which has spectral features which can be used to inspect, identify and characterize the analyte. The broadband plasmon excitation enables high-bandwidth photonic applications.

  7. Exploiting Optical Contrasts for Cervical Precancer Diagnosis via Diffuse Reflectance Spectroscopy

    Science.gov (United States)

    Chang, Vivide Tuan-Chyan

    Among women worldwide, cervical cancer is the third most common cancer with an incidence rate of 15.3 per 100,000 and a mortality rate of 7.8 per 100,000 women. This is largely attributed to the lack of infrastructure and resources in the developing countries to support the organized screening and diagnostic programs that are available to women in developed nations. Hence, there is a critical global need for a screening and diagnostic paradigm that is effective in low-resource settings. Various strategies are described to design an optical spectroscopic sensor capable of collecting reliable diffuse reflectance data to extract quantitative optical contrasts for cervical cancer screening and diagnosis. A scalable Monte Carlo based optical toolbox can be used to extract absorption and scattering contrasts from diffuse reflectance acquired in the cervix in vivo. [Total Hb] was shown to increase significantly in high-grade cervical intraepithelial neoplasia (CIN 2+), clinically the most important tissue grade to identify, compared to normal and low-grade intraepithelial neoplasia (CIN 1). Scattering was not significantly decreased in CIN 2+ versus normal and CIN 1, but was significantly decreased in CIN relative to normal cervical tissues. Immunohistochemistry via anti-CD34, which stains the endothelial cells that line blood vessels, was used to validate the observed absorption contrast. The concomitant increase in microvessel density and [total Hb] suggests that both are reactive to angiogenic forces from up-regulated expression of VEGF in CIN 2+. Masson's trichrome stain was used to assess collagen density changes associated with dysplastic transformation of the cervix, hypothesized as the dominant source of decreased scattering observed. Due to mismatch in optical and histological sampling, as well as the small sample size, collagen density and scattering did not change in a similar fashion with tissue grade. Dysplasia may also induce changes in cross-linking of

  8. Diagnosis of breast cancer using diffuse optical spectroscopy from 500 to 1600 nm: a comparison of classification methods

    NARCIS (Netherlands)

    Nachabe, R.; Evers, D.; Hendriks, B.H.W.; Lucassen, G.W.; Van der Voort, M.; Wesseling, J.; Rutgers, E. J.; Vrancken Peeters, M.J.; Hage, J.A.van der; Oldenbeng, H.S.; Ruers, T.

    2011-01-01

    We report on the use of diffuse optical spectroscopy analysis of breast spectra acquired in the wavelength range from 500 to 1600 nm with a fiber optic probe. A total of 102 ex vivo samples of five different breast tissue types, namely adipose, glandular, fibroadenoma, invasive carcinoma and ductal

  9. Analysis of ultra-broadband high-energy optical parametric chirped pulse amplifier based on YCOB crystal

    Institute of Scientific and Technical Information of China (English)

    Meizhi Sun; Lailin Ji; Qunyu Bi; Nannan Wang; Jun Kang; Xinglong Xie; Zunqi Lin

    2011-01-01

    A new type of optical parametric chirped pulse amplifier is designed and analyzed for the amplification of pulse centered at 808 nm.A novel crystal,yttrium calcium oxyborate YCa4O(BO3)3 (YCOB),is utilized in the power amplification stage of optical parametric amplification (OPA).Noncollinear phase matching parameters in the xoz principle plane of YCOB,compared with those in BBO and DKDP,are analyzed by numerical simulation.The results show that YCOB rather than DKDP can be used in the power amplification stage of OPA to realize the amplification of chirped pulse to several joules with a gain bandwidth exceeding 100 nm.This can be used to gain a high intensity pulse of ~10 fs after the compressor.The amplification of the femtosecond pulse is an important branch of ultra-intense laser technology,with Ti:sapphire as the medium for its large gain bandwidth.From the perspective of technical features and applications,such femtosecond pulses are used to study high field physics and other related areas in ultrashort time[1,2];however,the pursuit of higher energy femtosecond pulse should not be abandoned.Optical parametric chirped pulse amplification (OPCPA) has been successfully used in the front end of high intensity lasers[3-8],indicating the possibility of femtosecond pulse amplification.This has been verified by an increasing number of fine crystals being invented,such as YCa4O(BO3)3 (YCOB)[9-12].%A new type of optical parametric chirped pulse amplifier is designed and analyzed for the amplification of pulse centered at 808 nm. A novel crystal, yttrium calcium oxyborate YCa4O(BO3)3 (YCOB), is utilized in the power amplification stage of optical parametric amplification (OPA). Noncollinear phase matching parameters in the xoz principle plane of YCOB, compared with those in BBO and DKDP, are analyzed by numerical simulation. The results show that YCOB rather than DKDP can be used in the power amplification stage of OPA to realize the amplification of chirped pulse to

  10. Modelling the variable broad-band optical/UV/X-ray spectrum of PG1211+143: implications for the ionized outflow

    Science.gov (United States)

    Papadakis, I. E.; Nicastro, F.; Panagiotou, C.

    2016-06-01

    Context. We present the results from a detailed analysis of the 2007 Swift monitoring campaign of the quasar PG1211+143. Aims: We study its broad-band optical/UV-X-ray spectral energy distribution and its variations, with the use of physically motivated models. Methods: We constructed broad-band, optical/UV-X-ray spectral energy distributions over three X-ray flux intervals, and we fitted them with a model which accounts for the disc and the X-ray coronal emission. We also added a spectral model component to account for the presence of the warm absorber which has been well established from past observations of the source. Results: We detected no optical/UV variations over the two-month period of the monitoring campaign. On the other hand, the X-rays are highly variable in a correlated way in the soft and hard X-ray bands with an amplitude larger than has been commonly observed in nearby Seyferts, even on longer time scales. The three flux spectra are well fitted by the model we considered. The disc inner temperature remains constant at ~2 eV, while X-rays are variable in slope and normalization. The absorber covers almost 90% of the central source. It is outflowing with a velocity less than 2.3 × 104 km s-1 (3σ upper limit), and has a column density of log NH ~ 23.2. Its ionization parameter varies by a factor of 1.6, and it is in photo-ionizing equilibrium with the ionizing flux. It is located at a distance of less than 0.35 pc from the central source, and its relative thickness, ΔR/R, is less than 0.1. The absorber's ionization parameter variations can explain the larger than average amplitude of the X-ray variations. Conclusions: The absence of optical/UV variations are consistent with the high black hole mass estimate of ~108M⊙ for this object, which implies variability time scales longer than the period of the Swift observations. It argues against the presence of inward propagating fluctuations in the disc as the reason for the flux variability in this

  11. Performance of a lookup table-based approach for measuring tissue optical properties with diffuse optical spectroscopy.

    Science.gov (United States)

    Nichols, Brandon S; Rajaram, Narasimhan; Tunnell, James W

    2012-05-01

    Diffuse optical spectroscopy (DOS) provides a powerful tool for fast and noninvasive disease diagnosis. The ability to leverage DOS to accurately quantify tissue optical parameters hinges on the model used to estimate light-tissue interaction. We describe the accuracy of a lookup table (LUT)-based inverse model for measuring optical properties under different conditions relevant to biological tissue. The LUT is a matrix of reflectance values acquired experimentally from calibration standards of varying scattering and absorption properties. Because it is based on experimental values, the LUT inherently accounts for system response and probe geometry. We tested our approach in tissue phantoms containing multiple absorbers, different sizes of scatterers, and varying oxygen saturation of hemoglobin. The LUT-based model was able to extract scattering and absorption properties under most conditions with errors of less than 5 percent. We demonstrate the validity of the lookup table over a range of source-detector separations from 0.25 to 1.48 mm. Finally, we describe the rapid fabrication of a lookup table using only six calibration standards. This optimized LUT was able to extract scattering and absorption properties with average RMS errors of 2.5 and 4 percent, respectively. PMID:22612140

  12. Morphological characterization of cells in concentrated suspensions using multispectral diffuse optical tomography.

    Science.gov (United States)

    Hajihashemi, Mohammad Reza; Li, Xiaoqi; Jiang, Huabei

    2012-10-01

    Based on a non-spherical model of particle scattering, we investigate the capabilities and limitations of a T-matrix based inverse algorithm to morphologically characterize cells in concentrated suspensions. Here the cells are modeled as randomly orientated spheroidal particles with homogenous dielectric properties and suspended in turbid media. The inverse algorithm retrieves the geometrical parameters and the concentration of cells simultaneously by inverting the reduced scattering coefficient spectra obtained from multispectral diffuse optical tomography (MS-DOT). Both round and spheroidal cells are tested and the role of multiple and higher order scattering of particles on the performance of the algorithm is evaluated using different concentrations of cells.

  13. Dynamic diffuse optical tomography for assessing changes of breast tumors during neoadjuvant chemotherapy

    Science.gov (United States)

    Gunther, Jacqueline E.; Lim, Emerson; Kim, Hyun Keol; Brown, Mindy; Refice, Susan; Kalinsky, Kevin; Hershman, Dawn; Hielscher, Andreas H.

    2015-03-01

    We have developed a dynamic diffuse optical tomography imaging system that is capable of 3D imaging of both breasts simultaneously. In an ongoing study subjects receiving neoadjuvant chemotherapy are imaged at 6 time points throughout their 5-month treatment. At each time point the subjects preform a breath hold to observe the hemodynamic effects in the breasts. For each session the percent change of various hemodynamic parameters during the breath hold is determined. Preliminary results from show statistically significant differences in washout rates and deoxyhemoglobin changes at the 2-week imaging point between subjects that respond and do not respond to treatment.

  14. Volumetric Diffuse Optical Tomography for Small Animals Using a CCD-Camera-Based Imaging System

    Directory of Open Access Journals (Sweden)

    Zi-Jing Lin

    2012-01-01

    Full Text Available We report the feasibility of three-dimensional (3D volumetric diffuse optical tomography for small animal imaging by using a CCD-camera-based imaging system with a newly developed depth compensation algorithm (DCA. Our computer simulations and laboratory phantom studies have demonstrated that the combination of a CCD camera and DCA can significantly improve the accuracy in depth localization and lead to reconstruction of 3D volumetric images. This approach may present great interests for noninvasive 3D localization of an anomaly hidden in tissue, such as a tumor or a stroke lesion, for preclinical small animal models.

  15. Magnetic resonance diffusion tensor imaging-based evaluation of optic-radiation shape and position in meningioma

    Institute of Scientific and Technical Information of China (English)

    Xueming Lv; Xiaolei Chen; Bainan Xu; Gang Zheng; Jinjiang Li; Fangye Li; Guochen Sun; liusan

    2012-01-01

    Employing magnetic resonance diffusion tensor imaging, three-dimensional white-matter imaging and conventional magnetic resonance imaging can demonstrate the tumor parenchyma, peritumoral edema and compression on surrounding brain tissue. A color-coded tensor map and three-dimensional tracer diagram were applied to clearly display the optic-radiation location, course and damage. Results showed that the altered anisotropy values of meningioma patients corresponded with optic-radiation shape, size and position on both sides. Experimental findings indicate that the magnetic resonance diffusion tensor imaging technique is a means of tracing and clearly visualizing the optic radiation.

  16. Evaluation of arctic broadband surface radiation measurements

    OpenAIRE

    Matsui, N.; C. N. Long; J. Augustine; Halliwell, D.; T. Uttal; Longenecker, D.; O. Nievergall; Wendell, J.; Albee, R.

    2011-01-01

    The Arctic is a challenging environment for making in-situ radiation measurements. A standard suite of radiation sensors is typically designed to measure the total, direct and diffuse components of incoming and outgoing broadband shortwave (SW) and broadband thermal infrared, or longwave (LW) radiation. Enhancements can include various sensors for measuring irradiance in various narrower bandwidths. Many solar radiation/thermal infrared flux sensors utilize protective glass domes and some are...

  17. Three-dimensional surface reconstruction within noncontact diffuse optical tomography using structured light

    Science.gov (United States)

    Baum, Kirstin; Hartmann, Raimo; Bischoff, Tobias; Oelerich, Jan O.; Finkensieper, Stephan; Heverhagen, Johannes T.

    2012-12-01

    A main field in biomedical optics research is diffuse optical tomography, where intensity variations of the transmitted light traversing through tissue are detected. Mathematical models and reconstruction algorithms based on finite element methods and Monte Carlo simulations describe the light transport inside the tissue and determine differences in absorption and scattering coefficients. Precise knowledge of the sample's surface shape and orientation is required to provide boundary conditions for these techniques. We propose an integrated method based on structured light three-dimensional (3-D) scanning that provides detailed surface information of the object, which is usable for volume mesh creation and allows the normalization of the intensity dispersion between surface and camera. The experimental setup is complemented by polarization difference imaging to avoid overlaying byproducts caused by inter-reflections and multiple scattering in semitransparent tissue.

  18. Optical Design of a Broadband Infrared Spectrometer for Bunch Length Measurement at the Linac Coherent Light Source

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Kiel; /SLAC

    2012-09-07

    The electron pulses generated by the Linac Coherent Light Source at the SLAC National Accelerator Laboratory occur on the order of tens of femtoseconds and cannot be directly measured by conventional means. The length of the pulses can instead be reconstructed by measuring the spectrum of optical transition radiation emitted by the electrons as they move toward a conducting foil. Because the emitted radiation occurs in the mid-infrared from 0.6 to 30 microns a novel optical layout is required. Using a helium-neon laser with wavelength 633 nm, a series of gold-coated off-axis parabolic mirrors were positioned to direct a beam through a zinc selenide prism and to a focus at a CCD camera for imaging. Constructing this layout revealed a number of novel techniques for reducing the aberrations introduced into the system by the off-axis parabolic mirrors. The beam had a recorded radius of less than a millimeter at its final focus on the CCD imager. This preliminary setup serves as a model for the spectrometer that will ultimately measure the LCLS electron pulse duration.

  19. THE CHANDRA MULTI-WAVELENGTH PROJECT: OPTICAL SPECTROSCOPY AND THE BROADBAND SPECTRAL ENERGY DISTRIBUTIONS OF X-RAY-SELECTED AGNs

    Energy Technology Data Exchange (ETDEWEB)

    Trichas, Markos; Green, Paul J.; Aldcroft, Tom; Kim, Dong-Woo; Mossman, Amy [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Silverman, John D. [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba 277-8568 (Japan); Barkhouse, Wayne [Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202 (United States); Cameron, Robert A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Constantin, Anca [Department of Physics and Astronomy, James Madison University, PHCH, Harrisonburg, VA 22807 (United States); Ellison, Sara L. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 1A1 (Canada); Foltz, Craig [Division of Astronomical Sciences, National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22230 (United States); Haggard, Daryl [Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Jannuzi, Buell T. [NOAO, Kitt Peak National Observatory, Tucson, AZ 85726 (United States); Marshall, Herman L. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Perez, Laura M. [Department of Astronomy, California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125 (United States); Romero-Colmenero, Encarni [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Ruiz, Angel [Osservatorio Astronomico di Brera-INAF, Milan (Italy); Smith, Malcolm G., E-mail: mtrichas@cfa.harvard.edu [Cerro Tololo Interamerican Observatory, La Serena (Chile); and others

    2012-06-01

    From optical spectroscopy of X-ray sources observed as part of the Chandra Multi-wavelength Project (ChaMP), we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic follow-up using the FLWO/1.5 m, SAAO/1.9 m, WIYN 3.5 m, CTIO/4 m, KPNO/4 m, Magellan/6.5 m, MMT/6.5 m, and Gemini/8 m telescopes, and from archival Sloan Digital Sky Survey (SDSS) spectroscopy. We classify the optical counterparts as 50% broad-line active galactic nuclei (AGNs), 16% emission line galaxies, 14% absorption line galaxies, and 20% stars. We detect QSOs out to z {approx} 5.5 and galaxies out to z {approx} 3. We have compiled extensive photometry, including X-ray (ChaMP), ultraviolet (GALEX), optical (SDSS and ChaMP-NOAO/MOSAIC follow-up), near-infrared (UKIDSS, Two Micron All Sky Survey, and ChaMP-CTIO/ISPI follow-up), mid-infrared (WISE), and radio (FIRST and NVSS) bands. Together with our spectroscopic information, this enables us to derive detailed spectral energy distributions (SEDs) for our extragalactic sources. We fit a variety of template SEDs to determine bolometric luminosities, and to constrain AGNs and starburst components where both are present. While {approx}58% of X-ray Seyferts (10{sup 42} erg s{sup -1} < L{sub 2-10keV} <10{sup 44} erg s{sup -1}) require a starburst event (>5% starburst contribution to bolometric luminosity) to fit observed photometry only 26% of the X-ray QSO (L{sub 2-10keV} >10{sup 44} erg s{sup -1}) population appear to have some kind of star formation contribution. This is significantly lower than for the Seyferts, especially if we take into account torus contamination at z > 1 where the majority of our X-ray QSOs lie. In addition, we observe a rapid drop of the percentage of starburst contribution as X-ray luminosity increases. This is consistent with the quenching of star formation by powerful QSOs, as predicted by the merger model, or with a time lag between the peak of star formation and QSO

  20. THE CHANDRA MULTI-WAVELENGTH PROJECT: OPTICAL SPECTROSCOPY AND THE BROADBAND SPECTRAL ENERGY DISTRIBUTIONS OF X-RAY-SELECTED AGNs

    International Nuclear Information System (INIS)

    From optical spectroscopy of X-ray sources observed as part of the Chandra Multi-wavelength Project (ChaMP), we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic follow-up using the FLWO/1.5 m, SAAO/1.9 m, WIYN 3.5 m, CTIO/4 m, KPNO/4 m, Magellan/6.5 m, MMT/6.5 m, and Gemini/8 m telescopes, and from archival Sloan Digital Sky Survey (SDSS) spectroscopy. We classify the optical counterparts as 50% broad-line active galactic nuclei (AGNs), 16% emission line galaxies, 14% absorption line galaxies, and 20% stars. We detect QSOs out to z ∼ 5.5 and galaxies out to z ∼ 3. We have compiled extensive photometry, including X-ray (ChaMP), ultraviolet (GALEX), optical (SDSS and ChaMP-NOAO/MOSAIC follow-up), near-infrared (UKIDSS, Two Micron All Sky Survey, and ChaMP-CTIO/ISPI follow-up), mid-infrared (WISE), and radio (FIRST and NVSS) bands. Together with our spectroscopic information, this enables us to derive detailed spectral energy distributions (SEDs) for our extragalactic sources. We fit a variety of template SEDs to determine bolometric luminosities, and to constrain AGNs and starburst components where both are present. While ∼58% of X-ray Seyferts (1042 erg s–1 2–10keV 44 erg s–1) require a starburst event (>5% starburst contribution to bolometric luminosity) to fit observed photometry only 26% of the X-ray QSO (L2–10keV >1044 erg s–1) population appear to have some kind of star formation contribution. This is significantly lower than for the Seyferts, especially if we take into account torus contamination at z > 1 where the majority of our X-ray QSOs lie. In addition, we observe a rapid drop of the percentage of starburst contribution as X-ray luminosity increases. This is consistent with the quenching of star formation by powerful QSOs, as predicted by the merger model, or with a time lag between the peak of star formation and QSO activity. We have tested the hypothesis that there should be a

  1. A Combined Multiple-SLED Broadband Light Source at 1300 nm for High Resolution Optical Coherence Tomography.

    Science.gov (United States)

    Wang, Hui; Jenkins, Michael W; Rollins, Andrew M

    2008-04-01

    We demonstrate a compact, inexpensive, and reliable fiber-coupled light source with broad bandwidth and sufficient power at 1300 nm for high resolution optical coherence tomography (OCT) imaging in real-time applications. By combining four superluminescent diodes (SLEDs) with different central wavelengths, the light source has a bandwidth of 145 nm centered at 1325 nm with over 10 mW of power. OCT images of an excised stage 30 embryonic chick heart acquired with our combined SLED light source (<5 μm axial resolution in tissue) are compared with images obtained with a single SLED source (~10 μm axial resolution in tissue). The high resolution OCT system with the combined SLED light source provides better image quality (smaller speckle noise) and a greater ability to observe fine structures in the embryonic heart.

  2. Estimate of Aerosol Optical Depth Using Broadband Direct Normal Observations at Highest Polluted Area in the World

    Directory of Open Access Journals (Sweden)

    U. A. Rahoma

    2010-01-01

    Full Text Available Problem statement: The measurement of different components of direct solar radiation for this research has been carried out in Helwan, Egypt. Helwan (Latitude 29°52 N, Longitude 31°20 E. This is a considered as the largest polluted region in the world. The level of pollution in Helwan region is higher, compared to the international limit by about 7 or 10 times in industrial and populated region respectively. Approach: The daily variation for different components of solar radiation bands as global, direct (total, yellow, red and infrared and diffuse solar radiation had been studied and discussed. The data measurements have been taken for nine years (1991-2000. Hourly data of solar irradiance on a horizontal plane had also been recorded simultaneously together with relative humidity and wind speed along with some traditional techniques for selecting the clear sky days of the period examined. Results: The results clearly showed seasonal dynamics in aerosol loading, type and perceptible water. Conclusion: Background levels of aerosols, which we defined as yellow color less than 0.10, had observed at almost all sites but varying frequencies.

  3. Construction of the Jacobian matrix for fluorescence diffuse optical tomography using a perturbation Monte Carlo method

    Science.gov (United States)

    Zhang, Xiaofeng

    2012-03-01

    Image formation in fluorescence diffuse optical tomography is critically dependent on construction of the Jacobian matrix. For clinical and preclinical applications, because of the highly heterogeneous characteristics of the medium, Monte Carlo methods are frequently adopted to construct the Jacobian. Conventional adjoint Monte Carlo method typically compute the Jacobian by multiplying the photon density fields radiated from the source at the excitation wavelength and from the detector at the emission wavelength. Nonetheless, this approach assumes that the source and the detector in Green's function are reciprocal, which is invalid in general. This assumption is particularly questionable in small animal imaging, where the mean free path length of photons is typically only one order of magnitude smaller than the representative dimension of the medium. We propose a new method that does not rely on the reciprocity of the source and the detector by tracing photon propagation entirely from the source to the detector. This method relies on the perturbation Monte Carlo theory to account for the differences in optical properties of the medium at the excitation and the emission wavelengths. Compared to the adjoint methods, the proposed method is more valid in reflecting the physical process of photon transport in diffusive media and is more efficient in constructing the Jacobian matrix for densely sampled configurations.

  4. High-density diffuse optical tomography of term infant visual cortex in the nursery

    Science.gov (United States)

    Liao, Steve M.; Ferradal, Silvina L.; White, Brian R.; Gregg, Nicholas; Inder, Terrie E.; Culver, Joseph P.

    2012-08-01

    Advancements in antenatal and neonatal medicine over the last few decades have led to significant improvement in the survival rates of sick newborn infants. However, this improvement in survival has not been matched by a reduction in neurodevelopmental morbidities with increasing recognition of the diverse cognitive and behavioral challenges that preterm infants face in childhood. Conventional neuroimaging modalities, such as cranial ultrasound and magnetic resonance imaging, provide an important definition of neuroanatomy with recognition of brain injury. However, they fail to define the functional integrity of the immature brain, particularly during this critical developmental period. Diffuse optical tomography methods have established success in imaging adult brain function; however, few studies exist to demonstrate their feasibility in the neonatal population. We demonstrate the feasibility of using recently developed high-density diffuse optical tomography (HD-DOT) to map functional activation of the visual cortex in healthy term-born infants. The functional images show high contrast-to-noise ratio obtained in seven neonates. These results illustrate the potential for HD-DOT and provide a foundation for investigations of brain function in more vulnerable newborns, such as preterm infants.

  5. Broadband Tuning of Optomechanical Cavities

    CERN Document Server

    Wiederhecker, Gustavo S; Lee, Sunwoo; Lipson, Michal

    2010-01-01

    We demonstrate broadband tuning of an optomechanical microcavity optical resonance by exploring the large optomechanical coupling of a double-wheel microcavity and its uniquely low mechanical stiffness. Using a pump laser with only 13 mW at telecom wavelengths we show tuning of the silicon nitride microcavity resonances over 32 nm. This corresponds to a tuning power efficiency of only 400 $\\mu$W/nm. By choosing a relatively low optical Q resonance ($\\approx$18,000) we prevent the cavity from reaching the regime of regenerative optomechanical oscillations. The static mechanical displacement induced by optical gradient forces is estimated to be as large as 60 nm.

  6. Tomographic x-ray guided three-dimensional diffuse optical imaging of osteoarthritis in the finger joints: a clinical study

    Science.gov (United States)

    Yuan, Zhen; Jiang, Huizhu; Zhang, Qizhi; Sobel, Eric S.; Jiang, Huabei

    2009-02-01

    To investigate the typical optical findings that can be used to characterize osteoarthritis, the distal interphalangeal finger joints from 40 subjects including 22 patients and 18 healthy controllers were examined clinically and scanned by a novel hybrid imaging system. The hybrid imaging platform integrated a C-arm based x-ray tomosynthetic system with a multi-channel optic-fiber based diffuse optical imaging system. Optical images were recovered qualitatively and quantitatively based on a regularization-based reconstruction algorithm that can incorporate the fine structural maps obtained from x-ray as a priori spatial information into diffuse optical tomography reconstruction procedures. Our findings suggest statistically significant differences between healthy and osteoarthritis finger joints. X-ray guided diffuse optical imaging may not only detect radiologic features supporting the development of an inflammatory disorder but may also help discriminate specific optical features that differ between osteoarthritic and healthy joints. These quantitative optical features are also potentially important for a better understanding of inflammatory arthritis in humans.

  7. Noise-immune cavity-enhanced optical frequency comb spectroscopy: A sensitive technique for high-resolution broadband molecular detection

    CERN Document Server

    Khodabakhsh, Amir; Foltynowicz, Aleksandra

    2014-01-01

    Noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS) is a recently developed technique that utilizes phase modulation to obtain immunity to frequency-to-amplitude noise conversion by the cavity modes and yields high absorption sensitivity over a broad spectral range. We describe the principles of the technique and discuss possible comb-cavity matching solutions. We present a theoretical description of NICE-OFCS signals detected with a Fourier transform spectrometer (FTS), and validate the model by comparing it to experimental CO2 spectra around 1575 nm. Our system is based on an Er:fiber femtosecond laser locked to a cavity and phase-modulated at a frequency equal to a multiple of the cavity free spectral range (FSR). The NICE-OFCS signal is detected by a fast-scanning FTS equipped with a high-bandwidth commercial detector. We demonstrate a simple method of passive locking of the modulation frequency to the cavity FSR that significantly improves the long term stability of the system, a...

  8. Diffuse Optical Characterization of the Healthy Human Thyroid Tissue and Two Pathological Case Studies.

    Directory of Open Access Journals (Sweden)

    Claus Lindner

    Full Text Available The in vivo optical and hemodynamic properties of the healthy (n = 22 and pathological (n = 2 human thyroid tissue were measured non-invasively using a custom time-resolved spectroscopy (TRS and diffuse correlation spectroscopy (DCS system. Medical ultrasound was used to guide the placement of the hand-held hybrid optical probe. TRS measured the absorption and reduced scattering coefficients (μa, μs' at three wavelengths (690, 785 and 830 nm to derive total hemoglobin concentration (THC and oxygen saturation (StO2. DCS measured the microvascular blood flow index (BFI. Their dependencies on physiological and clinical parameters and positions along the thyroid were investigated and compared to the surrounding sternocleidomastoid muscle. The THC in the thyroid ranged from 131.9 μM to 144.8 μM, showing a 25-44% increase compared to the surrounding sternocleidomastoid muscle tissue. The blood flow was significantly higher in the thyroid (BFIthyroid = 16.0 × 10-9 cm2/s compared to the muscle (BFImuscle = 7.8 × 10-9 cm2/s, while StO2 showed a small (StO2, muscle = 63.8% to StO2, thyroid = 68.4%, yet significant difference. Two case studies with thyroid nodules underwent the same measurement protocol prior to thyroidectomy. Their THC and BFI reached values around 226.5 μM and 62.8 × 10-9 cm2/s respectively showing a clear contrast to the nodule-free thyroid tissue as well as the general population. The initial characterization of the healthy and pathologic human thyroid tissue lays the ground work for the future investigation on the use of diffuse optics in thyroid cancer screening.

  9. Diffuse Optical Characterization of the Healthy Human Thyroid Tissue and Two Pathological Case Studies.

    Science.gov (United States)

    Lindner, Claus; Mora, Mireia; Farzam, Parisa; Squarcia, Mattia; Johansson, Johannes; Weigel, Udo M; Halperin, Irene; Hanzu, Felicia A; Durduran, Turgut

    2016-01-01

    The in vivo optical and hemodynamic properties of the healthy (n = 22) and pathological (n = 2) human thyroid tissue were measured non-invasively using a custom time-resolved spectroscopy (TRS) and diffuse correlation spectroscopy (DCS) system. Medical ultrasound was used to guide the placement of the hand-held hybrid optical probe. TRS measured the absorption and reduced scattering coefficients (μa, μs') at three wavelengths (690, 785 and 830 nm) to derive total hemoglobin concentration (THC) and oxygen saturation (StO2). DCS measured the microvascular blood flow index (BFI). Their dependencies on physiological and clinical parameters and positions along the thyroid were investigated and compared to the surrounding sternocleidomastoid muscle. The THC in the thyroid ranged from 131.9 μM to 144.8 μM, showing a 25-44% increase compared to the surrounding sternocleidomastoid muscle tissue. The blood flow was significantly higher in the thyroid (BFIthyroid = 16.0 × 10-9 cm2/s) compared to the muscle (BFImuscle = 7.8 × 10-9 cm2/s), while StO2 showed a small (StO2, muscle = 63.8% to StO2, thyroid = 68.4%), yet significant difference. Two case studies with thyroid nodules underwent the same measurement protocol prior to thyroidectomy. Their THC and BFI reached values around 226.5 μM and 62.8 × 10-9 cm2/s respectively showing a clear contrast to the nodule-free thyroid tissue as well as the general population. The initial characterization of the healthy and pathologic human thyroid tissue lays the ground work for the future investigation on the use of diffuse optics in thyroid cancer screening. PMID:26815533

  10. Intraoperative evaluation of revascularization effect on ischemic muscle hemodynamics using near-infrared diffuse optical spectroscopies

    Science.gov (United States)

    Yu, Guoqiang; Shang, Yu; Zhao, Youquan; Cheng, Ran; Dong, Lixin; Saha, Sibu P.

