Models of optical quantum computing
Directory of Open Access Journals (Sweden)
Krovi Hari
2017-03-01
Full Text Available I review some work on models of quantum computing, optical implementations of these models, as well as the associated computational power. In particular, we discuss the circuit model and cluster state implementations using quantum optics with various encodings such as dual rail encoding, Gottesman-Kitaev-Preskill encoding, and coherent state encoding. Then we discuss intermediate models of optical computing such as boson sampling and its variants. Finally, we review some recent work in optical implementations of adiabatic quantum computing and analog optical computing. We also provide a brief description of the relevant aspects from complexity theory needed to understand the results surveyed.
Modeling of semiconductor optical amplifiers
DEFF Research Database (Denmark)
Mørk, Jesper; Bischoff, Svend; Berg, Tommy Winther
We discuss the modelling of semiconductor optical amplifiers with emphasis on their high-speed properties. Applications in linear amplification as well as ultrafast optical signal processing are reviewed. Finally, the possible role of quantum-dot based optical amplifiers is discussed.......We discuss the modelling of semiconductor optical amplifiers with emphasis on their high-speed properties. Applications in linear amplification as well as ultrafast optical signal processing are reviewed. Finally, the possible role of quantum-dot based optical amplifiers is discussed....
Optical-Microphysical Cirrus Model
Reichardt, J.; Reichardt, S.; Lin, R.-F.; Hess, M.; McGee, T. J.; Starr, D. O.
2008-01-01
A model is presented that permits the simulation of the optical properties of cirrus clouds as measured with depolarization Raman lidars. It comprises a one-dimensional cirrus model with explicit microphysics and an optical module that transforms the microphysical model output to cloud and particle optical properties. The optical model takes into account scattering by randomly oriented or horizontally aligned planar and columnar monocrystals and polycrystals. Key cloud properties such as the fraction of plate-like particles and the number of basic crystals per polycrystal are parameterized in terms of the ambient temperature, the nucleation temperature, or the mass of the particles. The optical-microphysical model is used to simulate the lidar measurement of a synoptically forced cirrostratus in a first case study. It turns out that a cirrus cloud consisting of only monocrystals in random orientation is too simple a model scenario to explain the observations. However, good agreement between simulation and observation is reached when the formation of polycrystals or the horizontal alignment of monocrystals is permitted. Moreover, the model results show that plate fraction and morphological complexity are best parameterized in terms of particle mass, or ambient temperature which indicates that the ambient conditions affect cirrus optical properties more than those during particle formation. Furthermore, the modeled profiles of particle shape and size are in excellent agreement with in situ and laboratory studies, i.e., (partly oriented) polycrystalline particles with mainly planar basic crystals in the cloud bottom layer, and monocrystals above, with the fraction of columns increasing and the shape and size of the particles changing from large thin plates and long columns to small, more isometric crystals from cloud center to top. The findings of this case study corroborate the microphysical interpretation of cirrus measurements with lidar as suggested previously.
Performance modeling of optical refrigerators
Energy Technology Data Exchange (ETDEWEB)
Mills, G.; Mord, A. [Ball Aerospace and Technologies Corp., Boulder, CO (United States). Cryogenic and Thermal Engineering
2006-02-15
Optical refrigeration using anti-Stokes fluorescence in solids has several advantages over more conventional techniques including low mass, low volume, low cost and no vibration. It also has the potential of allowing miniature cryocoolers on the scale of a few cubic centimeters. It has been the topic of analysis and experimental work by several organizations. In 2003, we demonstrated the first optical refrigerator. We have developed a comprehensive system-level performance model of optical refrigerators. Our current version models the refrigeration cycle based on the fluorescent material emission and absorption data at ambient and reduced temperature for the Ytterbium-ZBLAN glass (Yb:ZBLAN) cooling material. It also includes the heat transfer into the refrigerator cooling assembly due to radiation and conduction. In this paper, we report on modeling results which reveal the interplay between size, power input, and cooling load. This interplay results in practical size limitations using Yb:ZBLAN. (author)
Optical Coherence Tomography: Advanced Modeling
DEFF Research Database (Denmark)
Andersen, Peter E.; Thrane, Lars; Yura, Harold T.;
2013-01-01
Analytical and numerical models for describing and understanding the light propagation in samples imaged by optical coherence tomography (OCT) systems are presented. An analytical model for calculating the OCT signal based on the extended Huygens-Fresnel principle valid both for the single......- and multiple-scattering regimes is derived. An advanced Monte Carlo model for calculating the OCT signal is also derived, and the validity of this model is shown through a mathematical proof based on the extended Huygens-Fresnel principle. From the analytical model, an algorithm for enhancing OCT images...... is developed, the so-called true-reflection algorithm in which the OCT signal may be corrected for the attenuation caused by scattering. The algorithm is verified experimentally and by using the Monte Carlo model as a numerical tissue phantom. Applications of extraction of optical properties from tissue...
Socio-optics: optical knowledge applied in modeling social phenomena
Chisleag, Radu; Chisleag Losada, Ioana-Roxana
2011-05-01
The term "Socio-optics" (as a natural part of Socio-physics), is rather not found in literature or at Congresses. In Optics books, there are not made references to optical models applied to explain social phenomena, in spite of Optics relying on the duality particle-wave which seems convenient to model relationships among society and its members. The authors, who have developed a few models applied to explain social phenomena based on knowledge in Optics, along with a few other models applying, in Social Sciences, knowledge from other branches of Physics, give their own examples of such optical models, f. e., of relationships among social groups and their sub-groups, by using kowledge from partially coherent optical phenomena or to explain by tunnel effect, the apparently impossible penetration of social barriers by individuals. They consider that the term "Socio-optics" may come to life. There is mentioned the authors' expertise in stimulating Socio-optics approach by systematically asking students taken courses in Optics to find applications of the newly got Wave and Photon Optics knowledge, to model social and even everyday life phenomena, eventually engaging in such activities other possibly interested colleagues.
Optical models of the molecular atmosphere
Zuev, V. E.; Makushkin, Y. S.; Mitsel, A. A.; Ponomarev, Y. N.; Rudenko, V. P.; Firsov, K. M.
1986-01-01
The use of optical and laser methods for performing atmospheric investigations has stimulated the development of the optical models of the atmosphere. The principles of constructing the optical models of molecular atmosphere for radiation with different spectral composition (wideband, narrowband, and monochromatic) are considered in the case of linear and nonlinear absorptions. The example of the development of a system which provides for the modeling of the processes of optical-wave energy transfer in the atmosphere is presented. Its physical foundations, structure, programming software, and functioning were considered.
The Folding Deuteron Optical Model Potentials
Li, Xiaohua; Cai, Chonghai
2008-01-01
For 52 target nuclei with deuteron as projectile, we calculate the reaction cross sections and elastic scattering angular distributions, as well as the $\\chi^2$ values for 11 kinds of deuteron optical model potentials: our global deuteron optical potentials and 10 folding optical potentials calculated with 2 phenomenological global nucleon optical potentials given by Koning \\textit{et al}(KD) and by Varner\\textit{et al}(CH89), and 8 microscopic nucleon optical potentials with the generalized Skyrme force parameters(GS1-6) and modified Skyrme force parameters(SKa, SKb). We find that for constructing the folding deuteron optical potential, both SKa and SKb are the best Skyrme force parameters of the microscopic nucleon optical potential proposed by Q. Shen \\textit{et al}.
Optical Hall effect-model description: tutorial.
Schubert, Mathias; Kühne, Philipp; Darakchieva, Vanya; Hofmann, Tino
2016-08-01
The optical Hall effect is a physical phenomenon that describes the occurrence of magnetic-field-induced dielectric displacement at optical wavelengths, transverse and longitudinal to the incident electric field, and analogous to the static electrical Hall effect. The electrical Hall effect and certain cases of the optical Hall effect observations can be explained by extensions of the classic Drude model for the transport of electrons in metals. The optical Hall effect is most useful for characterization of electrical properties in semiconductors. Among many advantages, while the optical Hall effect dispenses with the need of electrical contacts, electrical material properties such as effective mass and mobility parameters, including their anisotropy as well as carrier type and density, can be determined from the optical Hall effect. Measurement of the optical Hall effect can be performed within the concept of generalized ellipsometry at an oblique angle of incidence. In this paper, we review and discuss physical model equations, which can be used to calculate the optical Hall effect in single- and multiple-layered structures of semiconductor materials. We define the optical Hall effect dielectric function tensor, demonstrate diagonalization approaches, and show requirements for the optical Hall effect tensor from energy conservation. We discuss both continuum and quantum approaches, and we provide a brief description of the generalized ellipsometry concept, the Mueller matrix calculus, and a 4×4 matrix algebra to calculate data accessible by experiment. In a follow-up paper, we will discuss strategies and approaches for experimental data acquisition and analysis.
Model of computation for Fourier optical processors
Naughton, Thomas J.
2000-05-01
We present a novel and simple theoretical model of computation that captures what we believe are the most important characteristics of an optical Fourier transform processor. We use this abstract model to reason about the computational properties of the physical systems it describes. We define a grammar for our model's instruction language, and use it to write algorithms for well-known filtering and correlation techniques. We also suggest suitable computational complexity measures that could be used to analyze any coherent optical information processing technique, described with the language, for efficiency. Our choice of instruction language allows us to argue that algorithms describable with this model should have optical implementations that do not require a digital electronic computer to act as a master unit. Through simulation of a well known model of computation from computer theory we investigate the general-purpose capabilities of analog optical processors.
Modeling and optimization of LCD optical performance
Yakovlev, Dmitry A; Kwok, Hoi-Sing
2015-01-01
The aim of this book is to present the theoretical foundations of modeling the optical characteristics of liquid crystal displays, critically reviewing modern modeling methods and examining areas of applicability. The modern matrix formalisms of optics of anisotropic stratified media, most convenient for solving problems of numerical modeling and optimization of LCD, will be considered in detail. The benefits of combined use of the matrix methods will be shown, which generally provides the best compromise between physical adequacy and accuracy with computational efficiency and optimization fac
Completely integrable models of nonlinear optics
Indian Academy of Sciences (India)
Andrey I Maimistov
2001-11-01
The models of the nonlinear optics in which solitons appeared are considered. These models are of paramount importance in studies of nonlinear wave phenomena. The classical examples of phenomena of this kind are the self-focusing, self-induced transparency and parametric interaction of three waves. At present there are a number of theories based on completely integrable systems of equations, which are, both, generations of the original known models and new ones. The modiﬁed Korteweg-de Vries equation, the nonlinear Schrödinger equation, the derivative nonlinear Schrödinger equation, Sine–Gordon equation, the reduced Maxwell–Bloch equation, Hirota equation, the principal chiral ﬁeld equations, and the equations of massive Thirring model are some soliton equations, which are usually to be found in nonlinear optics theory.
Optical models for silicon solar cells
Energy Technology Data Exchange (ETDEWEB)
Marshall, T.; Sopori, B. [National Renewable Energy Lab., Golden, CO (United States)
1995-08-01
Light trapping is an important design feature for high-efficiency silicon solar cells. Because light trapping can considerably enhance optical absorption, a thinner substrate can be used which, in turn, can lower the bulk carrier recombination and concommitantly increase open-circuit voltage, and fill factor of the cell. The basic concepts of light trapping are similar to that of excitation of an optical waveguide, where a prism or a grating structure increases the phase velocity of the incoming optical wave such that waves propagated within the waveguide are totally reflected at the interfaces. Unfortunately, these concepts break down because the entire solar cell is covered with such a structure, making it necessary to develop new analytical approaches to deal with incomplete light trapping in solar cells. This paper describes two models that analyze light trapping in thick and thin solar cells.
Advanced modelling of optical coherence tomography systems
DEFF Research Database (Denmark)
Andersen, Peter E.; Thrane, L.; Yura, H.T.;
2004-01-01
Analytical and numerical models for describing and understanding the light propagation in samples imaged by optical coherence tomography (OCT) systems are presented. An analytical model for calculating the OCT signal based on the extended Huygens–Fresnel principle valid both for the single...... and multiple scattering regimes is reviewed. An advanced Monte Carlo model for calculating the OCT signal is also reviewed, and the validity of this model is shown through a mathematical proof based on the extended Huygens–Fresnel principle. Moreover, for the first time the model is verified experimentally....... From the analytical model, an algorithm for enhancing OCT images is developed; the so-called true-reflection algorithm in which the OCT signal may be corrected for the attenuation caused by scattering. For the first time, the algorithm is demonstrated by using the Monte Carlo model as a numerical...
RxGen General Optical Model Prescription Generator
Sigrist, Norbert
2012-01-01
RxGen is a prescription generator for JPL's in-house optical modeling software package called MACOS (Modeling and Analysis for Controlled Optical Systems), which is an expert optical analysis software package focusing on modeling optics on dynamic structures, deformable optics, and controlled optics. The objectives of RxGen are to simplify and automate MACOS prescription generations, reducing errors associated with creating such optical prescriptions, and improving user efficiency without requiring MACOS proficiency. RxGen uses MATLAB (a high-level language and interactive environment developed by MathWorks) as the development and deployment platform, but RxGen can easily be ported to another optical modeling/analysis platform. Running RxGen within the modeling environment has the huge benefit that variations in optical models can be made an integral part of the modeling state. For instance, optical prescription parameters determined as external functional dependencies, optical variations by controlling the in-/exclusion of optical components like sub-systems, and/or controlling the state of all components. Combining the mentioned capabilities and flexibilities with RxGen's optical abstraction layer completely eliminates the hindering aspects for requiring proficiency in writing/editing MACOS prescriptions, allowing users to focus on the modeling aspects of optical systems, i.e., increasing productivity and efficiency. RxGen provides significant enhancements to MACOS and delivers a framework for fast prototyping as well as for developing very complex controlled optical systems.
Nonlinear optical model for strip plasmonic waveguides
DEFF Research Database (Denmark)
Lysenko, Oleg; Bache, Morten; Lavrinenko, Andrei
2016-01-01
This paper presents a theoretical model of nonlinear optical properties for strip plasmonic waveguides. The particular waveguides geometry that we investigate contains a gold core, adhesion layers, and silicon dioxide cladding. It is shown that the third-order susceptibility of the gold core...... significantly depends on the layer thickness and has the dominant contribution to the effective third-order susceptibility of the long-range plasmon polariton mode. This results in two nonlinear optical effects in plasmonic waveguides, which we experimentally observed and reported in [Opt. Lett. 41, 317 (2016......)]. The first effect is the nonlinear power saturation of the plasmonic mode, and the second effect is the spectral broadening of the plasmonic mode. Both nonlinear plasmonic effects can be used for practical applications and their appropriate model will be important for further developments in communication...
A Thermo-Optic Propagation Modeling Capability.
Energy Technology Data Exchange (ETDEWEB)
Schrader, Karl; Akau, Ron
2014-10-01
A new theoretical basis is derived for tracing optical rays within a finite-element (FE) volume. The ray-trajectory equations are cast into the local element coordinate frame and the full finite-element interpolation is used to determine instantaneous index gradient for the ray-path integral equation. The FE methodology (FEM) is also used to interpolate local surface deformations and the surface normal vector for computing the refraction angle when launching rays into the volume, and again when rays exit the medium. The method is implemented in the Matlab(TM) environment and compared to closed- form gradient index models. A software architecture is also developed for implementing the algorithms in the Zemax(TM) commercial ray-trace application. A controlled thermal environment was constructed in the laboratory, and measured data was collected to validate the structural, thermal, and optical modeling methods.
Optical Coherence Tomography: Modeling and Applications
DEFF Research Database (Denmark)
Thrane, Lars
in previous theoretical models of OCT systems. It is demonstrated that the shower curtain effect is of utmost importance in the theoretical description of an OCT system. The analytical model, together with proper noise analysis of the OCT system, enables calculation of the SNR, where the optical properties...... geometry, i.e., reflection geometry, is developed. As in the new OCT model, multiple scattered photons has been taken into account together with multiple scattering effects. As an important result, a novel method of creating images based on measurements of the momentum width of the Wigner phase......An analytical model is presented that is able to describe the performance of OCT systems in both the single and multiple scattering regimes simultaneously. This model inherently includes the shower curtain effect, well-known for light propagation through the atmosphere. This effect has been omitted...
Green Network Planning Model for Optical Backbones
DEFF Research Database (Denmark)
Gutierrez Lopez, Jose Manuel; Riaz, M. Tahir; Jensen, Michael
2010-01-01
Communication networks are becoming more essential for our daily lives and critically important for industry and governments. The intense growth in the backbone traffic implies an increment of the power demands of the transmission systems. This power usage might have a significant negative effect...... on the environment in general. In network planning there are existing planning models focused on QoS provisioning, investment minimization or combinations of both and other parameters. But there is a lack of a model for designing green optical backbones. This paper presents novel ideas to be able to define...
Symbolic modeling of high energy beam optics
Autin, Bruno
1999-01-01
A classical problem of computational physics consists of finding the minimum of a chi /sup 2/ like function of many variables. Powerful optimization algorithms have been developed but do not guarantee convergence towards an absolute minimum. Analytical methods can improve the insight into a physical problem but calculations quickly exceed the power of a human brain. There comes the interest of optical design of high energy particle accelerators. The physics background is sketched and emphasis is put on the methodology. In practice, algebraic models may not be precise enough but they usually provide excellent initial conditions for a final numerical optimization. (4 refs).
Optical Model and Cross Section Uncertainties
Energy Technology Data Exchange (ETDEWEB)
Herman,M.W.; Pigni, M.T.; Dietrich, F.S.; Oblozinsky, P.
2009-10-05
Distinct minima and maxima in the neutron total cross section uncertainties were observed in model calculations using spherical optical potential. We found this oscillating structure to be a general feature of quantum mechanical wave scattering. Specifically, we analyzed neutron interaction with 56Fe from 1 keV up to 65 MeV, and investigated physical origin of the minima.We discuss their potential importance for practical applications as well as the implications for the uncertainties in total and absorption cross sections.
Optical modeling and simulation of thin-film photovoltaic devices
Krc, Janez
2013-01-01
In wafer-based and thin-film photovoltaic (PV) devices, the management of light is a crucial aspect of optimization since trapping sunlight in active parts of PV devices is essential for efficient energy conversions. Optical modeling and simulation enable efficient analysis and optimization of the optical situation in optoelectronic and PV devices. Optical Modeling and Simulation of Thin-Film Photovoltaic Devices provides readers with a thorough guide to performing optical modeling and simulations of thin-film solar cells and PV modules. It offers insight on examples of existing optical models
Theoretical model for a Stark anomalous dispersion optical filter
Yin, B.; Shay, T. M.
1993-01-01
A theoretical model for the first atomic Stark anomalous dispersion optical filter is reported. The results show the filter may serve as a widely tunable narrow bandwidth and high throughput optical filter for freespace laser communications and remote sensing.
RECENT MATHEMATICAL STUDIES IN THE MODELING OF OPTICS AND ELECTROMAGNETICS
Institute of Scientific and Technical Information of China (English)
Gang Bao
2004-01-01
This work is concerned with mathematical modeling, analysis, and computation of optics and electromagnetics, motivated particularly by optical and microwave applications.The main technical focus is on Maxwell's equations in complex linear and nonlinear media.
Optical Performance Modeling of FUSE Telescope Mirror
Saha, Timo T.; Ohl, Raymond G.; Friedman, Scott D.; Moos, H. Warren
2000-01-01
We describe the Metrology Data Processor (METDAT), the Optical Surface Analysis Code (OSAC), and their application to the image evaluation of the Far Ultraviolet Spectroscopic Explorer (FUSE) mirrors. The FUSE instrument - designed and developed by the Johns Hopkins University and launched in June 1999 is an astrophysics satellite which provides high resolution spectra (lambda/Delta(lambda) = 20,000 - 25,000) in the wavelength region from 90.5 to 118.7 nm The FUSE instrument is comprised of four co-aligned, normal incidence, off-axis parabolic mirrors, four Rowland circle spectrograph channels with holographic gratings, and delay line microchannel plate detectors. The OSAC code provides a comprehensive analysis of optical system performance, including the effects of optical surface misalignments, low spatial frequency deformations described by discrete polynomial terms, mid- and high-spatial frequency deformations (surface roughness), and diffraction due to the finite size of the aperture. Both normal incidence (traditionally infrared, visible, and near ultraviolet mirror systems) and grazing incidence (x-ray mirror systems) systems can be analyzed. The code also properly accounts for reflectance losses on the mirror surfaces. Low frequency surface errors are described in OSAC by using Zernike polynomials for normal incidence mirrors and Legendre-Fourier polynomials for grazing incidence mirrors. The scatter analysis of the mirror is based on scalar scatter theory. The program accepts simple autocovariance (ACV) function models or power spectral density (PSD) models derived from mirror surface metrology data as input to the scatter calculation. The end product of the program is a user-defined pixel array containing the system Point Spread Function (PSF). The METDAT routine is used in conjunction with the OSAC program. This code reads in laboratory metrology data in a normalized format. The code then fits the data using Zernike polynomials for normal incidence
Optical modeling of Fresnel zoneplate microscopes.
Naulleau, Patrick P; Mochi, Iacopo; Goldberg, Kenneth A
2011-07-10
Defect free masks remain one of the most significant challenges facing the commercialization of extreme ultraviolet (EUV) lithography. Progress on this front requires high-performance wavelength-specific metrology of EUV masks, including high-resolution and aerial-image microscopy performed near the 13.5 nm wavelength. Arguably the most cost-effective and rapid path to proliferating this capability is through the development of Fresnel zoneplate-based microscopes. Given the relative obscurity of such systems, however, modeling tools are not necessarily optimized to deal with them and their imaging properties are poorly understood. Here we present a modeling methodology to analyze zoneplate microscopes based on commercially available optical modeling software and use the technique to investigate the imaging performance of an off-axis EUV microscope design. The modeling predicts that superior performance can be achieved by tilting the zoneplate, making it perpendicular to the chief ray at the center of the field, while designing the zoneplate to explicitly work in that tilted plane. Although the examples presented here are in the realm of EUV mask inspection, the methods described and analysis results are broadly applicable to zoneplate microscopes in general, including full-field soft-x-ray microscopes routinely used in the synchrotron community.
Optics damage modeling and analysis at the National Ignition Facility
Liao, Z. M.; Raymond, B.; Gaylord, J.; Fallejo, R.; Bude, J.; Wegner, P.
2014-10-01
Comprehensive modeling of laser-induced damage in optics for the National Ignition Facility (NIF) has been performed on fused silica wedge focus lenses with a metric that compares the modeled damage performance to online inspections. The results indicate that damage models are successful in tracking the performance of the fused silica final optics when properly accounting for various optical finishes and mitigation processes. This validates the consistency of the damage models and allows us to further monitor and evaluate different system parameters that potentially can affect optics performance.
Uncertainty Quantification for Optical Model Parameters
Lovell, A E; Sarich, J; Wild, S M
2016-01-01
Although uncertainty quantification has been making its way into nuclear theory, these methods have yet to be explored in the context of reaction theory. For example, it is well known that different parameterizations of the optical potential can result in different cross sections, but these differences have not been systematically studied and quantified. The purpose of this work is to investigate the uncertainties in nuclear reactions that result from fitting a given model to elastic-scattering data, as well as to study how these uncertainties propagate to the inelastic and transfer channels. We use statistical methods to determine a best fit and create corresponding 95\\% confidence bands. A simple model of the process is fit to elastic-scattering data and used to predict either inelastic or transfer cross sections. In this initial work, we assume that our model is correct, and the only uncertainties come from the variation of the fit parameters. We study a number of reactions involving neutron and deuteron p...
Classical Ising Models Realised on Optical Lattices
Cirio, Mauro; Brennen, G. K.; Twamley, J.; Iblisdir, S.; Boada, O.
2012-02-01
We describe a simple quantum algorithm acting on a register of qubits in d spatial dimensions which computes statistical properties of d+1 dimensional classical Ising models. The algorithm works by measuring scattering matrix elements for quantum processes and Wick rotating to provide estimates for real partition functions of classical systems. This method can be implemented in a straightforward way in ensembles of qubits, e.g. three dimensional optical lattices with only nearest neighbor Ising like interactions. By measuring noise in the estimate useful information regarding location of critical points and scaling laws can be extracted for classical Ising models, possibly with inhomogeneity. Unlike the case of quantum simulation of quantum hamiltonians, this algorithm does not require Trotter expansion of the evolution operator and thus has the advantage of being amenable to fault tolerant gate design in a straightforward manner. Through this setting it is possible to study the quantum computational complexity of the estimation of a classical partition function for a 2D Ising model with non uniform couplings and magnetic fields. We provide examples for the 2 dimensional case.
Modeling GMPLS and Optical MPLS Networks
DEFF Research Database (Denmark)
Christiansen, Henrik Lehrmann; Wessing, Henrik
2003-01-01
A consequence of migrating the existing Internet architecture to an all-optical one is that the network will consist of a mixture of equipment, ranging from electrical routers to all-optical packet switches. Hence, future networks will consist of multiple domains employing different technologies...
Quantum Modelling of Electro-Optic Modulators
Capmany, Jose
2011-01-01
Many components that are employed in quantum information and communication systems are well known photonic devices encountered in standard optical fiber communication systems, such as optical beamsplitters, waveguide couplers and junctions, electro-optic modulators and optical fiber links. The use of these photonic devices is becoming increasingly important especially in the context of their possible integration either in a specifically designed system or in an already deployed end-to-end fiber link. Whereas the behavior of these devices is well known under the classical regime, in some cases their operation under quantum conditions is less well understood. This paper reviews the salient features of the quantum scattering theory describing both the operation of the electro-optic phase and amplitude modulators in discrete and continuous-mode formalisms. This subject is timely and of importance in light of the increasing utilization of these devices in a variety of systems, including quantum key distribution an...
Novel applications of the dispersive optical model
Dickhoff, W H; Mahzoon, M H
2016-01-01
A review of recent developments of the dispersive optical model (DOM) is presented. Starting from the original work of Mahaux and Sartor, several necessary steps are developed and illustrated which increase the scope of the DOM allowing its interpretation as generating an experimentally constrained functional form of the nucleon self-energy. The method could therefore be renamed as the dispersive self-energy method. The aforementioned steps include the introduction of simultaneous fits of data for chains of isotopes or isotones allowing a data-driven extrapolation for the prediction of scattering cross sections and level properties in the direction of the respective drip lines. In addition, the energy domain for data was enlarged to include results up to 200 MeV where available. An important application of this work was implemented by employing these DOM potentials to the analysis of the (\\textit{d,p}) transfer reaction using the adiabatic distorted wave approximation (ADWA). We review the fully non-local DOM...
Optical Turbulence Characterization at LAMOST Site: Observations and Models
Liu, L -Y; Yao, Y -Q; Vernin, J; Chadid, M; Wang, H -S; Yin, J; Wang, Y -P
2015-01-01
Atmospheric optical turbulence seriously limits the performance of high angular resolution instruments. An 8-night campaign of measurements was carried out at the LAMOST site in 2011, to characterize the optical turbulence. Two instruments were set up during the campaign: a Differential Image Motion Monitor (DIMM) used to measure the total atmospheric seeing, and a Single Star Scidar (SSS) to measure the vertical profiles of the turbulence C_n^2(h) and the horizontal wind velocity V(h). The optical turbulence parameters are also calculated with the Weather Research and Forecasting (WRF) model coupled with the Trinquet-Vernin model, which describes optical effects of atmospheric turbulence by using the local meteorological parameters. This paper presents assessment of the optical parameters involved in high angular resolution astronomy. Its includes seeing, isoplanatic angle, coherence time, coherence etendue, vertical profiles of optical turbulence intensity _n^2(h)$ and horizontal wind speed V(h). The median...
A novel model on dynamic resource allocation in optical networks
Institute of Scientific and Technical Information of China (English)
TANG Yong; RAO Min; LI Lei; CHEN Yu; JIANG Jianfeng; ZHANG Mingde; SUN Xiaohan
2005-01-01
A novel model on dynamic resource allocation in the WDM optical networks is proposed, basing on the integrated considerations of the impacts of transmission impairments and service classification on dynamic resource allocation in the optical layer.In this model, the priorities of optical connection requests are mapped into different thresholds of transmission impairments, and a uniform method which is adopted to evaluate the virtual wavelength path (VWP) candidates is defined. The Advanced Preferred Wavelength Sets Algorithm (A-PWS) and the heuristic Dynamic Min-Cost & Optical Virtual Wavelength Path Algorithm (DMC-OVWP) are presented addressing the routing and wavelength assignment (RWA) problem based on dynamic traffic and multi priorities in wavelength-routed optical networks. For a received optical connection request,DMC-OVWP is employed to calculate a list of the VWP candidates, and an appropriate VWP which matches the request's priority is picked up to establish the lightpath by analyzing the transmission qualities of the VWP candidates.
On a Decomposition Model for Optical Flow
Abhau, Jochen; Belhachmi, Zakaria; Scherzer, Otmar
In this paper we present a variational method for determining cartoon and texture components of the optical flow of a noisy image sequence. The method is realized by reformulating the optical flow problem first as a variational denoising problem for multi-channel data and then by applying decomposition methods. Thanks to the general formulation, several norms can be used for the decomposition. We study a decomposition for the optical flow into bounded variation and oscillating component in greater detail. Numerical examples demonstrate the capabilities of the proposed approach.
Model GC1312S Multifunction Integrated Optical Circuit Devices
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Model GC1312S multifunction integrated optical circuit device (MIOC) used in inertial-grade interferometric fiber optics gyroscopes (IFOGs) is fabricated by annealing and proton exchange process (APE). The unique feature of the device is the incorporation of the beat detection circuit besides all the features the conventional single Y-branch multifunction integrated optical circuit devices have. The device structure, operation principle and typical characteristics, etc., are briefly presented in this paper.
Measuring optical properties of a blood vessel model using optical coherence tomography
Levitz, David; Hinds, Monica T.; Tran, Noi; Vartanian, Keri; Hanson, Stephen R.; Jacques, Steven L.
2006-02-01
In this paper we develop the concept of a tissue-engineered optical phantom that uses engineered tissue as a phantom for calibration and optimization of biomedical optics instrumentation. With this method, the effects of biological processes on measured signals can be studied in a well controlled manner. To demonstrate this concept, we attempted to investigate how the cellular remodeling of a collagen matrix affected the optical properties extracted from optical coherence tomography (OCT) images of the samples. Tissue-engineered optical phantoms of the vascular system were created by seeding smooth muscle cells in a collagen matrix. Four different optical properties were evaluated by fitting the OCT signal to 2 different models: the sample reflectivity ρ and attenuation parameter μ were extracted from the single scattering model, and the scattering coefficient μ s and root-mean-square scattering angle θ rms were extracted from the extended Huygens-Fresnel model. We found that while contraction of the smooth muscle cells was clearly evident macroscopically, on the microscopic scale very few cells were actually embedded in the collagen. Consequently, no significant difference between the cellular and acellular samples in either set of measured optical properties was observed. We believe that further optimization of our tissue-engineering methods is needed in order to make the histology and biochemistry of the cellular samples sufficiently different from the acellular samples on the microscopic level. Once these methods are optimized, we can better verify whether the optical properties of the cellular and acellular collagen samples differ.
Novel applications of the dispersive optical model
Dickhoff, W. H.; Charity, R. J.; Mahzoon, M. H.
2017-03-01
A review of recent developments of the dispersive optical model (DOM) is presented. Starting from the original work of Mahaux and Sartor, several necessary steps are developed and illustrated which increase the scope of the DOM allowing its interpretation as generating an experimentally constrained functional form of the nucleon self-energy. The method could therefore be renamed as the dispersive self-energy method. The aforementioned steps include the introduction of simultaneous fits of data for chains of isotopes or isotones allowing a data-driven extrapolation for the prediction of scattering cross sections and level properties in the direction of the respective drip lines. In addition, the energy domain for data was enlarged to include results up to 200 MeV where available. An important application of this work was implemented by employing these DOM potentials to the analysis of the (d, p) transfer reaction using the adiabatic distorted wave approximation. We review these calculations which suggest that physically meaningful results are easier to obtain by employing DOM ingredients as compared to the traditional approach which relies on a phenomenologically-adjusted bound-state wave function combined with a global (nondispersive) optical-model potential. Application to the exotic 132Sn nucleus also shows great promise for the extrapolation of DOM potentials towards the drip line with attendant relevance for the physics of FRIB. We note that the DOM method combines structure and reaction information on the same footing providing a unique approach to the analysis of exotic nuclei. We illustrate the importance of abandoning the custom of representing the non-local Hartree–Fock (HF) potential in the DOM by an energy-dependent local potential as it impedes the proper normalization of the solution of the Dyson equation. This important step allows for the interpretation of the DOM potential as representing the nucleon self-energy permitting the calculations of
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
On the basis of analysis on the temperature monitoring methods for high voltage devices, a new type of fiber optic sensor structure with reference channel is given. And the operation principle of fiber optic sensor is analysed at large based on the absorption of semiconductor chip. The mathematical model of both devices and the whole system are also given. It is proved by the experiment that this mathematical model is reliable.
The Maxwell-Lorentz Model for optical Pulses
DEFF Research Database (Denmark)
Sørensen, Mads Peter; Brio, Moysey
2007-01-01
Dynamics of optical pulses, especially of ultra short femtosecond pulses, are of great technological and theoretical interest. The dynamics of optical pulses is usually studied using the nonlinear Schrodinger (NLS) equation model. While such approach works surprisingly well for description of pulse...
HCMT models of optical microring-resonator circuits
Lohmeyer, Manfred
2010-01-01
Circuits of dielectric integrated optical microring resonators are addressed through a two-dimensional hybrid analytical/numerical coupled mode theory (HCMT) model. Analytical modes of all straight and curved cores form templates for the optical fields of the entire circuits. Our variational techniq
Activities at Los Alamos for the optical model segment of the RIPL CRP
Energy Technology Data Exchange (ETDEWEB)
Young, P.G.
1997-05-10
This report discusses activity at Los Alamos on the nuclear optical model. In particular, the following topics are discussed: format of the optical model parameter library; contents of the library; validation of the optical model library; and conclusions and recommendations.
BeamOptics : a Symbolic Platform for Modeling and the Solution of Beam Optics System
Energy Technology Data Exchange (ETDEWEB)
Yu-Chiu Chao
2000-11-01
BeamOptics [1] is a Mathematica-based computing platform devoted to the following objectives: (1) Structured representation and manipulation of particle beam optics systems with symbolic capabilities, (2) Analytical and numerical modeling of beam optics system behaviors, (3) Solution to specific beam optical or general accelerator system problems, in algebraic form in certain cases, through customized algorithms. Taking advantage of and conforming to the highly formal and self-contained structure of Mathematica, BeamOptics provides a unique platform for developing accelerator design and analysis programs. The feature of symbolic computation and the ability to manipulate the beam optics system at the programming language level enable the user to solve or optimize his system with considerably more efficiency, rigour and insight than can be easily achieved with passive modeling or numerical simulation methods. BeamOptics is developed with continuous evolution in mind. New features and algorithms from diverse sources can be incorporated without major modification, due to its formal and generic structure. In this report, a survey is given of the basic structure and methodology of BeamOptics, as well as a demonstration of some of its more specialized applications, and possible direction of evolution.
Analytical models of optical response in one-dimensional semiconductors
Energy Technology Data Exchange (ETDEWEB)
Pedersen, Thomas Garm, E-mail: tgp@nano.aau.dk
2015-09-04
The quantum mechanical description of the optical properties of crystalline materials typically requires extensive numerical computation. Including excitonic and non-perturbative field effects adds to the complexity. In one dimension, however, the analysis simplifies and optical spectra can be computed exactly. In this paper, we apply the Wannier exciton formalism to derive analytical expressions for the optical response in four cases of increasing complexity. Thus, we start from free carriers and, in turn, switch on electrostatic fields and electron–hole attraction and, finally, analyze the combined influence of these effects. In addition, the optical response of impurity-localized excitons is discussed. - Highlights: • Optical response of one-dimensional semiconductors including excitons. • Analytical model of excitonic Franz–Keldysh effect. • Computation of optical response of impurity-localized excitons.
Mark formation model for optical rewritable recording
Brusche, J.H.
2007-01-01
Optically rewritable discs contain one or more so-called recording stacks. These stacks consist of various grooved layers. At least one of these layers contains a so-called phase-change material. In the recording layer, amorphous regions are formed on a crystalline background by means of high power
Mark formation modeling in optical rewritable recording
Brusche, J.H.; Segal, A.; Vuik, C.; Urbach, H.P.
2006-01-01
In optical rewritable recording media, such as the Blu-ray Disc, amorphous marks are formed on a crystalline background of a phase-change layer, by means of short, high power laser pulses. In order to improve this data storage concept, it is of great importance to understand the mark formation
Mark formation modeling in optical rewritable recording
Brusche, J.H.; Segal, A.; Vuik, C.; Urbach, H.P.
2006-01-01
In optical rewritable recording media, such as the Blu-ray Disc, amorphous marks are formed on a crystalline background of a phase-change layer, by means of short, high power laser pulses. In order to improve this data storage concept, it is of great importance to understand the mark formation proce
DISSYMMETRY MODEL OF MOLECULAR POLARIZABILITY AND OPTICAL ACTIVITY
Institute of Scientific and Technical Information of China (English)
周志华; 汤杰
1991-01-01
Dissymmetry model of molecular polarizability divided into some layers within a sphere,some rules and sequence according to the magnitude of polarizability replaced by bond refraction for many groups have been suggested.The relationship between the dissymmetry of molecular polarizability arrounding the dissymmetric carbon atom and the direction of optical activity has been discussed .The accuracy is above 95 persent to use our model and rules to determine over 6000 compounds of optical activity.
Soliton models in resonant and nonresonant optical ﬁbers
Indian Academy of Sciences (India)
K Porsezian
2001-11-01
In this review, considering the important linear and nonlinear optical effects like group velocity dispersion, higher order dispersion, Kerr nonlinearity, self-steepening, stimulated Raman scattering, birefringence, self-induced transparency and various inhomogeneous effects in ﬁbers, the completely integrable concept and bright, dark and self-induced transparency soliton models in nonlinear ﬁber optics are discussed. Considering the above important optical effects, the different completely integrable soliton models in the form of nonlinear Schrödinger (NLS), NLS-MaxwellBloch (MB) type equations reported in the literature are discussed. Finally, solitons in stimulated Raman scattering (SRS) system is brieﬂy discussed.
Hamadou, A.; Thobel, J.-L.; Lamari, S.
2016-10-01
A four level rate equations model for a terahertz optically pumped electrically driven quantum cascade laser is here introduced and used to model the system both analytically and numerically. In the steady state, both in the presence and absence of the terahertz optical field, we solve the resulting nonlinear system of equations and obtain closed form expressions for the levels occupation, population inversion as well as the mid-infrared pump threshold intensity in terms of the device parameters. We also derive, for the first time for this system, an analytical formula for the optical external efficiency and analyze the simultaneous effects of the cavity length and pump intensity on it. At moderate to high pump intensities, we find that the optical external efficiency scales roughly as the reciprocal of the cavity length.
Study of Optical Models Regarding the Human Eye
Directory of Open Access Journals (Sweden)
Maryam Abolmasoomi
2011-03-01
Full Text Available Introduction: Until now, many models have been presented for optical study of the human eye. In recent years, surgery on the anterior section of the eye (such as cataract and photo-refractive surgery has increased, so a study on the optics of the eye and evaluation of vision quality has become more important. Material and Methods: In this article, some of these models are considered. They include models with spherical and conic-section surfaces (for cornea and lens, simple models and new models with complex surfaces. Results: Evaluation of the optical models of the eye provides the possibility of enhancing the representation of human vision and also increasing the accuracy of surgery on the anterior section of the eye to enable higher quality vision.
Theoretical model for a Faraday anomalous dispersion optical filter
Yin, B.; Shay, T. M.
1991-01-01
A model for the Faraday anomalous dispersion optical filter is presented. The model predicts a bandwidth of 0.6 GHz and a transmission peak of 0.98 for a filter operating on the Cs (D2) line. The model includes hyperfine effects and is valid for arbitrary magnetic fields.
Modeling plasmonic scattering combined with thin-film optics.
Schmid, M; Klenk, R; Lux-Steiner, M Ch; Topic, M; Krc, J
2011-01-14
Plasmonic scattering from metal nanostructures presents a promising concept for improving the conversion efficiency of solar cells. The determination of optimal nanostructures and their position within the solar cell is crucial to boost the efficiency. Therefore we established a one-dimensional optical model combining plasmonic scattering and thin-film optics to simulate optical properties of thin-film solar cells including metal nanoparticles. Scattering models based on dipole oscillations and Mie theory are presented and their integration in thin-film semi-coherent optical descriptions is explained. A plasmonic layer is introduced in the thin-film structure to simulate scattering properties as well as parasitic absorption in the metal nanoparticles. A proof of modeling concept is given for the case of metal-island grown silver nanoparticles on glass and ZnO:Al/glass substrates. Using simulations a promising application of the nanoparticle integration is shown for the case of CuGaSe(2) solar cells.
Optical Propagation Modeling for the National Ignition Facility
Energy Technology Data Exchange (ETDEWEB)
Williams, W H; Auerbach, J M; Henesian, M A; Jancaitis, K S; Manes, K R; Mehta, N C; Orth, C D; Sacks, R A; Shaw, M J; Widmayer, C C
2004-01-12
Optical propagation modeling of the National Ignition Facility has been utilized extensively from conceptual design several years ago through to early operations today. In practice we routinely (for every shot) model beam propagation starting from the waveform generator through to the target. This includes the regenerative amplifier, the 4-pass rod amplifier, and the large slab amplifiers. Such models have been improved over time to include details such as distances between components, gain profiles in the laser slabs and rods, transient optical distortions due to the flashlamp heating of laser slabs, measured transmitted and reflected wavefronts for all large optics, the adaptive optic feedback loop, and the frequency converter. These calculations allow nearfield and farfield predictions in good agreement with measurements.
Computer Modeling for Optical Waveguide Sensors.
1987-12-15
COSATI CODES 18 SUBJECT TERMS (Continue on reverse it necessary and cleritify by DIock numnerl FIEL GRUP SB-GOUP Optical waveguide sensors Computer...reflection. The resultant probe beam transmission may be plotted as a function of changes in the refractive index of the surrounding fluid medium. BASIC...all angles of incidence about the critical angle ecr. It should be noted that N in equation (3) is a function of e, since = sin - l sin 8 , see
Optical Turbulence Characterization by WRF model above Ali, Tibet
Wang, Hongshuai; Yao, Yongqiang; Liu, Liyong; Qian, Xuan; Yin, Jia
2015-04-01
Atmospheric optical turbulence modeling and forecast for astronomy is a relatively recent discipline, but has played important roles in site survey, optimization of large telescope observing tables, and in the applications of adaptive optics technique. The numerical approach, by using of meteorological parameters and parameterization of optical turbulence, can provide all the optical turbulence parameters related, such as C2n profile, coherent length, wavefront coherent time, seeing, isoplanatic angle, and so on. This is particularly interesting for searching new sites without the long and expensive site testing campaigns with instruments. Earlier site survey results by the site survey team of National Astronomical Observatories of China imply that the south-west Tibet, Ali, is one of the world best IR and sub-mm site. For searching the best site in Ali area, numerical approach by Weather and Research Forecasting (WRF) model had been used to evaluate the climatology of the optical turbulence. The WRF model is configured over a domain 200km×200km with 1km horizontal resolution and 65 vertical levels from ground to the model top(10millibars) in 2010. The initial and boundary conditions for the model are provided by the 1° × 1° Global Final Analysis data from NCEP. The distribution and seasonal variation of optical turbulence parameters over this area are presented.
An electrical model of VCSEL as optical transmitter for optical printed circuit board
Kim, Do-Kyoon; Yoon, Young-Seol; Choi, Jin-Ho; Kim, Kyung-Min; Choi, Young-Wan; Lee, Seok
2005-03-01
Optical interconnection is recent issue for high-speed data transmission. The limitation of high-speed electrical data transmission is caused by impedance mismatching, electric field coupling, microwave loss, and different length of the electrical signal lines. To overcome these limitations, the electrical signal in the current electrical system has to be changed by the optical signal. The most suitable optical source in the OPCB (Optical Printed Circuit Board) is VCSEL (Vertical Cavity Surface Emitting Lasers) that is low-priced and has the characteristic of vertical surface emitting. In this paper, we propose an electrical model of the VCSEL as E/O converting devices for the OPCB. The equivalent circuit of the VCSEL based on the rate equations includes carrier dynamics and material properties. The rate equation parameters are obtained by full analysis based on rate equation and experiment results. The electrical model of the VCSEL has the series resistance determined by I-V characteristic curve, and the parallel capacitance by the parasitic response of the VCSEL chip. The bandwidth of the optical interconnection is analyzed considering those parameters. We design and fabricate the optical transmitter for OPCB considering proposed electrical model of VCSEL.
Modeling of Nonlinear Signal Distortion in Fiber-Optical Networks
Johannisson, Pontus
2013-01-01
A low-complexity model for signal quality prediction in a nonlinear fiber-optical network is developed. The model, which builds on the Gaussian noise model, takes into account the signal degradation caused by a combination of chromatic dispersion, nonlinear signal distortion, and amplifier noise. The center frequencies, bandwidths, and transmit powers can be chosen independently for each channel, which makes the model suitable for analysis and optimization of resource allocation, routing, and scheduling in large-scale optical networks applying flexible-grid wavelength-division multiplexing.