    2011-02-01

    Arterial revascularization in patients with peripheral arterial disease (PAD) reestablishes large arterial blood supply to the ischemic muscles in lower extremities via bypass grafts or percutaneous transluminal angioplasty (PTA). Currently no gold standard is available for assessment of revascularization effects in lower extremity muscles. This study tests a novel near-infrared diffuse correlation spectroscopy flow-oximeter for monitoring of blood flow and oxygenation changes in medial gastrocnemius (calf) muscles during arterial revascularization. Twelve limbs with PAD undergoing revascularization were measured using a sterilized fiber-optic probe taped on top of the calf muscle. The optical measurement demonstrated sensitivity to dynamic physiological events, such as arterial clamping/releasing during bypass graft and balloon inflation/deflation during PTA. Significant elevations in calf muscle blood flow were observed after revascularization in patients with bypass graft (+48.1 +/- 17.5%) and patients with PTA (+43.2 +/- 11.0%), whereas acute post-revascularization effects in muscle oxygenation were not evident. The decoupling of flow and oxygenation after revascularization emphasizes the need for simultaneous measurement of both parameters. The acute elevations/improvements in calf muscle blood flow were associated with significant improvements in symptoms and functions. In total, the investigation corroborates potential of the optical methods for objectively assessing the success of arterial revascularization.

  11. Optimal Analysis Method for Dynamic Contrast-Enhanced Diffuse Optical Tomography

    Directory of Open Access Journals (Sweden)

    Michael Ghijsen

    2011-01-01

    Full Text Available Diffuse Optical Tomography (DOT is an optical imaging modality that has various clinical applications. However, the spatial resolution and quantitative accuracy of DOT is poor due to strong photon scatting in biological tissue. Structural a priori information from another high spatial resolution imaging modality such as Magnetic Resonance Imaging (MRI has been demonstrated to significantly improve DOT accuracy. In addition, a contrast agent can be used to obtain differential absorption images of the lesion by using dynamic contrast enhanced DOT (DCE-DOT. This produces a relative absorption map that consists of subtracting a reconstructed baseline image from reconstructed images in which optical contrast is included. In this study, we investigated and compared different reconstruction methods and analysis approaches for regular endogenous DOT and DCE-DOT with and without MR anatomical a priori information for arbitrarily-shaped objects. Our phantom and animal studies have shown that superior image quality and higher accuracy can be achieved using DCE-DOT together with MR structural a priori information. Hence, implementation of a combined MRI-DOT system to image ICG enhancement can potentially be a promising tool for breast cancer imaging.

  12. Local government broadband policies for areas with limited Internet access

    Directory of Open Access Journals (Sweden)

    Yoshio Arai

    2014-03-01

    Full Text Available Despite their wide diffusion in developed countries, broadband services are still limited in areas where providing them is not profitable for private telecom carriers. To address this, many local governments in Japan have implemented broadband deployment projects subsidized by the national government. In this paper, we discuss local government broadband policies based on survey data collected from municipalities throughout the country. With the support of national promotion policies, broadband services were rapidly introduced to most local municipalities in Japan during the 2000s. Local government deployment policies helped to reduce the number of areas with no broadband access. A business model based on the Indefeasible Right of Use (IRU contract between a private telecom carrier and a local government has been developed in recent years. Even local governments without the technical capacity to operate a broadband business can introduce broadband services into their territory using the IRU business model.

  13. Designing broadband plasmonic nanoantennas for ultrasensing

    Science.gov (United States)

    Yi, Zhenhuan; Wang, Kai; Voronine, Dmitri V.; Traverso, Andrew; Sokolov, Alexei

    2011-03-01

    Various designs of broadband plasmonic nanoantennas made of gold and silver nanospheres are considered and optimized for ultrasensitive spectroscopic applications. The simulated nanostructures show a broadband optical response which may be tuned by varying the size, position and composition of nanospheres. Near-field enhancement in nanoantenna hot spots is analyzed and compared with previous literature results in the case of a fractal plasmonic nanolens. Broadband plasmonic nanoantennas may allow detecting ultrasmall concentrations of toxic materials and may be used for decoding DNA and for ultrafast nanophotonics applications.

  14. Novel crystalline-waveguide broadband light sources for interferometry

    OpenAIRE

    Pollnau, Markus

    2003-01-01

    In recent years, broadband fiber interferometers have become very popular as basic instruments used in optical low-coherence reflectometry for diagnostics of fiber and integrated optics devices or in optical coherence tomography (OCT) for imaging applications in the biomedical field. The longitudinal resolution of such instruments is inversely proportional to the optical bandwidth of the light source. Broadband luminescence from transition-metal-ion doped materials can significantly improve t...

  15. Applications of hybrid diffuse optics for clinical management of adults after brain injury

    Science.gov (United States)

    Kim, Meeri Nam

    Information about cerebral blood flow (CBF) is valuable for clinical management of patients after severe brain injury. Unfortunately, current modalities for monitoring brain are often limited by hurdles that include high cost, low throughput, exposure to ionizing radiation, probe invasiveness, and increased risk to critically ill patients when transportation out of their room or unit is required. A further limitation of current technologies is an inability to provide continuous bedside measurements that are often desirable for unstable patients. Here we explore the clinical utility of diffuse correlation spectroscopy (DCS) as an alternative approach for bedside CBF monitoring. DCS uses the rapid intensity fluctuations of near-infrared light to derive a continuous measure of changes in blood flow without ionizing radiation or invasive probing. Concurrently, we employ another optical technique, called diffuse optical spectroscopy (DOS), to derive changes in cerebral oxyhemoglobin ( HbO2) and deoxyhemoglobin (Hb) concentrations. Our clinical studies integrate DCS with DOS into a single hybrid instrument that simultaneously monitors CBF and HbO2/Hb in the injured adult brain. The first parts of this dissertation present the motivations for monitoring blood flow in injured brain, as well as the theory underlying diffuse optics technology. The next section elaborates on details of the hybrid instrumentation. The final chapters describe four human subject studies carried out with these methods. Each of these studies investigates an aspect of the potential of the hybrid monitor in clinical applications involving adult brain. The studies include: (1) validation of DCS-measured CBF against xenon-enhanced computed tomography in brain-injured adults; (2) a study of the effects of age and gender on posture-change-induced CBF variation in healthy subjects; (3) a study of the efficacy of DCS/DOS for monitoring neurocritical care patients during various medical interventions such

  16. Exploiting Optical Contrasts for Cervical Precancer Diagnosis via Diffuse Reflectance Spectroscopy

    Science.gov (United States)

    Chang, Vivide Tuan-Chyan

    Among women worldwide, cervical cancer is the third most common cancer with an incidence rate of 15.3 per 100,000 and a mortality rate of 7.8 per 100,000 women. This is largely attributed to the lack of infrastructure and resources in the developing countries to support the organized screening and diagnostic programs that are available to women in developed nations. Hence, there is a critical global need for a screening and diagnostic paradigm that is effective in low-resource settings. Various strategies are described to design an optical spectroscopic sensor capable of collecting reliable diffuse reflectance data to extract quantitative optical contrasts for cervical cancer screening and diagnosis. A scalable Monte Carlo based optical toolbox can be used to extract absorption and scattering contrasts from diffuse reflectance acquired in the cervix in vivo. [Total Hb] was shown to increase significantly in high-grade cervical intraepithelial neoplasia (CIN 2+), clinically the most important tissue grade to identify, compared to normal and low-grade intraepithelial neoplasia (CIN 1). Scattering was not significantly decreased in CIN 2+ versus normal and CIN 1, but was significantly decreased in CIN relative to normal cervical tissues. Immunohistochemistry via anti-CD34, which stains the endothelial cells that line blood vessels, was used to validate the observed absorption contrast. The concomitant increase in microvessel density and [total Hb] suggests that both are reactive to angiogenic forces from up-regulated expression of VEGF in CIN 2+. Masson's trichrome stain was used to assess collagen density changes associated with dysplastic transformation of the cervix, hypothesized as the dominant source of decreased scattering observed. Due to mismatch in optical and histological sampling, as well as the small sample size, collagen density and scattering did not change in a similar fashion with tissue grade. Dysplasia may also induce changes in cross-linking of

  17. Thermal diffusivity of Zn1-xBexSe crystals and it's correlation with electrical conductivity and optical absorption spectra

    Science.gov (United States)

    Bodzenta, J.; Firszt, F.; Kaźmierczak-Bałata, A.; Pyka, M.; Szperlich, P.; Szydłowski, M.; Zakrzewski, J.

    2008-01-01

    This article presents results obtained for mixed crystal of Zn{1-x}Be{x}Se. Samples with different Be contents were examined to determine their thermal, optical and electrical properties. The influence of composition of investigated mixed crystals on the value of thermal diffusivity, electrical resistivity and energy gap was checked. An interesting problem is a correlation between thermal properties and other physical parameters. In this work possible correlations between the thermal diffusivity and either the optical band gap determined from photothermal spectra or electrical conductivity are studied. The current investigation is a part of research projects: BK-269/RMF-1/2006 and 1 P03B 092 27.

  18. MRI-Guided Diffuse Optical Spectroscopy of Malignant and Benign Breast Lesions

    Directory of Open Access Journals (Sweden)

    Vasilis Ntziachristos

    2002-01-01

    Full Text Available We present the clinical implementation of a novel hybrid system that combines magnetic resonance imaging (MRI and near-infrared (NIR optical measurements for the noninvasive study of breast cancer in vivo. Fourteen patients were studied with a MR-NIR prototype imager and spectrometer. A diffuse optical tomographic scheme employed the MR images as a priori information to implement an image-guided NIR localized spectroscopic scheme. All patients who entered the study also underwent gadolinium-enhanced MRI and biopsy so that the optical findings were crossvalidated with MR readings and histopathology. The technique quantified the oxy-and deoxyhemoglobin of five malignant and nine benign breast lesions in vivo. Breast cancers were found with decreased oxygen saturation and higher blood concentration than most benign lesions. The average hemoglobin concentration ([H] of cancers was 0.130±0.100 mM, and the average hemoglobin saturation (Y was 60±9% compared to [H]=0.018±0.005 mM and Y=69±6% of background tissue. Fibroadenomas exhibited high hemoglobin concentration [H]=0.060±0.010 mM and mild decrease in oxygen saturation Y=67±2%. Cysts and other normal lesions were easily differentiated based on intrinsic contrast information. This novel optical technology can be a significant add-on in MR examinations and can be used to characterize functional parameters of cancers with diagnostic and treatment prognosis potential. It is foreseen that the technique can play a major role in functional activation studies of brain and muscle as well.

  19. Efficient method for near real-time diffuse optical tomography of the human brain

    Science.gov (United States)

    Wu, Xue; Eggebrecht, Adam T.; Ferradal, Silvina L.; Culver, Joseph P.; Dehghani, Hamid

    2015-07-01

    Previous studies have showed only regions with a sensitivity higher that 1% of the maximum value can affect the recovery result for diffuse optical tomography (DOT). Two methods of efficient sensitivity map generation based on Finite Element Models (FEM) are developed based on (1) reduced sensitivity matrix and (2) parallelisation process. Time and memory efficiency of these processes are evaluated and compared with conventional methods. It is shown that the computational time for a full head model containing 200k nodes is reduced from 3 hours to 48 minutes and the required memory is reduced from 5.5 GB to 0.5 GB. For a range of mesh densities up to 320k nodes, the required memory is improved by ~1000% and computational time by ~400% to allow near real-time image recovery.

  20. Noninvasive characterization of the healthy human manubrium using diffuse optical spectroscopies

    International Nuclear Information System (INIS)

    The abnormal, uncontrolled production of blood cells in the bone marrow causes hematological malignancies which are common and tend to have a poor prognosis. These types of cancers may alter the hemodynamics of bone marrow. Therefore, noninvasive methods that measure the hemodynamics in the bone marrow have a potential impact on the earlier diagnosis, more accurate prognosis, and in treatment monitoring. In adults, the manubrium is one of the few sites of bone marrow that is rich in hematopoietic tissue and is also relatively superficial and accessible. To this end we have combined time resolved spectroscopy and diffuse correlation spectroscopy to evaluate the feasibility of the noninvasive measurement of the hemodynamics properties of the healthy manubrium in 32 subjects. The distribution of the optical properties (absorption and scattering) and physiological properties (hemoglobin concentration, oxygen saturation and blood flow index) of this tissue are presented as the first step toward investigating its pathology. (paper)

  1. An adaptive extended Kalman filter for fluorescence diffuse optical tomography of tumor pharmacokinetics

    Science.gov (United States)

    Wang, Xin; Wu, Linhui; Yi, Xi; Zhang, Limin; Gao, Feng; Zhao, Huijuan

    2014-03-01

    According to the morphological differences in the vascularization between healthy and diseased tissues, pharmacokinetic-rate images of fluorophore can provide diagnostic information for tumor differentiation, and especially have the potential for staging of tumors. In this paper, fluorescence diffuse optical tomography method is firstly used to acquire metabolism-related time-course images of the fluorophore concentration. Based on a two-compartment model comprised of plasma and extracelluar-extravascular space, we next propose an adaptive-EKF framework to estimate the pharmacokinetic-rate images. With the aid of a forgetting factor, the adaptive-EKF compensate the inaccuracy initial values and emphasize the effect of the current data in order to realize a better online estimation compared with the conventional EKF. We use simulate data to evaluate the performance of the proposed methodology. The results suggest that the adaptive-EKF can obtain preferable pharmacokinetic-rate images than the conventional EKF with higher quantitativeness and noise robustness.

  2. Visualized numerical assessment for near infrared diffuse optical tomography with contrast-and-size detail analysis

    Science.gov (United States)

    Chen, Liang-Yu; Pan, Min-Cheng; Pan, Min-Chun

    2013-01-01

    The purpose of this study is to propose an objective contrast-and-size detail (CSD) analysis for near infrared diffuse optical tomography (NIR DOT), of which the concept is derived from the subjective contrast detail (CD) analysis. We define a measure for numerical CSD analysis based on the resolution estimation of contrast and size. Following that, the contrast-and-size map of resolution can be calculated and displayed for each corresponding image in the map; furthermore, a CSD resolution curve can be plotted by calculating the average value of the projection corresponding to the physical quantity/axis (size or contrast). To provide some worked examples about the proposed CSD analysis evaluating the imaging performance of different reconstruction methods, Tikhonov regularization and edge-preserving regularization with different weighting functions were employed. Results suggested that using edge-preserving regularization with the generalized Lorentzian weighting function is the most attractive for the estimation of absorption-coefficient images.

  3. The predictive value of optical coherence tomography after grid laser photocoagulation for diffuse diabetic macular oedema

    DEFF Research Database (Denmark)

    Soliman, W.; Sander, B.; Soliman, K.A.E.N.;

    2008-01-01

    Purpose: To assess the predictive value of optical coherence tomography (OCT) mapping of retinal thickness and intraretinal morphological changes after macular grid for diffuse diabetic macular oedema (DMO). Methods: We carried out a prospective, non-controlled, case series study, in which 28 con...... patterns and foveal thickness can help to predict the final visual outcome and final foveal thickness; but not the absolute change in either of these parameters after macular laser therapy Udgivelsesdato: 2008/5......'s correlation coefficient (r = - 0.37, p = 0.05 and r = 0.5, p = 0.01, respectively). Conclusions: it seems that the 1-month time-point after macular laser treatment is a critical point for establishing the outcome of this modality of management of DMO. Baseline OCT mapping of intraretinal fluid accumulation...

  4. Identification of prefrontal cortex (BA10) activation while performing Stroop test using diffuse optical tomography

    Science.gov (United States)

    Khadka, Sabin; Chityala, Srujan R.; Tian, Fenghua; Liu, Hanli

    2011-03-01

    Stroop test is commonly used as a behavior-testing tool for psychological examinations that are related to attention and cognitive control of the human brain. Studies have shown activations in Broadmann area 10 (BA10) of prefrontal cortex (PFC) during attention and cognitive process. The use of diffuse optical tomography (DOT) for human brain mapping is becoming more prevalent. In this study we expect to find neural correlates between the performed cognitive tasks and hemodynamic signals detected by a DOT system. Our initial observation showed activation of oxy-hemoglobin concentration in BA 10, which is consistent with some results seen by positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Our study demonstrates the possibility of combining DOT with Stroop test to quantitatively investigate cognitive functions of the human brain at the prefrontal cortex.

  5. An extensive survey of dayside diffuse aurora based on optical observations at Yellow River Station

    CERN Document Server

    Han, De-Sheng; Liu, Jian-Jun; Qiu, Qi; Keika, K; Hu, Ze-Jun; Liu, Jun-Ming; Hu, Hong-Qiao; Yang, Hui-Gen

    2016-01-01

    By using 7 years optical auroral observations obtained at Yellow River Station (magnetic latitude $76.24\\,^{\\circ}{\\rm C}$N) at Ny-Alesund, Svalbard, we performed the first extensive survey for the dayside diffuse auroras (DDAs) and acquired observational results as follows. (1) The DDAs can be classified into two broad categories, i.e., unstructured and structured DDAs. The unstructured DDAs are mainly distributed in the morning and afternoon, but the structured DDAs predominantly occurred around the magnetic local noon (MLN). (2) The unstructured DDAs observed in morning and afternoon present obviously different properties. The afternoon ones are much stable and seldom show pulsating property. (3) The DDAs are more easily observed under geomagnetically quiet times. (4) The structured DDAsmainly show patchy, stripy, and irregular forms and are often pulsating and drifting. The drifting directions are mostly westward (with speed $\\sim$5km/s), but there are cases showing eastward or poleward drifting. (5) The ...

  6. Detection of brain tumors using fluorescence diffuse optical tomography and nanoparticles as contrast agents

    Science.gov (United States)

    Fortin, Pierre-Yves; Genevois, Coralie; Koenig, Anne; Heinrich, Emilie; Texier, Isabelle; Couillaud, Franck

    2012-12-01

    Near-infrared fluorescence-enhanced diffuse optical tomography (fDOT) is used to localize tumors in mice using fluorescent nanoparticles as a blood pool contrast agent. The infrared dye DiR is loaded in the lipid core of nontargeted nanoparticles (DiR-lipidots) and injected systemically via the tail vein in mice bearing U87 tumors. Distribution and time-course of DiR-lipidots are followed using in vivo fluorescence reflectance imaging and reveal enhanced fluorescent signal within the subcutaneous tumors up to seven days due to the enhanced permeability and retention effect. Tumor growth into the brain is followed using bioluminescent imaging, and tumor localization is further determined by magnetic resonance imaging. The fDOT provides three-dimensional fluorescent maps that allow for consistent localization for both subcutaneous and brain tumors.

  7. Improved Algorithms for Accurate Retrieval of UV - Visible Diffuse Attenuation Coefficients in Optically Complex, Inshore Waters

    Science.gov (United States)

    Cao, Fang; Fichot, Cedric G.; Hooker, Stanford B.; Miller, William L.

    2014-01-01

    Photochemical processes driven by high-energy ultraviolet radiation (UVR) in inshore, estuarine, and coastal waters play an important role in global bio geochemical cycles and biological systems. A key to modeling photochemical processes in these optically complex waters is an accurate description of the vertical distribution of UVR in the water column which can be obtained using the diffuse attenuation coefficients of down welling irradiance (Kd()). The Sea UV Sea UVc algorithms (Fichot et al., 2008) can accurately retrieve Kd ( 320, 340, 380,412, 443 and 490 nm) in oceanic and coastal waters using multispectral remote sensing reflectances (Rrs(), Sea WiFS bands). However, SeaUVSeaUVc algorithms are currently not optimized for use in optically complex, inshore waters, where they tend to severely underestimate Kd(). Here, a new training data set of optical properties collected in optically complex, inshore waters was used to re-parameterize the published SeaUVSeaUVc algorithms, resulting in improved Kd() retrievals for turbid, estuarine waters. Although the updated SeaUVSeaUVc algorithms perform best in optically complex waters, the published SeaUVSeaUVc models still perform well in most coastal and oceanic waters. Therefore, we propose a composite set of SeaUVSeaUVc algorithms, optimized for Kd() retrieval in almost all marine systems, ranging from oceanic to inshore waters. The composite algorithm set can retrieve Kd from ocean color with good accuracy across this wide range of water types (e.g., within 13 mean relative error for Kd(340)). A validation step using three independent, in situ data sets indicates that the composite SeaUVSeaUVc can generate accurate Kd values from 320 490 nm using satellite imagery on a global scale. Taking advantage of the inherent benefits of our statistical methods, we pooled the validation data with the training set, obtaining an optimized composite model for estimating Kd() in UV wavelengths for almost all marine waters. This

  8. Spatial characteristics of wave-like structures in diffuse aurora obtained using optical observations

    Directory of Open Access Journals (Sweden)

    K. Axelsson

    2012-12-01

    Full Text Available We present the results of a statistical study using optical images from ALIS (Auroral Large Imaging System to investigate the spatial and temporal variations of structures in diffuse aurora. Analysis of conjugate Reimei data shows that such fine structures are a result of modulation of high-energy precipitating electrons. Pitch angle diffusion into the loss cone due to interaction of whistler mode waves with plasma sheet electrons is the most feasible mechanism leading to high-energy electron precipitation. This suggests that the fine structure is an indication of modulations of the efficiency of the wave–particle interaction. The scale sizes and variations of these structures, mapped to the magnetosphere, can give us information about the characteristics of the modulating wave activity. We found the scale size of the auroral stripes and the spacing between them to be on average 13–14 km, which corresponds to 3–4 ion gyro radii for protons with an energy of 7 keV. The structures move southward with a speed close to zero in the plasma convection frame.

  9. A quantitative spatial comparison of high-density diffuse optical tomography and fMRI cortical mapping

    OpenAIRE

    Eggebrecht, Adam T.; White, Brian R.; Ferradal, Silvina L.; Chen, Chunxiao; Zhan, Yuxuan; Snyder, Abraham Z.; Dehghani, Hamid; Culver, Joseph P.

    2012-01-01

    Functional neuroimaging commands a dominant role in current neuroscience research. However its use in bedside clinical and certain neuro-scientific studies has been limited because the current tools lack the combination of being non-invasive, non-ionizing and portable while maintaining moderate resolution and localization accuracy. Optical neuroimaging satisfies many of these requirements, but, until recent advances in high-density diffuse optical tomography (HD-DOT), has been hampered by lim...

  10. Measuring sustainable broadband adoption: An innovative approach to understanding broadband adoption and use

    OpenAIRE

    Larose, Robert; De Maagd, Kurt; Chew, Han Ei; Tsai, Hsin-yi Sandy; Steinfield, Charles; Wildman, Steven S; Bauer, Johannes M.

    2012-01-01

    Efforts to promote sustainable broadband Internet adoption urge new attention to the classic diffusion of innovations paradigm. For this study, innovation attributes were reconceptualized following Social Cognitive Theory (SCT). In a sample of inner-city residents, the model accounted for 36% of the variance in intentions to adopt broadband technology and services, primarily from the SCT variables of expected outcomes and self-efficacy. Prior habitual use of the Internet was also a predictor....

  11. Patterns of white matter diffusivity abnormalities in Leber's hereditary optic neuropathy: a tract-based spatial statistics study.

    Science.gov (United States)

    Milesi, Jacopo; Rocca, Maria A; Bianchi-Marzoli, Stefania; Petrolini, Melissa; Pagani, Elisabetta; Falini, Andrea; Comi, Giancarlo; Filippi, Massimo

    2012-09-01

    Leber's hereditary optic neuropathy (LHON) is a mitochondrial disease characterized by retinal ganglion cell degeneration and optic nerve atrophy, leading to a loss of central vision. The aim of this study was to explore the topographical pattern of damage to the brain white matter (WM) tracts from patients with chronic LHON using diffusion tensor (DT) MRI and tract-based spatial statistics (TBSS). Brain dual-echo and DT MRI scans were acquired from 13 patients with chronic LHON and 25 matched controls using a 3.0 T scanner. TBSS analysis was performed using the FMRIB's Diffusion Toolbox. A complete neuro-ophthalmologic examination, including standardized automated Humphrey perimetry as well as average and temporal peripapillary retinal nerve fiber layer thickness (PRNFL) measurements, was obtained in all patients. Mean average and temporal PRNFL thicknesses were decreased significantly in LHON patients. Compared to controls, TBSS analysis revealed significant diffusivity abnormalities in these patients, which were characterized by a decreased fractional anisotropy (FA) and an increased mean diffusivity and radial diffusivity, affecting exclusively the optic tracts and optic radiations (OR). In patients, a significant correlation was found between optic tract average FA and mean visual acuity (r = 0.57, p = 0.04). In LHON patients, DT MRI reveals a microstructural alteration of the WM along the entire visual pathways, with a sparing of the other main WM tracts of the brain. Damage to the OR may be secondary either to trans-synaptic degeneration, which in turn is due to neuroaxonal loss in the retina and optic nerve, or to local mitochondrial dysfunction.

  12. Diffusion optical spectroscopy of cancerous and normal prostate tissues in time-resolved and frequency domain

    Science.gov (United States)

    Zhou, Kenneth J.; Pu, Yang; Chen, Jun

    2014-03-01

    It is well-known that light transport can be well described using Maxwell's electromagnetic theory. In biological tissue, the scattering particles cause the interaction of scattered waves from neighboring particles. Since such interaction cannot be ignored, multiple scattering occurs. The theoretical solution of multiple scattering is complicated. A suitable description is that the wavelike behavior of light is ignored and the transport of an individual photon is considered to be absorbed or scattered. This is known as the Radiative Transfer Equation (RTE) theory. Analytical solutions to the RTE that explicitly describes photon migration can be obtained by introducing some proper approximations. One of the most popular models used in the field of tissue optics is the Diffusion Approximation (DA). In this study, we report on the results of our initial study of optical properties of ex vivo normal and cancerous prostate tissues and how tissue parameters affect the near infrared light transporting in the two types of tissues. The time-resolved transport of light is simulated as an impulse isotropic point source of energy within a homogeneous unbounded medium with different absorption and scattering properties of cancerous and normal prostate tissues. Light source is also modulated sinusoidally to yield a varied fluence rate in frequency domain at a distant observation point within the cancerous and normal prostate tissues. Due to difference of the absorption and scattering coefficients between cancerous and normal tissues, the expansion of light pulse, intensity, phase are found to be different.

  13. Experimental validation of a high-resolution diffuse optical imaging modality: photomagnetic imaging

    Science.gov (United States)

    Nouizi, Farouk; Luk, Alex; Thayer, Dave; Lin, Yuting; Ha, Seunghoon; Gulsen, Gultekin

    2016-01-01

    We present experimental results that validate our imaging technique termed photomagnetic imaging (PMI). PMI illuminates the medium under investigation with a near-infrared light and measures the induced temperature increase using magnetic resonance imaging. A multiphysics solver combining light and heat propagation is used to model spatiotemporal distribution of temperature increase. Furthermore, a dedicated PMI reconstruction algorithm has been developed to reveal high-resolution optical absorption maps from temperature measurements. Being able to perform measurements at any point within the medium, PMI overcomes the limitations of conventional diffuse optical imaging. We present experimental results obtained on agarose phantoms mimicking biological tissue with inclusions having either different sizes or absorption contrasts, located at various depths. The reconstructed images show that PMI can successfully resolve these inclusions with high resolution and recover their absorption coefficient with high-quantitative accuracy. Even a 1-mm inclusion located 6-mm deep is recovered successfully and its absorption coefficient is underestimated by only 32%. The improved PMI system presented here successfully operates under the maximum skin exposure limits defined by the American National Standards Institute, which opens up the exciting possibility of its future clinical use for diagnostic purposes.

  14. Differential diagnosis of breast masses in South Korean premenopausal women using diffuse optical spectroscopic imaging

    Science.gov (United States)

    Leproux, Anaïs; Kim, You Me; Min, Jun Won; McLaren, Christine E.; Chen, Wen-Pin; O'Sullivan, Thomas D.; Lee, Seung-ha; Chung, Phil-Sang; Tromberg, Bruce J.

    2016-07-01

    Young patients with dense breasts have a relatively low-positive biopsy rate for breast cancer (˜1 in 7). South Korean women have higher breast density than Westerners. We investigated the benefit of using a functional and metabolic imaging technique, diffuse optical spectroscopic imaging (DOSI), to help the standard of care imaging tools to distinguish benign from malignant lesions in premenopausal Korean women. DOSI uses near-infrared light to measure breast tissue composition by quantifying tissue concentrations of water (ctH2O), bulk lipid (ctLipid), deoxygenated (ctHHb), and oxygenated (ctHbO2) hemoglobin. DOSI spectral signatures specific to abnormal tissue and absent in healthy tissue were also used to form a malignancy index. This study included 19 premenopausal subjects (average age 41±9), corresponding to 11 benign and 10 malignant lesions. Elevated lesion to normal ratio of ctH2O, ctHHb, ctHbO2, total hemoglobin (THb=ctHHb+ctHbO2), and tissue optical index (ctHHb×ctH2O/ctLipid) were observed in the malignant lesions compared to the benign lesions (p90% sensitivity and specificity. Malignant lesions showed significantly higher metabolism and perfusion than benign lesions. DOSI spectral features showed high discriminatory power for distinguishing malignant and benign lesions in dense breasts of the Korean population.