Photonic encryption : modeling and functional analysis of all optical logic.
Energy Technology Data Exchange (ETDEWEB)
Tang, Jason D.; Schroeppel, Richard Crabtree; Robertson, Perry J.
2004-10-01
With the build-out of large transport networks utilizing optical technologies, more and more capacity is being made available. Innovations in Dense Wave Division Multiplexing (DWDM) and the elimination of optical-electrical-optical conversions have brought on advances in communication speeds as we move into 10 Gigabit Ethernet and above. Of course, there is a need to encrypt data on these optical links as the data traverses public and private network backbones. Unfortunately, as the communications infrastructure becomes increasingly optical, advances in encryption (done electronically) have failed to keep up. This project examines the use of optical logic for implementing encryption in the photonic domain to achieve the requisite encryption rates. This paper documents the innovations and advances of work first detailed in 'Photonic Encryption using All Optical Logic,' [1]. A discussion of underlying concepts can be found in SAND2003-4474. In order to realize photonic encryption designs, technology developed for electrical logic circuits must be translated to the photonic regime. This paper examines S-SEED devices and how discrete logic elements can be interconnected and cascaded to form an optical circuit. Because there is no known software that can model these devices at a circuit level, the functionality of S-SEED devices in an optical circuit was modeled in PSpice. PSpice allows modeling of the macro characteristics of the devices in context of a logic element as opposed to device level computational modeling. By representing light intensity as voltage, 'black box' models are generated that accurately represent the intensity response and logic levels in both technologies. By modeling the behavior at the systems level, one can incorporate systems design tools and a simulation environment to aid in the overall functional design. Each black box model takes certain parameters (reflectance, intensity, input response), and models the optical ripple
Modelling of new generation plasma optical devices
Directory of Open Access Journals (Sweden)
Litovko Irina V.
2016-06-01
Full Text Available The paper presents new generation plasma optical devices based on the electrostatic plasma lens configuration that opens a novel attractive possibility for effective high-tech practical applications. Original approaches to use of plasma accelerators with closed electron drift and open walls for the creation of a cost-effective low-maintenance plasma lens with positive space charge and possible application for low-cost, low-energy rocket engine are described. The preliminary experimental, theoretical and simulation results are presented. It is noted that the presented plasma devices are attractive for many different applications in the state-of-the-art vacuum-plasma processing.
Modeling Coastal Ocean Optical Properties for Coupled Circulation and Ecosystem Models
2016-06-07
Modeling Coastal Ocean Optical Properties for Coupled Circulation and Ecosystem Models Curtis D. Mobley Sequoia Scientific , Inc. 2700 Richards...N00014D01610002 http://www.onr.navy.mil/sci_tech/32/322/ocean_optics_biology.asp LONG-TERM GOAL The overall goal of this work , now completed, was to...wrong by orders of magnitude in Case 2 or optically shallow waters. The objective of this work was develop a radiative transfer model that can be
Ray-tracing optical modeling of negative dysphotopsia
Hong, Xin; Liu, Yueai; Karakelle, Mutlu; Masket, Samuel; Fram, Nicole R.
2011-12-01
Negative dysphotopsia is a relatively common photic phenomenon that may occur after implantation of an intraocular lens. The etiology of negative dysphotopsia is not fully understood. In this investigation, optical modeling was developed using nonsequential-component Zemax ray-tracing technology to simulate photic phenomena experienced by the human eye. The simulation investigated the effects of pupil size, capsulorrhexis size, and bag diffusiveness. Results demonstrated the optical basis of negative dysphotopsia. We found that photic structures were mainly influenced by critical factors such as the capsulorrhexis size and the optical diffusiveness of the capsular bag. The simulations suggested the hypothesis that the anterior capsulorrhexis interacting with intraocular lens could induce negative dysphotopsia.
Directory of Open Access Journals (Sweden)
Yajie Jiang
2015-06-01
Full Text Available The optical properties of perovskites at ambient temperatures are important both to the design of optimised solar cells as well as in other areas such as the refinement of electronic band structure calculations. Limited previous information on the optical modelling has been published. The experimental fitting parameters for optical constants of CH3NH3PbI3−xClx and CH3NH3PbI3 perovskite films are reported at 297 K as determined by detailed analysis of reflectance and transmittance data. The data in this study is related to the research article “Room temperature optical properties of organic–inorganic lead halide perovskites” in Solar Energy Materials & Solar Cells [1].
Optical characterisation of nanostructures using a discretised forward model
DEFF Research Database (Denmark)
Karamehmedovic, Mirza; Sørensen, Mads Peter; Hansen, Poul-Erik
2012-01-01
Optical diffraction microscopy (ODM) is a non-destructive and relatively inexpensive means of characterisation of nanostructures. It is an essential tool in the design, production and quality control of functional nanomaterials. In ODM, the target is reconstructed from the measured optical power...... problem. Finally, the size of the measured nanostructure is typically comparable to the wavelength of the illuminating light, so the scattering needs to be described using the full Maxwellian electromagnetic model, rather than (numerically inexpensive) asymptotic formulations. We here describe...
Eikonal solutions to optical model coupled-channel equations
Cucinotta, Francis A.; Khandelwal, Govind S.; Maung, Khin M.; Townsend, Lawrence W.; Wilson, John W.
1988-01-01
Methods of solution are presented for the Eikonal form of the nucleus-nucleus coupled-channel scattering amplitudes. Analytic solutions are obtained for the second-order optical potential for elastic scattering. A numerical comparison is made between the first and second order optical model solutions for elastic and inelastic scattering of H-1 and He-4 on C-12. The effects of bound-state excitations on total and reaction cross sections are also estimated.
Particle-Hole Optical Model: Fantasy or Reality?
Urin, M H
2010-01-01
An attempt to formulate the optical model of particle-hole-type excitations (including giant resonances) is undertaken. The model is based on the Bethe--Goldstone equation for the particle-hole Green function. This equation involves a specific energy-dependent particle-hole interaction that is due to virtual excitation of many-quasiparticle configurations and responsible for the spreading effect. After energy averaging, this interaction involves an imaginary part. The analogy between the single-quasiparticle and particle-hole optical models is outlined.
Remark on: the neutron spherical optical-model absorption.
Energy Technology Data Exchange (ETDEWEB)
Smith, A. B.; Nuclear Engineering Division
2007-06-30
The energy-dependent behavior of the absorption term of the spherical neutron optical potential for doubly magic {sup 208}Pb and the neighboring {sup 209}Bi is examined. These considerations suggest a phenomenological model that results in an intuitively attractive energy dependence of the imaginary potential that provides a good description of the observed neutron cross sections and that is qualitatively consistent with theoretical concepts. At the same time it provides an alternative to some of the arbitrary assumptions involved in many conventional optical-model interpretations reported in the literature and reduces the number of the parameters of the model.
Event-Based Corpuscular Model for Quantum Optics Experiments
Michielsen, K.; Jin, F.; Raedt, H. De
2011-01-01
A corpuscular simulation model of optical phenomena that does not require the knowledge of the solution of a wave equation of the whole system and reproduces the results of Maxwell's theory by generating detection events one-by-one is presented. The event-based corpuscular model is shown to give a u
Event-Based Corpuscular Model for Quantum Optics Experiments
Michielsen, K.; Jin, F.; Raedt, H. De
A corpuscular simulation model of optical phenomena that does not require the knowledge of the solution of a wave equation of the whole system and reproduces the results of Maxwell's theory by generating detection events one-by-one is presented. The event-based corpuscular model is shown to give a
Event-based Simulation Model for Quantum Optics Experiments
De Raedt, H.; Michielsen, K.; Jaeger, G; Khrennikov, A; Schlosshauer, M; Weihs, G
2011-01-01
We present a corpuscular simulation model of optical phenomena that does not require the knowledge of the solution of a wave equation of the whole system and reproduces the results of Maxwell's theory by generating detection events one-by-one. The event-based corpuscular model gives a unified
Optical linear algebra processors: noise and error-source modeling.
Casasent, D; Ghosh, A
1985-06-01
The modeling of system and component noise and error sources in optical linear algebra processors (OLAP's) are considered, with attention to the frequency-multiplexed OLAP. General expressions are obtained for the output produced as a function of various component errors and noise. A digital simulator for this model is discussed.
Optical linear algebra processors - Noise and error-source modeling
Casasent, D.; Ghosh, A.
1985-01-01
The modeling of system and component noise and error sources in optical linear algebra processors (OLAPs) are considered, with attention to the frequency-multiplexed OLAP. General expressions are obtained for the output produced as a function of various component errors and noise. A digital simulator for this model is discussed.
Integrating Environmental Optics into Multidisciplinary, Predictive Models of Ocean Dynamics
2011-09-30
development has been based on decades of published research, our depth-integrated, spectral model of photosynthesis and the absorption -based model of...color, chlorophyll fluorescence, or spectral absorption coefficients. We extend the approach to include additional biological properties such as...of laboratory experiments in which photosynthesis , fluorescence and optical properties of phytoplankton are measured under a range of conditions
Extended Hubbard models for ultracold atoms in optical lattices
Energy Technology Data Exchange (ETDEWEB)
Juergensen, Ole
2015-06-05
In this thesis, the phase diagrams and dynamics of various extended Hubbard models for ultracold atoms in optical lattices are studied. Hubbard models are the primary description for many interacting particles in periodic potentials with the paramount example of the electrons in solids. The very same models describe the behavior of ultracold quantum gases trapped in the periodic potentials generated by interfering beams of laser light. These optical lattices provide an unprecedented access to the fundamentals of the many-particle physics that govern the properties of solid-state materials. They can be used to simulate solid-state systems and validate the approximations and simplifications made in theoretical models. This thesis revisits the numerous approximations underlying the standard Hubbard models with special regard to optical lattice experiments. The incorporation of the interaction between particles on adjacent lattice sites leads to extended Hubbard models. Offsite interactions have a strong influence on the phase boundaries and can give rise to novel correlated quantum phases. The extended models are studied with the numerical methods of exact diagonalization and time evolution, a cluster Gutzwiller approximation, as well as with the strong-coupling expansion approach. In total, this thesis demonstrates the high relevance of beyond-Hubbard processes for ultracold atoms in optical lattices. Extended Hubbard models can be employed to tackle unexplained problems of solid-state physics as well as enter previously inaccessible regimes.
Numerical model for thermal parameters in optical materials
Sato, Yoichi; Taira, Takunori
2016-04-01
Thermal parameters of optical materials, such as thermal conductivity, thermal expansion, temperature coefficient of refractive index play a decisive role for the thermal design inside laser cavities. Therefore, numerical value of them with temperature dependence is quite important in order to develop the high intense laser oscillator in which optical materials generate excessive heat across mode volumes both of lasing output and optical pumping. We already proposed a novel model of thermal conductivity in various optical materials. Thermal conductivity is a product of isovolumic specific heat and thermal diffusivity, and independent modeling of these two figures should be required from the viewpoint of a clarification of physical meaning. Our numerical model for thermal conductivity requires one material parameter for specific heat and two parameters for thermal diffusivity in the calculation of each optical material. In this work we report thermal conductivities of various optical materials as Y3Al5O12 (YAG), YVO4 (YVO), GdVO4 (GVO), stoichiometric and congruent LiTaO3, synthetic quartz, YAG ceramics and Y2O3 ceramics. The dependence on Nd3+-doping in laser gain media in YAG, YVO and GVO is also studied. This dependence can be described by only additional three parameters. Temperature dependence of thermal expansion and temperature coefficient of refractive index for YAG, YVO, and GVO: these are also included in this work for convenience. We think our numerical model is quite useful for not only thermal analysis in laser cavities or optical waveguides but also the evaluation of physical properties in various transparent materials.
Assimilation of Bio-Optical Properties into Coupled Physical, Bio-Optical Coastal Model
2013-01-01
analysis (updated) fields for the bio-optical model state variables are derived from: Proc. of SPIE Vol. 8724 87240E-3 Downloaded From: http...proceedings.spiedigitallibrary.org/ on 07/11/2013 Terms of Use: http://spiedl.org/terms ),XY(XX fofa HK −+= aX fX oY (1) where is vector of the
Classification of scalar and dyadic nonlocal optical response models.
Wubs, M
2015-11-30
Nonlocal optical response is one of the emerging effects on the nanoscale for particles made of metals or doped semiconductors. Here we classify and compare both scalar and tensorial nonlocal response models. In the latter case the nonlocality can stem from either the longitudinal response, the transverse response, or both. In phenomenological scalar models the nonlocal response is described as a smearing out of the commonly assumed infinitely localized response, as characterized by a distribution with a finite width. Here we calculate explicitly whether and how tensorial models, such as the hydrodynamic Drude model and generalized nonlocal optical response theory, follow this phenomenological description. We find considerable differences, for example that nonlocal response functions, in contrast to simple distributions, assume negative and complex values. Moreover, nonlocal response regularizes some but not all diverging optical near fields. We identify the scalar model that comes closest to the hydrodynamic model. Interestingly, for the hydrodynamic Drude model we find that actually only one third (1/3) of the free-electron response is smeared out nonlocally. In that sense, nonlocal response is stronger for transverse and scalar nonlocal response models, where the smeared-out fractions are 2/3 and 3/3, respectively. The latter two models seem to predict novel plasmonic resonances also below the plasma frequency, in contrast to the hydrodynamic model that predicts standing pressure waves only above the plasma frequency.
Polarization Drift Channel Model for Coherent Fibre-Optic Systems
Czegledi, Cristian B; Agrell, Erik; Johannisson, Pontus
2015-01-01
A theoretical framework is introduced to model the dynamical changes of the state of polarization during transmission in coherent fibre-optic systems. The model generalizes the one-dimensional phase noise random walk to higher dimensions, accounting for random polarization drifts. The model is described in the Jones, Stokes and real 4-dimensional formalisms, and the mapping between them is derived. Such a model will be increasingly important in simulating and optimizing future optical systems, which to a higher and higher degree rely on transmission and detection on both polarizations jointly using sophisticated digital signal processing. Such analysis cannot be carried out using the more rudimentary polarization drift models in use today, which only account for deterministic effects. The proposed polarization drift model is the first of its kind and will likely be useful in a wide-range of photonics applications where stochastic polarization fluctuation is an issue.
Modeling light–tissue interaction in optical coherence tomography systems
DEFF Research Database (Denmark)
Andersen, Peter E.; Jørgensen, Thomas Martini; Thrane, Lars
2015-01-01
Optical coherence tomography (OCT) performs high-resolution, cross-sectional tomographic imaging of the internal tissue microstructure by measuring backscattered or backreflected light. The scope of this chapter is to present analytical and numerical models that are able to describe light......-tissue interactions and its influence on the performance of OCT systems including multiple scattering effects in heterogeneous media. In general, these models, analytical as well as numerical, may serve as important tools for improving interpretation of OCT images and also serve as prerequisites for extraction...... of tissue optical scattering parameters....
Artificial Neural Network Model for Optical Fiber Direction Coupler Design
Institute of Scientific and Technical Information of China (English)
李九生; 鲍振武
2004-01-01
A new approach to the design of the optical fiber direction coupler by using neural network is proposed. To train the artificial neural network,the coupling length is defined as the input sample, and the coupling ratio is defined as the output sample. Compared with the numerical value calculation of the theoretical formula, the error of the neural network model output is 1% less.Then, through the model, to design a broadband or a single wavelength optical fiber direction coupler becomes easy. The method is proved to be reliable, accurate and time-saving. So it is promising in the field of both investigation and application.
A Fourier Optical Model for the Laser Doppler Velocimeter
DEFF Research Database (Denmark)
Lading, Lars
1972-01-01
The treatment is based on a fourier optical model. It is shown how the various configurations (i.e. ldquodifferential moderdquo and reference beam mode with both one and two incident beams) are incorporated in the model, and how it can be extended to three dimensions. The particles are represented...... filtering ability vanishes as the aperture size converges towards zero. The results based on fourier optics are compared with the rough estimates obtainable by using the "antenna formular" for heterodyning (ArΩr≈λ2)....
Optical-based spectral modeling of infrared focal plane arrays
Mouzali, Salima; Lefebvre, Sidonie; Rommeluère, Sylvain; Ferrec, Yann; Primot, Jérôme
2016-07-01
We adopt an optical approach in order to model and predict the spectral signature of an infrared focal plane array. The modeling is based on a multilayer description of the structure and considers a one-dimensional propagation. It provides a better understanding of the physical phenomena occurring within the pixels, which is useful to perform radiometric measurements, as well as to reliably predict the spectral sensitivity of the detector. An exhaustive model is presented, covering the total spectral range of the pixel response. A heuristic model is also described, depicting a complementary approach that separates the different optical phenomena inside the pixel structure. Promising results are presented, validating the models through comparison with experimental results. Finally, advantages and limitations of this approach are discussed.
Electron Correlation Models for Optical Activity
DEFF Research Database (Denmark)
Höhn, E. G.; O. E. Weigang, Jr.
1968-01-01
A two-system no-overlap model for rotatory strength is developed for electric-dipole forbidden as well as allowed transitions. General equations which allow for full utilization of symmetry in the chromophore and in the environment are obtained. The electron correlation terms are developed in full...
Modeling, fabrication and high power optical characterization of plasmonic waveguides
DEFF Research Database (Denmark)
Lavrinenko, Andrei; Lysenko, Oleg
2015-01-01
This paper describes modeling, fabrication and high power optical characterization of thin gold films embedded in silicon dioxide. The propagation vector of surface plasmon polaritons has been calculated by the effective index method for the wavelength range of 750-1700 nm and film thickness of 1...
Classification of scalar and dyadic nonlocal optical response models
DEFF Research Database (Denmark)
Wubs, Martijn
2015-01-01
Nonlocal optical response is one of the emerging effects on the nanoscale for particles made of metals or doped semiconductors. Here we classify and compare both scalar and tensorial nonlocal response models. In the latter case the nonlocality can stem from either the longitudinal response...
Fast Cherenkov model of optical photons generation and transportation
The ATLAS collaboration
2017-01-01
This note describes the technical details of Fast Cherenkov model of optical photons generation and transportation: in particular, the mechanism of Cherenkov photons transportation through the straight bar geometry. As an example of usage, the implemetation of the method inside Quartic detector simulation in GEANT4 will be presented and compared to the nominal results.
Modelling exciton–phonon interactions in optically driven quantum dots
DEFF Research Database (Denmark)
Nazir, Ahsan; McCutcheon, Dara
2016-01-01
We provide a self-contained review of master equation approaches to modelling phonon effects in optically driven self-assembled quantum dots. Coupling of the (quasi) two-level excitonic system to phonons leads to dissipation and dephasing, the rates of which depend on the excitation conditions...
Three dimensional rigorous model for optical scattering problems
Wei, X.
2006-01-01
We present a three-dimensional model based on the finite element method for solving the time-harmonic Maxwell equation in optics. It applies to isotropic or anisotropic dielectrics and metals, and to many configurations such as an isolated scatterer in a multilayer, bi-gratings and crystals. We shal
Quantum Electrostatic Model for Optical Properties of Nanoscale Gold Films
Directory of Open Access Journals (Sweden)
Qian Haoliang
2015-11-01
Full Text Available The optical properties of thin gold films with thickness varying from 2.5 nm to 30 nm are investigated. Due to the quantum size effect, the optical constants of the thin gold film deviate from the Drude model for bulk material as film thickness decreases, especially around 2.5 nm, where the electron energy level becomes discrete. A theory based on the self-consistent solution of the Schrödinger equation and the Poisson equation is proposed and its predictions agree well with experimental results.
Modeling, fabrication and high power optical characterization of plasmonic waveguides
DEFF Research Database (Denmark)
Lavrinenko, Andrei; Lysenko, Oleg
2015-01-01
This paper describes modeling, fabrication and high power optical characterization of thin gold films embedded in silicon dioxide. The propagation vector of surface plasmon polaritons has been calculated by the effective index method for the wavelength range of 750-1700 nm and film thickness of 15......, 30 and 45 nm. The fabrication process of such plasmonic waveguides with width in the range of 1-100 μm and their quality inspection are described. The results of optical characterization of plasmonic waveguides using a high power laser with the peak power wavelength 1064 nm show significant deviation...
Trapped ions in optical lattices for probing oscillator chain models
Pruttivarasin, Thaned; Talukdar, Ishan; Kreuter, Axel; Haeffner, Hartmut
2011-01-01
We show that a chain of trapped ions embedded in microtraps generated by an optical lattice can be used to study oscillator models related to dry friction and energy transport. Numerical calculations with realistic experimental parameters demonstrate that both static and dynamic properties of the ion chain change significantly as the optical lattice power is varied. Finally, we lay out an experimental scheme to use the spin degree of freedom to probe the phase space structure and quantum critical behavior of the ion chain.
Computational Modeling of Ultrafast Pulse Propagation in Nonlinear Optical Materials
Goorjian, Peter M.; Agrawal, Govind P.; Kwak, Dochan (Technical Monitor)
1996-01-01
There is an emerging technology of photonic (or optoelectronic) integrated circuits (PICs or OEICs). In PICs, optical and electronic components are grown together on the same chip. rib build such devices and subsystems, one needs to model the entire chip. Accurate computer modeling of electromagnetic wave propagation in semiconductors is necessary for the successful development of PICs. More specifically, these computer codes would enable the modeling of such devices, including their subsystems, such as semiconductor lasers and semiconductor amplifiers in which there is femtosecond pulse propagation. Here, the computer simulations are made by solving the full vector, nonlinear, Maxwell's equations, coupled with the semiconductor Bloch equations, without any approximations. The carrier is retained in the description of the optical pulse, (i.e. the envelope approximation is not made in the Maxwell's equations), and the rotating wave approximation is not made in the Bloch equations. These coupled equations are solved to simulate the propagation of femtosecond optical pulses in semiconductor materials. The simulations describe the dynamics of the optical pulses, as well as the interband and intraband.
Minimal model for optical transmission through holey metal films
Energy Technology Data Exchange (ETDEWEB)
MartIn-Moreno, L [Departamento de Fisica de la Materia Condensada-ICMA, Universidad de Zaragoza-CSIC, E-50009 Zaragoza (Spain); GarcIa-Vidal, F J [Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid, E-28049 Madrid (Spain)], E-mail: lmm@unizar.es
2008-07-30
This paper presents a tutorial on the computation of both extraordinary optical transmission and surface electromagnetic modes in holey metal films. Our model consists of a square array of square holes in a perfect conductor. It is shown that considering just the fundamental waveguide mode inside the holes captures the main features of the optical transmission, which allows us to obtain quasi-analytical results. Extraordinary optical transmission is unambiguously linked to the presence of surface electromagnetic modes in the corrugated structure. The particular case of surface electromagnetic modes in a perfect conductor is analyzed, paying attention to different strategies for increasing their confinement to the surface. The use of the energy loss of a charged particle passing close to the surface as a spectroscopic tool for these surface modes is also discussed.
Comprehensive analytical model to characterize randomness in optical waveguides.
Zhou, Junhe; Gallion, Philippe
2016-04-01
In this paper, the coupled mode theory (CMT) is used to derive the corresponding stochastic differential equations (SDEs) for the modal amplitude evolution inside optical waveguides with random refractive index variations. Based on the SDEs, the ordinary differential equations (ODEs) are derived to analyze the statistics of the modal amplitudes, such as the optical power and power variations as well as the power correlation coefficients between the different modal powers. These ODEs can be solved analytically and therefore, it greatly simplifies the analysis. It is demonstrated that the ODEs for the power evolution of the modes are in excellent agreement with the Marcuse' coupled power model. The higher order statistics, such as the power variations and power correlation coefficients, which are not exactly analyzed in the Marcuse' model, are discussed afterwards. Monte-Carlo simulations are performed to demonstrate the validity of the analytical model.
Field weighting model for tracking-integrated optics
Wheelwright, Brian; Angel, Roger; Coughenour, Blake; Hammer, Kimberly; Geary, Andrew; Stalcup, Thomas
2014-09-01
The emergent field of tracking-integrated optics enables a potentially low cost concentrating photovoltaic (CPV) implementation, where single-axis module tracking is complemented by an additional degree of freedom within the module [1,2,3,4,5]. Gross module tracking can take on multiple configurations, the most common being rotation about a polar or horizontal North-South oriented axis. Polar-axis tracking achieves >95% sunlight collection compared to dual-axis tracking[6], leaving the tracking-integrated optics to compensate for +/-23.5° seasonal variations. The collection efficiency of N-S horizontal axis tracking is latitude-dependent, with ˜90% collection relative to dual-axis tracking at 32.2° latitude. Horizontal tracking at higher latitudes shifts an increasing burden to the tracking-integrated optics, which must operate between two incidence angle extremes: summer solstice sunrise/sunset to winter solstice noon. An important aspect of tracking-integrated lens design is choosing a suitable field weighting to appropriately account for annual DNI received at each angle of incidence. We present a field weighting model, generalized for polar or horizontal module tracking at any latitude, which shows excellent agreement with measured insolation data. This model is particularly helpful for the design of tracking-integrated optics for horizontally-tracked modules, where the correct field weighting is asymmetric and significantly biased away from the normal incidence.
Some Advances in the Circuit Modeling of Extraordinary Optical Transmission
Directory of Open Access Journals (Sweden)
F. Medina
2009-06-01
Full Text Available The phenomenon of extraordinary optical transmission (EOT through electrically small holes perforated on opaque metal screens has been a hot topic in the optics community for more than one decade. This experimentally observed frequency-selective enhanced transmission of electromagnetic power through holes, for which classical Bethe's theory predicts very poor transmission, later attracted the attention of engineers working on microwave engineering or applied electromagnetics. Extraordinary transmission was ﬁrst linked to the plasma-like behavior of metals at optical frequencies. However, the primary role played by the periodicity of the distribution of holes was soon made evident, in such a way that extraordinary transmission was disconnected from the particular behavior of metals at optical frequencies. Indeed, the same phenomenon has been observed in the microwave and millimeter wave regime, for instance. Nowadays, the most commonly accepted theory explains EOT in terms of the interaction of the impinging plane wave with the surface plasmon-polariton-Bloch waves (SPP-Bloch supported by the periodically perforated plate. The authors of this paper have recently proposed an alternative model whose details will be brieﬂy summarized here. A parametric study of the predictions of the model and some new potential extensions will be reported to provide additional insight.
Time-domain model of quantum-dot semiconductor optical amplifiers for wideband optical signals.
Puris, D; Schmidt-Langhorst, C; Lüdge, K; Majer, N; Schöll, E; Petermann, K
2012-11-19
We present a novel theoretical time-domain model for a quantum dot semiconductor optical amplifier, that allows to simulate subpicosecond pulse propagation including power-based and phase-based effects. Static results including amplified spontaneous emission spectra, continuous wave amplification, and four-wave mixing experiments in addition to dynamic pump-probe simulations are presented for different injection currents. The model uses digital filters to describe the frequency dependent gain and microscopically calculated carrier-carrier scattering rates for the interband carrier dynamics. It can be used to calculate the propagation of multiple signals with different wavelengths or one wideband signal with high bitrate.
Multiple Fan-Beam Optical Tomography: Modelling Techniques
Directory of Open Access Journals (Sweden)
Pang Jon Fea
2009-10-01
Full Text Available This paper explains in detail the solution to the forward and inverse problem faced in this research. In the forward problem section, the projection geometry and the sensor modelling are discussed. The dimensions, distributions and arrangements of the optical fibre sensors are determined based on the real hardware constructed and these are explained in the projection geometry section. The general idea in sensor modelling is to simulate an artificial environment, but with similar system properties, to predict the actual sensor values for various flow models in the hardware system. The sensitivity maps produced from the solution of the forward problems are important in reconstructing the tomographic image.
Fiber optic displacement measurement model based on finite reflective surface
Li, Yuhe; Guan, Kaisen; Hu, Zhaohui
2016-10-01
We present a fiber optic displacement measurement model based on finite reflective plate. The theoretical model was derived, and simulation analysis of light intensity distribution, reflective plate width, and the distance between fiber probe and reflective plate were conducted in details. The three dimensional received light intensity distribution and the characteristic curve of light intensity were studied as functions of displacement of finite reflective plate. Experiments were carried out to verify the established model. The physical fundamentals and the effect of operating parameters on measuring system performance were revealed in the end.
Optical model for light distribution during transscleral cyclophotocoagulation
Energy Technology Data Exchange (ETDEWEB)
Nemati, B.; Dunn, A.; Welch, A.J.; Rylander, H.G. III [Medical Optics Laboratory, Biomedical Engineering Program, ENS 610, University of Texas, Austin, Texas 78712 (United States)
1998-02-01
Transscleral cyclophotocoagulation (TSCPC) is currently performed clinically as an effective treatment for end-stage glaucoma. We develop a theoretical model for the analysis of optical attenuation phenomena during TSCPC as a basis for selection of an optimal wavelength. A multilayered Monte Carlo model was developed to calculate the fluence and the rate of heat generation in each tissue layer for the wavelengths of Nd:YAG, diode, ruby, krypton yellow, and argon lasers. Of the five wavelengths under study, our theoretical results suggest that the diode laser wavelength offers the best penetration through the conjunctiva, sclera, and ciliary muscle and highest absorption within the ciliary pigment epithelium. {copyright} 1998 Optical Society of America.
Structural, thermal, optical and gravitational modelling for LISA
Energy Technology Data Exchange (ETDEWEB)
Merkowitz, Stephen M [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Conkey, Shelly [Swales Aerospace, 5050 Powder Mill Rd, Beltsville, MD 20705 (United States); Haile, William B [Swales Aerospace, 5050 Powder Mill Rd, Beltsville, MD 20705 (United States); KellyIII, William R [Swales Aerospace, 5050 Powder Mill Rd, Beltsville, MD 20705 (United States); Peabody, Hume [Swales Aerospace, 5050 Powder Mill Rd, Beltsville, MD 20705 (United States); Dumont, Philip J [Jet Propulsion Laboratory, Pasadena, CA 91109 (United States)
2004-03-07
The laser interferometer space antenna (LISA) mission uses laser interferometry to detect and observe gravitational waves from astrophysical sources. Modelling of LISA ultimately needs to forecast and interrelate the behaviour of the science input, structure, optics, control systems and many other factors that affect the performance of the flight hardware. These models include high precision STOP (structural-thermal-optical) analyses. In addition, self-gravity analyses of the spacecraft, based on the structural-thermal modelling results, are required for each analysis cycle to understand the gravitational interaction between the spacecraft components. The complete analysis cycle is called STOP-G. Several aspects of this analysis require unprecedented precision due to LISA's challenging design requirements. We present here a modelling approach designed to minimize analysis errors, particularly those that enter when mapping results from one modelling step to the next. Central to the approach is the use of a single model topology for all phases of the STOP-G analysis cycle. The feasibility of this approach was verified using a simplified model of the LISA spacecraft.
Optical Thin Film Modeling: Using FTG's FilmStar Software
Freese, Scott
2009-01-01
Every material has basic optical properties that define its interaction with light: The index of refraction (n) and extinction coefficient (k) vary for the material as a function of the wavelength of the incident light. Also significant are the phase velocity and polarization of the incident light These inherent properties allow for the accurate modeling of light s behavior upon contact with a surface: Reflectance, Transmittance, Absorptance.
Quantum-dot Semiconductor Optical Amplifiers in State Space Model
Institute of Scientific and Technical Information of China (English)
Hussein Taleb; Kambiz Abedi; Saeed Golmohammadi
2013-01-01
A state space model (SSM) is derived for quantum-dot semiconductor optical amplifiers (QD-SOAs).Rate equations of QD-SOA are formulated in the form of state update equations,where average occupation probabilities along QD-SOA cavity are considered as state variables of the system.Simulations show that SSM calculates QD-SOA's static and dynamic characteristics with high accuracy.
Probabilistic Modeling of Intracranial Pressure Effects on Optic Nerve Biomechanics
Ethier, C. R.; Feola, Andrew J.; Raykin, Julia; Myers, Jerry G.; Nelson, Emily S.; Samuels, Brian C.
2016-01-01
Altered intracranial pressure (ICP) is involved/implicated in several ocular conditions: papilledema, glaucoma and Visual Impairment and Intracranial Pressure (VIIP) syndrome. The biomechanical effects of altered ICP on optic nerve head (ONH) tissues in these conditions are uncertain but likely important. We have quantified ICP-induced deformations of ONH tissues, using finite element (FE) and probabilistic modeling (Latin Hypercube Simulations (LHS)) to consider a range of tissue properties and relevant pressures.
Modeling magneto-optical trapping of CaF molecules
Tarbutt, M. R.; Steimle, T. C.
2015-11-01
Magneto-optical trapping forces for molecules are far weaker than for alkali-metal atoms because the photon scattering rate is reduced when there are multiple ground states, and because of optical pumping into dark states. The force is further reduced when the upper state has a much smaller Zeeman splitting than the lower state. We use a rate model to estimate the strength of the trapping and damping forces in a magneto-optical trap (MOT) of CaF molecules, using either the A 2Π1 /2-X 2Σ+ transition or the B 2Σ+-X 2Σ+ transition. We identify a mechanism of magneto-optical trapping that arises when, in each beam of the MOT, two laser components with opposite polarizations and different detunings address the same transition. This mechanism produces a strong trapping force even when the upper state has little or no Zeeman splitting. It is the main mechanism responsible for the trapping force when the A 2Π1 /2-X 2Σ+ transition is used.
Modeling magneto-optical trapping of CaF molecules
Tarbutt, M R
2015-01-01
Magneto-optical trapping forces for molecules are far weaker than for alkali atoms because the photon scattering rate is reduced when there are multiple ground states, and because of optical pumping into dark states. The force is further reduced when the upper state has a much smaller Zeeman splitting than the lower state. We use a rate model to estimate the strength of the trapping and damping forces in a magneto-optical trap (MOT) of CaF molecules, using either the A$^{2}\\Pi_{1/2}$ - X$^{2}\\Sigma^{+}$ transition or the B$^{2}\\Sigma^{+}$ - X$^{2}\\Sigma^{+}$ transition. We identify a new mechanism of magneto-optical trapping that arises when, in each beam of the MOT, two laser components with opposite polarizations and different detunings address the same transition. This mechanism produces a strong trapping force even when the upper state has little or no Zeeman splitting. It is the main mechanism responsible for the trapping force when the A$^{2}\\Pi_{1/2}$ - X$^{2}\\Sigma^{+}$ transition is used.
Modeling of optical losses in perovskite solar cells
Taghavi, M. Javad; Houshmand, Mohammad; Zandi, M. Hossein; Gorji, Nima E.
2016-09-01
The optical losses within the structure of hybrid perovskite solar cells are investigated using only the optical properties of each layer e.g. refractive index and extinction coefficient. This model allows calculating the transmission/reflection rates at the interfaces and absorption loss within any layer. Then, the short circuit current density and loss percentage are calculated versus the perovskite and TiO2 thicknesses from 50 nm to 150 nm. To make our calculations closer to reality, we extracted the optical properties of each device component from the literature reports on glass/TCO/TiO2/perovskite/metal. The simulations were fitted with the experimental results of some relevant references. Our simulations show that ITO transmits the light better than SnO2 as the TCO front electrode, and the light reflection at both sides of the perovskite layer, e.g. at TiO2/perovskite and perovskite/Spiro-OMeTAD, is lower than 25%. The light interference and multiple reflections have been accounted in our calculations and finally we showed that a thicker TiO2 and perovskite cause more optical loss in current density due to stronger absorption.
Alliss, R.
2014-09-01
Optical turbulence (OT) acts to distort light in the atmosphere, degrading imagery from astronomical telescopes and reducing the data quality of optical imaging and communication links. Some of the degradation due to turbulence can be corrected by adaptive optics. However, the severity of optical turbulence, and thus the amount of correction required, is largely dependent upon the turbulence at the location of interest. Therefore, it is vital to understand the climatology of optical turbulence at such locations. In many cases, it is impractical and expensive to setup instrumentation to characterize the climatology of OT, so numerical simulations become a less expensive and convenient alternative. The strength of OT is characterized by the refractive index structure function Cn2, which in turn is used to calculate atmospheric seeing parameters. While attempts have been made to characterize Cn2 using empirical models, Cn2 can be calculated more directly from Numerical Weather Prediction (NWP) simulations using pressure, temperature, thermal stability, vertical wind shear, turbulent Prandtl number, and turbulence kinetic energy (TKE). In this work we use the Weather Research and Forecast (WRF) NWP model to generate Cn2 climatologies in the planetary boundary layer and free atmosphere, allowing for both point-to-point and ground-to-space seeing estimates of the Fried Coherence length (ro) and other seeing parameters. Simulations are performed using a multi-node linux cluster using the Intel chip architecture. The WRF model is configured to run at 1km horizontal resolution and centered on the Mauna Loa Observatory (MLO) of the Big Island. The vertical resolution varies from 25 meters in the boundary layer to 500 meters in the stratosphere. The model top is 20 km. The Mellor-Yamada-Janjic (MYJ) TKE scheme has been modified to diagnose the turbulent Prandtl number as a function of the Richardson number, following observations by Kondo and others. This modification
Modeling method and preliminary model of Asteroid Toutatis from Chang'E-2 optical images
Li, Xiang-Yu; Qiao, Dong
2014-06-01
Shape modeling is fundamental to the analysis of dynamic environment and motion around asteroid. Chang'E-2 successfully made a flyby of Asteroid 4179 Toutatis and obtained plenty of high-resolution images during the mission. In this paper, the modeling method and preliminary model of Asteroid Toutatis are discussed. First, the optical images obtained by Chang'E-2 are analyzed. Terrain and silhouette features in images are described. Then, the modeling method based on previous radar model and preliminary information from optical images is proposed. A preliminary polyhedron model of Asteroid Toutatis is established. Finally, the spherical harmonic coefficients of Asteroid Toutatis based on the polyhedron model are obtained. Some parameters of model are analyzed and compared. Although the model proposed in this paper is only a preliminary model, this work offers a valuable reference for future high-resolution models.
Model of optical response of marine aerosols to Forbush decreases
Directory of Open Access Journals (Sweden)
T. Bondo
2010-03-01
Full Text Available In order to elucidate the effect of galactic cosmic rays on cloud formation, we investigate the optical response of marine aerosols to Forbush decreases – abrupt decreases in galactic cosmic rays – by means of modeling. We vary the nucleation rate of new aerosols, in a sectional coagulation and condensation model, according to changes in ionization by the Forbush decrease. From the resulting size distribution we then calculate the aerosol optical thickness and Angstrom exponent, for the wavelength pairs 350, 450 nm and 550, 900 nm. In the cases where the output parameters from the model seem to compare best with atmospheric observations we observe, for the shorter wavelength pair, a change in Angstrom exponent, following the Forbush Decrease, of −6 to +3%. In some cases we also observe a delay in the change of Angstrom exponent, compared to the maximum of the Forbush decrease, which is caused by different sensitivities of the probing wavelengths to changes in aerosol number concentration and size. For the long wavelengths these changes are generally smaller. The types and magnitude of change is investigated for a suite of nucleation rates, condensable gas production rates, and aerosol loss rates. Furthermore we compare the model output with observations of 5 of the largest Forbush decreases after year 2000. For the 350, 450 nm pair we use AERONET data and find a comparable change in signal while the Angstrom Exponent is lower in the model than in the data, due to AERONET being mainly sampled over land. For 550, 900 nm we compare with both AERONET and MODIS and find little to no response in both model and observations. In summary our study shows that the optical properties of aerosols show a distinct response to Forbush Decreases, assuming that the nucleation of fresh aerosols is driven by ions. Shorter wavelengths seem more favorable for observing these effects and great care should be taken when analyzing observations, in order to avoid
Optical modeling of graphene contacted CdTe solar cells
Aldosari, Marouf; Sohrabpoor, Hamed; Gorji, Nima E.
2016-04-01
For the first time, an optical model is applied on CdS/CdTe thin film solar cells with graphene front or back contact. Graphene is highly conductive and is as thin as a single atom which reduces the light reflection and absorption, and thus enhances the light transmission to CdTe layer for a wide range of wavelengths including IR. Graphene as front electrode of CdTe devices led to loss in short circuit current density of 10% ΔJsc ≤ 15% compared to the conventional electrodes of TCO and ITO at CdS thickness of dCdS = 100 nm. In addition, all the multilayer graphene electrodes with 2, 4, and 7 graphene layers led to Jsc ≤ 20 mA/cm2. Therefore, we conclude that a single monolayer graphene with hexagonal carbon network reduces optical losses and enhances the carrier collection measured as Jsc. In another structure design, we applied the optical model to graphene back contacted CdS/CdTe device. This scheme allows double side irradiation of the cell which is expected to enhance the Jsc. We obtained 1 ∼ 6 , 23, and 38 mA/cm2 for back, front and bifacial illumination of graphene contacted CdTe cell with CdS = 100 nm. The bifacial irradiated cell, to be efficient, requires an ultrathin CdTe film with dCdTe ≤ 1 μm. In this case, the junction electric field extends to the back region and collects out the generated carriers efficiently. This was modelled by absorptivity rather than transmission rate and optical losses. Since the literature suggest that ZnO can increase the graphene conductivity and enhance the Jsc, we performed our simulations for a graphene/ZnO electrode (ZnO = 100 nm) instead of a single graphene layer.
An improved transfer-matrix model for optical superlenses.
Moore, Ciaran P; Blaikie, Richard J; Arnold, Matthew D
2009-08-01
The use of transfer-matrix analyses for characterizing planar optical superlensing systems is studied here, and the simple model of the planar superlens as an isolated imaging element is shown to be defective in certain situations. These defects arise due to neglected interactions between the superlens and the spatially varying shadow masks that are normally used as scattering objects for imaging, and which are held in near-field proximity to the superlenses. An extended model is proposed that improves the accuracy of the transfer-matrix analysis, without adding significant complexity, by approximating the reflections from the shadow mask by those from a uniform metal layer. Results obtained using both forms of the transfer matrix model are compared to finite element models and two example superlenses, one with a silver monolayer and the other with three silver sublayers, are characterized. The modified transfer matrix model gives much better agreement in both cases.
Adiabatic Floquet model for the optical response in femtosecond filaments
Hofmann, Michael
2016-01-01
The standard model of femtosecond filamentation is based on phenomenological assumptions which suggest that the ionization-induced carriers can be treated as free according to the Drude model, while the nonlinear response of the bound carriers follows the all-optical Kerr effect. Here, we demonstrate that the additional plasma generated at a multiphoton resonance dominates the saturation of the nonlinear refractive index. Since resonances are not captured by the standard model, we propose a modification of the latter in which ionization enhancements can be accounted for by an ionization rate obtained from non-Hermitian Floquet theory. In the adiabatic regime of long pulse envelopes, this augmented standard model is in excellent agreement with direct quantum mechanical simulations. Since our proposal maintains the structure of the standard model, it can be easily incorporated into existing codes of filament simulation.
Event-based Corpuscular Model for Quantum Optics Experiments
Michielsen, K; De Raedt, H
2010-01-01
A corpuscular simulation model of optical phenomena that does not require the knowledge of the solution of a wave equation of the whole system and reproduces the results of Maxwell's theory by generating detection events one-by-one is presented. The event-based corpuscular model is shown to give a unified description of multiple-beam fringes of a plane parallel plate, single-photon Mach-Zehnder interferometer, Wheeler's delayed choice, photon tunneling, quantum erasers, two-beam interference, double-slit, and Einstein-Podolsky-Rosen-Bohm and Hanbury Brown-Twiss experiments.
Computational Model Of Fiber Optic, Arc Fusion Splicing; Experimental Comparison
Ruffin, Paul; Frost, Walter; Long, Wayne
1989-02-01
Acknowledgement: The assistance and support of the MICOM Army Missile Command is gratefully appreciated. An analytical tool to investigate the arc fusion splicing of optical fibers is developed. The physical model incorporates heat transfer and thermal, visco elastic strain. The heat transfer equations governing radiation, conduction and convection during arc heating are formulated. The radiation heat flux impinging on the fiber optics is modeled based on reported experimental analysis of a generic type arc discharge. The fusion process considers deformation of the fiber due to thermal, viscous and elastic strain. A Maxwell stress-strain relationship is assumed. The model assumes an initial gap at the beginning of the arc which is closed by a press-stroke during the heating cycle. All physical properties of the fused silica glass fibers are considered as functions of temperature based on available experimental data. A computer algorithm has been developed to solve the system of governing equations and parametric studies carried out. An experiment using a FSM-20 arc fusion splicer manufactured by Fujikura Ltd. was carried out to provide experimental verification of the analytical model. In the experiment a continuous fiber was positioned in the arc and cyclic heating and cooling was carried out. One end of the fiber was clamped and the other was free to move. The fiber was heated for 6 seconds and cooled for 3 minutes for several cycles. At the end of each cooling process, photographs of the deformation of the fiber were taken. The results showed that the fiber necked down on the free end and buldged up on the fixed end. With repeated heating and cooling cycles, the optical fiber eventually necked down to the point that it melted in two. The analytical model was run for the conditions of the experiment. Comparisons of the predicted deformation of the optical fiber with those measured is given. The analytical model displays all of the physical phenomenon of fiber
Non-rotational aspherical models of the human optical system
Giovanzana, S.; Kasprzak, H. T.; Pałucki, B.; Ţălu, Ş.