  15. Lookup-table method for imaging optical properties with structured illumination beyond the diffusion theory regime.

    Science.gov (United States)

    Erickson, Tim A; Mazhar, Amaan; Cuccia, David; Durkin, Anthony J; Tunnell, James W

    2010-01-01

    Sinusoidally structured illumination is used in concert with a phantom-based lookup-table (LUT) to map wide-field optical properties in turbid media with reduced albedos as low as 0.44. A key advantage of the lookup-table approach is the ability to measure the absorption (mu(a)) and reduced scattering coefficients (mu(s) (')) over a much broader range of values than permitted by current diffusion theory methods. Through calibration with a single reflectance standard, the LUT can extract mu(s) (') from 0.8 to 2.4 mm(-1) with an average root-mean-square (rms) error of 7% and extract mu(a) from 0 to 1.0 mm(-1) with an average rms error of 6%. The LUT is based solely on measurements of two parameters, reflectance R and modulation M at an illumination period of 10 mm. A single set of three phase-shifted images is sufficient to measure both M and R, which are then used to generate maps of absorption and scattering by referencing the LUT. We establish empirically that each pair (M,R) maps uniquely to only one pair of (micro(s) ('),micro(a)) and report that the phase function (i.e., size) of the scatterers can influence the accuracy of optical property extraction. PMID:20615015

  16. Community Broadband Networks and the Opportunity for E-Government Services

    DEFF Research Database (Denmark)

    Williams, Idongesit

    2016-01-01

    Community Broadband Networks (CBN) facilitate Broadband connectivity in underserved areas in many countries. The lack of Broadband connectivity is one of the reasons for the slow diffusion of e-government services in many countries.This article explains how CBNs can be enabled by governments to f...

  17. Broadband absorption engineering of hyperbolic metafilm patterns

    OpenAIRE

    Ji, Dengxin; Song, Haomin; Zeng, Xie; Hu, Haifeng; Liu, Kai; Zhang, Nan; Gan, Qiaoqiang

    2014-01-01

    Perfect absorbers are important optical/thermal components required by a variety of applications, including photon/thermal-harvesting, thermal energy recycling, and vacuum heat liberation. While there is great interest in achieving highly absorptive materials exhibiting large broadband absorption using optically thick, micro-structured materials, it is still challenging to realize ultra-compact subwavelength absorber for on-chip optical/thermal energy applications. Here we report the experime...

  18. Improving the light quantification of near infrared (NIR) diffused light optical tomography with ultrasound localization

    Science.gov (United States)

    Ardeshirpour, Yasaman

    According to the statistics published by the American Cancer Society, currently breast cancer is the second most common cancer after skin cancer and the second cause of cancer death after lung cancer in the female population. Diffuse optical tomography (DOT) using near-infrared (NIR) light, guided by ultrasound localization, has shown great promise in distinguishing benign from malignant breast tumors and in assessing the response of breast cancer to chemotherapy. Our ultrasound-guided DOT system is based on reflection geometry, with patients scanned in supine position using a hand-held probe. For patients with chest-wall located at a depth shallower than 1 to 2cm, as in about 10% of our clinical cases, the semi-infinite imaging medium is not a valid assumption and the chest-wall effect needs to be considered in the imaging reconstruction procedure. In this dissertation, co-registered ultrasound images were used to model the breast-tissue and chest-wall as a two-layer medium. The effect of the chest wall on breast lesion reconstruction was systematically investigated. The performance of the two-layer model-based reconstruction, using the Finite Element Method, was evaluated by simulation, phantom experiments and clinical studies. The results show that the two-layer model can improve the accuracy of estimated background optical properties, the reconstructed absorption map and the total hemoglobin concentration of the lesion. For patients' data affected by chest wall, the perturbation, which is the difference between measurements obtained at lesion and normal reference sites, may include the information of background mismatch between these two sites. Because the imaging reconstruction is based on the perturbation approach, the effect of this mismatch between the optical properties at the two sites on reconstructed optical absorption was studied and a guideline for imaging procedure was developed to reduce these effects during data capturing. To reduce the artifacts

  19. Using diffuse optical tomograpy to monitor tumor response to neoadjuvant chemotherapy in breast cancer patients

    Science.gov (United States)

    Gunther, Jacqueline E.; Lim, Emerson; Kim, Hyun Keol; Flexman, Molly; Brown, Mindy; Refrice, Susan; Kalinsky, Kevin; Hershman, Dawn; Hielscher, Andreas H.

    2013-03-01

    Breast cancer patients often undergo neoadjuvant chemotherapy to reduce the size of the tumor before surgery. Tumors which demonstrate a pathologic complete response associate with improved disease-free survival; however, as low as 10% of patients may achieve this status. The goal is to predict response to anti-cancer therapy early, so as to develop personalized treatments and optimize the patient's results. Previous studies have shown that tumor response can be predicted within a few days of treatment initiation. We have developed a diffuse optical tomography (DOT) imaging system for monitoring the response of breast cancer patients to neoadjuvant chemotherapy. Our breast imaging system is a continuous wave system that uses four wavelengths in the near-infrared spectrum (765 nm, 808 nm, 827 nm, and 905 nm). Both breasts are imaged simultaneously with a total of 64 sources and 128 detectors. Three dimensional reconstructions for oxy-hemoglobin concentration ([HbO2]), deoxy-hemoglobin ([Hb]) concentrations, and water are performed using a PDE-constrained multispectral imaging method that uses the diffusion approximation as a model for light propagation. Each patient receives twelve weekly treatments of Taxane followed by four cycles of Doxorubicin and Cyclophosphamide (AC) given every other week. There are six DOT imaging time points: baseline, week 3 and 5 of Paclitaxel, before cycle 1 and 2 of AC, and before surgery. Preliminary results show that there is statistical significance for the percent change of [HbO2], [Hb], [HbT], and percent water at week 2 from the baseline between patients with a pathologic response to chemotherapy.

  20. Spatially-dense, multi-spectral, frequency-domain diffuse optical tomography of breast cancer

    Science.gov (United States)

    Ban, Han Yong

    Diffuse optical tomography (DOT) employs near-infrared light to image the concentration of chromophores and cell organelles in tissue and thereby providing access to functional parameters that can differentiate cancerous from normal tissues. This thesis describes research at the bench and in the clinic that explores and identifies the potential of DOT breast cancer imaging. The bench and clinic instrumentation differ but share important features: they utilize a very large, spatially dense, set of source-detector pairs (10 7) for imaging in the parallel-plate geometry. The bench experiments explored three-dimensional (3D) image resolution and fidelity as a function of numerous parameters and also ascertained the effects of a chest wall phantom. The chest wall is always present but is typically ignored in breast DOT. My experiments clarified chest wall influences and developed schemes to mitigate these effects. Mostly, these schemes involved selective data exclusion, but their efficacy also depended on reconstruction approach. Reconstruction algorithms based on analytic (fast) Fourier inversion and linear algebraic techniques were explored. The clinical experiments centered around a DOT instrument that I designed, constructed, and have begun to test (in-vitro and in-vivo). This instrumentation offers many features new to the field. Specifically, the imager employs spatially-dense, multi-spectral, frequency-domain data; it possesses the world's largest optical source-detector density yet reported, facilitated by highly-parallel CCD-based frequency-domain imaging based on gain-modulation heterodyne detection. The instrument thus measures both phase and amplitude of the diffusive light waves. Other features include both frontal and sagittal breast imaging capabilities, ancillary cameras for measurement of breast boundary profiles, real-time data normalization, and mechanical improvements for patient comfort. The instrument design and construction is my most significant

  1. Light illumination and detection patterns for fluorescence diffuse optical tomography based on compressive sensing.

    Science.gov (United States)

    Jin, An; Yazici, Birsen; Ntziachristos, Vasilis

    2014-06-01

    Fluorescence diffuse optical tomography (FDOT) is an emerging molecular imaging modality that uses near infrared light to excite the fluorophore injected into tissue; and to reconstruct the fluorophore concentration from boundary measurements. The FDOT image reconstruction is a highly ill-posed inverse problem due to a large number of unknowns and limited number of measurements. However, the fluorophore distribution is often very sparse in the imaging domain since fluorophores are typically designed to accumulate in relatively small regions. In this paper, we use compressive sensing (CS) framework to design light illumination and detection patterns to improve the reconstruction of sparse fluorophore concentration. Unlike the conventional FDOT imaging where spatially distributed light sources illuminate the imaging domain one at a time and the corresponding boundary measurements are used for image reconstruction, we assume that the light sources illuminate the imaging domain simultaneously several times and the corresponding boundary measurements are linearly filtered prior to image reconstruction. We design a set of optical intensities (illumination patterns) and a linear filter (detection pattern) applied to the boundary measurements to improve the reconstruction of sparse fluorophore concentration maps. We show that the FDOT sensing matrix can be expressed as a columnwise Kronecker product of two matrices determined by the excitation and emission light fields. We derive relationships between the incoherence of the FDOT forward matrix and these two matrices, and use these results to reduce the incoherence of the FDOT forward matrix. We present extensive numerical simulation and the results of a real phantom experiment to demonstrate the improvements in image reconstruction due to the CS-based light illumination and detection patterns in conjunction with relaxation and greedy-type reconstruction algorithms.

  2. Preclinical, fluorescence and diffuse optical tomography: non-contact instrumentation, modeling and time-resolved 3D reconstruction

    International Nuclear Information System (INIS)

    Time-Resolved Diffuse Optical Tomography (TR-DOT) is a new non-invasive imaging technique increasingly used in the clinical and preclinical fields. It yields optical absorption and scattering maps of the explored organs, and related physiological parameters. Time-Resolved Fluorescence Diffuse Optical Tomography (TR-FDOT) is based on the detection of fluorescence photons. It provides spatio-temporal maps of fluorescent probe concentrations and life times, and allows access to metabolic and molecular imaging which is important for diagnosis and therapeutic monitoring, particularly in oncology. The main goal of this thesis was to reconstruct 3D TR-DOT/TR-FDOT images of small animals using time-resolved optical technology. Data were acquired using optical fibers fixed around the animal without contact with its surface. The work was achieved in four steps: 1)- Setting up an imaging device to record the 3D coordinates of an animal's surface; 2)- Modeling the no-contact approach to solve the forward problem; 3)- Processing of the measured signals taking into account the impulse response of the device; 4)- Implementation of a new image reconstruction method based on a selection of carefully chosen points. As a result, good-quality 3D optical images were obtained owing to reduced cross-talk between absorption and scattering. Moreover, the computation time was cut down, compared to full-time methods using whole temporal profiles. (author)

  3. What can be learned from optical two-color diffusion and thermodiffusion experiments on ternary fluid mixtures?

    Energy Technology Data Exchange (ETDEWEB)

    Gebhardt, M.; Köhler, W., E-mail: werner.koehler@uni-bayreuth.de [Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth (Germany)

    2015-02-28

    A number of optical techniques have been developed during the recent years for the investigation of diffusion and thermodiffusion in ternary fluid mixtures, both on ground and on-board the International Space Station. All these methods are based on the simultaneous measurement of refractive index changes at two different wavelengths. Here, we discuss and compare different techniques with the emphasis on optical beam deflection (OBD), optical digital interferometry, and thermal diffusion forced Rayleigh scattering (TDFRS). We suggest to formally split the data evaluation into a phenomenological parameterization of the measured transients and a subsequent transformation from the refractive index into the concentration space. In all experiments, the transients measured at two different detection wavelengths can be described by four amplitudes and two eigenvalues of the diffusion coefficient matrix. It turns out that these six parameters are subjected to large errors and cannot be determined reliably. Five good quantities, which can be determined with a high accuracy, are the stationary amplitudes, the initial slopes as defined in TDFRS experiments and by application of a heuristic criterion for similar curves, a certain mean diffusion coefficient. These amplitudes and slopes are directly linked to the Soret and thermodiffusion coefficients after transformation with the inverse contrast factor matrix, which is frequently ill-conditioned. Since only five out of six free parameters are reliably determined, including the single mean diffusion coefficient, the determination of the four entries of the diffusion matrix is not possible. We apply our results to new OBD measurements of the symmetric (mass fractions 0.33/0.33/0.33) ternary benchmark mixture n-dodecane/isobutylbenzene/1,2,3,4-tetrahydronaphthalene and existing literature data for the same system.

  4. Optically induced spin-dependent diffusive transport in the presence of spin-orbit interaction for all-optical magnetization reversal

    Science.gov (United States)

    Elyasi, Mehrdad; Yang, Hyunsoo

    2016-07-01

    We have considered the effect of different spin-orbit interaction mechanisms on the process of demagnetization under the influence of short-pulse lasers. All-optical magnetization reversal of perpendicularly magnetized thin films can occur if there are sufficient strong spin-Hall, skew scattering, and Rashba interactions. In the presence of spin-orbit interactions, the transient charge currents provide the generation of transverse-spin currents and accumulations, which eventually exert spin-transfer torque on the magnetization. By combining the optically excited spin-dependent diffusive transport with the spin and charge currents due to skew scattering, spin-Hall, inverse spin-Hall, and Rashba interactions into a numerical model, we demonstrate a possibility of ultrafast all-optical magnetization reversal. This understanding provokes intriguing, more in-depth experimental studies on the role of spin-orbit interaction mechanisms in optimizing structures for all-optical magnetization reversal.

  5. Mapping cortical haemodynamics during neonatal seizures using diffuse optical tomography: A case study

    Directory of Open Access Journals (Sweden)

    Harsimrat Singh

    2014-01-01

    Full Text Available Seizures in the newborn brain represent a major challenge to neonatal medicine. Neonatal seizures are poorly classified, under-diagnosed, difficult to treat and are associated with poor neurodevelopmental outcome. Video-EEG is the current gold-standard approach for seizure detection and monitoring. Interpreting neonatal EEG requires expertise and the impact of seizures on the developing brain remains poorly understood. In this case study we present the first ever images of the haemodynamic impact of seizures on the human infant brain, obtained using simultaneous diffuse optical tomography (DOT and video-EEG with whole-scalp coverage. Seven discrete periods of ictal electrographic activity were observed during a 60 minute recording of an infant with hypoxic–ischaemic encephalopathy. The resulting DOT images show a remarkably consistent, high-amplitude, biphasic pattern of changes in cortical blood volume and oxygenation in response to each electrographic event. While there is spatial variation across the cortex, the dominant haemodynamic response to seizure activity consists of an initial increase in cortical blood volume prior to a large and extended decrease typically lasting several minutes. This case study demonstrates the wealth of physiologically and clinically relevant information that DOT–EEG techniques can yield. The consistency and scale of the haemodynamic responses observed here also suggest that DOT–EEG has the potential to provide improved detection of neonatal seizures.

  6. Prediction of post-operative necrosis after mastectomy: A pilot study utilizing optical diffusion imaging spectroscopy

    Directory of Open Access Journals (Sweden)

    Xie Xian-Jin

    2009-11-01

    Full Text Available Abstract Introduction Flap necrosis and epidermolysis occurs in 18-30% of all mastectomies. Complications may be prevented by intra-operative detection of ischemia. Currently, no technique enables quantitative valuation of mastectomy skin perfusion. Optical Diffusion Imaging Spectroscopy (ViOptix T.Ox Tissue Oximeter measures the ratio of oxyhemoglobin to deoxyhemoglobin over a 1 × 1 cm area to obtain a non-invasive measurement of perfusion (StO2. Methods This study evaluates the ability of ViOptix T.Ox Tissue Oximeter to predict mastectomy flap necrosis. StO2 measurements were taken at five points before and at completion of dissection in 10 patients. Data collected included: demographics, tumor size, flap length/thickness, co-morbidities, procedure length, and wound complications. Results One patient experienced mastectomy skin flap necrosis. Five patients underwent immediate reconstruction, including the patient with necrosis. Statistically significant factors contributing to necrosis included reduction in medial flap StO2 (p = 0.0189, reduction in inferior flap StO2 (p = 0.003, and flap length (p = 0.009. Conclusion StO2 reductions may be utilized to identify impaired perfusion in mastectomy skin flaps.

  7. Monitoring early tumor response to drug therapy with diffuse optical tomography

    Science.gov (United States)

    Flexman, Molly L.; Vlachos, Fotios; Kim, Hyun Keol; Sirsi, Shashank R.; Huang, Jianzhong; Hernandez, Sonia L.; Johung, Tessa B.; Gander, Jeffrey W.; Reichstein, Ari R.; Lampl, Brooke S.; Wang, Antai; Borden, Mark A.; Yamashiro, Darrell J.; Kandel, Jessica J.; Hielscher, Andreas H.

    2012-01-01

    Although anti-angiogenic agents have shown promise as cancer therapeutics, their efficacy varies between tumor types and individual patients. Providing patient-specific metrics through rapid noninvasive imaging can help tailor drug treatment by optimizing dosages, timing of drug cycles, and duration of therapy--thereby reducing toxicity and cost and improving patient outcome. Diffuse optical tomography (DOT) is a noninvasive three-dimensional imaging modality that has been shown to capture physiologic changes in tumors through visualization of oxygenated, deoxygenated, and total hemoglobin concentrations, using non-ionizing radiation with near-infrared light. We employed a small animal model to ascertain if tumor response to bevacizumab (BV), an anti-angiogenic agent that targets vascular endothelial growth factor (VEGF), could be detected at early time points using DOT. We detected a significant decrease in total hemoglobin levels as soon as one day after BV treatment in responder xenograft tumors (SK-NEP-1), but not in SK-NEP-1 control tumors or in non-responder control or BV-treated NGP tumors. These results are confirmed by magnetic resonance imaging T2 relaxometry and lectin perfusion studies. Noninvasive DOT imaging may allow for earlier and more effective control of anti-angiogenic therapy.

  8. Reproducibility of parameters of postocclusive reactive hyperemia measured by diffuse optical tomography

    Science.gov (United States)

    Vidal-Rosas, Ernesto E.; Billings, Stephen A.; Chico, Timothy; Coca, Daniel

    2016-06-01

    The application of near-infrared spectroscopy (NIRS) to assess microvascular function has shown promising results. An important limitation when using a single source-detector pair, however, is the lack of depth sensitivity. Diffuse optical tomography (DOT) overcomes this limitation using an array of sources and detectors that allow the reconstruction of volumetric hemodynamic changes. This study compares the key parameters of postocclusive reactive hyperemia measured in the forearm using standard NIRS and DOT. We show that while the mean parameter values are similar for the two techniques, DOT achieves much better reproducibility, as measured by the intraclass correlation coefficient (ICC). We show that DOT achieves high reproducibility for muscle oxygen consumption (ICC: 0.99), time to maximal HbO2 (ICC: 0.94), maximal HbO2 (ICC: 0.99), and time to maximal HbT (ICC: 0.99). Absolute reproducibility as measured by the standard error of measurement is consistently smaller and close to zero (ideal value) across all parameters measured by DOT compared to NIRS. We conclude that DOT provides a more robust characterization of the reactive hyperemic response and show how the availability of volumetric hemodynamic changes allows the identification of areas of temporal consistency, which could help characterize more precisely the microvasculature.

  9. Diffuse optical tomography with structured-light patterns to quantify breast density

    Science.gov (United States)

    Kwong, Jessica; Nouizi, Farouk; Cho, Jaedu; Zheng, Jie; Li, Yifan; Chen, Jeon-hor; Su, Min-Ying; Gulsen, Gultekin

    2016-02-01

    Breast density is an independent risk factor for breast cancer, where women with denser breasts are more likely to develop cancer. By identifying women at higher risk, healthcare providers can suggest screening at a younger age to effectively diagnose and treat breast cancer in its earlier stages. Clinical risk assessment models currently do not incorporate breast density, despite its strong correlation with breast cancer. Current methods to measure breast density rely on mammography and MRI, both of which may be difficult to use as a routine risk assessment tool. We propose to use diffuse optical tomography with structured-light to measure the dense, fibroglandular (FGT) tissue volume, which has a different chromophore signature than the surrounding adipose tissue. To test the ability of this technique, we performed simulations by creating numerical breast phantoms from segmented breast MR images. We looked at two different cases, one with a centralized FGT distribution and one with a dispersed distribution. As expected, the water and lipid volumes segmented at half-maximum were overestimated for the dispersed case. However, it was noticed that the recovered water and lipid concentrations were lower and higher, respectively, than the centralized case. This information may provide insight into the morphological distribution of the FGT and can be a correction in estimating the breast density.

  10. Functional Imaging of the Developing Brain at the Bedside Using Diffuse Optical Tomography.

    Science.gov (United States)

    Ferradal, Silvina L; Liao, Steve M; Eggebrecht, Adam T; Shimony, Joshua S; Inder, Terrie E; Culver, Joseph P; Smyser, Christopher D

    2016-04-01

    While histological studies and conventional magnetic resonance imaging (MRI) investigations have elucidated the trajectory of structural changes in the developing brain, less is known regarding early functional cerebral development. Recent investigations have demonstrated that resting-state functional connectivity MRI (fcMRI) can identify networks of functional cerebral connections in infants. However, technical and logistical challenges frequently limit the ability to perform MRI scans early or repeatedly in neonates, particularly in those at greatest risk for adverse neurodevelopmental outcomes. High-density diffuse optical tomography (HD-DOT), a portable imaging modality, potentially enables early continuous and quantitative monitoring of brain function in infants. We introduce an HD-DOT imaging system that combines advancements in cap design, ergonomics, and data analysis methods to allow bedside mapping of functional brain development in infants. In a cohort of healthy, full-term neonates scanned within the first days of life, HD-DOT results demonstrate strong congruence with those obtained using co-registered, subject-matched fcMRI and reflect patterns of typical brain development. These findings represent a transformative advance in functional neuroimaging in infants, and introduce HD-DOT as a powerful and practical method for quantitative mapping of early functional brain development in normal and high-risk neonates. PMID:25595183

  11. Brain specificity of diffuse optical imaging: improvements from superficial signal regression and tomography

    Directory of Open Access Journals (Sweden)

    Nicholas M Gregg

    2010-07-01

    Full Text Available Functional near infrared spectroscopy (fNIRS is a portable monitor of cerebral hemodynamics with wide clinical potential. However, in fNIRS, the vascular signal from the brain is often obscured by vascular signals present in the scalp and skull. In this paper, we evaluate two methods for improving in vivo data from adult human subjects through the use of high-density diffuse optical tomography (DOT. First, we test whether we can extend superficial regression methods (which utilize the multiple source-detector pair separations from sparse optode arrays to application with DOT imaging arrays. In order to accomplish this goal, we modify the method to remove physiological artifacts from deeper sampling channels using an average of shallow measurements. Second, DOT provides three-dimensional image reconstructions and should explicitly separate different tissue layers. We test whether DOT's depth-sectioning can completely remove superficial physiological artifacts. Herein, we assess improvements in signal quality and reproducibility due to these methods using a well-characterized visual paradigm and our high-density DOT system. Both approaches remove noise from the data, resulting in cleaner imaging and more consistent hemodynamic responses. Additionally, the two methods act synergistically, with greater improvements when the approaches are used together.

  12. Cerebral monitoring during carotid endarterectomy using near-infrared diffuse optical spectroscopies and electroencephalogram

    Science.gov (United States)

    Shang, Yu; Cheng, Ran; Dong, Lixin; Ryan, Stephen J.; Saha, Sibu P.; Yu, Guoqiang

    2011-05-01

    Intraoperative monitoring of cerebral hemodynamics during carotid endarterectomy (CEA) provides essential information for detecting cerebral hypoperfusion induced by temporary internal carotid artery (ICA) clamping and post-CEA hyperperfusion syndrome. This study tests the feasibility and sensitivity of a novel dual-wavelength near-infrared diffuse correlation spectroscopy technique in detecting cerebral blood flow (CBF) and cerebral oxygenation in patients undergoing CEA. Two fiber-optic probes were taped on both sides of the forehead for cerebral hemodynamic measurements, and the instantaneous decreases in CBF and electroencephalogram (EEG) alpha-band power during ICA clamping were compared to test the measurement sensitivities of the two techniques. The ICA clamps resulted in significant CBF decreases (-24.7 ± 7.3%) accompanied with cerebral deoxygenation at the surgical sides (n = 12). The post-CEA CBF were significantly higher (+43.2 ± 16.9%) than the pre-CEA CBF. The CBF responses to ICA clamping were significantly faster, larger and more sensitive than EEG responses. Simultaneous monitoring of CBF, cerebral oxygenation and EEG power provides a comprehensive evaluation of cerebral physiological status, thus showing potential for the adoption of acute interventions (e.g., shunting, medications) during CEA to reduce the risks of severe cerebral ischemia and cerebral hyperperfusion syndrome.

  13. Short-term Variability of Extinction by Broadband Stellar Photometry

    Energy Technology Data Exchange (ETDEWEB)

    Musat, I.C.; Ellingson, R.G.

    2005-03-18

    Aerosol optical depth variation over short-term time intervals is determined from broadband observations of stars with a whole sky imager. The main difficulty in such measurements consists of accurately separating the star flux value from the non-stellar diffuse skylight. Using correction method to overcome this difficulty, the monochromatic extinction at the ground due to aerosols is extracted from heterochromatic measurements. A form of closure is achieved by comparison with simultaneous or temporally close measurements with other instruments, and the total error of the method, as a combination of random error of measurements and systematic error of calibration and model, is assessed as being between 2.6 and 3% rms.

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

    Science.gov (United States)

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

    2016-03-01

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

  15. Broadband near-infrared luminescence and tunable optical amplification around 1.55 {mu}m and 1.33 {mu}m of PbS quantum dots in glasses

    Energy Technology Data Exchange (ETDEWEB)

    Dong Guoping, E-mail: dgp@suct.edu.cn [State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology, Guangzhou 510640 (China); Wu Botao [State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 (China); Zhang Fangteng; Zhang Liaolin; Peng Mingying; Chen Dongdan [State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology, Guangzhou 510640 (China); Wu, E. [State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 (China); Qiu Jianrong, E-mail: qjr@scut.edu.cn [State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology, Guangzhou 510640 (China)

    2011-09-22

    Highlights: > Optical amplification of PbS QDs in glasses at 1.55 {mu}m is characterized for the first time. > Using ZnS-PbO to replace PbS as precursor of PbS QDs, the size distribution of PbS QDs in glasses becomes more uniform and narrower. > Using ZnS-PbO to replace PbS as precursor of PbS QDs, optical amplification is remarkably improved, and the possible enhancing mechanism is also discussed. - Abstract: Silicate glasses containing PbS quantum dots (QDs) with narrow size distribution were prepared through heat treatment. Transmission electron microscopy (TEM) results show that spherical PbS QDs are densely dispersed in the glassy matrix. Using ZnS-PbO to replace PbS as precursor of PbS QDs, the size distribution of PbS QDs in glasses becomes more uniform. Tunable infrared luminescence from 1100 to 2200 nm has been obtained by controlling the glassy matrix and preparation parameters. Obvious optical amplification at communication windows of 1.55 {mu}m and 1.33 {mu}m is probed, and the PbS QDs doped glasses using ZnS-PbO as precursor exhibit larger optical amplification. The PbS QDs doped glasses with intense optical amplification are considered to be promising candidate as gain medium for broadband fiber amplifier and tunable fiber laser.

  16. Broadband near-infrared luminescence and tunable optical amplification around 1.55 μm and 1.33 μm of PbS quantum dots in glasses

    International Nuclear Information System (INIS)

    Highlights: → Optical amplification of PbS QDs in glasses at 1.55 μm is characterized for the first time. → Using ZnS-PbO to replace PbS as precursor of PbS QDs, the size distribution of PbS QDs in glasses becomes more uniform and narrower. → Using ZnS-PbO to replace PbS as precursor of PbS QDs, optical amplification is remarkably improved, and the possible enhancing mechanism is also discussed. - Abstract: Silicate glasses containing PbS quantum dots (QDs) with narrow size distribution were prepared through heat treatment. Transmission electron microscopy (TEM) results show that spherical PbS QDs are densely dispersed in the glassy matrix. Using ZnS-PbO to replace PbS as precursor of PbS QDs, the size distribution of PbS QDs in glasses becomes more uniform. Tunable infrared luminescence from 1100 to 2200 nm has been obtained by controlling the glassy matrix and preparation parameters. Obvious optical amplification at communication windows of 1.55 μm and 1.33 μm is probed, and the PbS QDs doped glasses using ZnS-PbO as precursor exhibit larger optical amplification. The PbS QDs doped glasses with intense optical amplification are considered to be promising candidate as gain medium for broadband fiber amplifier and tunable fiber laser.

  17. Heterogeneous broadband network

    Science.gov (United States)

    Dittmann, Lars

    1995-11-01

    Although the vision for the future Integrated Broadband Communication Network (IBCN) is an all optical network, it is certain that for a long period to come, the network will remain very heterogeneous, with a mixture of different physical media (fiber, coax and twisted pair), transmission systems (PDH, SDH, ADSL) and transport protocols (TCP/IP, AAL/ATM, frame relay). In the current work towards the IBCN, the ATM concept is considered the generic network protocol for both public and private network, with the ability to use different underlying transmission protocols and, through adaptation protocols, provide the appropriate services (old as well as new) to the customer. One of the major difficulties of heterogeneous network is the restriction that is usually given by the lowest common denominator, e.g. in terms of single channel capacity. A possible way to overcome these limitations is by extending the ATM concept with a multilink capability, that allows us to use separate resources as one common. The improved flexibility obtained by this protocol extension further allows a real time optimization of network and call configuration, without any impact on the quality of service seen from the user. This paper describes an example of an ATM based multilink protocol that has been experimentally implemented within the RACE project 'STRATOSPHERIC'. The paper outlines the complexity of introducing an extra network functionality compared with the added value, such as an improved ability to recover an error due to a malfunctioning network component.

  18. Broadband Telecommunications Benchmarking Study

    OpenAIRE

    2004-01-01

    This report assesses Ireland's competitiveness relative to 21 countries, with particular focus on the broadband telecommunications requirements of the enterprise sector. The report outlines strengths and weaknesses that currently exist and progress that has already been made. It also makes a series of recommendations to further promote the development of the broadband market in Ireland.

  19. The Broadband Buzz.

    Science.gov (United States)

    Buchanan, Bruce

    2003-01-01

    "Broadband," the term for a variety of high-speed Internet options, opens up many opportunities for online classroom learning. Challenges for school districts include keeping the network running, training teachers, and paying for it. A sidebar lists broadband resources. (MLF)

  20. Determination of Landscape Diffusivity Using Optically Stimulated Luminescence and Infrared Stimulated Luminescence Techniques

    Science.gov (United States)

    Stang, D.; Rhodes, E. J.; Heimsath, A. M.

    2011-12-01

    As landscapes undergo surface lowering by weathering and erosion, soil formation, mixing and transport processes play a key role. Determining the rates of soil mixing and transport is key to developing reliable models of hillslope erosion and landscape development, and is important in establishing a value for landscape diffusivity in numerical simulations. Mixing processes include biological mechanisms such as grains moving by gravity within burrows or root holes, grains being transported upwards by burrowing animals such as moles, gophers, rabbits, spiders, ants and other organisms, or larger scale processes such as tree throw. Non-biological mechanisms include surface wash and other slope transport processes, frost heave, movement caused by wetting and drying cycles, and grain transport by water within sediment pores. As optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) signals are light sensitive, they are reset by daylight exposure each time quartz or feldspar grains are brought to the surface. After re-burial, signals slowly re-grow as the grains are exposed to environmental radiation. We have adopted two complementary approaches that can provide information on processes and rates of grain mixing. Firstly we measured the apparent age distribution of single grains of quartz from discrete depths, providing in-depth data on the full range of grain histories since their last surface encounter. Secondly, we measured contiguous 1 cm spits of sediment from monoliths (vertical columns of sediment approx. 10 x 10 cm) using bulk IRSL, dominated by emissions from feldspars. The second approach sums the signals from all feldspar grains, and provides a rapid method to identify features such as burrows and root holes, as well as rapidly deposited surface events (e.g. small debris flow lobes). Combining both approaches, we are able to quantify the magnitude and timing of macroscale mixing processes (e.g. burrows, sediment slugs), while also

  1. Study on sputtered a-Si:H for micro optical diffusion sensor using laser-induced dielectrophoresis

    Science.gov (United States)

    Kamata, Makoto; Yamada, Kan; Taguchi, Yoshihiro; Nagasaka, Yuji

    2016-03-01

    In this study, a MEMS sensing device, which is applicable to point-of-care testing (POCT), is developed by integrating an optical manipulation and detection technique. The diffusion coefficient is a parameter, which is sensitive to the size, the construction and the interaction of the sample, thus, the measurement of the diffusion coefficient of the bio-sample, such as proteins, is useful for the clinical diagnosis to detect interactions and conformational changes with high sensitivity. Several diffusion sensing methods have been developed, however, the technique applicable to POCT is not established because of the difficulties due to the requirement of the measurement in a short time and a small sensing device. In this study, in order to realize a high-speed detection (ms ~ s) with small sample volume (~ μl) and small apparatus (tens of cm) without particular preparations, the micro optical diffusion sensor utilizing laser-induced dielectrophoresis (LIDEP), which is a manipulation technique based on optoelectronic tweezers, is developed. The microscale concentration distribution is formed in the microchannel by LIDEP and act as the transient diffraction grating, then, the diffusion phenomenon is optically observed. For these techniques, a photoconductive layer is essential and a hydrogenated amorphous silicon (a-Si:H) deposited by a plasma-enhanced chemical vapor deposition is generally utilized as the layer. In this study, the a-Si:H is deposited using a reactive RF magnetron sputtering method under several conditions, while changing the source gas compositions. The sensing device is fabricated with proposed a-Si:H, and the feasibility study for bio-sample measurement is conducted.

  2. Diffuse-light absorption spectroscopy by fiber optics for detecting and quantifying the adulteration of extra virgin olive oil

    Science.gov (United States)

    Mignani, A. G.; Ciaccheri, L.; Ottevaere, H.; Thienpont, H.; Conte, L.; Marega, M.; Cichelli, A.; Attilio, C.; Cimato, A.

    2010-09-01

    A fiber optic setup for diffuse-light absorption spectroscopy in the wide 400-1700 nm spectral range is experimented for detecting and quantifying the adulteration of extra virgin olive oil caused by lower-grade olive oils. Absorption measurements provide spectral fingerprints of authentic and adulterated oils. A multivariate processing of spectroscopic data is applied for discriminating the type of adulterant and for predicting its fraction.

  3. Numerical Study on Infrared Optical Property of Diffuse Coal Particles in Mine Fully Mechanized Working Combined with CFD Method

    OpenAIRE

    Wen-Zheng Wang; Yan-Ming Wang; Guo-Qing Shi; De-Ming Wang

    2015-01-01

    Coal dust seriously threatens the safety and occupational health of coal mines. Numerical simulation research on the infrared radiation characteristics of diffused coal dust is carried out in fully mechanized working faces based on the optical monitoring problem of dust particles in mine atmospheric environments. The CFD method is applied to obtain the law of dust transport and distribution. Combined with Mie scattering model, the infrared radiation change characteristics and spectral selecti...

  4. Reciprocity relation for the vector radiative transport equation and its application to diffuse optical tomography with polarized light

    CERN Document Server

    Tricoli, Ugo; Da Silva, Anabela; Markel, Vadim A

    2016-01-01

    We derive a reciprocity relation for vector radiative transport equation (vRTE) that describes propagation of polarized light in multiple-scattering media. We then show how this result, together with translational invariance of a plane-parallel sample, can be used to compute efficiently the sensitivity kernel of diffuse optical tomography (DOT) by Monte Carlo simulations. Numerical examples of polarization-selective sensitivity kernels thus computed are given.

  5. Quantification of joint inflammation in rheumatoid arthritis by time-resolved diffuse optical spectroscopy and tracer kinetic modeling

    Science.gov (United States)

    Ioussoufovitch, Seva; Morrison, Laura B.; Lee, Ting-Yim; St. Lawrence, Keith; Diop, Mamadou

    2015-03-01

    Rheumatoid arthritis (RA) is characterized by chronic synovial inflammation, which can cause progressive joint damage and disability. Diffuse optical spectroscopy (DOS) and imaging have the potential to become potent monitoring tools for RA. We devised a method that combined time-resolved DOS and tracer kinetics modeling to rapidly and reliably quantify blood flow in the joint. Preliminary results obtained from two animals show that the technique can detect joint inflammation as early as 5 days after onset.

  6. Fibre laser based broadband THz imaging systems

    DEFF Research Database (Denmark)

    Eichhorn, Finn

    State-of-the-art optical fiber technology can contribute towards complex multi-element broadband terahertz imaging systems. Classical table-top terahertz imaging systems are generally limited to a single emitter/receiver pair, which constrains their imaging capability to tedious raster scanning i...

  7. Full-Duplex Link Providing Alternative Wired and Wireless Broadband Access for the Wavelength-Division Multiplexing Passive Optical Network with a Uniform Converged Signal Format

    Science.gov (United States)

    Ma, Jianxin

    2014-05-01

    A full-duplex link implementing alternative wired and wireless access for wavelength-division multiplexing passive optical network is proposed with the uniformed three-tone converged optical signal, which provides a wired or wireless downlink access signal alternatively and an uplink optical carrier. The uplink optical carrier reversed by the converged optical signal makes the hybrid optical node unit free from the optical source. The simulation results show that the full-duplex link with a 10-Gb/s 16-quadrature amplitude modulation (16-QAM) downstream and 5 Gb/s binary upstream can provide both wired access with a bit-error rate below 10-9 and radio-over-fiber-based wireless access with a bit-error rate below 10-7 over 40 km of fiber without an optical source and optical amplifier in the hybrid optical node unit.

  8. Optimizing the regularization for image reconstruction of cerebral diffuse optical tomography.

    Science.gov (United States)

    Habermehl, Christina; Steinbrink, Jens; Müller, Klaus-Robert; Haufe, Stefan

    2014-09-01

    Functional near-infrared spectroscopy (fNIRS) is an optical method for noninvasively determining brain activation by estimating changes in the absorption of near-infrared light. Diffuse optical tomography (DOT) extends fNIRS by applying overlapping “high density” measurements, and thus providing a three-dimensional imaging with an improved spatial resolution. Reconstructing brain activation images with DOT requires solving an underdetermined inverse problem with far more unknowns in the volume than in the surface measurements. All methods of solving this type of inverse problem rely on regularization and the choice of corresponding regularization or convergence criteria. While several regularization methods are available, it is unclear how well suited they are for cerebral functional DOT in a semi-infinite geometry. Furthermore, the regularization parameter is often chosen without an independent evaluation, and it may be tempting to choose the solution that matches a hypothesis and rejects the other. In this simulation study, we start out by demonstrating how the quality of cerebral DOT reconstructions is altered with the choice of the regularization parameter for different methods. To independently select the regularization parameter, we propose a cross-validation procedure which achieves a reconstruction quality close to the optimum. Additionally, we compare the outcome of seven different image reconstruction methods for cerebral functional DOT. The methods selected include reconstruction procedures that are already widely used for cerebral DOT [minimum l2-norm estimate (l2MNE) and truncated singular value decomposition], recently proposed sparse reconstruction algorithms [minimum l1- and a smooth minimum l0-norm estimate (l1MNE, l0MNE, respectively)] and a depth- and noise-weighted minimum norm (wMNE). Furthermore, we expand the range of algorithms for DOT by adapting two EEG-source localization algorithms [sparse basis field expansions and linearly

  9. Evaluation of improvement of diffuse optical imaging of brain function by high-density probe arrangements and imaging algorithms

    Science.gov (United States)

    Sakakibara, Yusuke; Kurihara, Kazuki; Okada, Eiji

    2016-04-01

    Diffuse optical imaging has been applied to measure the localized hemodynamic responses to brain activation. One of the serious problems with diffuse optical imaging is the limitation of the spatial resolution caused by the sparse probe arrangement and broadened spatial sensitivity profile for each probe pair. High-density probe arrangements and an image reconstruction algorithm considering the broadening of the spatial sensitivity can improve the spatial resolution of the image. In this study, the diffuse optical imaging of the absorption change in the brain is simulated to evaluate the effect of the high-density probe arrangements and imaging methods. The localization error, equivalent full-width half maximum and circularity of the absorption change in the image obtained by the mapping and reconstruction methods from the data measured by five probe arrangements are compared to quantitatively evaluate the imaging methods and probe arrangements. The simple mapping method is sufficient for the density of the measurement points up to the double-density probe arrangement. The image reconstruction method considering the broadening of the spatial sensitivity of the probe pairs can effectively improve the spatial resolution of the image obtained from the probe arrangements higher than the quadruple density, in which the distance between the neighboring measurement points is 10.6 mm.

  10. Atlas-based high-density diffuse optical tomography for imaging the whole human cortex

    Science.gov (United States)

    Wu, Xue; Eggebrecht, Adam T.; Ferradal, Silvina L.; Culver, Joseph P.; Dehghani, Hamid

    2015-03-01

    Diffuse optical tomography (DOT) for brain imaging has the potential to be an alternative human brain mapping technique when MRI imaging is not applicable. It recovers tissue chromophore concentrations of brain tissue through measures of light transmission to monitor for example the resting-state brain dynamics. This imaging technique relies on simulation of the light propagation which can be generated based on a subject-specific model. There has been some study on using rigid atlas models as alternatives for model based DOT when subject-specific anatomical data is not available; but there is still a lack of detailed analysis between geometrical accuracy and internal light propagation in tissue for atlas-based DOT. This work is focused on High-Density DOT (HD-DOT) of the whole cortex based on atlas models from 11 different rigid registration algorithms across 24 subjects, and the results are evaluated in 19 areas of the human head. The correlation between geometrical surface error and internal light propagation errors is strong in most area but varies in different regions from R2 = 0.74 in the region around top of the head to R2 = 0.98 in the region around the temples. In the 11 registration methods, basic-4-landmark registration with 4.2mm average surface error and 50% average internal light propagation errors is shown to be the least accurate registration method whereas full-head landmark with non-iterative point to point with 1.7mm average surface error and 32% average internal light propagation error is shown to be the most accurate registration method for atlas-based DOT.

  11. Safety assessment of near infrared light emitting diodes for diffuse optical measurements

    Directory of Open Access Journals (Sweden)

    Onaral Banu

    2004-03-01

    Full Text Available Abstract Background Near infrared (NIR light has been used widely to monitor important hemodynamic parameters in tissue non-invasively. Pulse oximetry, near infrared spectroscopy, and diffuse optical tomography are examples of such NIR light-based applications. These and other similar applications employ either lasers or light emitting diodes (LED as the source of the NIR light. Although the hazards of laser sources have been addressed in regulations, the risk of LED sources in such applications is still unknown. Methods Temperature increase of the human skin caused by near infrared LED has been measured by means of in-vivo and in-vitro experiments. Effects of the conducted and radiated heat in the temperature increase have been analyzed separately. Results Elevations in skin temperature up to 10°C have been observed. The effect of radiated heat due to NIR absorption is low – less than 0.5°C – since emitted light power is comparable to the NIR part of sunlight. The conducted heat due to semiconductor junction of the LED can cause temperature increases up to 9°C. It has been shown that adjusting operational parameters by amplitude modulating or time multiplexing the LED decreases the temperature increase of the skin significantly. Conclusion In this study, we demonstrate that the major risk source of the LED in direct contact with skin is the conducted heat of the LED semiconductor junction, which may cause serious skin burns. Adjusting operational parameters by amplitude modulating or time multiplexing the LED can keep the LED within safe temperature ranges.

  12. In Vivo Measurements of Blood Hemodynamics in Rat Brain using Diffuse Optical Tomography and Diffuse Correlation Spectroscopy

    Science.gov (United States)

    Durduran, Turgut

    2002-03-01

    Cerebral blood flow (CBF), blood volume (CBV) and tissue averaged blood oxygen saturation (Y_t) are measurable quantities at the basis of functional neuroimaging techniques. The coupling of CBF, CBV and Yt affect the cerebral metabolic rate of oxygen utilization (CMRO_2) and is not yet well understood. CMRO2 is generally estimated from the measured quantities using physiological models. Near infrared spectroscopy and tomography (DOT) are important new methods to measure the temporal evolution of CBV and Yt with low spatial resolution. Diffuse correlation spectroscopy (DCS) can also be used to measure temporal and spatial variations of CBF. DOT and DCS allow minimally-invasive measurements with intact skull. I will present experiments on many physiological models such as hypercapnia, hypoxia, focal ischemia, cortical spreading depression and forepaw stimulation where all three quantities are measured simultaneously. The theoretical background for DOT and DCS measurements and basic image reconstruction as applicable to studies of brain hemodynamics will be outlined. State of the art instrumentation and its ongoing development will be presented. Finally, our spectroscopic and tomographic results from animal models will be shown in detail.

  13. Broadband Waveguide QED System on a Chip

    OpenAIRE

    Quan, Qimin; Bulu, Irfan; Loncar, Marko

    2009-01-01

    We demonstrate that a slot waveguide provides a broadband loss-free platform suitable for applications in quantum optics. We find that strong coupling between light quanta and a single quantum emitter placed in the waveguide slot can be achieved with efficiency higher than 96% and Purcell factor (spontaneous emission factor) larger than 200. The proposed system is a promising platform for quantum information processing and can be used to realize an efficient single photon source and optically...

  14. The properties of nano(ZnO-CeO2)@polysiloxane core-shell microspheres and their application for fabricating optical diffusers

    Science.gov (United States)

    Hu, Jingang; Zhou, Yuming

    2016-03-01

    In this study, we presented a novel hybrid material with good thermal stability. Moreover, its application for optical diffusers displayed excellent properties. Tensile testing indicated the improved mechanical properties of this novel film. It can improve the performance of polymer matrix in mechanic and thermal properties via adding nano(ZnO-CeO2)@polysiloxane into resin. Photoluminescence properties of nano(ZnO-CeO2)@polysiloxane proved the hybrid structure, and it can broaden the application of diffusers. In addition, the UV-vis-NIR spectra analysis confirmed that novel diffuser had a good UV-shielding effect and it owned a strong NIR absorption, which had a potential application in absorbing materials and night vision LCD monitor products. The results of lasers scattering showed the novel diffuser based on the fillers of nano(ZnO-CeO2)@polysiloxane microspheres possessed suitable light transmittance, good diffusion capacity, and low incident angle dependence, which were critical and necessary for excellent optical diffusers. When the concentration of nano(ZnO-CeO2)@polysiloxane was up to 15 wt%, the diffuser possessed superior light diffusing effect exceeding optical diffusers on market. Thus, it can be expectable for wild application in preparing various multifunctional diffusion materials such as monitors, touch-panel functions, military projectors, etc.

  15. Broadband External-Cavity Diode Laser

    Science.gov (United States)

    Pilgrim, Jeffrey S.

    2005-01-01

    A broadband external-cavity diode laser (ECDL) has been invented for use in spectroscopic surveys preparatory to optical detection of gases. Heretofore, commercially available ECDLs have been designed, in conjunction with sophisticated tuning assemblies, for narrow- band (and, typically, single-frequency) operation, as needed for high sensitivity and high spectral resolution in some gas-detection applications. However, for preparatory spectroscopic surveys, high sensitivity and narrow-band operation are not needed; in such cases, the present broadband ECDL offers a simpler, less-expensive, more-compact alternative to a commercial narrowband ECDL.

  16. Broadband adoption by SMES

    OpenAIRE

    Oni, Oluwasola

    2007-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. Because the benefits of broadband for businesses have been widely publicized, the UK government has tried to ensure that there is a wide and fast take-up of the technology. Initial figures showed that broadband adoption by SMEs was particularly slow and there has been little research on the use of broadband by businesses, particularly SMEs. An in-depth study into the roles and activities of t...

  17. The influence of diffusion temperature on the structural, optical and magnetic properties of manganese-doped zinc oxysulfide thin films

    International Nuclear Information System (INIS)

    We investigated the structural, optical and magnetic properties of Mn-doped zinc oxysulfide films. Zn(O,S) films were deposited by a spray pyrolysis method on glass substrate. A thin Mn layer evaporated on these films served as the source for the diffusion doping. The XRD pattern of undoped films revealed the presence of two wurtzite phases corresponding to ZnS and ZnO with a strong preferred orientation along the ZnS (0 0 2) hexagonal plane direction. SEM showed a similar surface morphology for the undoped and Mn-doped films, displaying regular arrays of hexagonal micro-rods perpendicular to the substrate. The optical transmission measurements showed that both undoped and Mn diffusion-doped films had a low average transmittance less than about 10%. The gap energy is decreased from 3.42 to 3.33 eV upon annealing at 400 deg. C. Photoluminescence studies at 300 K show that the incorporation of manganese leads to a decrease of deep level band intensity compared to undoped sample. Clear ferromagnetic loops were observed for the Mn-doped Zn(O,S) films, which might be due to the presence of point defects. - Graphical abstract: M-H variation of Mn diffusion-doped Zn(O,S) thin films measured at 300 K. Highlights: → Zinc oxysulfide thin films fabricated by spray pyrolysis and doped with Mn. → Regular arrays of hexagonal micro-rods perpendicular to the substrate. → Optical transmission measurements showed that both undoped and Mn diffusion-doped films had a low average transmittance less than about 10%. → Magnetic measurements show that Mn-doped zinc oxysulfide thin films exhibit a ferromagnetism behavior at room temperature.

  18. Optical parameter measurement of highly diffusive tissue body phantoms with specifically designed sample holder for photo diagnostic and PDT applications

    Science.gov (United States)

    Rehman, A.; Rehman, K.; Anwar, S.; Firdous, S.; Nawaz, M.

    2015-12-01

    Knowledge of optical properties (absorption coefficients, scattering Coefficients, and anisotropy) is necessary for understanding light tissue interactions. Optical parameters define the behavior of light in the tissues. Intralipid and Indian ink are well-established tissue body phantoms. Quantitative characterization of biological tissues in terms of optical properties is achieved with integrating sphere. However, samples having significantly higher scattering and absorption coefficients such as malignant tissues potentially reduce the signal to noise ratio (SNR) and accuracy of integrating sphere. We have measured the diffuse reflection and transmission of these phantoms by placing them in integrating sphere at 632.8 nm and then applied IAD method to determine the optical properties tissue phantoms composed of Indian ink (1.0%) and Intralipid (20%). We have fabricated a special sample holder with thin microscopic cover slips which can be used to measure signal from highly concentrated intralipid and Indian ink solutions. Experiments conducted with various phantoms reveal significant improvement of SNR for a wide range of optical properties. This approach opens up a field for potential applications in measurement of optical properties of highly diffusive biological tissues. For 20% intralipid μa =0.112+/-0.046 cm-1 and μs =392.299+/-10.090 cm-1 at 632.8 nm and for 1.0% Indian ink μa =9.808+/-0.490 cm-1 and μs =1.258+/-0.063 cm-1 at same wavelength. System shows good repeatability and reproducibility within 4.9% error. Work may have important biomedical applications in photo-diagnosis and Photodynamic therapy.

  19. Simulation of diffuse photon migration in tissue by a Monte Carlo method derived from the optical scattering of spheroids.

    Science.gov (United States)

    Hart, Vern P; Doyle, Timothy E

    2013-09-01

    A Monte Carlo method was derived from the optical scattering properties of spheroidal particles and used for modeling diffuse photon migration in biological tissue. The spheroidal scattering solution used a separation of variables approach and numerical calculation of the light intensity as a function of the scattering angle. A Monte Carlo algorithm was then developed which utilized the scattering solution to determine successive photon trajectories in a three-dimensional simulation of optical diffusion and resultant scattering intensities in virtual tissue. Monte Carlo simulations using isotropic randomization, Henyey-Greenstein phase functions, and spherical Mie scattering were additionally developed and used for comparison to the spheroidal method. Intensity profiles extracted from diffusion simulations showed that the four models differed significantly. The depth of scattering extinction varied widely among the four models, with the isotropic, spherical, spheroidal, and phase function models displaying total extinction at depths of 3.62, 2.83, 3.28, and 1.95 cm, respectively. The results suggest that advanced scattering simulations could be used as a diagnostic tool by distinguishing specific cellular structures in the diffused signal. For example, simulations could be used to detect large concentrations of deformed cell nuclei indicative of early stage cancer. The presented technique is proposed to be a more physical description of photon migration than existing phase function methods. This is attributed to the spheroidal structure of highly scattering mitochondria and elongation of the cell nucleus, which occurs in the initial phases of certain cancers. The potential applications of the model and its importance to diffusive imaging techniques are discussed. PMID:24085080

  20. Tuchola County Broadband Network (TCBN)

    DEFF Research Database (Denmark)

    Zabludowski, Antoni; Dubalski, B.; Zabludowski, Lukasz;

    2012-01-01

    In the paper the designing project (plan) of Tuchola City broadband IP optical network has been presented. The extended version of network plan constitute technical part of network Feasibility Study, that it is expected to be implemented in Tuchola and be financed from European Regional Development...... Funds. The network plan presented in the paper contains both topological structure of fiber optic network as well as the active equipment for the network. In the project described in the paper it has been suggested to use Modular Cable System - MCS for passive infrastructure and Metro Ethernet...... technology for active equipment. The presented solution provides low cost of construction (CAPEX), ease of implementation of the network and low operating cost (OPEX). Moreover the parameters of installed Metro Ethernet switches in the network guarantee the scalability of the network for at least 10 years....

  1. Multi-spectral and fluorescence diffuse optical tomography of breast cancer

    Science.gov (United States)

    Corlu, Alper

    Multi-spectral and fluorescence diffuse optical tomography (DOT) techniques are explored and applied to image human breast cancer in vivo. Image reconstruction algorithms that utilize first and second order gradient information are described in detail. Breast DOT requires large computational memory and long run times. To this end, parallel computation techniques were developed appropriate to each reconstruction algorithm. A parallel plate DOT instrument developed for breast cancer imaging is described. The system relies heavily on continuous-wave (CW) transmission measurements and utilizes frequency domain (FD) measurements on the reemission side. However, traditional DOT image reconstruction methods based on CW measurements fail to separate tissue absorption and scattering uniquely. In this manuscript, multi-spectral DOT is shown to be capable of minimizing cross-talk and retrieving spectral parameters almost uniquely when the measurement wavelengths are optimized. A theoretical framework to select optimum wavelengths is provided, and tested with computer simulations. Results from phantom spectroscopy experiments and in vivo patient measurements support the notion that multi-spectral methods are superior to traditional DOT image reconstruction schemes. The same breast DOT instrument is improved and utilized to obtain the first in vivo images of human breast cancer based on fluorescence DOT (FDOT). To this end the fluorophore Indocyanine Green (ICG) is injected intravenously and fluorescence excitation and detection are accomplished in the soft-compression, parallel-plane, transmission geometry using laser sources at 786 nm and spectrally filtered CCD detection. Careful phantom and in vivo measurements are carried on to assure that the signals are due to ICG fluorescence, rather than tissue autofluorescence and excitation light leakage. An in vivo measurement protocol is designed to maximize the ICG contrast by acquiring full fluorescence tomographic scan during

  2. Numerical Study on Infrared Optical Property of Diffuse Coal Particles in Mine Fully Mechanized Working Combined with CFD Method

    Directory of Open Access Journals (Sweden)

    Wen-Zheng Wang

    2015-01-01

    Full Text Available Coal dust seriously threatens the safety and occupational health of coal mines. Numerical simulation research on the infrared radiation characteristics of diffused coal dust is carried out in fully mechanized working faces based on the optical monitoring problem of dust particles in mine atmospheric environments. The CFD method is applied to obtain the law of dust transport and distribution. Combined with Mie scattering model, the infrared radiation change characteristics and spectral selection of diffused coal dust particles are simulated and analyzed along the working face. The comparison results show the following: the attenuation and scattering characteristics of mine dust particles system are first enhanced, and then they weaken as the distance from dust source increases. The infrared attenuation of mine dust at the center of the vertical cross-section is generally greater than that at the roof and floor in the same location. The dispersion of mine dust directly determines the attenuation contribution of respirable dust to total dust. Moreover, the infrared absorption effect of functional groups in coal causes the infrared attenuation effect of coal dust to have obvious optical selectivity along the roadway, the existing optical “window.”

  3. Optical diffusion property of cerumen from ear canal and correlation to metal content measured by synchrotron x-ray absorption

    Science.gov (United States)

    Holden, Todd; Dehipawala, Sumudu; Cheung, E.; Golebiewska, U.; Schneider, P.; Tremberger, G., Jr.; Kokkinos, D.; Lieberman, D.; Dehipawala, Sunil; Cheung, T.

    2012-03-01

    Human (and other mammals) would secrete cerumen (ear wax) to protect the skin of the ear canal against pathogens and insects. The studies of biodiversity of pathogen in human include intestine microbe colony, belly button microbe colony, etc. Metals such as zinc and iron are essentials to bio-molecular pathways and would be related to the underlying pathogen vitality. This project studies the biodiversity of cerumen via its metal content and aims to develop an optical probe for metal content characterization. The optical diffusion mean free path and absorption of human cerumen samples dissolved in solvent have been measured in standard transmission measurements. EXFAS and XANES have been measured at Brookhaven Synchrotron Light Source for the determination of metal contents, presumably embedded within microbes/insects/skin cells. The results show that a calibration procedure can be used to correlate the optical diffusion parameters to the metal content, thus expanding the diagnostic of cerumen in the study of human pathogen biodiversity without the regular use of a synchrotron light source. Although biodiversity measurements would not be seriously affected by dead microbes and absorption based method would do well, the scattering mean free path method would have potential to further study the cell based scattering centers (dead or live) via the information embedded in the speckle pattern in the deep-Fresnel zone.

  4. Diffusion, thermalization, and optical pumping of YbF molecules in a cold buffer-gas cell

    Science.gov (United States)

    Skoff, S. M.; Hendricks, R. J.; Sinclair, C. D. J.; Hudson, J. J.; Segal, D. M.; Sauer, B. E.; Hinds, E. A.; Tarbutt, M. R.

    2011-02-01

    We produce YbF molecules with a density of 1018 m-3 using laser ablation inside a cryogenically cooled cell filled with a helium buffer gas. Using absorption imaging and absorption spectroscopy we study the formation, diffusion, thermalization, and optical pumping of the molecules. The absorption images show an initial rapid expansion of molecules away from the ablation target followed by a much slower diffusion to the cell walls. We study how the time constant for diffusion depends on the helium density and temperature and obtain values for the YbF-He diffusion cross section at two different temperatures. We measure the translational and rotational temperatures of the molecules as a function of time since formation, obtain the characteristic time constant for the molecules to thermalize with the cell walls, and elucidate the process responsible for limiting this thermalization rate. Finally, we make a detailed study of how the absorption of the probe laser saturates as its intensity increases, showing that the saturation intensity is proportional to the helium density. We use this to estimate collision rates and the density of molecules in the cell.

  5. X-ray guided three-dimensional diffuse optical tomography: in vivo study of osteoarthritis in the finger joints

    Science.gov (United States)

    Zhang, Qizhi; Yuan, Zhen; Sobel, Eric; Jiang, Huabei

    2007-02-01

    Osteoarthritis (OA), characterized by the damage of the articular cartilage, is the most common joint problem worldwide. In the effort of developing new clinical tools with the potential to alter the natural history of OA, near-infrared diffuse optical tomography (DOT) has received much attention due to its unique advantages. For optical imaging in highly heterogeneous media such as the finger joints, prior information could improve the quality of optical imaging. We report a hybrid imaging system for early detection of OA in the finger joints by imposing the geometry information obtained by X-ray on three-dimensional near-infrared DOT. X-ray tomosynthesis was employed to recover the three-dimensional structure of the two bones based on 16 X-ray projections generated with a mini C-arm system at different directions within a range of 180 degrees. The interface was carefully designed to guarantee an accurate co-registration of the optical and x-ray modalities. The prior structural information of bones was incorporated into our multi-modality imaging reconstruction algorithm to enhance the recovery of the optical properties of joint tissues. Several healthy and OA finger joints were examined. The initial clinical results showed that this hybrid imaging system had the ability to provide much enhanced image resolution and contrast than DOT alone for OA detection.