2013-12-01
The aim of this work was to define three-dimensional (3D) non-rotational aspherical parametric models for the human cornea and lens using computational geometry and CAD representations. The hyperbolic cosine based function is used for the cornea and a parametric model is used for lens modeling. Data analysis and visualization of 3D non-rotational models were made using the Rhinoceros CAD software and MATLAB software was used for numeric computation. We combined, implemented, and evaluated these models with a 3D ray-tracing in order to fully analyze the human eye model. It was found that 3D non-rotational aspherical models for the human eye could be more accurately modeled and rendered for analysis with finite element method. The objective of this study is to present and analyze mathematical models of the cornea and lens and to highlight the potential of optical applications of the eye models containing astigmatic surfaces, which are more close to the real eye than spherosymmetric eye models.
Multiple Scattering Model for Optical Coherence Tomography with Rytov Approximation
Li, Muxingzi
2017-04-24
Optical Coherence Tomography (OCT) is a coherence-gated, micrometer-resolution imaging technique that focuses a broadband near-infrared laser beam to penetrate into optical scattering media, e.g. biological tissues. The OCT resolution is split into two parts, with the axial resolution defined by half the coherence length, and the depth-dependent lateral resolution determined by the beam geometry, which is well described by a Gaussian beam model. The depth dependence of lateral resolution directly results in the defocusing effect outside the confocal region and restricts current OCT probes to small numerical aperture (NA) at the expense of lateral resolution near the focus. Another limitation on OCT development is the presence of a mixture of speckles due to multiple scatterers within the coherence length, and other random noise. Motivated by the above two challenges, a multiple scattering model based on Rytov approximation and Gaussian beam optics is proposed for the OCT setup. Some previous papers have adopted the first Born approximation with the assumption of small perturbation of the incident field in inhomogeneous media. The Rytov method of the same order with smooth phase perturbation assumption benefits from a wider spatial range of validity. A deconvolution method for solving the inverse problem associated with the first Rytov approximation is developed, significantly reducing the defocusing effect through depth and therefore extending the feasible range of NA.
Optical modeling of volcanic ash particles using ellipsoids
Merikallio, Sini; Muñoz, Olga; Sundström, Anu-Maija; Virtanen, Timo H.; Horttanainen, Matti; de Leeuw, Gerrit; Nousiainen, Timo
2015-05-01
The single-scattering properties of volcanic ash particles are modeled here by using ellipsoidal shapes. Ellipsoids are expected to improve the accuracy of the retrieval of aerosol properties using remote sensing techniques, which are currently often based on oversimplified assumptions of spherical ash particles. Measurements of the single-scattering optical properties of ash particles from several volcanoes across the globe, including previously unpublished measurements from the Eyjafjallajökull and Puyehue volcanoes, are used to assess the performance of the ellipsoidal particle models. These comparisons between the measurements and the ellipsoidal particle model include consideration of the whole scattering matrix, as well as sensitivity studies on the point of view of the Advanced Along Track Scanning Radiometer (AATSR) instrument. AATSR, which flew on the ENVISAT satellite, offers two viewing directions but no information on polarization, so usually only the phase function is relevant for interpreting its measurements. As expected, ensembles of ellipsoids are able to reproduce the observed scattering matrix more faithfully than spheres. Performance of ellipsoid ensembles depends on the distribution of particle shapes, which we tried to optimize. No single specific shape distribution could be found that would perform superiorly in all situations, but all of the best-fit ellipsoidal distributions, as well as the additionally tested equiprobable distribution, improved greatly over the performance of spheres. We conclude that an equiprobable shape distribution of ellipsoidal model particles is a relatively good, yet enticingly simple, approach for modeling volcanic ash single-scattering optical properties.
Adaptive optics sky coverage modeling for extremely large telescopes.
Clare, Richard M; Ellerbroek, Brent L; Herriot, Glen; Véran, Jean-Pierre
2006-12-10
A Monte Carlo sky coverage model for laser guide star adaptive optics systems was proposed by Clare and Ellerbroek [J. Opt. Soc. Am. A 23, 418 (2006)]. We refine the model to include (i) natural guide star (NGS) statistics using published star count models, (ii) noise on the NGS measurements, (iii) the effect of telescope wind shake, (iv) a model for how the Strehl and hence NGS wavefront sensor measurement noise varies across the field, (v) the focus error due to imperfectly tracking the range to the sodium layer, (vi) the mechanical bandwidths of the tip-tilt (TT) stage and deformable mirror actuators, and (vii) temporal filtering of the NGS measurements to balance errors due to noise and servo lag. From this model, we are able to generate a TT error budget for the Thirty Meter Telescope facility narrow-field infrared adaptive optics system (NFIRAOS) and perform several design trade studies. With the current NFIRAOS design, the median TT error at the galactic pole with median seeing is calculated to be 65 nm or 1.8 mas rms.
Wavefront Sensing for WFIRST with a Linear Optical Model
Jurling, Alden S.; Content, David A.
2012-01-01
In this paper we develop methods to use a linear optical model to capture the field dependence of wavefront aberrations in a nonlinear optimization-based phase retrieval algorithm for image-based wavefront sensing. The linear optical model is generated from a ray trace model of the system and allows the system state to be described in terms of mechanical alignment parameters rather than wavefront coefficients. This approach allows joint optimization over images taken at different field points and does not require separate convergence of phase retrieval at individual field points. Because the algorithm exploits field diversity, multiple defocused images per field point are not required for robustness. Furthermore, because it is possible to simultaneously fit images of many stars over the field, it is not necessary to use a fixed defocus to achieve adequate signal-to-noise ratio despite having images with high dynamic range. This allows high performance wavefront sensing using in-focus science data. We applied this technique in a simulation model based on the Wide Field Infrared Survey Telescope (WFIRST) Intermediate Design Reference Mission (IDRM) imager using a linear optical model with 25 field points. We demonstrate sub-thousandth-wave wavefront sensing accuracy in the presence of noise and moderate undersampling for both monochromatic and polychromatic images using 25 high-SNR target stars. Using these high-quality wavefront sensing results, we are able to generate upsampled point-spread functions (PSFs) and use them to determine PSF ellipticity to high accuracy in order to reduce the systematic impact of aberrations on the accuracy of galactic ellipticity determination for weak-lensing science.
Model of optical response of marine aerosols to Forbush decreases
Directory of Open Access Journals (Sweden)
T. Bondo
2009-10-01
Full Text Available In order to elucidate the effect of galactic cosmic rays on cloud formation, we investigate the optical response of marine aerosols to Forbush decreases – abrupt decreases in galactic cosmic rays – by means of modeling. We vary the nucleation rate of new aerosols, in a sectional coagulation and condensation model, according to changes in ionization by the Forbush decrease. From the resulting size distribution we then calculate the aerosol optical thickness and Angstrom exponent, for the wavelength pairs 350, 450 nm and 550, 900 nm. For the shorter wavelength pair we observe a change in Angstrom exponent, following the Forbush Decrease, of −6 to +3% in the cases with atmospherically realistic output parameters. For some parameters we also observe a delay in the change of Angstrom exponent, compared to the maximum of the Forbush decrease, which is caused by different sensitivities of the probing wavelengths to changes in aerosol number concentration and size. For the long wavelengths these changes are generally smaller. The types and magnitude of change is investigated for a suite of nucleation rates, condensable gas production rates, and aerosol loss rates. Furthermore we compare the model output with observations of 5 of the largest Forbush decreases after year 2000. For the 350, 450 nm pair we use AERONET data and find a comparable change in signal while the Angstrom Exponent is lower in the model than in the data, due to AERONET being mainly sampled over land. For 550, 900 nm we compare with both AERONET and MODIS and find little to no response in both model and observations. In summary our study shows that the optical properties of aerosols show a distinct response to Forbush Decreases, assuming that the nucleation of fresh aerosols is driven by ions. Shorter wavelengths seem more favorable for observing these effects and great care should be taken when analyzing observations, in order to avoid the signal being drowned out by noise.
Wavefront sensing for WFIRST with a linear optical model
Jurling, Alden S.; Content, David A.
2012-09-01
In this paper we develop methods to use a linear optical model to capture the field dependence of wavefront aberrations in a nonlinear optimization-based phase retrieval algorithm for image-based wavefront sensing. The linear optical model is generated from a ray trace model of the system and allows the system state to be described in terms of mechanical alignment parameters rather than wavefront coefficients. This approach allows joint optimization over images taken at different field points and does not require separate convergence of phase retrieval at individual field points. Because the algorithm exploits field diversity, multiple defocused images per field point are not required for robustness. Furthermore, because it is possible to simultaneously fit images of many stars over the field, it is not necessary to use a fixed defocus to achieve adequate signal-to-noise ratio despite having images with high dynamic range. This allows high performance wavefront sensing using in-focus science data. We applied this technique in a simulation model based on the Wide Field Infrared Survey Telescope (WFIRST) Intermediate Design Reference Mission (IDRM) imager using a linear optical model with 25 field points. We demonstrate sub-thousandth-wave wavefront sensing accuracy in the presence of noise and moderate undersampling for both monochromatic and polychromatic images using 25 high-SNR target stars. Using these high-quality wavefront sensing results, we are able to generate upsampled point-spread functions (PSFs) and use them to determine PSF ellipticity to high accuracy in order to reduce the systematic impact of aberrations on the accuracy of galactic ellipticity determination for weak-lensing science.
Numerical modelling of multimode fibre-optic communication lines
Energy Technology Data Exchange (ETDEWEB)
Sidelnikov, O S; Fedoruk, M P [Novosibirsk State University, Novosibirsk (Russian Federation); Sygletos, S; Ferreira, F [Aston University, England, Birmingham, B4 7ET (United Kingdom)
2016-01-31
The results of numerical modelling of nonlinear propagation of an optical signal in multimode fibres with a small differential group delay are presented. It is found that the dependence of the error vector magnitude (EVM) on the differential group delay can be reduced by increasing the number of ADC samples per symbol in the numerical implementation of the differential group delay compensation algorithm in the receiver. The possibility of using multimode fibres with a small differential group delay for data transmission in modern digital communication systems is demonstrated. It is shown that with increasing number of modes the strong coupling regime provides a lower EVM level than the weak coupling one. (fibre-optic communication lines)
Optical properties of CdTe: Experiment and modeling
Adachi, Sadao; Kimura, Toshifumi; Suzuki, Norihiro
1993-09-01
The real epsilon(sub 1) and imaginary epsilon(sub 2) portions of the dielectric function of CdTe were measured by spectroscopic ellipsometry (SE) in the 1.1-5.6 eV photon-energy range at room temperature. The data obtained were analyzed using different theoretical models, namely the harmonic-oscillator approximation, the standard critical point, and the model dielectric function. These models include the E(sub 0), E(sub 0) + Delta(sub 0), E(sub 1), E(sub 1) + Delta(sub 1), and E(sub 2) gaps as the main dispersion mechanisms. The consequences were reported and of particular interest was the difference in the analyzed results between these theoretical models. Dielectric-related optical constants of CdTe, such as the complex refractive index, the absorption coefficient, and normal-incidence reflectivity, were also investigated.
Synthetic Modeling of Astronomical Closed Loop Adaptive Optics
Jolissaint, Laurent
2010-01-01
We present an analytical model of a single natural guide star astronomical adaptive optics system, in closed loop mode. The model is used to simulate the long exposure system point spread function, using the spatial frequency (or Fourier) approach, and complement an initial open loop model. Applications range from system design, science case analysis and AO data reduction. All the classical phase errors have been included: deformable mirror fitting error, wavefront sensor spatial aliasing, wavefront sensor noise, and the correlated anisoplanatic and servo-lag error. The model includes the deformable mirror spatial transfer function, and the actuator array geometry can be different from the wavefront sensor lenslet array geometry. We also include the dispersion between the sensing and the correction wavelengths. Illustrative examples are given at the end of the paper.
Fincham, W H A
2013-01-01
Optics: Ninth Edition Optics: Ninth Edition covers the work necessary for the specialization in such subjects as ophthalmic optics, optical instruments and lens design. The text includes topics such as the propagation and behavior of light; reflection and refraction - their laws and how different media affect them; lenses - thick and thin, cylindrical and subcylindrical; photometry; dispersion and color; interference; and polarization. Also included are topics such as diffraction and holography; the limitation of beams in optical systems and its effects; and lens systems. The book is recommen
Integrated modeling of the GMT laser tomography adaptive optics system
Piatrou, Piotr
2014-08-01
Laser Tomography Adaptive Optics (LTAO) is one of adaptive optics systems planned for the Giant Magellan Telescope (GMT). End-to-end simulation tools that are able to cope with the complexity and computational burden of the AO systems to be installed on the extremely large telescopes such as GMT prove to be an integral part of the GMT LTAO system development endeavors. SL95, the Fortran 95 Simulation Library, is one of the software tools successfully used for the LTAO system end-to-end simulations. The goal of SL95 project is to provide a complete set of generic, richly parameterized mathematical models for key elements of the segmented telescope wavefront control systems including both active and adaptive optics as well as the models for atmospheric turbulence, extended light sources like Laser Guide Stars (LGS), light propagation engines and closed-loop controllers. The library is implemented as a hierarchical collection of classes capable of mutual interaction, which allows one to assemble complex wavefront control system configurations with multiple interacting control channels. In this paper we demonstrate the SL95 capabilities by building an integrated end-to-end model of the GMT LTAO system with 7 control channels: LGS tomography with Adaptive Secondary and on-instrument deformable mirrors, tip-tilt and vibration control, LGS stabilization, LGS focus control, truth sensor-based dynamic noncommon path aberration rejection, pupil position control, SLODAR-like embedded turbulence profiler. The rich parameterization of the SL95 classes allows to build detailed error budgets propagating through the system multiple errors and perturbations such as turbulence-, telescope-, telescope misalignment-, segment phasing error-, non-common path-induced aberrations, sensor noises, deformable mirror-to-sensor mis-registration, vibration, temporal errors, etc. We will present a short description of the SL95 architecture, as well as the sample GMT LTAO system simulation
Advanced optical position sensors for magnetically suspended wind tunnel models
Lafleur, S.
1985-01-01
A major concern to aerodynamicists has been the corruption of wind tunnel test data by model support structures, such as stings or struts. A technique for magnetically suspending wind tunnel models was considered by Tournier and Laurenceau (1957) in order to overcome this problem. This technique is now implemented with the aid of a Large Magnetic Suspension and Balance System (LMSBS) and advanced position sensors for measuring model attitude and position within the test section. Two different optical position sensors are discussed, taking into account a device based on the use of linear CCD arrays, and a device utilizing area CID cameras. Current techniques in image processing have been employed to develop target tracking algorithms capable of subpixel resolution for the sensors. The algorithms are discussed in detail, and some preliminary test results are reported.
Mathematical model of an optically pumped molecular laser
CSIR Research Space (South Africa)
Botha, LR
2009-07-01
Full Text Available pumped molecular laser Dr L R Botha, Dr C Bollig, D Esser, C Jacobs, D Preussler SAIP 2009 Durban Page 2 © CSIR 2008 www.csir.co.za Structure of talk • Introduction • Overview of HBr laser • Numerical Model • Comparison... µm laser ring oscillator & pre-amplifier 1.9 µm Optically Pumped Molecular laser @ 4 µm 95:5 HBr Absorption cell Fast detector 2.064 µm ± 1 nm Feedback control box Feedback loop 1 P ie zo m o u nt Fast detector Feedback loop 2 Gas...
Modeling of Self-Pumped Singly Resonant Optical Parametric Oscillator
Deng, Chengxian
2016-01-01
A model of the steady-state operating, self-pumped singly resonant optical parametric oscillator (SPSRO) has been developed. The characteristics of quasi three-level laser gain medium pumped longitudinally have been taken into account. The characteristics of standing wave cavity, reabsorption losses, focusing Gaussian beams of the pump laser, fundamental laser and signal wave have been considered in the analyses. Furthermore, The power characteristics of threshold and efficiency have been analyzed, employing a Yb3+-doped periodically poled lithium niobate co-doped with MgO (Yb3+:MgO:PPLN) as the medium of laser gain and second-order nonlinear crystal.
Fluctuations and entropy in models of quantum optical resonance
Phoenix, S. J. D.; Knight, P. L.
1988-09-01
We use variances, entropy, and the Shannon entropy to analyse the fluctuations and quantum evolution of various simple models of quantum optical resonance. We discuss at length the properties of the single-mode radiation field coupled to a single two-level atom, and then extend our analysis to describe the micromaser in which a cavity mode is repeatedly pumped by a succession of atoms passing through the cavity. We also discuss the fluctuations in the single-mode laser theory of Scully and Lamb.
Purely optical navigation with model-based state prediction
Sendobry, Alexander; Graber, Thorsten; Klingauf, Uwe
2010-10-01
State-of-the-art Inertial Navigation Systems (INS) based on Micro-Electro-Mechanical Systems (MEMS) have a lack of precision especially in GPS denied environments like urban canyons or in pure indoor missions. The proposed Optical Navigation System (ONS) provides bias free ego-motion estimates using triple redundant sensor information. In combination with a model based state prediction our system is able to estimate velocity, position and attitude of an arbitrary aircraft. Simulating a high performance flow-field estimator the algorithm can compete with conventional low-cost INS. By using measured velocities instead of accelerations the system states drift behavior is not as distinctive as for an INS.
Numerical modelling of multimode fibre-optic communication lines
Sidelnikov, O. S.; Sygletos, S.; Ferreira, F.; Fedoruk, M. P.
2016-01-01
The results of numerical modelling of nonlinear propagation of an optical signal in multimode fibres with a small differential group delay are presented. It is found that the dependence of the error vector magnitude (EVM) on the differential group delay can be reduced by increasing the number of ADC samples per symbol in the numerical implementation of the differential group delay compensation algorithm in the receiver. The possibility of using multimode fibres with a small differential group delay for data transmission in modern digital communication systems is demonstrated. It is shown that with increasing number of modes the strong coupling regime provides a lower EVM level than the weak coupling one.
Modeling of laser-induced damage and optic usage at the National Ignition Facility
Liao, Zhi M.; Nostrand, Mike; Carr, Wren; Bude, Jeff; Suratwala, Tayyab I.
2016-07-01
Modeling of laser-induced optics damage has been introduced to benchmark existing optic usage at the National Ignition Facility (NIF) which includes the number of optics exchanged for damage repair. NIF has pioneered an optics recycle strategy to allow it to run the laser at capacity since fully commissioned in 2009 while keeping the cost of optics usage manageable. We will show how the damage model is being used to evaluate strategies to streamline our optics loop efficiency, as we strive to increase the laser shot rate without increasing operating costs.
Tonkyn, Russell G.; Danby, Tyler O.; Birnbaum, Jerome L.; Taubman, Matthew S.; Bernacki, Bruce E.; Johnson, Timothy J.; Myers, Tanya L.
2017-05-01
The complex optical refractive index contains the optical constants, n(ῦ)and k(ῦ), which correspond to the dispersion and absorption of light within a medium, respectively. By obtaining the optical constants one can in principle model most optical phenomena in media and at interfaces including reflection, refraction and dispersion. We have developed improved protocols based on the use of multiple path lengths to determine the optical constants for dozens of liquids, including organic and organophosphorous compounds. Detailed description of the protocols to determine the infrared indices will be presented, along with preliminary results using the constants with their applications to optical modeling.
Energy Technology Data Exchange (ETDEWEB)
Tonkyn, Russell G.; Danby, Tyler O.; Birnbaum, Jerome C.; Taubman, Matthew S.; Bernacki, Bruce E.; Johnson, Timothy J.; Myers, Tanya L.
2017-05-03
The complex optical refractive index contains the optical constants, n($\\tilde{u}$)and k($\\tilde{u}$), which correspond to the dispersion and absorption of light within a medium, respectively. By obtaining the optical constants one can in principle model most optical phenomena in media and at interfaces including reflection, refraction and dispersion. We have developed improved protocols based on the use of multiple path lengths to determine the optical constants for dozens of liquids, including organic and organophosphorous compounds. Detailed description of the protocols to determine the infrared indices will be presented, along with preliminary results using the constants with their applications to optical modeling.
2008-10-01
Remote sensing of ocean color provides synoptic surface ocean bio -optical properties but is limited to real-time or climatological applications. Many...this, we couple satellite imagery with numerical circulation models to provide short-term (24-48 hr) forecasts of bio -optical properties. These are...physical processes control the bio -optical distribution patterns. We compare optical forecast results from three Navy models and two advection
Optical properties of soot particles: measurement - model comparison
Forestieri, S.; Lambe, A. T.; Lack, D.; Massoli, P.; Cross, E. S.; Dubey, M.; Mazzoleni, C.; Olfert, J.; Freedman, A.; Davidovits, P.; Onasch, T. B.; Cappa, C. D.
2013-12-01
Soot, a product of incomplete combustion, plays an important role in the earth's climate system through the absorption and scattering of solar radiation. In order to accurately model the direct radiative impact of black carbon (BC), the refractive index and shape dependent scattering and absorption characteristics must be known. At present, the assumed shape remains highly uncertain because BC particles are fractal-like, being agglomerates of smaller (20-40 nm) spherules, yet traditional optical models such as Mie theory typically assume a spherical particle morphology. To investigate the ability of various optical models to reproduce observed BC optical properties, we measured light absorption and extinction coefficients of methane and ethylene flame soot particles. Optical properties were measured by multiple instruments: absorption by a dual cavity ringdown photoacoustic spectrometer (CRD-PAS), absorption and scattering by a 3-wavelength photoacoustic/nephelometer spectrometer (PASS-3) and extinction and scattering by a cavity attenuated phase shift spectrometer (CAPS). Soot particle mass was quantified using a centrifugal particle mass analyzer (CPMA) and mobility size was measured with a scanning mobility particle sizer (SMPS). Measurements were made for nascent soot particles and for collapsed soot particles following coating with dioctyl sebacate or sulfuric acid and thermal denuding to remove the coating. Wavelength-dependent refractive indices for the sampled particles were derived by fitting the observed absorption and extinction cross-sections to spherical particle Mie theory and Rayleigh-Debye-Gans theory. The Rayleigh-Debye-Gans approximation assumes that the absorption properties of soot are dictated by the individual spherules and neglects interaction between them. In general, Mie theory reproduces the observed absorption and extinction cross-sections for particles with volume equivalent diameters (VED) VED > ~160 nm. The discrepancy is most
Fincham, W H A
2013-01-01
Optics: Eighth Edition covers the work necessary for the specialization in such subjects as ophthalmic optics, optical instruments and lens design. The text includes topics such as the propagation and behavior of light; reflection and refraction - their laws and how different media affect them; lenses - thick and thin, cylindrical and subcylindrical; photometry; dispersion and color; interference; and polarization. Also included are topics such as diffraction and holography; the limitation of beams in optical systems and its effects; and lens systems. The book is recommended for engineering st
Multiscale modeling and computation of optically manipulated nano devices
Bao, Gang; Liu, Di; Luo, Songting
2016-07-01
We present a multiscale modeling and computational scheme for optical-mechanical responses of nanostructures. The multi-physical nature of the problem is a result of the interaction between the electromagnetic (EM) field, the molecular motion, and the electronic excitation. To balance accuracy and complexity, we adopt the semi-classical approach that the EM field is described classically by the Maxwell equations, and the charged particles follow the Schrödinger equations quantum mechanically. To overcome the numerical challenge of solving the high dimensional multi-component many-body Schrödinger equations, we further simplify the model with the Ehrenfest molecular dynamics to determine the motion of the nuclei, and use the Time-Dependent Current Density Functional Theory (TD-CDFT) to calculate the excitation of the electrons. This leads to a system of coupled equations that computes the electromagnetic field, the nuclear positions, and the electronic current and charge densities simultaneously. In the regime of linear responses, the resonant frequencies initiating the out-of-equilibrium optical-mechanical responses can be formulated as an eigenvalue problem. A self-consistent multiscale method is designed to deal with the well separated space scales. The isomerization of azobenzene is presented as a numerical example.