  6. Bragg-Berry mirrors: reflective broadband q-plates.

    Science.gov (United States)

    Rafayelyan, Mushegh; Brasselet, Etienne

    2016-09-01

    We report on the experimental realization of flat mirrors enabling the broadband generation of optical vortices upon reflection. The effect is based on the geometric Berry phase associated with the circular Bragg reflection phenomenon from chiral uniaxial media. We show the reflective optical vortex generation from both diffractive and nondiffractive paraxial light beams using spatially patterned chiral liquid crystal films. The intrinsic spectrally broadband character of spin-orbit generation of optical phase singularities is demonstrated over the full visible domain. Our results do not rely on any birefringent retardation requirement and, consequently, foster the development of a novel generation of robust optical elements for spin-orbit photonic technologies. PMID:27607950

  7. Bragg-Berry mirrors: reflective broadband q-plates

    CERN Document Server

    Rafayelyan, Mushegh

    2016-01-01

    We report on the experimental realization of flat mirrors enabling the broadband generation of optical vortices upon reflection. The effect is based on the geometric Berry phase associated with the circular Bragg reflection phenomenon from chiral uniaxial media. We show the reflective optical vortex generation from both diffractive and nondiffractive paraxial light beams using spatially patterned chiral liquid crystal films. The intrinsic spectrally broadband character of spin-orbit generation of optical phase singularities is demonstrated over the full visible domain. Our results do not rely on any birefringent retardation requirement and consequently foster the development of a novel generation of robust optical elements for spin-orbit photonic technologies.

  8. Edge-promoting reconstruction of absorption and diffusivity in optical tomography

    DEFF Research Database (Denmark)

    Hannukainen, A.; Harhanen, Lauri Oskari; Hyvönen, N.;

    2015-01-01

    object is composed of an approximately homogeneous background with clearly distinguishable embedded inhomogeneities. An algorithm for finding the maximum a posteriori estimate for the absorption and diffusion coefficients is introduced assuming an edge-preferring prior and an additive Gaussian...

  9. Measurements of Diffusion Resonances for the Atom Optics Quantum Kicked Rotor

    CERN Document Server

    Williams, M E K; Daley, A J; Gray, R N C; Tan, S M; Parkins, A S; Leonhardt, R; Christensen, N

    2002-01-01

    We present experimental observations of diffusion resonances for the quantum kicked rotor with weak decoherence. Cold caesium atoms are subject to a pulsed standing wave of near-resonant light, with spontaneous emission providing environmental coupling. The mean energy as a function of the pulse period is determined during the late-time diffusion period for a constant probability of spontaneous emission. Structure in the late-time energy is seen to increase with physical kicking strength. The observed structure is related to Shepelyansky's predictions of the initial quantum diffusion rates. Additional results of diffusion rates as a function of the effective Planck's constant are given, showing non-trivial behaviour in the quantum-to-classical transition regime.

  10. Optical Transient-Grating Measurements of Spin Diffusion andRelaxation in a Two-Dimensional Electron Gas

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Christopher Phillip [Univ. of California, Berkeley, CA (United States)

    2005-01-01

    Spin diffusion in n-GaAs quantum wells, as measured by our optical transient-grating technique, is strongly suppressed relative to that of charge. Over a broad range of temperatures and dopings, the suppression of Ds relative to Dc agrees quantitatively with the prediction of ''spin Coulomb dra'' theory, which takes into account the exchange of spin in electron-electron collisions. Moreover, the spin-diffusion length, Ls, is a nearly constant 1 micrometer over the same range of T and n, despite Ds's varying by nearly two orders of magnitude. This constancy supports the D'yakonov-Perel'-Kachorovskii model of spin relaxation through interrupted precessional dephasing in the spin-orbit field.

  11. Real-Time In Vivo Characterization of Primary Liver Tumors With Diffuse Optical Spectroscopy During Percutaneous Needle Interventions: Feasibility Study in Woodchucks

    NARCIS (Netherlands)

    Nachabe, Rami; Hendriks, Benno H.W.; Schierling, Ross; Hales, Jasmine; Racadio, Judy M.; Rottenberg, Sven; Ruers, Theo J.M.; Babic, Drazenko; Racadio, John M.

    2015-01-01

    Objective: This study presents the first in vivo real-time optical tissue characterization during image-guided percutaneous intervention using near-infrared diffuse optical spectroscopy sensing at the tip of a needle. The goal of this study was to indicate transition boundaries from healthy tissue t

  12. Improving depth resolution of diffuse optical tomography with an exponential adjustment method based on maximum singular value of layered sensitivity

    Institute of Scientific and Technical Information of China (English)

    Haijing Niu; Ping Guo; Xiaodong Song; Tianzi Jiang

    2008-01-01

    The sensitivity of diffuse optical tomography (DOT) imaging exponentially decreases with the increase of photon penetration depth, which leads to a poor depth resolution for DOT. In this letter, an exponential adjustment method (EAM) based on maximum singular value of layered sensitivity is proposed. Optimal depth resolution can be achieved by compensating the reduced sensitivity in the deep medium. Simulations are performed using a semi-infinite model and the simulation results show that the EAM method can substantially improve the depth resolution of deeply embedded objects in the medium. Consequently, the image quality and the reconstruction accuracy for these objects have been largely improved.

  13. Early detection of chemotherapy-refractory patients by monitoring textural alterations in diffuse optical spectroscopic images

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghi-Naini, Ali; Falou, Omar; Czarnota, Gregory J., E-mail: Gregory.Czarnota@sunnybrook.ca [Physical Sciences, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Vorauer, Eric [Department of Medical Physics, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Department of Physics, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Chin, Lee [Department of Radiation Oncology, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Department of Medical Physics, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Department of Physics, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Tran, William T. [Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Wright, Frances C. [Division of General Surgery, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Department of Surgery, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Gandhi, Sonal [Division of Medical Oncology, Sunnybrook Health Sciences Centre, and Faculty of Medicine, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Yaffe, Martin J. [Physical Sciences, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5 (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario M4N 3M5 (Canada)

    2015-11-15

    Purpose: Changes in textural characteristics of diffuse optical spectroscopic (DOS) functional images, accompanied by alterations in their mean values, are demonstrated here for the first time as early surrogates of ultimate treatment response in locally advanced breast cancer (LABC) patients receiving neoadjuvant chemotherapy (NAC). NAC, as a standard component of treatment for LABC patient, induces measurable heterogeneous changes in tumor metabolism which were evaluated using DOS-based metabolic maps. This study characterizes such inhomogeneous nature of response development, by determining alterations in textural properties of DOS images apparent at early stages of therapy, followed later by gross changes in mean values of these functional metabolic maps. Methods: Twelve LABC patients undergoing NAC were scanned before and at four times after treatment initiation, and tomographic DOS images were reconstructed at each time. Ultimate responses of patients were determined clinically and pathologically, based on a reduction in tumor size and assessment of residual tumor cellularity. The mean-value parameters and textural features were extracted from volumetric DOS images for several functional and metabolic parameters prior to the treatment initiation. Changes in these DOS-based biomarkers were also monitored over the course of treatment. The measured biomarkers were applied to differentiate patient responses noninvasively and compared to clinical and pathologic responses. Results: Responding and nonresponding patients demonstrated different changes in DOS-based textural and mean-value parameters during chemotherapy. Whereas none of the biomarkers measured prior the start of therapy demonstrated a significant difference between the two patient populations, statistically significant differences were observed at week one after treatment initiation using the relative change in contrast/homogeneity of seven functional maps (0.001 < p < 0.049), and mean value of water

  14. Early detection of chemotherapy-refractory patients by monitoring textural alterations in diffuse optical spectroscopic images

    International Nuclear Information System (INIS)

    Purpose: Changes in textural characteristics of diffuse optical spectroscopic (DOS) functional images, accompanied by alterations in their mean values, are demonstrated here for the first time as early surrogates of ultimate treatment response in locally advanced breast cancer (LABC) patients receiving neoadjuvant chemotherapy (NAC). NAC, as a standard component of treatment for LABC patient, induces measurable heterogeneous changes in tumor metabolism which were evaluated using DOS-based metabolic maps. This study characterizes such inhomogeneous nature of response development, by determining alterations in textural properties of DOS images apparent at early stages of therapy, followed later by gross changes in mean values of these functional metabolic maps. Methods: Twelve LABC patients undergoing NAC were scanned before and at four times after treatment initiation, and tomographic DOS images were reconstructed at each time. Ultimate responses of patients were determined clinically and pathologically, based on a reduction in tumor size and assessment of residual tumor cellularity. The mean-value parameters and textural features were extracted from volumetric DOS images for several functional and metabolic parameters prior to the treatment initiation. Changes in these DOS-based biomarkers were also monitored over the course of treatment. The measured biomarkers were applied to differentiate patient responses noninvasively and compared to clinical and pathologic responses. Results: Responding and nonresponding patients demonstrated different changes in DOS-based textural and mean-value parameters during chemotherapy. Whereas none of the biomarkers measured prior the start of therapy demonstrated a significant difference between the two patient populations, statistically significant differences were observed at week one after treatment initiation using the relative change in contrast/homogeneity of seven functional maps (0.001 < p < 0.049), and mean value of water

  15. Diffusion Resonances in Action Space for an Atom Optics Kicked Rotor with Decoherence

    CERN Document Server

    Daley, A J; Leonhardt, R; Tan, S M

    2001-01-01

    We numerically investigate momentum diffusion rates for the pulse kicked rotor across the quantum to classical transition as the dynamics are made more macroscopic by increasing the total system action. For initial and late time rates we observe an enhanced diffusion peak which shifts and scales with changing kick strength, and we also observe distinctive peaks around quantum resonances. Our investigations take place in the context of a system of ultracold atoms which is coupled to its environment via spontaneous emission decoherence, and the effects should be realisable in ongoing experiments.

  16. Research of on-board mixed optical/electric switching of GEO broadband multimedia satellite%通信卫星光电混合交换技术研究

    Institute of Scientific and Technical Information of China (English)

    李瑞欣; 赵尚弘; 幺周石; 郑伟; 李勇军; 刘振霞

    2011-01-01

    On-board switching has been the development trend of satellite communication. There is electronic bottleneck in the development of on-board ATM switch, so the optical switch is the inevitable direction of future broadband multimedia satellite. The paper brings forward a scheme about on-board mixed optical/electronic switching of GEO, analyses the switching mode of the scheme, discusses the key techniques.%星上交换已成为卫星通信发展的趋势之一.星上ATM交换在发展过程中存在着电子瓶颈,星上光交换是未来宽带多媒体卫星的必然发展方向.提出了一种光电混合星上交换技术方案,对星上光交换的方式进行了分析,讨论了光电混合星上交换技术涉及的关键技术,对未来星上交换技术的发展进行了总结.

  17. Passive broadband acoustic thermometry

    Science.gov (United States)

    Anosov, A. A.; Belyaev, R. V.; Klin'shov, V. V.; Mansfel'd, A. D.; Subochev, P. V.

    2016-04-01

    The 1D internal (core) temperature profiles for the model object (plasticine) and the human hand are reconstructed using the passive acoustothermometric broadband probing data. Thermal acoustic radiation is detected by a broadband (0.8-3.5 MHz) acoustic radiometer. The temperature distribution is reconstructed using a priori information corresponding to the experimental conditions. The temperature distribution for the heated model object is assumed to be monotonic. For the hand, we assume that the temperature distribution satisfies the heat-conduction equation taking into account the blood flow. The average error of reconstruction determined for plasticine from the results of independent temperature measurements is 0.6 K for a measuring time of 25 s. The reconstructed value of the core temperature of the hand (36°C) generally corresponds to physiological data. The obtained results make it possible to use passive broadband acoustic probing for measuring the core temperatures in medical procedures associated with heating of human organism tissues.

  18. Direct UV-written broadband directional broadband planar waveguide couplers

    DEFF Research Database (Denmark)

    Olivero, Massimo; Svalgaard, Mikael

    2005-01-01

    We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation.......We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation....

  19. Polarization-insensitive, shallow Ti-diffused near-stoichiometric LiTaO3 strip waveguide for integrated optics.

    Science.gov (United States)

    Yang, Xiao-Fei; Zhang, Zi-Bo; Du, Wan-Ying; Zhang, Qun; Wong, Wing-Han; Yu, Dao-Yin; Pun, Edwin Yue-Bun; Zhang, De-Long

    2016-06-01

    We report on a Ti-diffused near-stoichiometric (NS) LiTaO3 strip waveguide fabricated by diffusion of an 8 μm wide, 160 nm thick Ti-strip followed by Li-rich vapor transport equilibration. It is found that the waveguide surface caves in ∼60  nm below the crystal surface. X-ray single-crystal diffraction shows that the indentation is due to Ti-induced lattice contraction. Optical studies show that the waveguide is in an NS composition environment, supports TE and TM single-mode propagation at 1.5 μm wavelength, is polarization insensitive, and has a shallow mode field profile and a loss of 0.2/0.3 dB/cm for the TE/TM mode. Secondary ion mass spectrometry analysis shows that the Ti profile follows a sum of two error functions in the width direction and a Gaussian function in the depth direction of the waveguide. With the optimized fabrication condition, the waveguide is promising for developing an optical-damage-resistant device that requires a shallow mode field profile.

  20. Vertical diffuse attenuation coefficient () based optical classification of IRS-P3 MOS-B satellite ocean colour data

    Indian Academy of Sciences (India)

    R K Sarangi; Prakash Chauhan; S R Nayak

    2002-09-01

    The optical classification of the different water types provides vital input for studies related to primary productivity, water clarity and determination of euphotic depth. Image data of the IRS- P3 MOS-B, for Path 90 of 27th February, 1998 was used for deriving vertical diffuse attenuation Coeffcient () and an optical classification based on values was performed. An atmospheric correction scheme was used for retrieving water leaving radiances in blue and green channels of 412, 443, 490 and 550 nm. The upwelling radiances from 443nm and 550nm spectral channels were used for computation of vertical diffuse attenuation coeffcient at 490 nm. The waters off the Gujarat coast were classified into different water types based on Jerlov classification scheme. The oceanic water type IA ( range 0.035-0.040m-1), type IB (0.042-0.065m-1), type II (0.07-0.1m-1) and type III (0.115-0.14m-1) were identified. For the coastal waters along Gujarat coast and Gulf of Kachchh, (490) values ranged between 0.15m-1 and 0.35m-1. The depth of 1% of surface light for water type IA, IB, II and III corresponds to 88, 68, 58 and 34 meters respectively. Classification of oceanic and coastal waters based on is useful in understanding the light transmission characteristics for sub-marine navigation and under-water imaging.

  1. The influence of diffusion temperature on the structural, optical and magnetic properties of manganese-doped zinc oxysulfide thin films

    Science.gov (United States)

    Polat, İ.; Aksu, S.; Altunbaş, M.; Yılmaz, S.; Bacaksız, E.

    2011-10-01

    We investigated the structural, optical and magnetic properties of Mn-doped zinc oxysulfide films. Zn(O,S) films were deposited by a spray pyrolysis method on glass substrate. A thin Mn layer evaporated on these films served as the source for the diffusion doping. The XRD pattern of undoped films revealed the presence of two wurtzite phases corresponding to ZnS and ZnO with a strong preferred orientation along the ZnS (0 0 2) hexagonal plane direction. SEM showed a similar surface morphology for the undoped and Mn-doped films, displaying regular arrays of hexagonal micro-rods perpendicular to the substrate. The optical transmission measurements showed that both undoped and Mn diffusion-doped films had a low average transmittance less than about 10%. The gap energy is decreased from 3.42 to 3.33 eV upon annealing at 400 °C. Photoluminescence studies at 300 K show that the incorporation of manganese leads to a decrease of deep level band intensity compared to undoped sample. Clear ferromagnetic loops were observed for the Mn-doped Zn(O,S) films, which might be due to the presence of point defects.

  2. Diffusion-weighted and dynamic contrast-enhanced imaging as markers of clinical behavior in children with optic pathway glioma

    Energy Technology Data Exchange (ETDEWEB)

    Jost, Sarah C. [Swedish Neuroscience Institute, Department of Neurosurgery, Seattle, WA (United States); Ackerman, Joseph W. [Washington University School of Medicine, Department of Radiology, 660 South Euclid Ave., Box 8131, St. Louis, MO (United States); Garbow, Joel R. [Washington University School of Medicine, Department of Radiology, 660 South Euclid Ave., Box 8131, St. Louis, MO (United States); Alvin J. Siteman Cancer Center, St. Louis, MO (United States); Manwaring, Linda P. [Washington University School of Medicine, Department of Pediatrics, St. Louis, MO (United States); Washington University School of Medicine, Department of Genetics and Genomic Medicine, St. Louis, MO (United States); Gutmann, David H. [Washington University School of Medicine, Department of Neurology, St. Louis, MO (United States); Alvin J. Siteman Cancer Center, St. Louis, MO (United States); McKinstry, Robert C. [Washington University School of Medicine, Department of Radiology, 660 South Euclid Ave., Box 8131, St. Louis, MO (United States); Washington University School of Medicine, Department of Pediatrics, St. Louis, MO (United States)

    2008-12-15

    Optic pathway gliomas (OPGs) are common pediatric brain tumors that pose significant clinical challenges with regard to predicting which tumors are likely to become symptomatic and require treatment. These tumors can arise sporadically or in the context of the inherited cancer predisposition syndrome neurofibromatosis type 1 (NF1). Few studies have suggested biological or imaging markers that predict the clinical course of this disease. In this cross-sectional study, we hypothesized that the clinical behavior of OPGs in children can be differentiated by diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) MRI. A total of 27 children with OPG were studied using DW and DCE MRI protocols. Diffusivity and permeability were calculated and correlated with the clinical behavior the OPG. Mean diffusivity values of 1.39 {mu}m{sup 2}/ms and mean permeability values of 2.10 ml/min per 100 cm{sup 3} of tissue were measured. Clinically aggressive OPGs had significantly higher mean permeability values (P = 0.05) than clinically stable tumors. In addition, there was a strong correlation between clinical aggressiveness and the absence of NF1 (P < 0.01). These results suggest that DCE MRI might be a useful biomarker for clinically aggressive OPG, which should be confirmed in larger prospective longitudinal studies. (orig.)

  3. Diffuse reflectance spectroscopy for optical nerve identification. Preliminary ex vivo results for feedback controlled oral and maxillofacial laser surgery

    Science.gov (United States)

    Stelzle, Florian; Zam, Azhar; Adler, Werner; Douplik, Alexandre; Tangermann-Gerk, Katja; Nkenke, Emeka; Neukam, Friedrich Wilhelm; Schmidt, Michael

    Objective: Laser surgery has many advantages. However, due to a lack of haptic feedback it is accompanied by the risk of iatrogenic nerve damage. The aim of this study was to evaluate the possibilities of optical nerve identification by diffuse reflectance spectroscopy to set the base for a feedback control system to enhance nerve preservation in oral and maxillofacial laser surgery. Materials and Methods: Diffuse reflectance spectra of nerve tissue, skin, mucosa, fat tissue, muscle, cartilage and bone (15120 spectra) of ex vivo pig heads were acquired in the wavelength range of 350-650 nm. Tissue differentiation was performed by principal components analysis (PCA) followed by linear discriminant analysis (LDA). Specificity and sensitivity were calculated by receiver operating characteristic (ROC) analysis and the area under curve (AUC). Results: Nerve tissue could correctly be identified and differed from skin, mucosa, fat tissue, muscle, cartilage and bone in more than 90% of the cases (AUC results) with a specificity of over 78% and a sensitivity of more than 86%. Conclusion: Nerve tissue can be identified by diffuse reflectance spectroscopy with high precision and reliability. The results may set the base for a feedback system to prevent iatrogenic nerve damage performing oral and maxillofacial laser surgery.

  4. Diffuse idiopathic skeletal hyperostosis of cervical spine - An unusual cause of difficult flexible fiber optic intubation

    Directory of Open Access Journals (Sweden)

    Baxi Vaibhavi

    2010-01-01

    Full Text Available This is a report of anterior osteophytes on the cervical vertebra resulting in distortion of the airway and leading to difficulty during intubation. The osteophytes associated with the syndrome of diffuse idiopathic skeletal hyperostosis were at the C2-3 and C6-7, T1 level and resulted in anterior displacement of the pharynx and the trachea respectively.

  5. Effects of Optical-density and Phase Dispersion of an Imperfect Band-limited Occulting Mask on the Broadband Performance of a TPF Coronagraph

    Science.gov (United States)

    Sidiek, Erkin; Balasubramanian, Kunjithapatham

    2007-01-01

    Practical image-plane occulting masks required by high-contrast imaging systems such as the TPF-Coronagraph introduce phase errors into the transmitting beam., or, equivalently, diffracts the residual starlight into the area of the final image plane used for detecting exo-planets. Our group at JPL has recently proposed spatially Profiled metal masks that can be designed to have zero parasitic phase at the center wavelength of the incoming broadband light with small amounts of' 00 and phase dispersions at other wavelengths. Work is currently underway to design. fabricate and characterize such image-plane masks. In order to gain some understanding on the behaviors of these new imperfect band-limited occulting masks and clarify how such masks utilizing different metals or alloys compare with each other, we carried out some modeling and simulations on the contrast performance of the high-contrast imaging testbed (HCIT) at .JPL. In this paper we describe the details of our simulations and present our results.

  6. Omnidirectional and broadband optical absorption enhancement in small molecule organic solar cells by a patterned MoO3/Ag/MoO3 transparent anode

    Science.gov (United States)

    Tian, Ximin; Hao, Yuying; Zhang, Ye; Cui, Yanxia; Ji, Ting; Wang, Hua; Wei, Bin; Huang, Wei

    2015-03-01

    We designed and calculated a novel organic solar cell (OSC) with MoO3/Ag/MoO3 (MAM) grating as transparent anode and the patterned copper phthalocyanine (CuPc)/fullerence (C60) as active layer. The numerical results indicate that a broadband, omnidirectional light absorption enhancement is realized by utilizing such a one-dimensional (1D) grating with core-shell structure. The total absorption efficiency of the active layer over the wavelength range from 400 to 900 nm is enhanced by 178.88%, 19.44% and 99.16% relative to the equivalent planar cell considering the weight of air-mass 1.5 global (AM 1.5G) solar spectrum at normally incident transverse magnetic (TM), transverse electric (TE) and TM/TE hybrid polarized light, respectively. The improved light trapping is attributed to the multiple modes hybridization of propagating surface plasmon polaritons (SPPs), localized surface plasmons (LSPs) and the strong coupling of SPP waves at TM polarization along with the Floquet modes at TE polarization. Furthermore, the proposed optimized architecture also exhibits an expected short-circuit current density (Jsc) with the value of 11.11 mA/cm2 in theory, which is increased by 116.6% compared with that of the planar control device.

  7. Diffusion-sensitive optical coherence tomography for real-time monitoring of mucus thinning treatments

    Science.gov (United States)

    Blackmon, Richard L.; Kreda, Silvia M.; Sears, Patrick R.; Ostrowski, Lawrence E.; Hill, David B.; Chapman, Brian S.; Tracy, Joseph B.; Oldenburg, Amy L.

    2016-03-01

    Mucus hydration (wt%) has become an increasingly useful metric in real-time assessment of respiratory health in diseases like cystic fibrosis and COPD, with higher wt% indicative of diseased states. However, available in vivo rheological techniques are lacking. Gold nanorods (GNRs) are attractive biological probes whose diffusion through tissue is sensitive to the correlation length of comprising biopolymers. Through employment of dynamic light scattering theory on OCT signals from GNRs, we find that weakly-constrained GNR diffusion predictably decreases with increasing wt% (more disease-like) mucus. Previously, we determined this method is robust against mucus transport on human bronchial epithelial (hBE) air-liquid interface cultures (R2=0.976). Here we introduce diffusion-sensitive OCT (DS-OCT), where we collect M-mode image ensembles, from which we derive depth- and temporally-resolved GNR diffusion rates. DS-OCT allows for real-time monitoring of changing GNR diffusion as a result of topically applied mucus-thinning agents, enabling monitoring of the dynamics of mucus hydration never before seen. Cultured human airway epithelial cells (Calu-3 cell) with a layer of endogenous mucus were doped with topically deposited GNRs (80x22nm), and subsequently treated with hypertonic saline (HS) or isotonic saline (IS). DS-OCT provided imaging of the mucus thinning response up to a depth of 600μm with 4.65μm resolution, over a total of 8 minutes in increments of >=3 seconds. For both IS and HS conditions, DS-OCT captured changes in the pattern of mucus hydration over time. DS-OCT opens a new window into understanding mechanisms of mucus thinning during treatment, enabling real-time efficacy feedback needed to optimize and tailor treatments for individual patients.

  8. Quantitative volumetric analysis of the optic radiation in the normal human brain using diffusion tensor magnetic resonance imaging-based tractography

    Institute of Scientific and Technical Information of China (English)

    Dong-Hoon Lee; Ji-Won Park; Cheol-Pyo Hong

    2014-01-01

    To attain the volumetric information of the optic radiation in normal human brains, we per-formed diffusion tensor imaging examination in 13 healthy volunteers. Simultaneously, we used a brain normalization method to reduce individual brain variation and increase the accuracy of volumetric information analysis. In addition, tractography-based group mapping method was also used to investigate the probability and distribution of the optic radiation pathways. Our results showed that the measured optic radiation ifber tract volume was a range of about 0.16%and that the fractional anisotropy value was about 0.53. Moreover, the optic radiation probability ifber pathway that was determined with diffusion tensor tractography-based group mapping was able to detect the location relatively accurately. We believe that our methods and results are help-ful in the study of optic radiation ifber tract information.

  9. Broadband Approximations for Doubly Curved Reflector Antenna

    OpenAIRE

    V. Schejbal; J. Pidanic

    2010-01-01

    The broadband approximations for shaped-beam doubly curved reflector antennas with primary feed (rectangular horn) producing uniform amplitude and phase aperture distribution are derived and analyzed. They are very valuable for electromagnetic compatibility analyses both from electromagnetic interference and susceptibility point of view, because specialized more accurate methods such as physical optics are only used by antenna designers. To allow quick EMC analyses, typical values, beamwidth ...

  10. Intraoperative evaluation of revascularization effect on ischemic muscle hemodynamics using near-infrared diffuse optical spectroscopies

    OpenAIRE

    Yu, Guoqiang; Shang, Yu; Zhao, Youquan; Cheng, Ran; Dong, Lixin; Saha, Sibu P

    2011-01-01

    Arterial revascularization in patients with peripheral arterial disease (PAD) reestablishes large arterial blood supply to the ischemic muscles in lower extremities via bypass grafts or percutaneous transluminal angioplasty (PTA). Currently no gold standard is available for assessment of revascularization effects in lower extremity muscles. This study tests a novel near-infrared diffuse correlation spectroscopy flow-oximeter for monitoring of blood flow and oxygenation changes in medial gastr...

  11. Preliminary results for the diffusion of water into fibre optic oil well sensors

    International Nuclear Information System (INIS)

    Preliminary results are presented on a measurement technique for determination of water penetration into fibre optic sensors under high pressure, high temperature conditions. Both fibre optic sensors and communication fibres were subjected to prolonged treatment in heavy water at temperatures up to 250 deg. C and pressures of 40 bar. Deuterium penetration is measured by a nuclear reaction technique based on a 3He micro-focussed ion beam, which permits two-dimensional mapping of the deuterium penetration into cleaved fibres. Water penetration can be detected whilst still confined to the cladding, well before any optical effects become apparent, permitting prediction of likely fibre lifetime under down-hole conditions after realistic experimental times

  12. Coupled light transport-heat diffusion model for laser dosimetry with dynamic optical properties

    Energy Technology Data Exchange (ETDEWEB)

    London, R.A.; Glinsky, M.E.; Zimmerman, G.B.; Eder, D.C. [Lawrence Livermore National Lab., CA (United States); Jacques, S.L. [Texas Univ., Houston, TX (United States). M.D. Anderson Cancer Center

    1995-03-01

    The effect of dynamic optical properties on the spatial distribution of light in laser therapy is studied via numerical simulations. A two-dimensional, time dependent computer program called LATIS is used. Laser light transport is simulated with a Monte Carlo technique including anisotropic scattering and absorption. Thermal heat transport is calculated with a finite difference algorithm. Material properties are specified on a 2-D mesh and can be arbitrary functions of space and time. Arrhenius rate equations are solved for tissue damage caused by elevated temperatures. Optical properties are functions of tissue damage, as determined by previous measurements. Results are presented for the time variation of the light distribution and damage within the tissue as the optical properties of the tissue are altered.

  13. Ultra-broadband photonic internet

    Science.gov (United States)

    Romaniuk, Ryszard S.

    2011-06-01

    In this paper, there is presented a review of our today's understanding of the ultimately broadband photonic Internet. A simple calculation is presented showing the estimate of the throughput of the core photonic network branches. Optoelectronic components, circuits, systems and signals, together with analogous electronic entities and common software layers, are building blocks of the contemporary Internet. Participation of photonics in development of the physical layer in the future Internet will probably increase. The photonics leads now to a better usage of the available bandwidth (increase of the spectral efficiency measured in Bit/s/Hz), increase in the transmission rate (from Gbps, via Tbps up to probably Pbps), increase in the transmission distance without signal regeneration (in distortion compensated active optical cables), increase in energy/power efficiency measured in W/Gbps, etc. Photonics may lead, in the future, to fully transparent optical networks and, thus, to essential increase in bandwidth and network reliability. It is expected that photonics (with biochemistry, electronics and mechatronics) may build psychological and physiological interface for humans to the future global network. The following optical signal multiplexing methods were considered, which are possible without O/E/O conversion: TDM-OTDM, FDM-CO-OFDM, OCDM-OCDMA, WDM-DWDM.

  14. Investigation of stimulated Brillouin scattering for broadband KrF laser

    Institute of Scientific and Technical Information of China (English)

    Wang Xiao-Hui; Lǘ Zhi-Wei; Lin Dian-Yang; Wang Chao; Zhao Xiao-Yan; Tang Xiu-Zhang; Zhang Hai-Feng; Shan Yu-Sheng

    2004-01-01

    Stimulated Brillouin scattering (SBS) numerical mode for broadband multimode KrF laser pump with optical breakdown has been built up in this paper. The basic premises of the model are that KrF spectrum is composed of a number of lines and SBS arises from these lines with coupling to some extent. The broadband SBS threshold strongly depends on pump bandwidth. SBS and optical breakdown occur nearly simultaneously when broadband SBS and breakdown have the same threshold. The decrease of saturation reflectivity for broadband pump radiation is explained with this model. Experimental results agree well with the model.