Simulations of Keratoconus Patient Vision with Optical Eye Modeling
Tan, Bo; Chen, Ying-Ling; Lewis, J. W. L.; Shi, Lei; Wang, Ming
2007-11-01
Keratoconus (KC) is an eye condition that involves progressive corneal thinning. Pushed by the intraocular pressure, the weakened cornea bulges outward and creates an irregular surface shape. The result is degraded vision that is difficult to correct with regular eye glasses or contact lens. In this study we use the optical lens design software, ZeMax, and patient data including cornea topography and refraction prescription to construct KC eye models. The variation of KC ``cone height'' on the cornea is used to simulate KC progression. The consequent patients' night vision and Snellen letter chart vision at 20 feet are simulated using these anatomically accurate 3-dimensional models. 100 million rays are traced for each image simulation. Animated results illustrate the change of KC visual acuity with the progression of disease. This simulation technique provides a comprehensive tool for medical training and patient consultation/education.
Protein folding: the optically induced electronic excitations model
Energy Technology Data Exchange (ETDEWEB)
Jeknic-Dugic, J [Department of Physics, Faculty of Science, Nis (Serbia)], E-mail: jjeknic@pmf.ni.ac.yu
2009-07-15
The large-molecules conformational transitions problem (the 'protein folding problem') is an open issue of vivid current science research work of fundamental importance for a number of modern science disciplines as well as for nanotechnology. Here, we elaborate the recently proposed quantum-decoherence-based approach to the issue. First, we emphasize a need for detecting the elementary quantum mechanical processes (whose combinations may give a proper description of the realistic experimental situations) and then we design such a model. As distinct from the standard approach that deals with the conformation system, we investigate the optically induced transitions in the molecule electrons system that, in effect, may give rise to a conformation change in the molecule. Our conclusion is that such a model may describe the comparatively slow conformational transitions.
Structural model constructing for optical handwritten character recognition
Khaustov, P. A.; Spitsyn, V. G.; Maksimova, E. I.
2017-02-01
The article is devoted to the development of the algorithms for optical handwritten character recognition based on the structural models constructing. The main advantage of these algorithms is the low requirement regarding the number of reference images. The one-pass approach to a thinning of the binary character representation has been proposed. This approach is based on the joint use of Zhang-Suen and Wu-Tsai algorithms. The effectiveness of the proposed approach is confirmed by the results of the experiments. The article includes the detailed description of the structural model constructing algorithm’s steps. The proposed algorithm has been implemented in character processing application and has been approved on MNIST handwriting characters database. Algorithms that could be used in case of limited reference images number were used for the comparison.
Dual permeability FEM models for distributed fiber optic sensors development
Aguilar-López, Juan Pablo; Bogaard, Thom
2017-04-01
Fiber optic cables are commonly known for being robust and reliable mediums for transferring information at the speed of light in glass. Billions of kilometers of cable have been installed around the world for internet connection and real time information sharing. Yet, fiber optic cable is not only a mean for information transfer but also a way to sense and measure physical properties of the medium in which is installed. For dike monitoring, it has been used in the past for detecting inner core and foundation temperature changes which allow to estimate water infiltration during high water events. The DOMINO research project, aims to develop a fiber optic based dike monitoring system which allows to directly sense and measure any pore pressure change inside the dike structure. For this purpose, questions like which location, how many sensors, which measuring frequency and which accuracy are required for the sensor development. All these questions may be initially answered with a finite element model which allows to estimate the effects of pore pressure change in different locations along the cross section while having a time dependent estimation of a stability factor. The sensor aims to monitor two main failure mechanisms at the same time; The piping erosion failure mechanism and the macro-stability failure mechanism. Both mechanisms are going to be modeled and assessed in detail with a finite element based dual permeability Darcy-Richards numerical solution. In that manner, it is possible to assess different sensing configurations with different loading scenarios (e.g. High water levels, rainfall events and initial soil moisture and permeability conditions). The results obtained for the different configurations are later evaluated based on an entropy based performance evaluation. The added value of this kind of modelling approach for the sensor development is that it allows to simultaneously model the piping erosion and macro-stability failure mechanisms in a time
Hansen, Anja; Krueger, Alexander; Ripken, Tammo
2013-03-01
In ophthalmic microsurgery tissue dissection is achieved using femtosecond laser pulses to create an optical breakdown. For vitreo-retinal applications the irradiance distribution in the focal volume is distorted by the anterior components of the eye causing a raised threshold energy for breakdown. In this work, an adaptive optics system enables spatial beam shaping for compensation of aberrations and investigation of wave front influence on optical breakdown. An eye model was designed to allow for aberration correction as well as detection of optical breakdown. The eye model consists of an achromatic lens for modeling the eye's refractive power, a water chamber for modeling the tissue properties, and a PTFE sample for modeling the retina's scattering properties. Aberration correction was performed using a deformable mirror in combination with a Hartmann-Shack-sensor. The influence of an adaptive optics aberration correction on the pulse energy required for photodisruption was investigated using transmission measurements for determination of the breakdown threshold and video imaging of the focal region for study of the gas bubble dynamics. The threshold energy is considerably reduced when correcting for the aberrations of the system and the model eye. Also, a raise in irradiance at constant pulse energy was shown for the aberration corrected case. The reduced pulse energy lowers the potential risk of collateral damage which is especially important for retinal safety. This offers new possibilities for vitreo-retinal surgery using femtosecond laser pulses.
Directory of Open Access Journals (Sweden)
Y. H. Lee
2014-09-01
Full Text Available The TwO-Moment Aerosol Sectional microphysics model (TOMAS has been integrated into the state-of-the-art general circulation model, GISS ModelE2. TOMAS has the flexibility to select a size resolution as well as the lower size cutoff. A computationally efficient version of TOMAS is used here, which has 15 size bins covering 3 nm to 10 μm aerosol dry diameter. For each bin, it simulates the total aerosol number concentration and mass concentrations of sulphate, pure elementary carbon (hydrophobic, mixed elemental carbon (hydrophilic, hydrophobic organic matter, hydrophilic organic matter, sea salt, mineral dust, ammonium, and aerosol-associated water. This paper provides a detailed description of the ModelE2-TOMAS model and evaluates the model against various observations including aerosol precursor gas concentrations, aerosol mass and number concentrations, and aerosol optical depths. Additionally, global budgets in ModelE2-TOMAS are compared with those of other global aerosol models, and the TOMAS model is compared to the default aerosol model in ModelE2, which is a bulk aerosol model. Overall, the ModelE2-TOMAS predictions are within the range of other global aerosol model predictions, and the model has a reasonable agreement with observations of sulphur species and other aerosol components as well as aerosol optical depth. However, ModelE2-TOMAS (as well as the bulk aerosol model cannot capture the observed vertical distribution of sulphur dioxide over the Pacific Ocean possibly due to overly strong convective transport. The TOMAS model successfully captures observed aerosol number concentrations and cloud condensation nuclei concentrations. Anthropogenic aerosol burdens in the bulk aerosol model running in the same host model as TOMAS (ModelE2 differ by a few percent to a factor of 2 regionally, mainly due to differences in aerosol processes including deposition, cloud processing, and emission parameterizations. Larger differences are found
Modeling silica aerogel optical performance by determining its radiative properties
Directory of Open Access Journals (Sweden)
Lin Zhao
2016-02-01
Full Text Available Silica aerogel has been known as a promising candidate for high performance transparent insulation material (TIM. Optical transparency is a crucial metric for silica aerogels in many solar related applications. Both scattering and absorption can reduce the amount of light transmitted through an aerogel slab. Due to multiple scattering, the transmittance deviates from the Beer-Lambert law (exponential attenuation. To better understand its optical performance, we decoupled and quantified the extinction contributions of absorption and scattering separately by identifying two sets of radiative properties. The radiative properties are deduced from the measured total transmittance and reflectance spectra (from 250 nm to 2500 nm of synthesized aerogel samples by solving the inverse problem of the 1-D Radiative Transfer Equation (RTE. The obtained radiative properties are found to be independent of the sample geometry and can be considered intrinsic material properties, which originate from the aerogel’s microstructure. This finding allows for these properties to be directly compared between different samples. We also demonstrate that by using the obtained radiative properties, we can model the photon transport in aerogels of arbitrary shapes, where an analytical solution is difficult to obtain.
Modelling the optical properties of aerosols in a chemical transport model
Andersson, E.; Kahnert, M.
2015-12-01
According to the IPCC fifth assessment report (2013), clouds and aerosols still contribute to the largest uncertainty when estimating and interpreting changes to the Earth's energy budget. Therefore, understanding the interaction between radiation and aerosols is both crucial for remote sensing observations and modelling the climate forcing arising from aerosols. Carbon particles are the largest contributor to the aerosol absorption of solar radiation, thereby enhancing the warming of the planet. Modelling the radiative properties of carbon particles is a hard task and involves many uncertainties arising from the difficulties of accounting for the morphologies and heterogeneous chemical composition of the particles. This study aims to compare two ways of modelling the optical properties of aerosols simulated by a chemical transport model. The first method models particle optical properties as homogeneous spheres and are externally mixed. This is a simple model that is particularly easy to use in data assimilation methods, since the optics model is linear. The second method involves a core-shell internal mixture of soot, where sulphate, nitrate, ammonia, organic carbon, sea salt, and water are contained in the shell. However, by contrast to previously used core-shell models, only part of the carbon is concentrated in the core, while the remaining part is homogeneously mixed with the shell. The chemical transport model (CTM) simulations are done regionally over Europe with the Multiple-scale Atmospheric Transport and CHemistry (MATCH) model, developed by the Swedish Meteorological and Hydrological Institute (SMHI). The MATCH model was run with both an aerosol dynamics module, called SALSA, and with a regular "bulk" approach, i.e., a mass transport model without aerosol dynamics. Two events from 2007 are used in the analysis, one with high (22/12-2007) and one with low (22/6-2007) levels of elemental carbon (EC) over Europe. The results of the study help to assess the
Experimentation and modeling of organic photocontamination on lithographic optics
Kunz, Roderick R.; Liberman, Vladimir; Downs, Deanna K.
2000-07-01
Photodeposition of organic films on transparent substrates irradiated in the presence of trace levels of hydrocarbons has been experimentally investigated and a model is presented that describes the film growth behavior. The efficacy of a given organic precursor at forming a deposit is proportional to the product of its surface coverage and by its photon absorption cross section. These measurement are important in predicting the transmission characteristics of lithographic optics operating at 157-, 193-, and 248-nm wavelength. For example, a lens element irradiated continuously for one year in the presence of 1 part per billion of t-butyl benzene would exhibit a transmission of approximately 87 percent at 193 nm. The effects of oxygen- containing ambients are also documented, and methods for elimination and/or prevention of organic contamination are suggested.
Coupled-channel optical model potential for rare earth nuclei
Herman, M; Palumbo, A; Dietrich, F S; Brown, D; Hoblit, S
2013-01-01
Inspired by the recent work by Dietrich et al., substantiating validity of the adiabatic assumption in coupled-channel calculations, we explore the possibility of generalizing a global spherical optical model potential (OMP) to make it usable in coupled-channel calculations on statically deformed nuclei. The generalization consists in adding the coupling of the ground state rotational band, deforming the potential by introducing appropriate quadrupole and hexadecupole deformation and correcting the OMP radius to preserve volume integral of the spherical OMP. We choose isotopes of three rare-earth elements (W, Ho, Gd), which are known to be nearly perfect rotors, to perform a consistent test of our conjecture on integrated cross sections as well as on angular distributions for elastic and inelastic neutron scattering. When doing this we employ the well-established Koning-Delaroche global spherical potential and experimentally determined deformations without any adjustments. We observe a dramatically improved a...
Model of a thin film optical fiber fluorosensor
Egalon, Claudio O.; Rogowski, Robert S.
1991-03-01
The efficiency of core-light injection from sources in the cladding of an optical fiber is modeled analytically by means of the exact field solution of a step-profile fiber. The analysis is based on the techniques by Marcuse (1988) in which the sources are treated as infinitesimal electric currents with random phase and orientation that excite radiation fields and bound modes. Expressions are developed based on an infinite cladding approximation which yield the power efficiency for a fiber coated with fluorescent sources in the core/cladding interface. Marcuse's results are confirmed for the case of a weakly guiding cylindrical fiber with fluorescent sources uniformly distributed in the cladding, and the power efficiency is shown to be practically constant for variable wavelengths and core radii. The most efficient fibers have the thin film located at the core/cladding boundary, and fibers with larger differences in the indices of refraction are shown to be the most efficient.
Microscopic model for all optical switching in ferromagnets
Cornelissen, T. D.; Córdoba, R.; Koopmans, B.
2016-04-01
The microscopic mechanism behind the all optical switching (AOS) in ferromagnets has triggered intense scientific debate. Here, the microscopic three-temperature model is utilized to describe AOS in a perpendicularly magnetized ferromagnetic Co/Pt system. We demonstrate that AOS in such a ferromagnet can be explained with the Inverse Faraday Effect (IFE). The influence of the strength and lifetime of the IFE induced field pulse on the switching process are investigated. We found that because of strong spin-orbit coupling, the minimal lifetime of the IFE needed to obtain switching is of the order of 0.1 ps, which is shorter than previously assumed. Moreover, spatial images of the domain pattern after AOS in Co/Pt, as well as their dependence on applying an opposite magnetic field, are qualitatively reproduced.
Ionization Modeling Astrophysical Gaseous Structures. I. The Optically Thin Regime
Churchill, Christopher W; Medina, Amber; Vliet, Jacob R Vander
2014-01-01
We present a code for modelling the ionization conditions of optically thin astrophysical gas structures. Given the gas hydrogen density, equilibrium temperature, elemental abundances, and the ionizing spectrum, the code solves the equilibrium ionization fractions and number densities for all ions from hydrogen to zinc. The included processes are photoionization, Auger ionization, direct collisional ionization, excitation auto-ionization, charge exchange ionization, two-body radiative recombination, dielectronic recombination, and charge exchange recombination. The ionizing spectrum can be generalized to include the ultraviolet background (UVB) and/or Starburst99 stellar populations of various masses, ages, metallicities, and distances. The ultimate goal with the code is to provide fast computation of the ionization conditions of gas in N-body + hydrodynamics cosmological simulations, in particular adaptive mesh refinement codes, in order to facilitate absorption line analysis of the simulated gas for compari...
Some optical and dynamical phenomena in the Rindler model
Birsin, E
2014-01-01
In Rindler's model of a uniformly accelerated reference frame we analyze the apparent shape of rods and marked light rays for the case that the observers as well as the rods and the sources of light are at rest with respect to the Rindler observers. Contrary to the expectation suggested by the strong principle of equivalence, there is no apparent "bending down" of a light ray with direction transversal to the direction of acceleration, but a straight rod oriented orthogonal to the direction of acceleration appears bended "upwards". These optical phenomena are in accordance with the dynamical experience of observers guided by a straight track or a track curved in the same way as the marked light ray, respectively: While the former observer feels a centrifugal force directed "downwards", the centrifugal force for the latter vanishes. The properties of gyroscope transport along such tracks are correspondingly.
MILES extended : Stellar population synthesis models from the optical to the infrared
Rock, B.; Vazdekis, A.; Ricciardelli, E.; Peletier, R. F.; Knapen, J. H.; Falcon-Barroso, J.
2016-01-01
We present the first single-burst stellar population models, which covers the optical and the infrared wavelength range between 3500 and 50 000 angstrom and which are exclusively based on empirical stellar spectra. To obtain these joint models, we combined the extended MILES models in the optical wi
Modeling the reverberation of optical polarization in AGN
Lobos, P Andrea Rojas; Marin, Frederic
2016-01-01
According to the standard paradigm, the strong and compact luminosity of active galactic nuclei (AGN) is due to multi-temperature black body emission originating from an accretion disk formed around a supermassive black hole. This central engine is thought to be surrounded by a dusty region along the equatorial plane and by ionized winds along the poles. The innermost regions cannot yet be resolved neither in the optical nor in the infrared and it is fair to say that we still lack a satisfactory understanding of the physical processes, geometry and composition of the central (sub-parsec) components of AGN. Like spectral or polarimetric observations, the reverberation data needs to be modeled in order to infer constraints on the AGN geometry (such as the inner radius or the half-opening angle of the dusty torus). In this research note, we present preliminary modeling results using a time-dependent Monte Carlo method to solve the radiative transfer in a simplified AGN set up. We investigate different model conf...
Institute of Scientific and Technical Information of China (English)
LIU Ji-yan; SI Yong-min
2004-01-01
Fibre-optic magnetic sensors with magnetostrictive films are used as all-fibre Mach-Zehnder interferometer to detect the optical phase shift, which is caused by the magnetostriction-induced strains transferred from the msgnetostrictive film to the fibre. A theoretical model based on the plane strain approximation and uniform axial strain is developed to determine the magneto-mechano-optical transfer relations in this kind of sensors. The expression for the model is presented as well as relation of the phase shift in the fibre to the magnetic and elastic properties of the magnetostrictive film coated on the fibre. And from the model, the thickness of the film has significant influence on the phase shift.
Modelling the Electro-Optic Properties of Liquid Crystals.
MacGregor, Alastair R.
Available from UMI in association with The British Library. Requires signed TDF. Liquid crystals (LCs) have been recognised as a phase of matter intermediate between solid and liquid for about 100 years. During this time a large variety of mesophases have been discovered but it is only recently that their physics have begun to be understood. However if LCs are to continue to compete successfully in the displays market an improved understanding of their electro-optic properties must be gained. This thesis describes work carried out on two different types of LC: nematic and ferroelectric chiral smectic C (SmC^{*} ). In the former the molecules are orientationally ordered and randomly positioned while in the latter they are orientationally ordered and arranged in layers. The local mean molecular orientation is called the director and defines the uniaxial optic axis in both types of LC. In a nematic guest-host (NGH) LC an anisotropically absorbing dye is dissolved in the LC and the dye molecules align so that their maximum absorption axis is parallel to the director. When an electric field is applied to a cell containing NGHLC the molecules tend to rotate, because of their dielectric anisotropy, and alter the cell's transmittance. Previous attempts to model the change in optical transmittance with voltage have assumed that the LC and dye molecules are perfectly aligned with the director. In this work the disorder of the molecules about the director is taken into account and the overall agreement between theory and experiment is improved considerably. A method of calculating how the SmC^ {*} director configuration and layer orientation vary with voltage is presented. This method is tested by calculating the transmittance of a 7 mu m thick SmC^{* } LC cell for different azimuthal orientations of the cell between crossed polarisers. It is shown that the theoretical and measured orientations which give minimum transmittance are in good agreement. It is also shown that the
Wavelength Division Multiplexing Passive Optical Network modeling Using Optical System Simulator
Directory of Open Access Journals (Sweden)
Nahla Abdulrahman Hussain
2015-09-01
Full Text Available Due to the continuing demand for larger bandwidth, the optical transport becoming general in the access network. Using optical fiber technologies, the communications infrastructure becomes powerful, providing very high speeds to transfer a high capacity of data. Existing telecommunications infrastructures is currently widely used Passive Optical Network that apply Wavelength Division Multiplexing (WDM and is awaited to play an important role in the future Internet supporting a large diversity of services and next generation networks. This paper presents a design of WDM-PON network, the simulation and analysis of transmission parameters in the Optisystem 7.0 environment for bidirectional traffic. The simulation shows the behavior of optical fiber links when the signal passes through all the components such as optical fiber, splitters, multiplexers then find a good quality of signal in all receivers. The system performance is presented through various parameters such as BER analyzer and the Eye Diagram.
Design-oriented analytic model of phase and frequency modulated optical links
Monsurrò, Pietro; Saitto, Antonio; Tommasino, Pasquale; Trifiletti, Alessandro; Vannucci, Antonello; Cimmino, Rosario F.
2016-07-01
An analytic design-oriented model of phase and frequency modulated microwave optical links has been developed. The models are suitable for design of broadband high dynamic range optical links for antenna remoting and optical beamforming, where noise and linearity of the subsystems are a concern Digital filter design techniques have been applied to the design of optical filters working as frequency discriminator, that are the bottleneck in terms of linearity for these systems. The models of frequency modulated, phase modulated, and coherent I/Q link have been used to compare performance of the different architectures in terms of linearity and SFDR.
Modeling the reverberation of optical polarization in AGN
Rojas Lobos, P. A.; Goosmann, R.; Marin, F.
2016-12-01
According to the standard paradigm, the strong and compact luminosity of active galactic nuclei (AGN) is due to multi-temperature black body emission originating from an accretion disk formed around a supermassive black hole. This central engine is thought to be surrounded by a dusty region along the equatorial plane and by ionized winds along the poles. The innermost regions cannot yet be resolved neither in the optical nor in the infrared and it is fair to say that we still lack a satisfactory understanding of the physical processes, geometry and composition of the central (sub-parsec) components of AGN. Like spectral or polarimetric observations, the reverberation data needs to be modeled in order to infer constraints on the AGN geometry (such as the inner radius or the half-opening angle of the dusty torus). In this research note, we present preliminary modeling results using a time-dependent Monte Carlo method to solve the radiative transfer in a simplified AGN set up. We investigate different model configurations using both polarization and time lags and find a high dependency on the geometry to the time-lag response. For all models there is a clear distinction between edge-on or face-on viewing angles for fluxes and time lags, the later showing a higher wavelength-dependence than the former. Time lags, polarization and fluxes point toward a clear dichotomy between the different inclinations of AGN, a method that could help us to determine the true orientation of the nucleus in Seyfert galaxies.
Optical character recognition of handwritten Arabic using hidden Markov models
Energy Technology Data Exchange (ETDEWEB)
Aulama, Mohannad M. [University of Jordan; Natsheh, Asem M. [University of Jordan; Abandah, Gheith A. [University of Jordan; Olama, Mohammed M [ORNL
2011-01-01
The problem of optical character recognition (OCR) of handwritten Arabic has not received a satisfactory solution yet. In this paper, an Arabic OCR algorithm is developed based on Hidden Markov Models (HMMs) combined with the Viterbi algorithm, which results in an improved and more robust recognition of characters at the sub-word level. Integrating the HMMs represents another step of the overall OCR trends being currently researched in the literature. The proposed approach exploits the structure of characters in the Arabic language in addition to their extracted features to achieve improved recognition rates. Useful statistical information of the Arabic language is initially extracted and then used to estimate the probabilistic parameters of the mathematical HMM. A new custom implementation of the HMM is developed in this study, where the transition matrix is built based on the collected large corpus, and the emission matrix is built based on the results obtained via the extracted character features. The recognition process is triggered using the Viterbi algorithm which employs the most probable sequence of sub-words. The model was implemented to recognize the sub-word unit of Arabic text raising the recognition rate from being linked to the worst recognition rate for any character to the overall structure of the Arabic language. Numerical results show that there is a potentially large recognition improvement by using the proposed algorithms.
Optical character recognition of handwritten Arabic using hidden Markov models
Aulama, Mohannad M.; Natsheh, Asem M.; Abandah, Gheith A.; Olama, Mohammed M.
2011-04-01
The problem of optical character recognition (OCR) of handwritten Arabic has not received a satisfactory solution yet. In this paper, an Arabic OCR algorithm is developed based on Hidden Markov Models (HMMs) combined with the Viterbi algorithm, which results in an improved and more robust recognition of characters at the sub-word level. Integrating the HMMs represents another step of the overall OCR trends being currently researched in the literature. The proposed approach exploits the structure of characters in the Arabic language in addition to their extracted features to achieve improved recognition rates. Useful statistical information of the Arabic language is initially extracted and then used to estimate the probabilistic parameters of the mathematical HMM. A new custom implementation of the HMM is developed in this study, where the transition matrix is built based on the collected large corpus, and the emission matrix is built based on the results obtained via the extracted character features. The recognition process is triggered using the Viterbi algorithm which employs the most probable sequence of sub-words. The model was implemented to recognize the sub-word unit of Arabic text raising the recognition rate from being linked to the worst recognition rate for any character to the overall structure of the Arabic language. Numerical results show that there is a potentially large recognition improvement by using the proposed algorithms.
Accurate mask model implementation in optical proximity correction model for 14-nm nodes and beyond
Zine El Abidine, Nacer; Sundermann, Frank; Yesilada, Emek; Farys, Vincent; Huguennet, Frederic; Armeanu, Ana-Maria; Bork, Ingo; Chomat, Michael; Buck, Peter; Schanen, Isabelle
2016-04-01
In a previous work, we demonstrated that the current optical proximity correction model assuming the mask pattern to be analogous to the designed data is no longer valid. An extreme case of line-end shortening shows a gap up to 10 nm difference (at mask level). For that reason, an accurate mask model has been calibrated for a 14-nm logic gate level. A model with a total RMS of 1.38 nm at mask level was obtained. Two-dimensional structures, such as line-end shortening and corner rounding, were well predicted using scanning electron microscopy pictures overlaid with simulated contours. The first part of this paper is dedicated to the implementation of our improved model in current flow. The improved model consists of a mask model capturing mask process and writing effects, and a standard optical and resist model addressing the litho exposure and development effects at wafer level. The second part will focus on results from the comparison of the two models, the new and the regular.
Bogoni, Antonella; Potì, Luca; Ponzini, Filippo; Ghelfi, Paolo
2006-01-01
The electrical modeling of complex electrooptical devices is a useful task for the correct design of its schemes and for the estimation of its performance. In this paper, we consider an electrooptical phase-locked loop (PLL) used to synchronize an RF system clock to the repetition rate of an optical pulsed source, realized by an active fiber mode-locking (ML) technique in the regenerative configuration. The synchronization scheme is suggested by a description of the pulsed source, for the first time, as an optical voltage-control oscillator (VCO). In particular, we present a simple new all-electrical model for the proposed optical VCO, and we verify its accuracy by the implementation of the whole PLL scheme at 2.5 and 10 GHz.
Optical Network Models and Their Application to Software-Defined Network Management
Directory of Open Access Journals (Sweden)
Thomas Szyrkowiec
2017-01-01
Full Text Available Software-defined networking is finding its way into optical networks. Here, it promises a simplification and unification of network management for optical networks allowing automation of operational tasks despite the highly diverse and vendor-specific commercial systems and the complexity and analog nature of optical transmission. Common abstractions and interfaces are a fundamental component for software-defined optical networking. Currently, a number of models for optical networks are available. They all claim to provide open and vendor agnostic management of optical equipment. In this work, we survey and compare the most important models and propose an intent interface for creating virtual topologies which is integrated in the existing model ecosystem.
Feng, Ying; Zeng, Xin; Li, Wei-hua; Wang, Wen-cong; Ou-Yang, Li-si; Sun, Xi; Lv, Zhiyue; Wu, Zhong-Dao
2014-11-01
Human Angiostrongylus cantonensis (A. cantonensis) is a food-borne parasitic disease and can cause optic neuritis. Increasing clinical angiostrongyliasis cases with optic neuritis have been reported, but the pathogenesis has not been fully understood until now. Here, we applied rats with A. cantonensis infection as an animal model to study the pathogenesis of optic neuritis caused by the infection. We observed that the optic disk of experimental rats appeared hyperemic, the retina vein became thick, and the visual evoked potential (VEP) latency was prolonged. There were obvious inflammatory cell infiltration in the retina and optic nerve adventitia followed with obvious optic nerve fiber demyelination and retina ganglion swelling. We also evaluated the effect of dexamethasone combined with albendazole on optic neuritis of rats infected with A. cantonensis. The results showed it had no obvious effect to prevent progressive visual deterioration for optic neuritis caused by A. cantonensis. The studies provided evidence that the pathogenesis of optic neuritis in infected rats was correlated to optic nerve demyelination and ganglion cell damage caused by optic nerve inflammation, and the common therapy to this disease was not so effective. Based on the above results, it may be necessary to combine neuroprotective agents with common therapy to treat and protect optic nerve and ganglion cells from their secondary injury.
Modeling of coherent ultrafast magneto-optical experiments: Light-induced molecular mean-field model
Energy Technology Data Exchange (ETDEWEB)
Hinschberger, Y. [Instituto de Física dos Materiais da Universidade do Porto, Departamento de Física et Astronomia, Rua do campo Alegre, 687, 4169-007 Porto (Portugal); Hervieux, P.-A. [Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504 BP 43 - F-67034 Strasbourg Cedex 2 (France)
2015-12-28
We present calculations which aim to describe coherent ultrafast magneto-optical effects observed in time-resolved pump-probe experiments. Our approach is based on a nonlinear semi-classical Drude-Voigt model and is used to interpret experiments performed on nickel ferromagnetic thin film. Within this framework, a phenomenological light-induced coherent molecular mean-field depending on the polarizations of the pump and probe pulses is proposed whose microscopic origin is related to a spin-orbit coupling involving the electron spins of the material sample and the electric field of the laser pulses. Theoretical predictions are compared to available experimental data. The model successfully reproduces the observed experimental trends and gives meaningful insight into the understanding of magneto-optical rotation behavior in the ultrafast regime. Theoretical predictions for further experimental studies are also proposed.
The Dynamics of Semiconductor Optical Amplifiers – Modeling and Applications
DEFF Research Database (Denmark)
Mørk, Jesper; Nielsen, Mads Lønstrup; Berg, Tommy Winther
2003-01-01
The importance of semiconductor optical amplifiers is discussed. A semiconductor optical amplifier (SOA) is a semiconductor laser with anti-reflection coated facets that amplifies an injected light signal by means of stimulated emission. SOAs have a number of unique properties that open up...
General Theoretical Model for Resonantly Enhanced Optical Modulators
Institute of Scientific and Technical Information of China (English)
Yuvaraja; S.; Visagathilagar; Arnan; Mitchell; Michael; W.; Austin
2003-01-01
1 IntroductionLiNbO3 optical modulators have become essential transmission devices for current and future wideband fibre-optic communications for both military and telecommunications applications. For many telecommunications applications, only a narrow bandwidth is required and thus resonantly enhancedMach-Zehndermodulators(RE-MZMs)have been developed to improve modulation efficiency at the expense of bandwidth.
Analytic Models for Radiation Induced Loss in Optical Fibers II. A Physical Model,
1984-06-01
and identify by Mock number) PIEL GRUP UB.GR. Optical fibers Analytical models Radiation effects 19. ABSTRACT (ConinueII. anl mwr,f fneciua,, and...conditions specified in the derivation of the equations existed during the irradiations. This is because the functional form of the equations is not...tion is not necessarily incorrect. If one assumes a relatively simple form of re- covery as a function of time, such as an exponential recovery, it can
Modelling Thermoelastic Distortion of Optics Using Elastodynamic Reciprocity
King, Eleanor; Veitch, Peter; Levin, Yuri
2015-01-01
Thermoelastic distortion resulting from optical absorption by transmissive and reflective optics can cause unacceptable changes in optical systems that employ high power beams. In advanced-generation laser-interferometric gravitational wave detectors for example, optical absorption is expected to result in wavefront distortions that would compromise the sensitivity of the detector; thus necessitating the use of adaptive thermal compensation. Unfortunately, these systems have long thermal time constants and so predictive feed-forward control systems could be required - but the finite-element analysis is computationally expensive. We describe here the use of the Betti-Maxwell elastodynamic reciprocity theorem to calculate the response of linear elastic bodies (optics) to heating that has arbitrary spatial distribution. We demonstrate using a simple example, that it can yield accurate results in computational times that are significantly less than those required for finite-element analyses.
Multimodal nonlinear optical imaging of cartilage development in mouse model
He, Sicong; Xue, Wenqian; Sun, Qiqi; Li, Xuesong; Huang, Jiandong; Qu, Jianan Y.
2017-02-01
Kinesin-1 is a kind of motor protein responsible for intracellular transportation and has been studied in a variety of tissues. However, its roles in cartilage development are not clear. In this study, a kinesin-1 heavy chain (Kif5b) knockout mouse model is used to study the functions of kinesin-1 in the cartilage development. We developed a multimodal nonlinear optical (NLO) microscope system integrating stimulated Raman scattering (SRS), second harmonic generation (SHG) and two-photon excited fluorescence (TPEF) to investigate the morphological and biomedical characteristics of fresh tibial cartilage from normal and mutant mice at different developmental stages. The combined forward and backward SHG imaging resolved the fine structure of collagen fibrils in the extracellular matrix of cartilage. Meanwhile, the chondrocyte morphology in different zones of cartilage was visualized by label-free SRS and TPEF images. The results show that the fibrillar collagen in the superficial zone of cartilage in postnatal day 10 and 15 (P10 and P15) knockout mice was significantly less than that of control mice. Moreover, we observed distorted morphology and disorganization of columnar arrangement of chondrocytes in the growth plate cartilage of mutant mice. This study reveals the significant roles of kinesin-1 in collagen formation and chondrocyte morphogenesis.
Modelling of bio-optical parameters of open ocean waters
Directory of Open Access Journals (Sweden)
Vadim N. Pelevin
2001-12-01
Full Text Available An original method for estimating the concentration of chlorophyll pigments, absorption of yellow substance and absorption of suspended matter without pigments and yellow substance in detritus using spectral diffuse attenuation coefficient for downwelling irradiance and irradiance reflectance data has been applied to sea waters of different types in the open ocean (case 1. Using the effective numerical single parameter classification with the water type optical index m as a parameter over the whole range of the open ocean waters, the calculations have been carried out and the light absorption spectra of sea waters tabulated. These spectra are used to optimize the absorption models and thus to estimate the concentrations of the main admixtures in sea water. The value of m can be determined from direct measurements of the downward irradiance attenuation coefficient at 500 nm or calculated from remote sensing data using the regressions given in the article. The sea water composition can then be readily estimated from the tables given for any open ocean area if that one parameter m characterizing the basin is known.
Powell, Samuel; Arridge, Simon R.; Leung, Terence S.
2015-03-01
Ultrasound-modulated optical tomography is an emerging biomedical imaging modality which uses the spatially localised acoustically-driven modulation of coherent light as a probe of the structure and optical properties of biological tissues. In this work we model the first-harmonic flux generated by the coupled physics using a simple linearised diffusion-style forward model. We derive analytical expressions for the sensitivity of this measurement type with respect to the optical absorption and scattering coefficients. These correlation measurement density functions can be employed as part of an image-reconstruction procedure capable of reconstructing quantitative images of the optical properties of a medium under investigation.
A traffic model of optical networks based on time-space complexity and traffic grooming
Institute of Scientific and Technical Information of China (English)
Zhao Yongli; Zhang Jie; Han Dahai; Wang Lei; Chen Xiuzhong; Gu Wanyi
2009-01-01
This paper researched the traffic of optical networks in time-space complexity, proposed a novel traffic model for complex optical networks based on traffic grooming, designed a traffic generator GTS (generator based on time and space) with "centralized + distributed" idea, and then made a simulation in C language. Experiments results show that GTS can produce the virtual network topology which can change dynamically with the characteristic of scaling-free network. GTS can also groom the different traffic and trigger them under real-time or scheduling mechanisms, generating different optical connections. This traffic model is convenient for the simulation of optical networks considering the traffic complexity.
A model of the mammalian optic nerve fibre based on experimental data.
Oozeer, M; Veraart, C; Legat, V; Delbeke, J
2006-08-01
Several experimental data about membrane dynamics and pharmacological sensitivities of optic nerve axons have been published. The present work summarizes these data and computer simulations have been used to develop a model of the mammalian optic nerve fibre. The ionic currents description were derived from existing membrane models and particularly from a model of the somatic retinal ganglion cell (RGC) impulse generation. However, original equations had to be modified to match experimental data, which suggests that in RGCs, axonal and somatic ion channel expression are different. The new model is consistent with recent experimental results about optic nerve axonal excitability.
Dabirian, Ali
2017-02-15
High-efficiency crystalline silicon (c-Si) solar cells increasingly feature sophisticated electron and hole contacts aimed at minimizing electronic losses. At the rear of photovoltaic devices, such contacts—usually consisting of stacks of functional layers—offer opportunities to enhance the infrared response of the solar cells. Here, we propose an accurate and simple modeling procedure to evaluate the infrared performance of rear contacts in c-Si solar cells. Our method combines full-wave electromagnetic modeling of the rear contact with a statistical ray optics model to obtain the fraction of optical energy dissipated from the rear contact relative to that absorbed by the Si wafer. Using this technique, we study the impact of the refractive index, extinction coefficient, and thickness of the rear-passivating layer and establish basic design rules. In addition, we evaluate novel optical structures, including stratified thin films, nanoparticle composites, and conductive nanowires embedded in a low-index dielectric matrix, for integration into advanced rear contacts in c-Si photovoltaic devices. From an optical perspective, nanowire structures preserving low contact resistance appear to be the most effective approach to mitigating dissipation losses from the rear contact.
Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination.
You, Yuyi; Gupta, Vivek K; Chitranshi, Nitin; Reedman, Brittany; Klistorner, Alexander; Graham, Stuart L
2015-07-29
The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to monitor the disease course in the follow-up period. Changes in the VEP parameters closely correlate with pathological damage in the optic nerve. This protocol provides a detailed description about the rodent model of optic nerve microinjection, in which a partial demyelination lesion is produced in the optic nerve. VEP recording techniques are also discussed. Using skull implanted electrodes, we are able to acquire reproducible intra-session and between-session VEP traces. VEPs can be recorded on individual animals over a period of time to assess the functional changes in the optic nerve longitudinally. The optic nerve demyelination model, in conjunction with the VEP recording protocol, provides a tool to investigate the disease processes associated with demyelination and remyelination, and can potentially be employed to evaluate the effects of new remyelinating drugs or neuroprotective therapies.
Eng, Ron; Arnold, William R.; Baker, Markus A.; Bevan, Ryan M.; Burdick, Gregory; Effinger, Michael R.; Gaddy, Darrell E.; Goode, Brian K.; Hanson, Craig; Hogue, William D.; Kegley, Jeffrey R.; Kirk, Charlie; Maffett, Steven P.; Matthews, Gary W.; Siler, Richard D.; Smith, W. Scott; Stahl, H. Philip; Tucker, John M.; Wright, Ernest R.
2013-09-01
A 43cm diameter stacked core mirror demonstrator was interferometrically tested at room temperature down to 250 degrees Kelvin for thermal deformation. The 2.5m radius of curvature spherical mirror assembly was constructed by low temperature fusing three abrasive waterjet core sections between two CNC pocket milled face sheets. The 93% lightweighted Corning ULE® mirror assembly represents the current state of the art for future UV, optical, near IR space telescopes. During the multiple thermal test cycles, test results of interferometric test, thermal IR images of the front face were recorded in order to validate thermal optical model.
Eng, Ron; Arnold, William R.; Baker, Marcus A.; Bevan, Ryan M.; Burdick, Gregory; Effinger, Michael R.; Gaddy, Darrell E.; Goode, Brian K.; Hanson, Craig; Hogue, William D.; Kegley, Jeffrey R.; Kirk, Charlie; Maffett, Steven P.; Matthews, Gary W.; Siler, Richard D.; Smith, W. Scott; Stahl, H. Philip; Tucker, John M.; Wright, Ernest R.
2013-01-01
A 43cm diameter stacked core mirror demonstrator was interferometrically tested at room temperature down to 250 degrees Kelvin for thermal deformation. The 2.5m radius of curvature spherical mirror assembly was constructed by low temperature fusing three abrasive waterjet core sections between two CNC pocket milled face sheets. The 93% lightweighted Corning ULE® mirror assembly represents the current state of the art for future UV, optical, near IR space telescopes. During the multiple thermal test cycles, test results of interferometric test, thermal IR images of the front face were recorded in order to validate thermal optical model.
Eng, Ron; Arnold, William; Baker, Markus A.; Bevan, Ryan M.; Carpenter, James R.; Effinger, Michael R.; Gaddy, Darrell E.; Goode, Brian K.; Kegley, Jeffrey R.; Hogue, William D.; Siler, Richard D.; Smith, W. Scott; Stahl. H. Philip; Tucker, John M.; Wright, Ernest R.; Kirk, Charles S.; Hanson, Craig; Burdick, Gregory; Maffett, Steven
2013-01-01
A 40 cm diameter mirror assembly was interferometrically tested at room temperature down to 250 degrees Kelvin for thermal deformation. The 2.5 m radius of curvature spherical mirror assembly was constructed by low temperature fusing three abrasive waterjet core sections between two face sheets. The 93% lightweighted Corning ULE mirror assembly represents the current state of the art for future UV, optical, near IR space telescopes. During the multiple thermal test cycles, test results of interferometric test, thermal IR images of the front face were recorded in order to validate thermal optical model.
Modeling and model-aware signal processing methods for enhancement of optical systems
Aksoylar, Aydan
Theoretical and numerical modeling of optical systems are increasingly being utilized in a wide range of areas in physics and engineering for characterizing and improving existing systems or developing new methods. This dissertation focuses on determining and improving the performance of imaging and non-imaging optical systems through modeling and developing model-aware enhancement methods. We evaluate the performance, demonstrate enhancements in terms of resolution and light collection efficiency, and improve the capabilities of the systems through changes to the system design and through post-processing techniques. We consider application areas in integrated circuit (IC) imaging for fault analysis and malicious circuitry detection, and free-form lens design for creating prescribed illumination patterns. The first part of this dissertation focuses on sub-surface imaging of ICs for fault analysis using a solid immersion lens (SIL) microscope. We first derive the Green's function of the microscope and use it to determine its resolution limits for bulk silicon and silicon-on-insulator (SOI) chips. We then propose an optimization framework for designing super-resolving apodization masks that utilizes the developed model and demonstrate the trade-offs in designing such masks. Finally, we derive the full electromagnetic model of the SIL microscope that models the image of an arbitrary sub-surface structure. With the rapidly shrinking dimensions of ICs, we are increasingly limited in resolving the features and identifying potential modifications despite the resolution improvements provided by the state-of-the-art microscopy techniques and enhancement methods described here. In the second part of this dissertation, we shift our focus away from improving the resolution and consider an optical framework that does not require high resolution imaging for detecting malicious circuitry. We develop a classification-based high-throughput gate identification method that utilizes
Zhu, Guangzhi; Qiu, Yuli; Wang, Zexiong; Zhu, Xiao; Zhu, Changhong
2016-08-01
An analytical model is developed to analyze the optical field distribution of thin disk laser with a thermal-optical aberration gain medium. The fundamental mode field distribution is calculated by using the eigenvector method of the resonator transit matrix for different pumping parameters. The analytical results show that the uniformity of the pumping spot is an important factor that impacts the beam quality of thin disk laser. The uniform pumping spot is beneficial to decrease thermal aberration and Optical Path Difference (OPD) of thin disk crystal, and to improve the beam quality. However, the beam quality still decreases slightly with the increasing of pumping intensity under the uniform pumping condition. The main reason for degradation of beam quality is the aspherical part of OPD which leads to diffraction losses of the resonator and wavefront deformation.
Holzlöhner, R.; Taubenberger, S.; Rakich, A. P.; Noethe, L.; Schipani, P.; Kuijken, K.
2016-08-01
We study a novel focal plane wavefront sensing and active optics control scheme at the VST on Cerro Paranal, an f/5.5 survey telescope with a 1x1 degree field of view and a 2.6m primary mirror. This scheme analyzes the elongation pattern of stellar PSFs across the full science image (256 Mpixels) and compares their second moments with an analytical model based on 5th-order geometrical optics. We consider 11 scalar degrees of freedom in mirror misalignments and deformations (M2 piston, tip/tilt and lateral displacement, detector tip/tilt, plus M1 figure astigmatism and trefoil). Using a numerical optimization method, we extract up to 4000 stars and complete the fitting process in under one minute. We demonstrate successful closed-loop active optics control based on maximum likelihood filtering.