  15. Self-contained diffuse optical imaging system for real-time detection and localization of vascular occlusions.

    Science.gov (United States)

    Pollonini, Luca; Forseth, Kiefer J; Dacso, Clifford C; Parazynski, Scott E; Friedman, Jeffrey D

    2015-08-01

    Free flap surgery is a procedure where healthy tissue is transferred from a donor site to a recipient site of the body to fill a defect without maintaining the original blood supply to the flap. The anastomosis of the vascular network of the flap to the blood vessels adjacent to the recipient site has associated risks of arterial and/or venous occlusions that must be promptly detected to avoid temporary or permanent tissue damage. In this work, we present a skin-contact diffusion optical imaging (DOI) system able to continuously provide a three-dimensional representation of the flap oxygenation to promptly detect vascular occlusions potentially occurring in the flap. Multiple near-infrared LEDs and photodetectors were embedded into a self-contained optical sensor for prolonged monitoring of concentration changes of oxygenated (HbO) and deoxygenated hemoglobin (HbR) at multiple locations and depths. A time-efficient algorithm mapped measured oxygenation changes in a three-dimensional volume to allow surgeons and clinical personnel to detect and localize abnormal blood perfusion changes during or after surgery, in time for corrective intervention. The image reconstruction algorithm was validated using computerized flap models in which oxygenation was synthetically altered, whereas the optical system was preliminarily tested on a healthy forearm simulating a flap undergoing arterial and venous occlusions, proving the feasibility of implementing DOI in the form of a wearable patch for prolonged perfusion monitoring. PMID:26737630

  16. Diffusion coefficient in photon diffusion theory

    NARCIS (Netherlands)

    Graaff, R; Ten Bosch, JJ

    2000-01-01

    The choice of the diffusion coefficient to be used in photon diffusion theory has been a subject of discussion in recent publications on tissue optics. We compared several diffusion coefficients with the apparent diffusion coefficient from the more fundamental transport theory, D-app. Application to

  17. Near-infrared and optical broadband surface photometry of 86 face-on disk dominated galaxies .3. The statistics of the disk and bulge parameters

    NARCIS (Netherlands)

    deJong, RS

    1996-01-01

    The statistics of the fundamental bulge and disk parameters of galaxies and their relation to the Hubble sequence were investigated by an analysis of optical and near-infrared observations of 86 face-on spiral galaxies. The availability of near-infrared K passband data made it possible for the first

  18. Limitations of the commonly used simplified laterally uniform optical fiber probe-tissue interface in Monte Carlo simulations of diffuse reflectance.

    Science.gov (United States)

    Naglič, Peter; Pernuš, Franjo; Likar, Boštjan; Bürmen, Miran

    2015-10-01

    Light propagation models often simplify the interface between the optical fiber probe tip and tissue to a laterally uniform boundary with mismatched refractive indices. Such simplification neglects the precise optical properties of the commonly used probe tip materials, e.g. stainless steel or black epoxy. In this paper, we investigate the limitations of the laterally uniform probe-tissue interface in Monte Carlo simulations of diffuse reflectance. In comparison to a realistic probe-tissue interface that accounts for the layout and properties of the probe tip materials, the simplified laterally uniform interface is shown to introduce significant errors into the simulated diffuse reflectance.

  19. Linearization Technologies for Broadband Radio-Over-Fiber Transmission Systems

    Directory of Open Access Journals (Sweden)

    Xiupu Zhang

    2014-11-01

    Full Text Available Linearization technologies that can be used for linearizing RoF transmission are reviewed. Three main linearization methods, i.e. electrical analog linearization, optical linearization, and electrical digital linearization are presented and compared. Analog linearization can be achieved using analog predistortion circuits, and can be used for suppression of odd order nonlinear distortion components, such as third and fifth order. Optical linearization includes mixed-polarization, dual-wavelength, optical channelization and the others, implemented in optical domain, to suppress both even and odd order nonlinear distortion components, such as second and third order. Digital predistortion has been a widely used linearization method for RF power amplifiers. However, digital linearization that requires analog to digital converter is severely limited to hundreds of MHz bandwidth. Instead, analog and optical linearization provide broadband linearization with up to tens of GHz. Therefore, for broadband radio over fiber transmission that can be used for future broadband cloud radio access networks, analog and optical linearization are more appropriate than digital linearization. Generally speaking, both analog and optical linearization are able to improve spur-free dynamic range greater than 10 dB over tens of GHz. In order for current digital linearization to be used for broadband radio over fiber transmission, the reduced linearization complexity and increased linearization bandwidth are required. Moreover, some digital linearization methods in which the complexity can be reduced, such as Hammerstein type, may be more promising and require further investigation.

  20. The Transport Equation in Optically Thick Media: Discussion of IMC and its Diffusion Limit

    Energy Technology Data Exchange (ETDEWEB)

    Szoke, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Brooks, E. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-07-12

    We discuss the limits of validity of the Implicit Monte Carlo (IMC) method for the transport of thermally emitted radiation. The weakened coupling between the radiation and material energy of the IMC method causes defects in handling problems with strong transients. We introduce an approach to asymptotic analysis for the transport equation that emphasizes the fact that the radiation and material temperatures are always different in time-dependent problems, and we use it to show that IMC does not produce the correct diffusion limit. As this is a defect of IMC in the continuous equations, no improvement to its discretization can remedy it.

  1. Broadband measurements of electron cyclotron emission in TFTR (Tokamak Fusion Test Reactor) using a quasi-optical light collection system and a polarizing Michelson interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Stauffer, F.J.; Boyd, D.A.; Cutler, R.C.; Diesso, M.; McCarthy, M.P.; Montague, J.; Rocco, R.

    1988-04-01

    For the past three years, a Fourier transform spectrometer diagnostic system, employing a fast-scanning polarizing Michelson interferometer, has been operating on the TFTR tokamak at Princeton Plasma Physics Laboratory. It is used to measure the electron cyclotron emission spectrum over the range 2.5 to 18 cm/sup /minus/1/ (75-540 GHz) with a resolution of 0.123 cm/sup /minus/1/(3.7 GHz), at a rate of 72 spectra per second. The quasi-optical system for collecting the light and transporting it through the interferometer to the detector has been designed using the concepts of both Gaussian and geometrical optics in order to produce a system that is efficient over the entire spectral range. The commerical Michelson interferometer was custom-made for this project and is at the state of the art for this type of specialized instrument. Various pre-installation and post-installation tests of the optical system and the interferometer were performed and are reported here. An error propagation analysis of the absolute calibration process is given. Examples of electron cyclotron emission spectra measured in two polarization directions are given, and electron temperature profiles derived from each of them are compared. 34 refs., 17 figs.

  2. Mechanism to synthesize a ‘moving optical mark’ at solid-ambient interface for the estimation of thermal diffusivity of solid

    Directory of Open Access Journals (Sweden)

    Settu Balachandar

    2016-01-01

    Full Text Available A novel mechanism is proposed, involving a novel interaction between solid-sample supporting unsteady heat flow with its ambient-humidity; invokes phase transformation of water-vapour molecule and synthesize a ‘moving optical-mark’ at sample-ambient-interface. Under tailored condition, optical-mark exhibits a characteristic macro-scale translatory motion governed by thermal diffusivity of solid. For various step-temperature inputs via cooling, position-dependent velocities of moving optical-mark are measured at a fixed distance. A new approach is proposed. ‘Product of velocity of optical-mark and distance’ versus ‘non-dimensional velocity’ is plotted. The slope reveals thermal diffusivity of solid at ambient-temperature; preliminary results obtained for Quartz-glass is closely matching with literature.

  3. In situ optical diagnostic for monitoring or control of sodium diffusion in photovoltaics manufacturing

    Science.gov (United States)

    Li, Jian; Levi, Dean; Contreras, Miguel; Glynn, Stephen

    2015-09-15

    A method of fabricating a photovoltaic device 100, includes the steps of providing a glass substrate 102, depositing a molybdenum layer 104 on a surface of the glass substrate, directing light through the glass substrate to the near-substrate region of the molybdenum layer 206, detecting an optical property of the near-substrate region of the molybdenum layer after interaction with the incident light 208 and determining a density of the near-substrate region of the molybdenum layer from the detected optical property 210. A molybdenum deposition parameter may be controlled based upon the determined density of the near-substrate region of the molybdenum layer 218. A non-contact method measures a density of the near-substrate region of a molybdenum layer and a deposition chamber 300.

  4. Noninvasive assessment of breast cancer risk using time-resolved diffuse optical spectroscopy

    Science.gov (United States)

    Taroni, Paola; Pifferi, Antonio; Quarto, Giovanna; Spinelli, Lorenzo; Torricelli, Alessandro; Abbate, Francesca; Villa, Anna; Balestreri, Nicola; Menna, Simona; Cassano, Enrico; Cubeddu, Rinaldo

    2010-11-01

    Breast density is a recognized strong and independent risk factor for breast cancer. We propose the use of time-resolved transmittance spectroscopy to estimate breast tissue density and potentially provide even more direct information on breast cancer risk. Time-resolved optical mammography at seven wavelengths (635 to 1060 nm) is performed on 49 subjects. Average information on breast tissue of each subject is obtained on oxy- and deoxyhemoglobin, water, lipids, and collagen content, as well as scattering amplitude and power. All parameters, except for blood volume and oxygenation, correlate with mammographic breast density, even if not to the same extent. A synthetic optical index proves to be quite effective in separating different breast density categories. Finally, the estimate of collagen content as a more direct means for the assessment of breast cancer risk is discussed.

  5. Testing and modeling of diffusion bonded prototype optical windows under ITER conditions

    NARCIS (Netherlands)

    Jacobs, M.; Oost, G. van; Degrieck, J.; Baere, I. De; Gusarov, A.; Gubbels, F.; Massaut, V.

    2011-01-01

    Glass-metal joints are a part of ITER optical diagnostics windows. These joints must be leak tight for the safety (presence of tritium in ITER) and to preserve the vacuum. They must also withstand the ITER environment: temperatures up to 220°C and fast neutron fluxes of ∼3·10 9 n/cm 2·s. At the mome

  6. Simulation study of magnetic resonance imaging-guided cortically constrained diffuse optical tomography of human brain function.

    Science.gov (United States)

    Boas, David A; Dale, Anders M

    2005-04-01

    Diffuse optical imaging can measure brain activity noninvasively in humans through the scalp and skull by measuring the light intensity modulation arising from localized-activity-induced absorption changes within the cortex. Spatial resolution and localization accuracy are currently limited by measurement geometry to approximately 3 cm in the plane parallel to the scalp. Depth resolution is a more significant challenge owing to the limited angle tomography permitted by reflectance-only measurements. We combine previously established concepts for improving image quality and demonstrate, through simulation studies, their application for improving the image quality of adult human brain function. We show in a three-dimensional human head model that localization accuracy is significantly improved by the addition of measurements that provide overlapping samples of brain tissue. However, the reconstructed absorption contrast is significantly underestimated because its depth is underestimated. We show that the absorption contrast amplitude accuracy can be significantly improved by providing a cortical spatial constraint in the image reconstruction to obtain a better depth localization. The cortical constraint makes physiological sense since the brain-activity-induced absorption changes are occurring in the cortex and not in the scalp, skull, and cerebral spinal fluid. This spatial constraint is provided by segmentation of coregistered structural magnetic resonance imaging (MRI). However, the absorption contrast deep within the cortex is reconstructed superficially, resulting in an underestimation of the absorption contrast. The synthesis of techniques described here indicates that multimodality imaging of brain function with diffuse optical imaging and MRI has the potential to provide more quantitative estimates of the total and deoxyhemoglobin response to brain activation, which is currently not provided by either method independently. However, issues of depth resolution

  7. Diffuse optical measurements of head and neck tumor hemodynamics for early prediction of radiation therapy (Conference Presentation)

    Science.gov (United States)

    Dong, Lixin; Kudrimoti, Mahesh; Irwin, Daniel; Chen, Li; Shang, Yu; Li, Xingzhe; Stevens, Scott D.; Shelton, Brent J.; Yu, Guoqiang

    2016-03-01

    Radiation therapy is a principal modality for head and neck cancers and its efficacy depends on tumor hemodynamics. Our laboratory developed a hybrid diffuse optical instrument allowing for simultaneous measurements of tumor blood flow and oxygenation. In this study, the clinically involved cervical lymph node was monitored by the hybrid instrument once a week over the treatment period of seven weeks. Based on treatment outcomes within one year, patients were classified into a complete response group (CR) and an incomplete response group (IR) with remote metastasis and/or local recurrence. A linear mixed models was used to compare tumor hemodynamic responses to the treatment between the two groups. Interestingly, we found that human papilloma virus (HPV-16) status largely affected tumor hemodynamic responses. For HPV-16 negative tumors, significant differences in blood flow index (BFI, p = 0.007) and reduced scattering coefficient (μs', p = 0.0005) were observed between the two groups; IR tumors exhibited higher μs' values and a continuous increase in BFI over the treatment period. For HPV-16 positive tumors, oxygenated hemoglobin concentration ([HbO2]) and blood oxygen saturation (StO2) were significant different (p = 0.003 and 0.01, respectively); IR group showed lower [HbO2] and StO2. Our results imply HPV-16 negative tumors with higher density of vasculature (μs') and higher blood flow show poor responses to radiotherapy and HPV-16 positive tumors with lower tissue oxygenation level (lower StO2 and [HbO2]) exhibit poor treatment outcomes. Our diffuse optical measurements show the great potential for early prediction of radiotherapy in head and neck cancers.

  8. Simulation study of magnetic resonance imaging-guided cortically constrained diffuse optical tomography of human brain function

    Science.gov (United States)

    Boas, David A.; Dale, Anders M.

    2005-04-01

    Diffuse optical imaging can measure brain activity noninvasively in humans through the scalp and skull by measuring the light intensity modulation arising from localized-activity-induced absorption changes within the cortex. Spatial resolution and localization accuracy are currently limited by measurement geometry to approximately 3 cm in the plane parallel to the scalp. Depth resolution is a more significant challenge owing to the limited angle tomography permitted by reflectance-only measurements. We combine previously established concepts for improving image quality and demonstrate, through simulation studies, their application for improving the image quality of adult human brain function. We show in a three-dimensional human head model that localization accuracy is significantly improved by the addition of measurements that provide overlapping samples of brain tissue. However, the reconstructed absorption contrast is significantly underestimated because its depth is underestimated. We show that the absorption contrast amplitude accuracy can be significantly improved by providing a cortical spatial constraint in the image reconstruction to obtain a better depth localization. The cortical constraint makes physiological sense since the brain-activity-induced absorption changes are occurring in the cortex and not in the scalp, skull, and cerebral spinal fluid. This spatial constraint is provided by segmentation of coregistered structural magnetic resonance imaging (MRI). However, the absorption contrast deep within the cortex is reconstructed superficially, resulting in an underestimation of the absorption contrast. The synthesis of techniques described here indicates that multimodality imaging of brain function with diffuse optical imaging and MRI has the potential to provide more quantitative estimates of the total and deoxyhemoglobin response to brain activation, which is currently not provided by either method independently. However, issues of depth resolution

  9. Implementation of a computationally efficient least-squares algorithm for highly under-determined three-dimensional diffuse optical tomography problems

    OpenAIRE

    Yalavarthy, Phaneendra K; Lynch, Daniel R.; Pogue, Brian W.; Dehghani, Hamid; Paulsen, Keith D.

    2008-01-01

    Three-dimensional (3D) diffuse optical tomography is known to be a nonlinear, ill-posed and sometimes under-determined problem, where regularization is added to the minimization to allow convergence to a unique solution. In this work, a generalized least-squares (GLS) minimization method was implemented, which employs weight matrices for both data-model misfit and optical properties to include their variances and covariances, using a computationally efficient scheme. This allows inversion of ...

  10. Optical system design of broadband astigmatism-free czerny-turner spectrometer%宽谱段消像散Czerny-Turner光谱仪光学系统设计

    Institute of Scientific and Technical Information of China (English)

    赵意意; 杨建峰; 薛彬; 闫兴涛

    2014-01-01

    针对光谱仪小型化、高分辨率的发展趋势,设计了一种结构简单、宽谱段、消像散的小型光谱仪。具体分析了折叠光路Czerny-Turner光谱仪各种像差的原理和校正方法。推导了柱透镜宽谱段消像散的理论方程。作为实例,设计了一款谱段为300~900 nm、物方数值孔径0.08的小型光谱仪。该光谱仪采用折叠光路结构以减小尺寸,添加柱透镜以消除整个谱段的像散。结果表明:该光谱仪结构简单紧凑,体积小,实现了宽谱段的消像散,全谱段光谱分辨率优于0.5 nm。%For the development trend of miniaturization and high-resolution of spectrometer, an optical design with a simple structure, broadband, astigmatism-corrected micro spectrometer was designed. The principle and correction method of the aberration of crossed beam czerny-turner spectrometer were analyzed in detail. The broadband astigmatism-corrected theory equations using cylindrical lens were deduced. For example, a micro spectrometer operating in 300-900 nm with an object NA of 0.08 has been designed. This spectrometer adopted crossed beam structure to minish its volume and used a cylindrical lens to remove astigmatism over the full bandwidth. The analyzed results demonstrated that this spectrometer with compact configuration and small volume corrected the astigmatism in the wide spectral region. The resolution of the spectrometer was better than 0.5 nm in the whole spectral region.

  11. Metasurface Broadband Solar Absorber

    OpenAIRE

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Milan Sykora; Nina R. Weisse-Bernstein; Luk, Ting S.; Antoinette J. Taylor; Dalvit, Diego A. R.; Hou-Tong Chen

    2016-01-01

    We demonstrate a broadband, polarization independent, omnidirectional absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low emissivity at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experiment...

  12. Exploring Optical Contrast in Ex-Vivo Breast Tissue Using Diffuse Reflectance Spectroscopy and Tissue Morphology

    Science.gov (United States)

    Kennedy, Stephanie Ann

    In this research, ex-vivo breast tissue is evaluated to determine which sources of optical contrast have the potential to detect malignancy at the margins in women of differing breast composition. Then, H&E images of ex-vivo breast tissue sites are quantified to further deconstruct the relationship between optical scattering and the underlying tissue morphology. H&E images were taken of the malignant and benign sites and quantified to describe the % adipose, % collagen and % glands. Adipose sites, images at 10x, were predominantly fatty and quantified according to adipocyte morphology. H&E-stained adipose tissue sections were analyzed with an automated image processing algorithm to extract average cell area and cell density. Non-adipose sites were imaged with a 2.5x objective. Grids of 200µm boxes corresponding to the 3mm x 2mm area were overlaid on each non-adipose image. The non-adipose images were classified as the following: adipose and collagen (fibroadipose); collagen and glands (fibroglandular); adipose, collagen and glands (mixed); and malignant sites. Correlations between and % collagen in were determined in benign sites. Age, BMI, and MBD were then correlated to in the adipose and non-adipose sites. Variability in was determined to be related to collagen and not adipose content. In order to further investigate this relationship, the importance of age, BMI and MBD was analyzed after adjusting for the % collagen. Lastly, the relationship between % collagen and % glands was analyzed to determine the relative contributions of % collagen and % glands . Statistics were calculated using Wilcoxon rank-sum tests, Pearson correlation coefficients and linear fits in R. Further deconstructing the relationship between optical scattering and tissue morphology resulted in a positive relationship between and % collagen. Increased variability was observed in sites with a higher percentage of collagen. In adipose tissues MBD was negatively correlated with age, BMI and

  13. An ultra-broadband multilayered graphene absorber

    KAUST Repository

    Amin, Muhammad

    2013-01-01

    An ultra-broadband multilayered graphene absorber operating at terahertz (THz) frequencies is proposed. The absorber design makes use of three mechanisms: (i) The graphene layers are asymmetrically patterned to support higher order surface plasmon modes that destructively interfere with the dipolar mode and generate electromagnetically induced absorption. (ii) The patterned graphene layers biased at different gate voltages backedup with dielectric substrates are stacked on top of each other. The resulting absorber is polarization dependent but has an ultra-broadband of operation. (iii) Graphene\\'s damping factor is increased by lowering its electron mobility to 1000cm 2=Vs. Indeed, numerical experiments demonstrate that with only three layers, bandwidth of 90% absorption can be extended upto 7THz, which is drastically larger than only few THz of bandwidth that can be achieved with existing metallic/graphene absorbers. © 2013 Optical Society of America.

  14. Experimental Demonstration of Quantum Teleportation of Broadband Squeezing

    Science.gov (United States)

    Yonezawa, Hidehiro; Braunstein, Samuel L.; Furusawa, Akira

    2007-09-01

    We demonstrate an unconditional high-fidelity teleporter capable of preserving the broadband entanglement in an optical squeezed state. In particular, we teleport a squeezed state of light and observe -0.8±0.2dB of squeezing in the teleported (output) state. We show that the squeezing criterion translates directly into a sufficient criterion for entanglement of the upper and lower sidebands of the optical field. Thus, this result demonstrates the first unconditional teleportation of broadband entanglement. Our teleporter achieves sufficiently high fidelity to allow the teleportation to be cascaded, enabling, in principle, the construction of deterministic non-Gaussian operations.

  15. Symmetry-Breaking Plasmonic Metasurfaces for Broadband Light Bending

    DEFF Research Database (Denmark)

    Ni, Xingjie; Emani, Naresh K.; Kildishev, Alexander V.;

    2012-01-01

    We experimentally demonstrate unparalleled wave-front control in a broadband, optical wavelength range from 1.0 μm to 1.9 μm, using a thin plasmonic layer (metasurface) consisting of a nanoantenna array that breaks the symmetry along the interface.......We experimentally demonstrate unparalleled wave-front control in a broadband, optical wavelength range from 1.0 μm to 1.9 μm, using a thin plasmonic layer (metasurface) consisting of a nanoantenna array that breaks the symmetry along the interface....

  16. Broadband Radio Service (BRS) and Educational Broadband Service (EBS) Transmitters

    Data.gov (United States)

    Department of Homeland Security — The Broadband Radio Service (BRS), formerly known as the Multipoint Distribution Service (MDS)/Multichannel Multipoint Distribution Service (MMDS), is a commercial...

  17. Switched Broadband Services For The Home

    Science.gov (United States)

    Sawyer, Don M.

    1990-01-01

    In considering the deployment of fiber optics to the residence, two critical questions arise: what are the leading services that could be offered to justify the required investment; and what is the nature of the business that would offer these services to the consumer ? This talk will address these two questions together with the related issue of how the "financial engine" of today's television distribution infrastructure - TV advertising - would be affected by an open access system based on fiber optics coupled with broadband switching. On the business side, the talk concludes that the potential for open ended capacity expansion, fair competition between service providers, and new interactive services inherent in an open access, switched broadband system are the critical items in differentiating it from existing video and TV distribution systems. On the question of broadband services, the talk will highlight several new opportunities together with some findings from recent market research conducted by BNR. The talk will show that there are variations on existing services plus many new services that could be offered and which have real consumer appeal. The postulated open access system discussed here is visualized as having ultimately 1,000 to 2,000 video channels available to the consumer. Although this may appear to hopelessly fragment the TV audience and destroy the current TV advertising infrastructure, the technology of open access, switched broadband will present many new advertising techniques, which have the potential to be far more effective than those available today. Some of these techniques will be described in this talk.

  18. Detecting lower extremity vascular dynamics in patients with peripheral artery disease using diffuse optical tomography

    Science.gov (United States)

    Khalil, Michael A.; Kim, Hyun-Keol K.; Kim, In-Kyong; Dayal, Rajeev; Hielscher, Andreas H.

    2011-02-01

    Peripheral Artery Disease (PAD) affects over 10 million Americans and is associated with significant morbidity and mortality. While in many cases the ankle-brachial index (ABI) can be used for diagnosing the disease, this parameter is not dependable in the diabetic and elderly population. These populations tend to have calcified arteries, which leads to elevated ABI values. Dynamic optical tomography (DDOT) promises to overcome the limitations of the current diagnostic techniques and has the potential to initiate a paradigm shift in the diagnosis of vascular disease. We have performed initial pilot studies involving 5 PAD patients and 3 healthy volunteers. The time traces and tomographic reconstruction obtained from measurements on the feet show significant differences between healthy and affected vasculatures. In addition, we found that DOT is capable of identifying PAD in diabetic patients, who are misdiagnosed by the traditional ABI screening.

  19. [Optical properties and remote sensing retrieval model of diffuse attenuation coefficient of Taihu Lake water body].

    Science.gov (United States)

    Le, Cheng-Feng; Li, Yun-Mei; Zha, Yong; Sun, De-Yong; Wang, Li-Zhen

    2009-02-01

    The spectral and chemical analytical data of Taihu Lake water quality in Nov. 8-22, 2007 were used to analyze the spectral characteristics of diffuse attenuation coefficient (Kd) of the water body in autumn and related affecting factors. On the basis of this analysis, the Kd at band 490 nm, Kd (490), was used as a variable to build the relationship between Kd and remote sensing reflectance. The results indicated that within the scope of visible band, the Kd of the water body at most locations of Taihu Lake presented an exponent decreasing trend with the increase of wave length. Due to the higher concentration of phytoplankton in some locations, a peak value of Kd was presented at band 675 nm. Non-organic suspended particles, because of their higher content in suspended sediment, had larger effects on Kd than organic suspended ones. There was a good correlation between Kd and remote sensing reflectance. Taking Rrs (550), Rrs (675) and Rrs (731) as independent variables and doing regression analysis with Kd (490), a good linear relationship was found between Kd (490) and Rrs (731), and multi-variate linear regression analysis using variables Rrs (550), Rrs (675) and Rrs (731) could get better effect (R2 > 0.96) than the regression analysis using variable Rrs (731). PMID:19459373

  20. Noncontact diffuse optical assessment of blood flow changes in head and neck free tissue transfer flaps

    Science.gov (United States)

    Huang, Chong; Radabaugh, Jeffrey P.; Aouad, Rony K.; Lin, Yu; Gal, Thomas J.; Patel, Amit B.; Valentino, Joseph; Shang, Yu; Yu, Guoqiang

    2015-07-01

    Knowledge of tissue blood flow (BF) changes after free tissue transfer may enable surgeons to predict the failure of flap thrombosis at an early stage. This study used our recently developed noncontact diffuse correlation spectroscopy to monitor dynamic BF changes in free flaps without getting in contact with the targeted tissue. Eight free flaps were elevated in patients with head and neck cancer; one of the flaps failed. Multiple BF measurements probing the transferred tissue were performed during and post the surgical operation. Postoperative BF values were normalized to the intraoperative baselines (assigning "1") for the calculation of relative BF change (rBF). The rBF changes over the seven successful flaps were 1.89±0.15, 2.26±0.13, and 2.43±0.13 (mean±standard error), respectively, on postoperative days 2, 4, and 7. These postoperative values were significantly higher than the intraoperative baseline values (pflap vascularity after the tissue transfer. By contrast, rBF changes observed from the unsuccessful flaps were 1.14 and 1.34, respectively, on postoperative days 2 and 4, indicating less flow recovery. Measurement of BF recovery after flap anastomosis holds the potential to act early to salvage ischemic flaps.

  1. Aggregates of plasmonic nanoparticles for broadband light trapping in dye-sensitized solar cells

    International Nuclear Information System (INIS)

    Metallic nanoparticles (NPs) have not been effective in improving the overall performance of the cells with micrometer-thick absorbing layers mainly due to the parasitic optical dissipation in the metal. Here, using both experiment and theory, we demonstrate that aggregates of metallic NPs enhance the light absorption of dye-sensitized solar cells of a few micrometer-thick light absorbing layers. The composite electrode containing the optimal concentration of 5 wt% Au@SiO2 aggregates shows the enhancement of 80% and 52% in external quantum efficiency and photocurrent density, respectively. The superior performance of the aggregates relative to NP is attributed to their larger scattering efficiency using full-wave optical simulations. This is further confirmed by optical spectroscopic measurements showing that a large fraction of the incident light couples into the diffused components because of the presence of these metallic aggregates. The optical absorption enhancement is broadband and it is particularly strong at wavelengths larger than 680 nm where the optical absorption of dye molecules is weak. (paper)

  2. Near-field imaging and nano-Fourier-transform infrared spectroscopy using broadband synchrotron radiation.

    Science.gov (United States)

    Hermann, Peter; Hoehl, Arne; Patoka, Piotr; Huth, Florian; Rühl, Eckart; Ulm, Gerhard

    2013-02-11

    We demonstrate scanning near-field optical microscopy with a spatial resolution below 100 nm by using low intensity broadband synchrotron radiation in the IR regime. The use of such a broadband radiation source opens up the possibility to perform nano-Fourier-transform infrared spectroscopy over a wide spectral range. PMID:23481749

  3. The diffusivity-mobility ratio in heavily doped nonlinear optical, optoelectronic and related materials

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, S. [Nano Scale Device Research Laboratory, Centre for Electronics Design and Technology, Indian Institute of Science, Bangalore 560 012 (India); Pahari, S. [Administrative Department, Jadavpur University, Kolkata 700 032 (India); Sarkar, R. [Department of Computer Science and Engineering, West Bengal University of Technology, BF-142, Salt Lake City, Sector-1, Kolkata 700064 (India); Ghosh, S. [Department of Electronics and Telecommunication Engineering, Bengal Engineering and Science University, Howrah 711 103 (India); Ghatak, K.P. [Department of Electronic Science, University of Calcutta, 92, Achryya Prafulla Chandra Road, Kolkata 700 009 (India)], E-mail: kamakhyaghatak@yahoo.co.in

    2008-10-01

    We study the diffusivity-mobility ratio (DMR) in heavily doped nonlinear compounds forming band tails on the basis of a newly formulated electron dispersion law and III-V, ternary and quaternary materials form a special case of our generalized analysis. The complex nature of the energy spectrum and creation of a new forbidden zone is the consequence of anisotropic energy band constants and the interaction of the impurity atoms in the tails with spin-orbit splitting of valence bands for the other compounds. Analytically, the presence of non-removable poles in the dispersion relation of the undoped material creates the complex energy spectrum for the corresponding heavily doped sample. The DMR for the heavily doped II-VI, IV-VI and stressed materials has been studied. It has been found taking n-type CdGeAs{sub 2,}, Cd{sub 3}As{sub 2}, InAs, InSb, Hg{sub 1-x}Cd{sub x}Te, In{sub 1-x}Ga{sub x}As{sub y}P{sub 1-y} lattice matched to InP, CdS, PbTe, PbSnTe, Pb{sub 1-x}Sn{sub x}Se and stressed InSb as examples that the DMR increases with the increasing electron concentration with different numerical values and the nature of variations are totally band structure dependent. An experimental method of determining the DMR in heavily doped materials for arbitrary dispersion relations together with three applications in the area of material science in general has been suggested.

  4. Non-invasive assessment of cerebral microcirculation with diffuse optics and coherent hemodynamics spectroscopy

    Science.gov (United States)

    Fantini, Sergio; Sassaroli, Angelo; Kainerstorfer, Jana M.; Tgavalekos, Kristen T.; Zang, Xuan

    2016-03-01

    We describe the general principles and initial results of coherent hemodynamics spectroscopy (CHS), which is a new technique for the quantitative assessment of cerebral hemodynamics on the basis of dynamic near-infrared spectroscopy (NIRS) measurements. The two components of CHS are (1) dynamic measurements of coherent cerebral hemodynamics in the form of oscillations at multiple frequencies (frequency domain) or temporal transients (time domain), and (2) their quantitative analysis with a dynamic mathematical model that relates the concentration and oxygen saturation of hemoglobin in tissue to cerebral blood volume (CBV), cerebral blood flow (CBF), and cerebral metabolic rate of oxygen (CMRO2). In particular, CHS can provide absolute measurements and dynamic monitoring of CBF, and quantitative measures of cerebral autoregulation. We report initial results of CBF measurements in hemodialysis patients, where we found a lower CBF (54 +/- 16 ml/(100 g-min)) compared to a group of healthy controls (95 +/- 11 ml/(100 g-min)). We also report CHS measurements of cerebral autoregulation, where a quantitative index of autoregulation (its cutoff frequency) was found to be significantly greater in healthy subjects during hyperventilation (0.034 +/- 0.005 Hz) than during normal breathing (0.017 +/- 0.002 Hz). We also present our approach to depth resolved CHS, based on multi-distance, frequency-domain NIRS data and a two-layer diffusion model, to enhance sensitivity to cerebral tissue. CHS offers a potentially powerful approach to the quantitative assessment and continuous monitoring of local brain perfusion at the microcirculation level, with prospective brain mapping capabilities of research and clinical significance.

  5. Spectroscopic and laser properties of Er3+ doped fluoro-phosphate glasses as promising candidates for broadband optical fiber lasers and amplifiers

    International Nuclear Information System (INIS)

    Highlights: • Erbium doped different fluoro-phosphate glasses are prepared and characterized. • Spectroscopic properties have been determined using Judd–Ofelt and Mc-Cumber theory. • Prominent laser transition Er3+:4I13/2 → 4I15/2 is observed at 1.53 μm. - Abstract: Different fluoro-phosphate glasses doped with 0.5 mol% Er3+ doped are prepared by melt quenching method. Both structural and spectroscopic properties have been characterized in order to evaluate their potential as both laser source and amplifier materials. Optical absorption measurements are carried out and analyzed through Judd–Ofelt and Mc-Cumber theories where spectroscopic parameters such as intensity parameters Ωl (λ = 2,4,6), transition probabilities, radiative lifetimes, stimulated absorption cross-sections and emission cross-sections at 1.5 μm have been evaluated for Er3+ doped different fluorophosphate glasses. The various luminescence and gain properties are explained from photoluminescence studies. The decay curve analysis have been done for obtaining the decay time constants of Er3+ excited level 4I13/2 in all the fluoro-phosphate glasses. The obtained results of each glass matrix are compared with the equivalent parameters for several other host glasses. These fluoro-phosphate glasses are found to be suitable candidates for laser and amplifier applications

  6. Broadband optical absorption enhancement of N719 dye in ethanol by gold-silver alloy nanoparticles fabricated under laser ablation technique

    Science.gov (United States)

    Al-Azawi, Mohammed A.; Bidin, Noriah; Abbas, Khaldoon N.; Bououdina, Mohamed; Azzez, Shrook A.

    2016-04-01

    The formation of gold-silver alloy nanoparticles (Au-Ag alloy NPs) by a two-step process with a pulsed Nd:YAG laser without any additives is presented. Mixtures of Au and Ag colloidal suspensions were separately obtained by 1064-nm laser ablation of metallic targets immersed in ethanol. Subsequently, the as-mixed colloidal suspensions were reirradiated by laser-induced heating at the second-harmonic generation (532 nm) for different irradiation periods of time. The absorption spectra and morphology of the colloidal alloys were studied as a function of exposure time to laser irradiation. Transmission electron microscopy revealed the formation of monodispersed spherical nanoparticles with a homogeneous size distribution in all the synthesized samples. UV-vis and photoluminescence spectroscopy measurements were also employed to characterize the changes in the light absorption and emission of N719 dye solution with different concentrations of Au-Ag colloidal alloys, respectively. The localized surface plasmon resonance (LSPR) of Au-Ag alloy NPs enhanced the absorption and fluorescence peak of the dye solution. The mixture of dye molecules with a higher concentration of alloy NPs exhibited an additional coupling of dipole moments with the LSPR, thereby contributing to the improvement of the optical properties of the mixture.

  7. Spectroscopic and laser properties of Er{sup 3+} doped fluoro-phosphate glasses as promising candidates for broadband optical fiber lasers and amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Babu, S. [Department of Physics, Sri Venkateswara University, Tirupati 517 502, A.P. (India); Seshadri, M. [Institute of Physics, University of Campinas, UNICAMP, P.O. Box 6165, Campinas 13083-970 (Brazil); Reddy Prasad, V. [Department of Physics, Sri Venkateswara University, Tirupati 517 502, A.P. (India); Ratnakaram, Y.C., E-mail: ratnakaramsvu@gmail.com [Department of Physics, Sri Venkateswara University, Tirupati 517 502, A.P. (India)

    2015-10-15

    Highlights: • Erbium doped different fluoro-phosphate glasses are prepared and characterized. • Spectroscopic properties have been determined using Judd–Ofelt and Mc-Cumber theory. • Prominent laser transition Er{sup 3+}:{sup 4}I{sub 13/2} → {sup 4}I{sub 15/2} is observed at 1.53 μm. - Abstract: Different fluoro-phosphate glasses doped with 0.5 mol% Er{sup 3+} doped are prepared by melt quenching method. Both structural and spectroscopic properties have been characterized in order to evaluate their potential as both laser source and amplifier materials. Optical absorption measurements are carried out and analyzed through Judd–Ofelt and Mc-Cumber theories where spectroscopic parameters such as intensity parameters Ω{sub l} (λ = 2,4,6), transition probabilities, radiative lifetimes, stimulated absorption cross-sections and emission cross-sections at 1.5 μm have been evaluated for Er{sup 3+} doped different fluorophosphate glasses. The various luminescence and gain properties are explained from photoluminescence studies. The decay curve analysis have been done for obtaining the decay time constants of Er{sup 3+} excited level {sup 4}I{sub 13/2} in all the fluoro-phosphate glasses. The obtained results of each glass matrix are compared with the equivalent parameters for several other host glasses. These fluoro-phosphate glasses are found to be suitable candidates for laser and amplifier applications.

  8. Molecular anisotropy effects in carbon K-edge scattering: depolarized diffuse scattering and optical anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Stone, Kevin H.

    2014-07-14

    Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K-edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence, and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylene-like backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.

  9. A Physics-Based Modeling and Real-Time Simulation of Biomechanical Diffusion Process Through Optical Imaged Alveolar Tissues on Graphical Processing Units

    Science.gov (United States)

    Kaya, Ilhan; Santhanam, Anand P.; Lee, Kye-Sung; Meemon, Panomsak; Papp, Nicolene; Rolland, Jannick P.

    Tissue engineering has broad applications from creating the much-needed engineered tissue and organ structures for regenerative medicine to providing in vitro testbeds for drug testing. In the latter, application domain, creating alveolar lung tissue, and simulating the diffusion process of oxygen and other possible agents from the air into the blood stream as well as modeling the removal of carbon dioxide and other possible entities from the blood stream are of critical importance to simulating lung functions in various environments. In this chapter, we propose a physics-based model to simulate the alveolar gas exchange and the alveolar diffusionDiffusion alveolar process. Tissue engineers, for the first time, may utilize these simulation results to better understand the underlying gas exchange process and properly adjust the tissue growing cycles. In this work, alveolar tissues are imaged by means of an optical coherence microscopyOptical coherence microscopy (OCM Modality OCM ) system developed in our laboratory. As a consequence, 3D alveoli tissue data with its inherent complex boundary is taken as input to the simulationSimulation diffusion system, which is based on computational fluid mechanics in simulating the alveolar gas exchange. The visualizationVisualization and the simulation of diffusion of the air into the blood through the alveoli tissue is performed using a state-of-art graphics processing unitGraphics processing unit (GPU). Results show the real-time simulation of the gas exchange through the 2D alveoli tissue.

  10. Broadband pendulum energy harvester

    Science.gov (United States)

    Liang, Changwei; Wu, You; Zuo, Lei

    2016-09-01

    A novel electromagnetic pendulum energy harvester with mechanical motion rectifier (MMR) is proposed and investigated in this paper. MMR is a mechanism which rectifies the bidirectional swing motion of the pendulum into unidirectional rotation of the generator by using two one-way clutches in the gear system. In this paper, two prototypes of pendulum energy harvester with MMR and without MMR are designed and fabricated. The dynamic model of the proposed MMR pendulum energy harvester is established by considering the engagement and disengagement of the one way clutches. The simulation results show that the proposed MMR pendulum energy harvester has a larger output power at high frequencies comparing with non-MMR pendulum energy harvester which benefits from the disengagement of one-way clutch during pendulum vibration. Moreover, the proposed MMR pendulum energy harvester is broadband compare with non-MMR pendulum energy harvester, especially when the equivalent inertia is large. An experiment is also conducted to compare the energy harvesting performance of these two prototypes. A flywheel is attached at the end of the generator to make the disengagement more significant. The experiment results also verify that MMR pendulum energy harvester is broadband and has a larger output power at high frequency over the non-MMR pendulum energy harvester.

  11. Assessment of diffusion parameters of new passive samplers using optical chemical sensor for on-site measuring formaldehyde in indoor air: experimental and numerical studies.

    Science.gov (United States)

    Vignau-Laulhere, Jane; Mocho, Pierre; Plaisance, Hervé; Raulin, Katarzyna; Desauziers, Valérie

    2016-03-01

    New passive samplers using a sensor consisting of a sol-gel matrix entrapping Fluoral-P as sampling media were developed for the determination of formaldehyde in indoor air. The reaction between Fluoral-P and formaldehyde produces a colored compound which is quantified on-site by means of a simple optical reading module. The advantages of this sensor are selectivity, low cost, ppb level limit of detection, and on-site direct measurement. In the development process, it is necessary to determine the sampling rate, a key parameter that cannot be directly assessed in the case of diffusive samplers using optical chemical sensor. In this study, a methodology combining experimental tests and numerical modeling is proposed and applied at five different radial diffusive samplers equipped with the same optical chemical sensor to assess the sampled material flows and sampling rates. These radial diffusive samplers differ in the internal volume of the sampler (18.97 and 6.14 cm(3)), the position of sensor inside the sampler (in front and offset of 1.2 cm above the membrane) and the width of the diffusion slot (1.4 and 5.9 mm). The influences of these three parameters (internal volume, position of sensor inside the sampler, and width of the diffusion slot) were assessed and discussed with regard to the formaldehyde sampling rate and water uptake by sensor (potential interference of measure). Numerical simulations based on Fick's laws are in agreement with the experimental results and provide to estimate the effective diffusion coefficient of formaldehyde through the membrane (3.50 × 10(-6) m(2) s(-1)). Conversion factors between the sensor response, sampled formaldehyde mass and sampling rate were also assessed. PMID:26847188

  12. Assessment of diffusion parameters of new passive samplers using optical chemical sensor for on-site measuring formaldehyde in indoor air: experimental and numerical studies.

    Science.gov (United States)

    Vignau-Laulhere, Jane; Mocho, Pierre; Plaisance, Hervé; Raulin, Katarzyna; Desauziers, Valérie

    2016-03-01

    New passive samplers using a sensor consisting of a sol-gel matrix entrapping Fluoral-P as sampling media were developed for the determination of formaldehyde in indoor air. The reaction between Fluoral-P and formaldehyde produces a colored compound which is quantified on-site by means of a simple optical reading module. The advantages of this sensor are selectivity, low cost, ppb level limit of detection, and on-site direct measurement. In the development process, it is necessary to determine the sampling rate, a key parameter that cannot be directly assessed in the case of diffusive samplers using optical chemical sensor. In this study, a methodology combining experimental tests and numerical modeling is proposed and applied at five different radial diffusive samplers equipped with the same optical chemical sensor to assess the sampled material flows and sampling rates. These radial diffusive samplers differ in the internal volume of the sampler (18.97 and 6.14 cm(3)), the position of sensor inside the sampler (in front and offset of 1.2 cm above the membrane) and the width of the diffusion slot (1.4 and 5.9 mm). The influences of these three parameters (internal volume, position of sensor inside the sampler, and width of the diffusion slot) were assessed and discussed with regard to the formaldehyde sampling rate and water uptake by sensor (potential interference of measure). Numerical simulations based on Fick's laws are in agreement with the experimental results and provide to estimate the effective diffusion coefficient of formaldehyde through the membrane (3.50 × 10(-6) m(2) s(-1)). Conversion factors between the sensor response, sampled formaldehyde mass and sampling rate were also assessed.

  13. Optical Design of Spaceborne Broadband Limb Sounder for Detecting Atmospheric Trace Gas%星载宽波段大气痕量气体临边探测仪光学设计

    Institute of Scientific and Technical Information of China (English)

    薛庆生

    2012-01-01

    In order to meet the urgent requirements of delecting atmospheric trace gas in limb observation geometry, an optical system of spaceborne broadband limb sounder for detecting atmospheric trace gas is designed. The system is an imaging spectrometer with the working wavelength band from 0. 3 μm to 0. 7 μm, and its full field of view is 2. 4% focal length is 120 mm, and the relative aperture is 1 : 6. To avoid the problems of the classical Czerny-Truncr spectrometer, such as low spatial resolution caused by large astigmatism, a modified Czerny-Turner spectrometer is designed, in which astigmatism can be corrected simultaneously in a wide band. By matching the modified Czerny-Turner spectrometer with a off-axis parabolic telescope,an examplc of limb sounder optical system is designed. Ray tracing, optimization and analysing are performed by ZEMAX software. The analyzed results demonstrate that the astigmatism is substantially corrected, and the MTF for different spectral band is more than 0. 69 which satisfies the pre-designed requirement and proves the feasibility of the astigmatism-correction method.%为满足大气痕量气体临边探测的迫切需求,克服传统Czerny-Turner光谱仪由于像散大导致空间分辨率低的缺点,设计了一种可以在宽波段内同时校正像散的改进型Czerny-Turner光谱仪,光谱范围为0.3~0.7μm,全视场角为2.4°,焦距为120 mm,相对孔径为1∶6.将离轴抛物面镜与改进型Czerny-Turner光谱仪匹配设计了一个临边探测仪光学系统并运用光学设计软件ZEMAX对临边探测仪光学系统进行了光线追迹和优化并对设计结果进行了分析,结果表明该系统的像散得到充分校正,光学系统在各个谱段的光学传递函数均达到0.69以上,完全满足设计指标要求,也证明了所提出的在宽波段内同时像散校正方法是可行的.

  14. Broadband terahertz fiber directional coupler

    DEFF Research Database (Denmark)

    Nielsen, Kristian; Rasmussen, Henrik K.; Jepsen, Peter Uhd;

    2010-01-01

    We present the design of a short broadband fiber directional coupler for terahertz (THz) radiation and demonstrate a 3 dB coupler with a bandwidth of 0:6 THz centered at 1:4 THz. The broadband coupling is achieved by mechanically downdoping the cores of a dual-core photonic crystal fiber...

  15. Anatomical and Functional Images of in vitro and in vivo Tissues by NIR Time-domain Diffuse Optical Tomography

    Science.gov (United States)

    Zhao, Huijuan; Gao, Feng; Tanikawa, Yukari; Homma, Kazuhiro; Onodera, Yoichi; Yamada, Yukio

    Near infra-red (NIR) diffuse optical tomography (DOT) has gained much attention and it will be clinically applied to imaging breast, neonatal head, and the hemodynamics of the brain because of its noninvasiveness and deep penetration in biological tissue. Prior to achieving the imaging of infant brain using DOT, the developed methodologies need to be experimentally justified by imaging some real organs with simpler structures. Here we report our results of an in vitro chicken leg and an in vivo exercising human forearm from the data measured by a multi-channel time-resolved NIR system. Tomographic images were reconstructed by a two-dimensional image reconstruction algorithm based on a modified generalized pulse spectrum technique for simultaneous reconstruction of the µa and µs´. The absolute µa- and µs´-images revealed the inner structures of the chicken leg and the forearm, where the bones were clearly distinguished from the muscle. The Δµa-images showed the blood volume changes during the forearm exercise, proving that the system and the image reconstruction algorithm could potentially be used for imaging not only the anatomic structure but also the hemodynamics in neonatal heads.

  16. Comparison of cobinamide to hydroxocobalamin in reversing cyanide physiologic effects in rabbits using diffuse optical spectroscopy monitoring

    Science.gov (United States)

    Brenner, Matthew; Mahon, Sari B.; Lee, Jangwoen; Kim, Jae; Mukai, David; Goodman, Seth; Kreuter, Kelly A.; Ahdout, Rebecca; Mohammad, Othman; Sharma, Vijay S.; Blackledge, William; Boss, Gerry R.

    2010-01-01

    Our purpose is to compare cobinamide to hydroxocobalamin in reversing cyanide (CN)-induced physiologic effects in an animal model using diffuse optical spectroscopy (DOS). Cyanide poisoning is a major threat worldwide. Cobinamide is a novel molecule that can bind two molecules of cyanide, has a much higher binding affinity than hydroxocobalamin, and is more water soluble. We investigated the ability of equimolar doses of cobinamide and hydroxocobalamin to reverse the effects of cyanide exposure in an animal model monitored continuously by DOS. Cyanide toxicity was induced in 16 New Zealand white rabbits by intravenous infusion. Animals were divided into three groups: controls (n=5) received saline following cyanide, hydroxocobalamin (N=6) following cyanide, and cobinamide (N=5) following cyanide. Cobinamide caused significantly faster and more complete recovery of oxy- and deoxyhemoglobin concentrations in cyanide-exposed animals than hydroxocobalamin- or saline-treated animals, with a recovery time constant of 13.8+/-7.1 min compared to 75.4+/-25.1 and 76.4+/-42.7 min, for hydroxocobalamin- and saline-treated animals, respectively (p<0.0001). This study indicates that cobinamide more rapidly and completely reverses the physiologic effects of cyanide than equimolar doses of cobalamin at the dose used in this study, and CN effects and response can be followed noninvasively using DOS.

  17. Simultaneous Retrieval of Aerosol and Surface Optical Properties from Combined Airborne- and Ground-Based Direct and Diffuse Radiometric Measurements

    Science.gov (United States)

    Gatebe, C. K.; Dubovik, O.; King, M. D.; Sinyuk, A.

    2010-01-01

    This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET) method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer (CAR) and AERONET data). A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34-2.30 m) and angular range (180 ) of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a) the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b) the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c) Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM) Central Facility, Oklahoma, USA, and (d) the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

  18. Image quality analysis of high-density diffuse optical tomography incorporating a subject-specific head model

    Directory of Open Access Journals (Sweden)

    Yuxuan eZhan

    2012-05-01

    Full Text Available High-density diffuse optical tomography (HD-DOT methods have shown significant improvement in localization accuracy and image resolution compared to traditional topographic near infrared spectroscopy (NIRS of the human brain. In this work we provide a comprehensive evaluation of image quality in visual cortex mapping via a simulation study with the use of an anatomical head model derived from MRI data of a human subject. A model of individual head anatomy provides the surface shape and internal structure that allow for the construction of a more realistic physical model for the forward problem, as well as the use of a structural constraint in the inverse problem. The HD-DOT model utilized here incorporates multiple source-detector separations with continuous-wave data with added noise based on experimental results. To evaluate image quality we quantify the localization error and localized volume at half maximum (LVHM throughout a region of interest (ROI within the visual cortex and systematically analyze the use of whole brain tissue spatial constraint within image reconstruction. Our results demonstrate that an image quality with less than 10 mm in localization error and 1000 m3 in LVHM can be obtained up to 13 mm below the scalp surface with a typical unconstrained reconstruction and up to 18 mm deep when a spatial constraint based on the brain tissue is utilized.

  19. In-Plane Thermal Diffusivity Measurement of Thin Films Based on the Alternating-Current Calorimetric Method Using an Optical Reflectivity Technique

    Institute of Scientific and Technical Information of China (English)

    黄正兴; 唐祯安; 许自强; 丁海涛; 顾毓沁

    2004-01-01

    An advanced ac calorimetric method to measure thermal diffusivity of a thin sample is developed by using an optical reflectivity technique. A modulated infrared laser is used to heat the front surface ofa foil specimen. The reflectivity of a continuous-wave He-Ne laser at the rear surface of the specimen is detected by a photoreceiver.According to the temperature dependence of reflectivity, the ac temperature response is obtained. Thermal diffusivity is deduced from a one-dimensional heat conduction equation. A stainless-steel foil and a copper foil are chosen as the samples. The present results agree well with the data in the literature.

  20. Broadband microwave photonic phase shifter based on polarisation rotation

    DEFF Research Database (Denmark)

    Xue, Weiqi; Öhman, Filip; Blaaberg, Søren;

    2008-01-01

    A broadband microwave photonic phase shifter is presented based on the polarisation properties of a Mach-Zehnder intensity modulator and nonlinear polarisation rotation in a semiconductor optical amplifier. The system can realise about 150deg phase shift in the frequency range from 50 MHz to 19 GHz....

  1. Broad-band hard X-ray reflectors

    DEFF Research Database (Denmark)

    Joensen, K.D.; Gorenstein, P.; Hoghoj, P.;

    1997-01-01

    Interest in optics for hard X-ray broad-band application is growing. In this paper, we compare the hard X-ray (20-100 keV) reflectivity obtained with an energy-dispersive reflectometer, of a standard commercial gold thin-film with that of a 600 bilayer W/Si X-ray supermirror. The reflectivity of ...

  2. Broadband infrared absorption enhancement by electroless-deposited silver nanoparticles

    DEFF Research Database (Denmark)

    Gritti, Claudia; Raza, Søren; Kadkhodazadeh, Shima;

    2016-01-01

    . Optical characterization confirms that the random array of electroless-deposited NPs improves absorption by up to 20% in a broadband of nearinfrared frequencies from the bandgap edge to 2000 nm. Due to the small filling fraction of particles, the reflection in the visible range is practically unchanged...

  3. Determination of diffusion coefficients of carbon dioxide in water between 268 and 473 K in a high-pressure capillary optical cell with in situ Raman spectroscopic measurements

    Science.gov (United States)

    Lu, Wanjun; Guo, Huirong; Chou, I.-Ming; Burruss, R.C.; Li, Lanlan

    2013-01-01

    Accurate values of diffusion coefficients for carbon dioxide in water and brine at reservoir conditions are essential to our understanding of transport behavior of carbon dioxide in subsurface pore space. However, the experimental data are limited to conditions at low temperatures and pressures. In this study, diffusive transfer of carbon dioxide in water at pressures up to 45 MPa and temperatures from 268 to 473 K was observed within an optical capillary cell via time-dependent Raman spectroscopy. Diffusion coefficients were estimated by the least-squares method for the measured variations in carbon dioxide concentration in the cell at various sample positions and time. At the constant pressure of 20 MPa, the measured diffusion coefficients of carbon dioxide in water increase with increasing temperature from 268 to 473 K. The relationship between diffusion coefficient of carbon dioxide in water [D(CO2) in m2/s] and temperature (T in K) was derived with Speedy–Angell power-law approach as: D(CO2)=D0[T/Ts-1]m where D0 = 13.942 × 10−9 m2/s, Ts = 227.0 K, and m = 1.7094. At constant temperature, diffusion coefficients of carbon dioxide in water decrease with pressure increase. However, this pressure effect is rather small (within a few percent).

  4. Continuous Wave Spectroscopy with Diffusion Theory for Quantification of Optical Properties: Comparison Between Multi-distance and Multi-wavelength Data Fitting Methods.

    Science.gov (United States)

    Lin, Yung-Chi; Lin, Zhi-Fong; Nioka, Shoko; Chen, Li-Hsin; Tseng, Sheng-Hao; Chung, Pau-Choo

    2016-01-01

    Typically, continuous wave spectroscopy (CWS) can be used to accurately quantify biological tissue optical properties (μ a and μ s ') by employing the diffuse reflectance information acquired at multiple source-detector separations (multi-distance). On the other hand, sample optical properties can also be obtained by fitting multi-wavelength light reflectance acquired at a single source detector separation to the diffusion theory equation. To date, multi-wavelength and multi-distance methods have not yet been rigorously compared for their accuracy in quantification of the sample optical properties. In this investigation, we compared the accuracy of the two above-mentioned quantifying methods in the optical properties recovery. The liquid phantoms had μ a between 0.004 and 0.011 mm(-1) and μ s ' between 0.55 and 1.07 mm(-1) whose optical properties mimic the human breast. Multi-distance data and multi-wavelength data were fitted to the same diffusion equation for consistency. The difference between benchmark μ a and μ s ' and the fitted results, ΔError (ΔE) was used to evaluate the accuracy of the two methods. The results showed that either method yielded ΔE within 15-30 % when values were within certain limits to standard values applicable to μ s ' and μ a for human adipose tissue. Both methods showed no significant differences in ΔE values. Our results suggest that both multi-distance and multi-wavelength methods can yield similar reasonable optical properties in biological tissue with a proper calibration. PMID:27526161

  5. Metasurface Broadband Solar Absorber

    CERN Document Server

    Azad, A K; Sykora, M; Weisse-Bernstein, N R; Luk, T S; Taylor, A J; Dalvit, D A R; Chen, H -T

    2015-01-01

    We demonstrate a broadband, polarization independent, omnidirectional absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low emissivity at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. Furthermore, we discuss the potential use of our metasurface absorber design in solar thermophotovoltaics by exploiting refractory plasmonic materials.

  6. Metasurface Broadband Solar Absorber

    Science.gov (United States)

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong

    2016-02-01

    We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure.

  7. Metamaterial Broadband Angular Selectivity

    CERN Document Server

    Shen, Yichen; Wang, Zhiyu; Wang, Li; Celanovic, Ivan; Ran, Lixin; Joannopoulos, John D; Soljacic, Marin

    2014-01-01

    We demonstrate how broadband angular selectivity can be achieved with stacks of one-dimensionally periodic photonic crystals, each consisting of alternating isotropic layers and effective anisotropic layers, where each effective anisotropic layer is constructed from a multilayered metamaterial. We show that by simply changing the structure of the metamaterials, the selective angle can be tuned to a broad range of angles; and, by increasing the number of stacks, the angular transmission window can be made as narrow as desired. As a proof of principle, we realize the idea experimentally in the microwave regime. The angular selectivity and tunability we report here can have various applications such as in directional control of electromagnetic emitters and detectors.

  8. Metasurface Broadband Solar Absorber.

    Science.gov (United States)

    Azad, Abul K; Kort-Kamp, Wilton J M; Sykora, Milan; Weisse-Bernstein, Nina R; Luk, Ting S; Taylor, Antoinette J; Dalvit, Diego A R; Chen, Hou-Tong

    2016-01-01

    We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. PMID:26828999

  9. Experimental demonstration of quantum teleportation of broadband squeezing

    OpenAIRE

    Yonezawa, Hidehiro; Braunstein, Samuel L.; Furusawa, Akira

    2007-01-01

    We demonstrate an unconditional high-fidelity teleporter capable of preserving the broadband entanglement in an optical squeezed state. In particular, we teleport a squeezed state of light and observe $-0.8 \\pm 0.2$dB of squeezing in the teleported (output) state. We show that the squeezing criterion translates directly into a sufficient criterion for entanglement of the upper and lower sidebands of the optical field. Thus, this result demonstrates the first unconditional teleportation of bro...

  10. Broadband quasi-phase-matched second-harmonic generation in MgO: LiNbO3 waveguide

    Institute of Scientific and Technical Information of China (English)

    LIU Gui-hua; GUO Hai-run; FU Xing-hu; ZENG Xiang-long

    2011-01-01

    The quasi-phase-matched (QPM) condition of broadband second harmonic generation (SHG) in Ti-diffused MgO:LiNbOwaveguide is theoretically simulated. The results show that the center wavelength of broadband SHG dependent on the waveguide width is around 1550 nm and the bandwidth is 50 nm.

  11. Feasibility of U-curve method to select the regularization parameter for fluorescence diffuse optical tomography in phantom and small animal studies

    OpenAIRE

    Chamorro-Servent, Judit; Aguirre, Juan; Ripoll, Jorge; Vaquero, Juan José; Desco, Manuel

    2011-01-01

    When dealing with ill-posed problems such as fluorescence diffuse optical tomography (fDOT) the choice of the regularization parameter is extremely important for computing a reliable reconstruction. Several automatic methods for the selection of the regularization parameter have been introduced over the years and their performance depends on the particular inverse problem. Herein a U-curve-based algorithm for the selection of regularization parameter has been applied for the first time to fDO...

  12. Broadband nanophotonic wireless links and networks using on-chip integrated plasmonic antennas

    Science.gov (United States)

    Yang, Yuanqing; Li, Qiang; Qiu, Min

    2016-01-01

    Owing to their high capacity and flexibility, broadband wireless communications have been widely employed in radio and microwave regimes, playing indispensable roles in our daily life. Their optical analogs, however, have not been demonstrated at the nanoscale. In this paper, by exploiting plasmonic nanoantennas, we demonstrate the complete design of broadband wireless links and networks in the realm of nanophotonics. With a 100-fold enhancement in power transfer superior to previous designs as well as an ultrawide bandwidth that covers the entire telecommunication wavelength range, such broadband nanolinks and networks are expected to pave the way for future optical integrated nanocircuits.

  13. Broadband nanophotonic wireless links and networks using on-chip integrated plasmonic antennas.

    Science.gov (United States)

    Yang, Yuanqing; Li, Qiang; Qiu, Min

    2016-01-19

    Owing to their high capacity and flexibility, broadband wireless communications have been widely employed in radio and microwave regimes, playing indispensable roles in our daily life. Their optical analogs, however, have not been demonstrated at the nanoscale. In this paper, by exploiting plasmonic nanoantennas, we demonstrate the complete design of broadband wireless links and networks in the realm of nanophotonics. With a 100-fold enhancement in power transfer superior to previous designs as well as an ultrawide bandwidth that covers the entire telecommunication wavelength range, such broadband nanolinks and networks are expected to pave the way for future optical integrated nanocircuits.

  14. Diffuse optical tomography activation in the somatosensory cortex: specific activation by painful vs. non-painful thermal stimuli.

    Directory of Open Access Journals (Sweden)

    Lino Becerra

    Full Text Available BACKGROUND: Pain is difficult to assess due to the subjective nature of self-reporting. The lack of objective measures of pain has hampered the development of new treatments as well as the evaluation of current ones. Functional MRI studies of pain have begun to delineate potential brain response signatures that could be used as objective read-outs of pain. Using Diffuse Optical Tomography (DOT, we have shown in the past a distinct DOT signal over the somatosensory cortex to a noxious heat stimulus that could be distinguished from the signal elicited by innocuous mechanical stimuli. Here we further our findings by studying the response to thermal innocuous and noxious stimuli. METHODOLOGY/PRINCIPAL FINDINGS: Innocuous and noxious thermal stimuli were applied to the skin of the face of the first division (ophthalmic of the trigeminal nerve in healthy volunteers (N = 6. Stimuli temperatures were adjusted for each subject to evoke warm (equivalent to a 3/10 and painful hot (7/10 sensations in a verbal rating scale (0/10 = no/max pain. A set of 26 stimuli (5 sec each was applied for each temperature with inter-stimulus intervals varied between 8 and 15 sec using a Peltier thermode. A DOT system was used to capture cortical responses on both sides of the head over the primary somatosensory cortical region (S1. For the innocuous stimuli, group results indicated mainly activation on the contralateral side with a weak ipsilateral response. For the noxious stimuli, bilateral activation was observed with comparable amplitudes on both sides. Furthermore, noxious stimuli produced a temporal biphasic response while innocuous stimuli produced a monophasic response. CONCLUSIONS/SIGNIFICANCE: These results are in accordance with fMRI and our other DOT studies of innocuous mechanical and noxious heat stimuli. The data indicate the differentiation of DOT cortical responses for pain vs. innocuous stimuli that may be useful in assessing objectively acute pain.

  15. Simultaneous retrieval of aerosol and surface optical properties from combined airborne- and ground-based direct and diffuse radiometric measurements

    Directory of Open Access Journals (Sweden)

    C. K. Gatebe

    2010-03-01

    Full Text Available This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer (CAR and AERONET data. A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34–2.30 μm and angular range (180° of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM Central Facility, Oklahoma, USA, and (d the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

  16. Simultaneous retrieval of aerosol and surface optical properties from combined airborne- and ground-based direct and diffuse radiometric measurements

    Directory of Open Access Journals (Sweden)

    C. K. Gatebe

    2009-12-01

    Full Text Available This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer, CAR, and AERONET data. A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34–2.30 μm and angular range (180° of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM Central Facility, Oklahoma, USA, and (d the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

  17. A broadband transformation-optics metasurface lens

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Xiang; Xiang Jiang, Wei; Feng Ma, Hui; Jun Cui, Tie, E-mail: tjcui@seu.edu.cn [State Key Laboratory of Millimeter Waves, School of Information Science and Engineering, Southeast University, Nanjing 210096 (China)

    2014-04-14

    We present a transformational metasurface Luneburg lens based on the quasi-conformal mapping method, which has weakly anisotropic constitutive parameters. We design the metasurface lens using inhomogeneous artificial structures to realize the required surface refractive indexes. The transformational metasurface Luneburg lens is fabricated and the measurement results demonstrate very good performance in controlling the radiated surface waves.

  18. Bottle microresonator broadband and low repetition rate frequency comb generator

    CERN Document Server

    Dvoyrin, V

    2016-01-01

    We propose a new type of broadband and low repetition rate frequency comb generator which has the shape of an elongated and nanoscale-shallow optical bottle microresonator created at the surface of an optical fiber. The free spectral range (FSR) of the broadband azimuthal eigenfrequency series of this resonator is the exact multiple of the FSR of the dense and narrowband axial series. The effective radius variation of the microresonator is close to a parabola with a nanoscale height which is greater or equal to lambda/2pi*n0 (here lambda is the characteristic radiation wavelength and n0 is the refractive index of the microresonator material). Overall, the microresonator possesses a broadband, small FSR, and accurately equidistant spectrum convenient for the generation of a broadband and low repetition rate optical frequency comb. It is shown that this comb can be generated by pumping with a cw laser, which radiation frequency matches a single axial eigenfrequency of the microresonator, or, alternatively, by p...

  19. Broadband Advanced Spectral System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NovaSol proposes to develop an advanced hyperspectral imaging system for earth science missions named BRASS (Broadband Advanced Spectral System). BRASS combines...

  20. Laser-matter interactions, phase changes and diffusion phenomena during laser annealing of plasmonic AlN:Ag templates and their applications in optical encoding

    International Nuclear Information System (INIS)

    Nanocomposite thin films incorporating silver nanoparticles are emerging as photosensitive templates for optical encoding applications. However, a deep understanding of the fundamental physicochemical mechanisms occurring during laser-matter interactions is still lacking. In this work, the photosensitivity of AlN:Ag plasmonic nanocomposites is thoroughly examined and a series of UV laser annealing parameters, such as wavelength, fluence and the number of pulses are investigated. We report and study effects such as the selective crystallization of the AlN matrix, the enlargement of the Ag nanoparticle inclusions by diffusion of laser-heated Ag and the outdiffusion of Ag to the film’s surface. Detailed optical calculations contribute to the identification and understanding of the aforementioned physical mechanisms and of their dependency on the laser processing parameters. We are then able to predetermine the plasmonic response of processed AlN:Ag nanocomposites and demonstrate its potential by means of optically encoding an overt or covert cryptographic pattern. (paper)

  1. In vivo comparison of kinetics of saline and ICG for the detection of normal and tumor tissue using NIR diffuse optical technique

    Science.gov (United States)

    Liu, Ning; Nalcioglu, Orhan; Gulsen, Gultekin

    2011-03-01

    We investigated the kinetics of a bolus intravenous administrated normal saline by using near-infrared diffuse optical technique, and compared it with the kinetics of a non-targeted contrast agent indocyanine green (ICG) on small animal tumor model. Two-compartment model was used to fit the dynamic curves at early stage, which considered saline and ICG as either a negative or positive contrast agent. The purposes of the designed experiment reported here are to (1) study the effect of saline administration on optical pharmacokinetics; (2) investigate the possibility of using normal saline as contrast agent for the study of tumor pathophysiology. The study indicates that saline has different contrast mechanism as ICG, and saline can provide enough optical contrast for the tumor kinetic study.

  2. Broadband second harmonic generation in whispering gallery mode resonators

    CERN Document Server

    Lin, Guoping; Strekalov, Dmitry V; Yu, Nan

    2013-01-01

    Optical frequency conversion processes in nonlinear materials are limited in wavelength by the accessible phase matching and the required high pump powers. In this letter, we report a novel broadband phase matching (PM) technique in high quality factor (Q) whispering gallery mode (WGM) resonators made of birefringent crystalline materials. This technique relies on two interacting WGMs, one with constant and the other with spatially oscillating phase velocity. Thus, phase matching occurs cyclically. The technique can be implemented with a WGM resonator with its disk plane parallel to the optic axis of the crystal. With a single beta barium borate (BBO) resonator in that configuration, we experimentally demonstrated efficient second harmonic generation (SHG) to harmonic wavelengths from 780 nm in the near infrared to 317 nm in the ultraviolet (UV). The observed SHG conversion efficiency is as high as 4.6% (mW)-1. This broadband PM technique opens a new way for nonlinear optics applications in WGM resonators. Th...

  3. 星载宽波段远紫外高光谱成像仪光学系统设计%Optical System Design of a Spaceborne Broadband Far Ultraviolet Hyperspectral Imager

    Institute of Scientific and Technical Information of China (English)

    薛庆生

    2013-01-01

    According to the application requirements for remote sensing of upper atmosphere, a reflective optical system of spaceborne far ultraviolet hyperspectral imager is designed. Which is composed of a scan mirror, an off-axis parabolic telescope and a toroidal grating spectrometer. An aberration-correction method for concave toroidal grating is developed. The initial parameters are solved based on the geometrical aberration theory of concave grating and then optimized using the optical design software Zemax, and the toroidal gating spectrometer is designed. The root mean square of spot radius is less than 16 μm in the working waveband. Aberration is corrected simultaneously in broadband and the requirement of spectral resolution of 0. 6 nm is satisfied, which indicates the aberration-correction method is feasible. Ray tracing and analysing are performed by Zemax software. Analyzed results demonstrate that the modulation transfer function for different wavelength is more than 0.8, which satisfies the design requirements. The construction is compact and suitable for application in space remote sensing.%根据高层大气遥感的应用要求,设计了一个全反射式的远紫外高光谱成像仪光学系统,该系统由扫描镜、离轴抛物面望远镜和超环面光栅光谱仪组成.提出了一种凹面超环面光栅光谱仪像差校正方法,根据凹面光栅的几何像差理论求解初始结构参数,然后利用光学设计软件Zemax进行优化,完成了超环面光栅光谱仪的设计,在工作波段内,点列图半径的方均根均小于16 μm,实现了宽波段像差同时校正,满足光谱分辨率0.6 nm的指标要求,也证明了提出的像差校正方法是可行的.运用光学设计软件Zemax对远紫外高光谱成像仪光学系统进行了光线追迹,并对设计结果进行了分析,分析结果表明,各波长的光学传递函数均达到0.8以上,完全满足设计指标要求,且结构紧凑,适合空间遥感应用.

  4. Broadband transmission EPR spectroscopy.

    Directory of Open Access Journals (Sweden)

    Wilfred R Hagen

    Full Text Available EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9-10 GHz range. Most (biomolecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin - nuclear spin interactions and electron spin - electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8-2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed.

  5. TU-A-9A-11: Gold Nanoparticles Enhanced Diffuse Optical Tomography: A Proof of Concept Study

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Y; Dogan, N [Department of Radiation Oncology, University of Miami School of Medicine, Miami, FL (United States)

    2014-06-15

    Purpose: To investigate the feasibility and potential of gold nanoparticles (GNP) enhanced diffuse optical tomography (DOT) as a novel imaging strategy for tumor detection. Methods: Simulation was performed on a digital homogeneous cylindrical phantom of 30mm×30mm. Gold nanorods (GNR) with aspect ratio 3.9 and effective radius 21.86nm were used as contrast agent. The peak light absorption for these GNR occurs at 842nm within the near-infrared region, with the absorption cross-section of 1.97×10{sup -14}m{sup -2} and scatter cross-section of 1.07×10{sup -14}m{sup -2}. A 6mmdiameter sphere of GNR solution was positioned inside the tissue-simulating phantom. Simulations were performed at the GNR concentration level of 1nM, 100pM and 10pM, respectively. The points representing laser sources and light detectors were around the phantom with 30o apart tangentially and 1mm apart axially for 9 rows. As one point being source, all the other points within the current row and nearby four rows become detectors. Hence there are 108 source points in total and 55 detector points corresponding to each source. Forward light transport at 842nm wavelength was run on a three-dimensional mesh of 33186 nodes (∼0.5mm resolution) to acquire the light emission data. Reconstruction was performed on a coarse mesh of 19408 nodes (∼1mm resolution) with ∼20minutes on a 2.4GHz CPU and 8GB RAM computer. Results: The position of the GNR solution at 1nM, 100pM and 10pM concentration was reconstructed, respectively, with <1mm error. The GNR concentration was interpreted from the reconstructed absorption coefficient within the enhanced volume. The reconstructed maximum concentrations were 0.3nM, 120.0pM, and 5.3pM, respectively. Conclusion: To the best of our knowledge, this is the first time to apply GNP to enhance DOT. The simulation results showed the high sensitivity of GNP enhanced DOT, which is in pM concentration level, compared to the μM level for MRI agents and nM level for PET

  6. TU-A-9A-11: Gold Nanoparticles Enhanced Diffuse Optical Tomography: A Proof of Concept Study

    International Nuclear Information System (INIS)

    Purpose: To investigate the feasibility and potential of gold nanoparticles (GNP) enhanced diffuse optical tomography (DOT) as a novel imaging strategy for tumor detection. Methods: Simulation was performed on a digital homogeneous cylindrical phantom of 30mm×30mm. Gold nanorods (GNR) with aspect ratio 3.9 and effective radius 21.86nm were used as contrast agent. The peak light absorption for these GNR occurs at 842nm within the near-infrared region, with the absorption cross-section of 1.97×10-14m-2 and scatter cross-section of 1.07×10-14m-2. A 6mmdiameter sphere of GNR solution was positioned inside the tissue-simulating phantom. Simulations were performed at the GNR concentration level of 1nM, 100pM and 10pM, respectively. The points representing laser sources and light detectors were around the phantom with 30o apart tangentially and 1mm apart axially for 9 rows. As one point being source, all the other points within the current row and nearby four rows become detectors. Hence there are 108 source points in total and 55 detector points corresponding to each source. Forward light transport at 842nm wavelength was run on a three-dimensional mesh of 33186 nodes (∼0.5mm resolution) to acquire the light emission data. Reconstruction was performed on a coarse mesh of 19408 nodes (∼1mm resolution) with ∼20minutes on a 2.4GHz CPU and 8GB RAM computer. Results: The position of the GNR solution at 1nM, 100pM and 10pM concentration was reconstructed, respectively, with <1mm error. The GNR concentration was interpreted from the reconstructed absorption coefficient within the enhanced volume. The reconstructed maximum concentrations were 0.3nM, 120.0pM, and 5.3pM, respectively. Conclusion: To the best of our knowledge, this is the first time to apply GNP to enhance DOT. The simulation results showed the high sensitivity of GNP enhanced DOT, which is in pM concentration level, compared to the μM level for MRI agents and nM level for PET agents

  7. Broadband Dielectric Spectroscopy on Human Blood

    CERN Document Server

    Wolf, M; Lunkenheimer, P; Loidl, A

    2011-01-01

    Dielectric spectra of human blood reveal a rich variety of dynamic processes. Achieving a better characterization and understanding of these processes not only is of academic interest but also of high relevance for medical applications as, e.g., the determination of absorption rates of electromagnetic radiation by the human body. The dielectric properties of human blood are studied using broadband dielectric spectroscopy, systematically investigating the dependence on temperature and hematocrit value. By covering a frequency range from 1 Hz to 40 GHz, information on all the typical dispersion regions of biological matter is obtained. We find no evidence for a low-frequency relaxation (alpha-relaxation) caused, e.g., by counterion diffusion effects as reported for some types of biological matter. The analysis of a strong Maxwell-Wagner relaxation arising from the polarization of the cell membranes in the 1-100 MHz region (beta-relaxation) allows for the test of model predictions and the determination of variou...

  8. Broadband circular polarizers constructed using helix-like chiral metamaterials

    Science.gov (United States)

    Ji, Ruonan; Wang, Shao-Wei; Liu, Xingxing; Chen, Xiaoshuang; Lu, Wei

    2016-08-01

    In this paper, one kind of helix-like chiral metamaterial which can be realized by multiple conventional lithography or electron beam lithographic techniques is proposed to have a broadband bianisotropic optical response analogous to helical metamaterials. On the basis of twisted metamaterials, via tailoring the relative orientation within the lattice, the anisotropy of arcs is converted into magneto-electric coupling of closely spaced arc pairs, which leads to a broad bianisotropic optical response. By connecting the adjacent upper and lower arcs, the coupling of metasurface pairs is transformed into the coupling of the three-dimensional inclusions, and provides a much broader and higher bianisotropic optical response. For only a four-layer helix-like metamaterial, the maximum extinction ratio can reach 19.7. The operation band is in the wavelength range of 4.69 μm to 8.98 μm with an average extinction ratio of 6.9. And the transmittance for selective polarization is above 0.8 in the entire operation band. Such a structure is a promising candidate for integratable and scalable broadband circular polarizers, especially it has great potential to act as a broadband circular micropolarizer in the field of the full-Stokes division of focal plane polarimeters.In this paper, one kind of helix-like chiral metamaterial which can be realized by multiple conventional lithography or electron beam lithographic techniques is proposed to have a broadband bianisotropic optical response analogous to helical metamaterials. On the basis of twisted metamaterials, via tailoring the relative orientation within the lattice, the anisotropy of arcs is converted into magneto-electric coupling of closely spaced arc pairs, which leads to a broad bianisotropic optical response. By connecting the adjacent upper and lower arcs, the coupling of metasurface pairs is transformed into the coupling of the three-dimensional inclusions, and provides a much broader and higher bianisotropic optical

  9. Broadband Rotational Spectroscopy

    Science.gov (United States)

    Pate, Brooks

    2014-06-01

    The past decade has seen several major technology advances in electronics operating at microwave frequencies making it possible to develop a new generation of spectrometers for molecular rotational spectroscopy. High-speed digital electronics, both arbitrary waveform generators and digitizers, continue on a Moore's Law-like development cycle that started around 1993 with device bandwidth doubling about every 36 months. These enabling technologies were the key to designing chirped-pulse Fourier transform microwave (CP-FTMW) spectrometers which offer significant sensitivity enhancements for broadband spectrum acquisition in molecular rotational spectroscopy. A special feature of the chirped-pulse spectrometer design is that it is easily implemented at low frequency (below 8 GHz) where Balle-Flygare type spectrometers with Fabry-Perot cavity designs become technologically challenging due to the mirror size requirements. The capabilities of CP-FTMW spectrometers for studies of molecular structure will be illustrated by the collaborative research effort we have been a part of to determine the structures of water clusters - a project which has identified clusters up to the pentadecamer. A second technology trend that impacts molecular rotational spectroscopy is the development of high power, solid state sources in the mm-wave/THz regions. Results from the field of mm-wave chirped-pulse Fourier transform spectroscopy will be described with an emphasis on new problems in chemical dynamics and analytical chemistry that these methods can tackle. The third (and potentially most important) technological trend is the reduction of microwave components to chip level using monolithic microwave integrated circuits (MMIC) - a technology driven by an enormous mass market in communications. Some recent advances in rotational spectrometer designs that incorporate low-cost components will be highlighted. The challenge to the high-resolution spectroscopy community - as posed by Frank De

  10. Driving demand for broadband networks and services

    CERN Document Server

    Katz, Raul L

    2014-01-01

    This book examines the reasons why various groups around the world choose not to adopt broadband services and evaluates strategies to stimulate the demand that will lead to increased broadband use. It introduces readers to the benefits of higher adoption rates while examining the progress that developed and emerging countries have made in stimulating broadband demand. By relying on concepts such as a supply and demand gap, broadband price elasticity, and demand promotion, this book explains differences between the fixed and mobile broadband demand gap, introducing the notions of substitution and complementarity between both platforms. Building on these concepts, ‘Driving Demand for Broadband Networks and Services’ offers a set of best practices and recommendations aimed at promoting broadband demand.  The broadband demand gap is defined as individuals and households that could buy a broadband subscription because they live in areas served by telecommunications carriers but do not do so because of either ...

  11. Thermodynamic Upper Bound on Broadband Light Coupling with Photonic Structures

    KAUST Repository

    Yu, Zongfu

    2012-10-01

    The coupling between free space radiation and optical media critically influences the performance of optical devices. We show that, for any given photonic structure, the sum of the external coupling rates for all its optical modes are subject to an upper bound dictated by the second law of thermodynamics. Such bound limits how efficient light can be coupled to any photonic structure. As one example of application, we use this upper bound to derive the limit of light absorption in broadband solar absorbers. © 2012 American Physical Society.

  12. Nondispersive optical activity of meshed helical metamaterials.

    Science.gov (United States)

    Park, Hyun Sung; Kim, Teun-Teun; Kim, Hyeon-Don; Kim, Kyungjin; Min, Bumki

    2014-11-17

    Extreme optical properties can be realized by the strong resonant response of metamaterials consisting of subwavelength-scale metallic resonators. However, highly dispersive optical properties resulting from strong resonances have impeded the broadband operation required for frequency-independent optical components or devices. Here we demonstrate that strong, flat broadband optical activity with high transparency can be obtained with meshed helical metamaterials in which metallic helical structures are networked and arranged to have fourfold rotational symmetry around the propagation axis. This nondispersive optical activity originates from the Drude-like response as well as the fourfold rotational symmetry of the meshed helical metamaterials. The theoretical concept is validated in a microwave experiment in which flat broadband optical activity with a designed magnitude of 45° per layer of metamaterial is measured. The broadband capabilities of chiral metamaterials may provide opportunities in the design of various broadband optical systems and applications.

  13. Cascaded frequency doublers for broadband laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, N F; Vlasova, K V; Davydov, V S; Kulikov, S M; Makarov, A I; Sukharev, Stanislav A; Freidman, Gennadii I; Shubin, S V

    2012-10-31

    A new scheme of a cascaded converter of the first harmonic of broadband cw laser radiation into the second harmonic (SH) with compensation for the group walk-off in cascades is proposed and investigated. The conditions under which high conversion coefficients of broadband ({approx}33 cm{sup -1}) single-mode fibre laser radiation with low peak power ({approx}300 W) into the SH are determined for frequency doublers based on the most promising LBO crystal. Conversion of cw radiation with an average power of 300 W and efficiency {eta} = 4.5 % into the SH is obtained in a single LBO crystal. Effect of coherent addition of SH radiation excited in different cascades is demonstrated for two- and three-stage schemes. The expected conversion efficiencies, calculated disregarding loss but taking into account real aberrations of elements, are 18 % and 38 %, respectively. The effect of pumping depletion begins to manifest itself in the third cascade of a three-stage converter; it may reduce the latter value to {approx}30 %. (nonlinear optical phenomena)

  14. Multi-wavelength and time-domain diffuse optical tomography data processing by using a material basis and Mellin-Laplace transform

    Science.gov (United States)

    Hervé, Lionel; Planat-Chrétien, Anne; Di Sieno, Laura; Berger, Michel; Puszka, Agathe; Dalla Mora, Alberto; Contini, Davide; Boso, Gianluca; Dinten, Jean-Marc

    2014-03-01

    In order to increase sensitivity in the depth of diffusive media and to separate chromophores with distinct spectral signatures, we developed a method to process time-domain/multi-wavelength diffuse optical acquisitions: 3D Reconstructions of chromophore concentrations are performed with an algorithm based on the use of Mellin-Laplace Transform and material basis. A noise weighted data matching term is optimized by using the conjugated gradients method without expressing the Jacobian matrix of the system. As the algorithm uses reference measurements on a known medium, it does not require measurements or computations of the instrument response function of the system. Validations are performed in the reflectance geometry on a tissue-mimicking phantom composed of intralipid and black ink and a cylindrical blue dye inclusion with a radius of 4mm located at 15mm in depth. The optical tomography setup includes a laser whose picosecond pulses are injected via an optical fiber to the probed diffusive medium and the light collected by two fibers (located 15mm apart from the source), is sent to a Single-Photon Avalanche Diode (SPAD) connected to a Time-Correlated Single-Photon Counting (TCSPC) board. The source and two detectors scan the surface of the medium so as to provide 30 source-detector couples, 900 time-bins and 5 wavelength signals. 3D reconstructions performed on the black ink and blue dye materials on a mesh of around 10000 nodes show that we are able to detect, localize and determine the composition of the inclusion and the background.

  15. Development of Surfaces Optically Suitable for Flat Solar Panels. [using a reflectometer which separately evaluates spectral and diffuse reflectivities of surfaces

    Science.gov (United States)

    1979-01-01

    A reflectometer which can separately evaluate the spectral and diffuse reflectivities of surfaces is described. A phase locked detection system for the reflectometer is also described. A selective coating on aluminum potentially useful for flat plate solar collector applications is presented. The coating is composed of strongly bound copper oxide (divalent) and is formed by an etching process performed on an aluminum alloy with high copper content. Fabrication costs are expected to be small due to the one stop fabrication process. A number of conclusions gathered from the literature as to the required optical properties of flat plate solar collectors are discussed.

  16. Broadband Quantum Cryptography

    CERN Document Server

    Rogers, Daniel

    2010-01-01

    Quantum cryptography is a rapidly developing field that draws from a number of disciplines, from quantum optics to information theory to electrical engineering. By combining some fundamental quantum mechanical principles of single photons with various aspects of information theory, quantum cryptography represents a fundamental shift in the basis for security from numerical complexity to the fundamental physical nature of the communications channel. As such, it promises the holy grail of data security: theoretically unbreakable encryption. Of course, implementing quantum cryptography in real br

  17. Novel broadband glass phosphors for high CRI WLEDs.

    Science.gov (United States)

    Chen, Li-Yin; Cheng, Wei-Chih; Tsai, Chun-Chin; Chang, Jin-Kai; Huang, Yi-Chung; Huang, Jhih-Ci; Cheng, Wood-Hi

    2014-05-01

    New broadband glass phosphors with excellent thermal stability were proposed and experimentally demonstrated for white light-emitting-diodes (WLEDs). The novel glass phosphors were realized through dispersing multiple phosphors into SiO₂ based glass (SiO₂-Na₂O-Al₂O₃-CaO) at 680°C. Y₃Al₅O₁₂:Ce³⁺ (YAG), Lu₃Al₅O₁₂:Ce³⁺ (LuAG), and CaAlSiN₃: Eu²⁺ (nitride) phosphor crystals were chosen respectively as the yellow, green, and red emitters of the glass phosphors. The effect of sintering temperature on inter-diffusion reduction between phosphor crystals and amorphous SiO₂ in nitride-doped glass phosphors was studied and evidenced by the aid of high-resolution transmission electron microscopy (HRTEM). Broadband glass phosphors with high quantum-yield of 55.6% were thus successfully realized through the implementation of low sintering temperature. Proof-of-concept devices utilizing the novel broadband phosphors were developed to generate high-quality cool-white light with trisstimulus coordinates (x, y) = (0.358, 0.288), color-rending index (CRI) = 85, and correlated color temperature (CCT) = 3923K. The novel broadband glass phosphors with excellent thermal stability are essentially beneficial to the applications for next-generation solid-state indoor lighting, especially in the area where high power and absolute reliability are required. PMID:24922375

  18. Multispectral breast imaging using a ten-wavelength, 64x64 source/detector channels silicon photodiode-based diffuse optical tomography system

    International Nuclear Information System (INIS)

    We describe a compact diffuse optical tomography system specifically designed for breast imaging. The system consists of 64 silicon photodiode detectors, 64 excitation points, and 10 diode lasers in the near-infrared region, allowing multispectral, three-dimensional optical imaging of breast tissue. We also detail the system performance and optimization through a calibration procedure. The system is evaluated using tissue-like phantom experiments and an in vivo clinic experiment. Quantitative two-dimensional (2D) and three-dimensional (3D) images of absorption and reduced scattering coefficients are obtained from these experiments. The ten-wavelength spectra of the extracted reduced scattering coefficient enable quantitative morphological images to be reconstructed with this system. From the in vivo clinic experiment, functional images including deoxyhemoglobin, oxyhemoglobin, and water concentration are recovered and tumors are detected with correct size and position compared with the mammography

  19. Design of a stacked diode array pumped Nd:YAG laser with a truncated compound parabolic concentrator and a diffusive optical cavity

    CERN Document Server

    Lee, S M; Yun, M J; Cha, B H; Lee, J M

    1999-01-01

    We designed and analyzed a new Nd:YAG laser which employs a combination of a truncated compound parabolic concentrator (CPC) and a diffusive optical pump cavity for pumping with a stacked diode array. A design code based on a ray-tracing algorithm was developed to analyze the Nd:YAG laser system. The optimum truncated CPC profile was determined from analyses of the dependences of the pump-beam distribution and the total absorbed power in the laser crystal upon the acceptance angle and the slit width of the CPC. In addition, the analyses show the importance of the acceptance angle in designing an efficient laser system with a truncated CPC. Using conservative design parameters, the design code predicted a Nd:YAG laser output of 130 W with a corresponding optical slope efficiency of 44%.

  20. Omnidirectional and broadband absorption enhancement from trapezoidal Mie resonators in semiconductor metasurfaces

    CERN Document Server

    Pala, Ragip A; Aydin, Koray; Atwater, Harry A

    2015-01-01

    Light trapping in planar ultrathin-film solar cells is limited due to a small number of optical modes available in the thin-film slab. A nanostructured thin-film design could surpass this limit by providing broadband increase in the local density of states in a subwavelength volume and maintaining efficient coupling of light. Here we report a broadband metasurface design, enabling efficient and broadband absorption enhancement by direct coupling of incoming light to resonant modes of subwavelength-scale Mie nanoresonators defined in the thin-film active layer. Absorption was investigated both theoretically and experimentally in prototypes consisting of lithographically patterned, two-dimensional periodic arrays of silicon nanoresonators on silica substrates. A crossed trapezoid resonator shape of rectangular cross section is used to excite broadband Mie resonances across the visible and near-IR spectra. Our numerical simulations, optical absorption measurements and photocurrent spectral response measurements ...