Helium-3 Microscopic Optical Model Potential Based on Skyrme Interaction
Institute of Scientific and Technical Information of China (English)
2008-01-01
<正>The helium-3 microscopic optical potential is obtained by Green function method through nuclear matter approximation and local density approximation based on the effective Skyrme interaction. The reaction cross
A General Epipolar-Line Model between Optical and SAR Images and Used in Image Matching
Directory of Open Access Journals (Sweden)
Shuai Xing
2014-02-01
Full Text Available The search space and strategy are important for optical and SAR image matching. In this paper a general epipolar-line model has been proposed between linear array push-broom optical and SAR images. Then a dynamic approximate epipolar-line constraint model (DAELCM has been constructed and used to construct a new image matching algorithm with Harris operator and CRA. Experimental results have shown that the general epipolar-line model is valid and successfully used in optical and SAR image matching, and effectively limits the search space and decreased computation.
Problems of large neurodynamics system modeling: optical synergetics and neural networks
Vorontsov, Mikhail A.
1991-04-01
The possibilities of modeling developed neuronetwork dynamics are investigated by nonlinear coherent optical systems with a 2-D feedback. A comparative analysis of neuron-like systems of various physical nature has been made. The results of experimental investigations of nonlinear optical system dynamics with nonlocal connections are discussed.
Modelling of optically stimulated luminescence of zircon : assessment of the suitability for dating
Turkin, A.A.; Vainshtein, D.I.; Hartog, H.W. den
2006-01-01
The mineral zircon, ZrSiO4, is a candidate material for optical dating because it exhibits luminescence after exposure to natural radioactivity. The kinetic model of zircon thermally stimulated luminescence proposed before has been modified and used to investigate optically Stimulated luminescence (
Modeling of semiconductor devices for high-speed all-optical signal processing
DEFF Research Database (Denmark)
Bischoff, Svend; Højfeldt, Sune; Mørk, Jesper
2001-01-01
The all-optical signal processing performance of devices based on active semiconductor waveguides is investigated. A large signal model is used to analyse the physical mechanisms limiting the high-speed performance of both semiconductor optical amplifiers (SOAs) and electro-absorption modulators ...
Directory of Open Access Journals (Sweden)
S. Dutkiewicz
2015-07-01
This new model that captures bio-optical feedbacks will be important for improving our understanding of the role of light and optical constituents on ocean biogeochemistry, especially in a changing environment. Further, resolving surface upwelling irradiance will make it easier to connect to satellite-derived products in the future.
Modelling of the Optical Detector System in a Compact Disc Player
DEFF Research Database (Denmark)
Odgaard, Peter Fogh; Stoustrup, Jakob; Andersen, Palle;
2003-01-01
The cross-couplings between focus and radial tracking servos in compact disc players are important, but the optical cross couplings are not well described in the literature. In this paper an optical model of a compact disc player based on the three beam single foucault detector principle is found......, which includes the cross couplings between focus and radial loops....
Modeling the video distribution link in the Next Generation Optical Access Networks
DEFF Research Database (Denmark)
Amaya, F.; Cárdenas, A.; Tafur Monroy, Idelfonso
2011-01-01
In this work we present a model for the design and optimization of the video distribution link in the next generation optical access network. We analyze the video distribution performance in a SCM-WDM link, including the noise, the distortion and the fiber optic nonlinearities. Additionally, we...
Lin, Alex W H; Lewinski, Nastassja A; West, Jennifer L; Halas, Naomi J; Drezek, Rebekah A
2005-01-01
Many optical diagnostic approaches rely on changes in scattering and absorption properties to generate optical contrast between normal and diseased tissue. Recently, there has been increasing interest in using exogenous agents to enhance this intrinsic contrast with particular emphasis on the development for targeting specific molecular features of disease. Gold nanoshells are a class of core-shell nanoparticles with an extremely tunable peak optical resonance ranging from the near-UV to the mid-IR wavelengths. Using current chemistries, nanoshells of a wide variety of core and shell sizes can easily be fabricated to scatter and/or absorb light with optical cross sections often several times larger than the geometric cross section. Using gold nanoshells of different size and optical parameters, we employ Monte Carlo models to predict the effect of varying concentrations of nanoshells on tissue reflectance. The models demonstrate the importance of absorption from the nanoshells on remitted signals even when the optical extinction is dominated by scattering. Furthermore, because of the strong optical response of nanoshells, a considerable change in reflectance is observed with only a very small concentration of nanoshells. Characterizing the optical behavior of gold nanoshells in tissue will aid in developing nanoshells as contrast agents for optical diagnostics.
Quantum simulation of correlated-hopping models with fermions in optical lattices
Liberto, M. Di; Creffield, C. E.; Japaridze, G. I.; Smith, C. Morais
2014-01-01
By using a modulated magnetic field in a Feshbach resonance for ultracold fermionic atoms in optical lattices, we show that it is possible to engineer a class of models usually referred to as correlated-hopping models. These models differ from the Hubbard model in exhibiting additional density-depen
Modeling and Control of Magnetic Fluid Deformable Mirrors for Adaptive Optics Systems
Wu, Zhizheng; Ben Amara, Foued
2013-01-01
Modeling and Control of Magnetic Fluid Deformable Mirrors for Adaptive Optics Systems presents a novel design of wavefront correctors based on magnetic fluid deformable mirrors (MFDM) as well as corresponding control algorithms. The presented wavefront correctors are characterized by their linear, dynamic response. Various mirror surface shape control algorithms are presented along with experimental evaluations of the performance of the resulting adaptive optics systems. Adaptive optics (AO) systems are used in various fields of application to enhance the performance of optical systems, such as imaging, laser, free space optical communication systems, etc. This book is intended for undergraduate and graduate students, professors, engineers, scientists and researchers working on the design of adaptive optics systems and their various emerging fields of application. Zhizheng Wu is an associate professor at Shanghai University, China. Azhar Iqbal is a research associate at the University of Toronto, Canada. Foue...
Full wave model of image formation in optical coherence tomography applicable to general samples.
Munro, Peter R T; Curatolo, Andrea; Sampson, David D
2015-02-09
We demonstrate a highly realistic model of optical coherence tomography, based on an existing model of coherent optical microscopes, which employs a full wave description of light. A defining feature of the model is the decoupling of the key functions of an optical coherence tomography system: sample illumination, light-sample interaction and the collection of light scattered by the sample. We show how such a model can be implemented using the finite-difference time-domain method to model light propagation in general samples. The model employs vectorial focussing theory to represent the optical system and, thus, incorporates general illumination beam types and detection optics. To demonstrate its versatility, we model image formation of a stratified medium, a numerical point-spread function phantom and a numerical phantom, based upon a physical three-dimensional structured phantom employed in our laboratory. We show that simulated images compare well with experimental images of a three-dimensional structured phantom. Such a model provides a powerful means to advance all aspects of optical coherence tomography imaging.
Experimental verification of optical models of graphene with multimode slab waveguides.
Chang, Zeshan; Chiang, Kin Seng
2016-05-01
We compare three optical models of graphene, namely, the interface model, the isotropic model, and the anisotropic model, and verify them experimentally with two multimode slab waveguide samples operating at the wavelengths of 632.8 and 1536 nm. By comparing the calculated graphene-induced losses and the measurement data, we confirm that the interface model and the anisotropic model give correct results for both the transverse electric (TE) and transverse magnetic modes, while the isotropic model gives correct results only for the TE modes. With the experimental data, we also quantitatively verify the widely used expression for the surface conductivity of graphene in the optical regime. Our findings clarify the issue of modeling graphene in the analysis of graphene-incorporated waveguides and offer deeper insight into the optical properties of graphene for waveguide applications.
Surface modeling for optical fabrication with linear ion source
Wu, Lixiang; Shao, Jianda
2016-01-01
We present a concept of surface decomposition extended from double Fourier series to nonnegative sinusoidal wave surfaces, on the basis of which linear ion sources apply to the ultra-precision fabrication of complex surfaces and diffractive optics. It is the first time that we have a surface descriptor for building a relationship between the fabrication process of optical surfaces and the surface characterization based on PSD analysis, which akin to Zernike polynomials used for mapping the relationship between surface errors and Seidel aberrations. Also, we demonstrate that the one-dimensional scanning of linear ion source is applicable to the removal of surface errors caused by small-tool polishing in raster scan mode as well as the fabrication of beam sampling grating of high diffractive uniformity without a post-processing procedure. The simulation results show that, in theory, optical fabrication with linear ion source is feasible and even of higher output efficiency compared with the conventional approac...
The value of adding optics to ecosystem models: a case study
Directory of Open Access Journals (Sweden)
M. Fujii
2007-10-01
Full Text Available Many ecosystem models have been developed to study the ocean's biogeochemical properties, but most of these models use simple formulations to describe light penetration and spectral quality. Here, an optical model is coupled with a previously published ecosystem model that explicitly represents two phytoplankton (picoplankton and diatoms and two zooplankton functional groups, as well as multiple nutrients and detritus. Surface ocean color fields and subsurface light fields are calculated by coupling the ecosystem model with an optical model that relates biogeochemical standing stocks with inherent optical properties (absorption, scattering; this provides input to a commercially available radiative transfer model (Ecolight. We apply this bio-optical model to the equatorial Pacific upwelling region, and find the model to be capable of reproducing many measured optical properties and key biogeochemical processes in this region. Our model results suggest that non-algal particles largely contribute to the total scattering or attenuation (>50% at 660 nm but have a much smaller contribution to particulate absorption (<20% at 440 nm, while picoplankton dominate the total phytoplankton absorption (>95% at 440 nm. These results are consistent with the field observations. In order to achieve such good agreement between data and model results, however, key model parameters, for which no field data are available, have to be constrained. Sensitivity analysis of the model results to optical parameters reveals a significant role played by colored dissolved organic matter through its influence on the quantity and quality of the ambient light. Coupling explicit optics to an ecosystem model provides advantages in generating: (1 a more accurate subsurface light-field, which is important for light sensitive biogeochemical processes such as photosynthesis and photo-oxidation, (2 additional constraints on model parameters that help to reduce uncertainties in
Optical fiber communication systems with Matlab and Simulink models
Binh, Le Nguyen
2014-01-01
""This book adds an aspect of programming and simulation not so well developed in other books. It is complete in this sense and enables directly linking the physics of optical components and systems to realistic results.""-Martin Rochette, Associate Professor, McGill University, Quebec, Canada""…this will be an excellent textbook since it has all new development and information on optical communication systems…I think this book can easily replace many other textbooks in this field.""-Massoud Moussavi, California State Polytechnic University-Pomona""The book is well written. It describes the fu
Directory of Open Access Journals (Sweden)
Wei Bengang
2016-01-01
Full Text Available In this paper, the different types of discharge in transformer were simulated based on the real transformer fault model. The optical partial discharge detection system was established based on optical sensors which were capturing partial discharge accompanied by optical effects. In this research, surface discharge and suspended discharge defect model was pressurized to generate partial discharge signal. The results showed that: Partial discharge optical signals could effectively respond the production and development process of transformer partial discharge. It was able to assess discharge level also. When the discharge phenomenon stabilized, the phase of surface discharge mainly between 60°~150°and 240°~330°, the phase of suspended discharge mainly between 260°~320°. According to the phase characteristic of discharge pattern, the creeping discharge and suspended discharge phenomenon of transformer can be distinguished. It laid the foundation for the application of transformer optical partial discharge detection technology.
Directory of Open Access Journals (Sweden)
Jana Sajgalikova
2015-01-01
Full Text Available Mathematical models for description of physical phenomena often use the statistical description of the individual phenomena and solve those using suitable methods. If we want to develop numerical model of optical communication system based on transmission through single mode optical fibres, we need to consider whole series of phenomena that affect various parts of the system. In the single-mode optical fibre we often encounter influence of chromatic dispersion and nonlinear Kerr effects. By observing various different degradation mechanisms, every numerical model should have its own limits, which fulfil more detailed specification. It is inevitable to consider them in evaluation. In this paper, we focus on numerical modelling of degradation mechanisms in single-mode optical fibre. Numerical solution of non-linear Schroedinger equation is performed by finite difference method applied in MATLAB environment and split-step Fourier method, which is implemented by VPIphotonics software.
Iso-spin Dependent Microscopic Optical Model Potential Based on Dirac Bruckner Haretree Fock Method
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
The microscopic optical model is investigated in the Dirac-Brueckner-Hartree-Fock (DBHF) framework with Bonn B meson exchange potential. Both real and imaginary parts of isospin-dependent self-energies are derived from a strict projection
Xin, Q.; Gong, P.; Li, W.
2015-02-01
Modeling vegetation photosynthesis is essential for understanding carbon exchanges between terrestrial ecosystems and the atmosphere. The radiative transfer process within plant canopies is one of the key drivers that regulate canopy photosynthesis. Most vegetation cover consists of discrete plant crowns, of which the physical observation departs from the underlying assumption of a homogenous and uniform medium in classic radiative transfer theory. Here we advance the Geometric Optical Radiative Transfer (GORT) model to simulate photosynthesis activities for discontinuous plant canopies. We separate radiation absorption into two components that are absorbed by sunlit and shaded leaves, and derive analytical solutions by integrating over the canopy layer. To model leaf-level and canopy-level photosynthesis, leaf light absorption is then linked to the biochemical process of gas diffusion through leaf stomata. The canopy gap probability derived from GORT differs from classic radiative transfer theory, especially when the leaf area index is high, due to leaf clumping effects. Tree characteristics such as tree density, crown shape, and canopy length affect leaf clumping and regulate radiation interception. Modeled gross primary production (GPP) for two deciduous forest stands could explain more than 80% of the variance of flux tower measurements at both near hourly and daily time scales. We also demonstrate that the ambient CO2 concentration influences daytime vegetation photosynthesis, which needs to be considered in state-of-the-art biogeochemical models. The proposed model is complementary to classic radiative transfer theory and shows promise in modeling the radiative transfer process and photosynthetic activities over discontinuous forest canopies.
Nonlocal dispersive optical model ingredients for ${}^{40}$Ca
Mahzoon, M H; Dickhoff, W H; Dussan, H; Waldecker, S J
2013-01-01
A comprehensive description of all single-particle properties associated with the nucleus ${}^{40}$Ca has been generated by employing a nonlocal dispersive optical potential capable of simultaneously reproducing all relevant data above and below the Fermi energy. We gather all relevant functional forms and the numerical values of the parameters in this contribution.
Modeling delamination due to thermal stress in optical storage media
Nkansah, M. A.; Evans, K. E.
1990-04-01
Finite element analysis is used to calculate the shape of blisters formed in bilayer optical storage media due to the buildup of thermal stresses during laser writing. It is shown that practically usable blisters may be expected to form in a time period of about 15 ns. Such a thermal stress delamination process may also precede melting in conventional pit formation processes.
Advanced optical modelling of dynamically deposited silicon nitride layers
Borojevic, N.; Hameiri, Z.; Winderbaum, S.
2016-07-01
Dynamic deposition of silicon nitrides using in-line plasma enhanced chemical vapor deposition systems results in non-uniform structure of the dielectric layer. Appropriate analysis of such layers requires the optical characterization to be performed as a function of the layer's depth. This work presents a method to characterize dynamically deposited silicon nitride layers. The method is based on the fitting of experimental spectroscopic ellipsometry data via grading of Tauc-Lorentz optical parameters through the depth of the layer. When compared with the standard Tauc-Lorentz fitting procedure, used in previous studies, the improved method is demonstrating better quality fits to the experimental data and revealing more accurate optical properties of the dielectric layers. The most significant advantage of the method is the ability to extract the depth profile of the optical properties along the direction of the layer normal. This is enabling a better understanding of layers deposited using dynamic plasma enhanced chemical vapor deposition systems frequently used in the photovoltaic industry.
Ruiz Moreno, Sergio; Guitart Felip, Jorge
1993-01-01
The authors present a simple model of a travelling wave semiconductor optical amplifier with an appreciable degree of saturation. The model uses a particular way of linearising the total carrier recombination R(N) to find useful expressions for the saturation parameter and/or the carrier lifetime. By combining these expressions and the gain measurements realised, it is possible to establish the dependence between the mentioned parameters and the input optical power. Peer Reviewed
Second Approximation Model for Optical Head in Super High Density Storage Technology
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The paper presents second approximation model for optical head in super high-density storage technology firstly and it is an important part for three grades approximate model of ultra-small-size quantum well corn-shaped laser and simulative calculations. It supplies the important and useful results for the NFOD optical head design with ultra thin active layer and ultra small spot laser.
Numerical models and experiment of air flow in a simulation box for optical wireless communications
Directory of Open Access Journals (Sweden)
Latal Jan
2016-01-01
Full Text Available In this article, the authors focused on real measurements of mechanical turbulence generated by ventilators in the simulation box for Optical Wireless Communications. The mechanical turbulences disturb the optical beam that propagates along the central axis of the simulation box. The aim of authors is to show the effect of mechanical turbulence on optical beams at different heights in the simulation box. In the Ansys Fluent, we created numerical models which were then compared with real measurements. Authors compared the real and numerical models according to statistical methods.
A general numerical solution of dispersion relations for the nuclear optical model
Capote, R; Quesada, J M; Capote, Roberto; Molina, Alberto; Quesada, Jose Manuel
2001-01-01
A general numerical solution of the dispersion integral relation between the real and the imaginary parts of the nuclear optical potential is presented. Fast convergence is achieved by means of the Gauss-Legendre integration method, which offers accuracy, easiness of implementation and generality for dispersive optical model calculations. The use of this numerical integration method in the optical-model parameter search codes allows for a fast and accurate dispersive analysis. PACS number(s): 11.55.Fv, 24.10.Ht, 02.60.Jh
Light Path Model of Fiber Optic Liquid Level Sensor Considering Residual Liquid Film on the Wall
Directory of Open Access Journals (Sweden)
Zhijun Zhang
2015-01-01
Full Text Available The working principle of the refractive-type fiber optic liquid level sensor is analyzed in detail based on the light refraction principle. The optic path models are developed in consideration of common simplification and the residual liquid film on the glass tube wall. The calculating formulae for the model are derived, constraint conditions are obtained, influencing factors are discussed, and the scopes and skills of application are analyzed through instance simulations. The research results are useful in directing the correct usage of the fiber optic liquid level sensor, especially in special cases, such as those involving viscous liquid in the glass tube monitoring.
Modeling, Simulation, and Characterization of Electro-Optic Polymer Waveguide Devices.
Ma, Jiong
The primary objective of this thesis is to investigate the properties of optical polymer waveguides and switches, develop a phenomenological CAD tool, and to use this phenomenological tool to design optical polymer devices for high-speed interconnects in VLSI systems. In the investigations of optical polymer waveguides, a new phenomenological bleaching model that is able to predict optical index profiles for photobleached polymer films was developed. The theoretical model shows good agreement with measured results for the effective index and optical field distributions of waveguides, and the absorption of films. Based on this bleaching model, we can predict the index profile for polymer channel waveguides and formulate design rules for active optical switches and modulators. The model has been successfully applied to photobleached PMMA/DR1 and Ultem/DEDR1 waveguides. An experimental technique to determine the poling -induced optical birefringence and optical nonlinearity is also discussed. In this technique, absorption measurements are performed immediately after poling. The poling-induced index changes as a function of wavelength are obtained from the absorption changes using a Kramers-Kronig transformation. An alternative method for predicting the poling-induced index changes, requiring a combination of waveguide measurement techniques and order parameter calculations, exhibits good agreement. By combining the poling effects with the photobleaching index profile, a CAD tool has been developed to calculate the optical field distribution and loss which allows the design of active electro-optical modulators. Using the CAD tool together with an equivalent circuit model of electro-optic polymer switches, circuit level comparisons of a CMOS strip line interconnect with an external polymer modulator interconnect were performed in terms of power dissipation, bandwidth, and connection density. HSPICE was used as a circuit simulation tool. Based on this analysis, it is
New optical and radio frequency angular tropospheric refraction models for deep space applications
Berman, A. L.; Rockwell, S. T.
1976-01-01
The development of angular tropospheric refraction models for optical and radio frequency usage is presented. The models are compact analytic functions, finite over the entire domain of elevation angle, and accurate over large ranges of pressure, temperature, and relative humidity. Additionally, FORTRAN subroutines for each of the models are included.
Institute of Scientific and Technical Information of China (English)
Niu Chun-Hui; Li Zhi-Yuan; Ye Jia-Sheng; Gu Ben-Yuan
2005-01-01
Scalar diffraction theory, although simple and efficient, is too rough for analysing diffractive micro-optical elements.Rigorous vectorial diffraction theory requires extensive numerical efforts, and is not a convenient design tool. In this paper we employ a simple approximate vectorial diffraction model which combines the principle of the scalar diffraction theory with an approximate local field model to analyse the diffraction of optical waves by some typical two-dimensional diffractive micro-optical elements. The TE and TM polarization modes are both considered. We have found that the approximate vectorial diffraction model can agree much better with the rigorous electromagnetic simulation results than the scalar diffraction theory for these micro-optical elements.
Solar optical codes evaluation for modeling and analyzing complex solar receiver geometries
Yellowhair, Julius; Ortega, Jesus D.; Christian, Joshua M.; Ho, Clifford K.
2014-09-01
Solar optical modeling tools are valuable for modeling and predicting the performance of solar technology systems. Four optical modeling tools were evaluated using the National Solar Thermal Test Facility heliostat field combined with flat plate receiver geometry as a benchmark. The four optical modeling tools evaluated were DELSOL, HELIOS, SolTrace, and Tonatiuh. All are available for free from their respective developers. DELSOL and HELIOS both use a convolution of the sunshape and optical errors for rapid calculation of the incident irradiance profiles on the receiver surfaces. SolTrace and Tonatiuh use ray-tracing methods to intersect the reflected solar rays with the receiver surfaces and construct irradiance profiles. We found the ray-tracing tools, although slower in computation speed, to be more flexible for modeling complex receiver geometries, whereas DELSOL and HELIOS were limited to standard receiver geometries such as flat plate, cylinder, and cavity receivers. We also list the strengths and deficiencies of the tools to show tool preference depending on the modeling and design needs. We provide an example of using SolTrace for modeling nonconventional receiver geometries. The goal is to transfer the irradiance profiles on the receiver surfaces calculated in an optical code to a computational fluid dynamics code such as ANSYS Fluent. This approach eliminates the need for using discrete ordinance or discrete radiation transfer models, which are computationally intensive, within the CFD code. The irradiance profiles on the receiver surfaces then allows for thermal and fluid analysis on the receiver.
Optical-Model Description of Time-Reversal Violation
Hnizdo, V
1994-01-01
A time-reversal-violating spin-correlation coefficient in the total cross section for polarized neutrons incident on a tensor rank-2 polarized target is calculated by assuming a time-reversal-noninvariant, parity-conserving ``five-fold" interaction in the neutron-nucleus optical potential. Results are presented for the system $n + {^{165}{\\rm Ho}}$ for neutron incident energies covering the range 1--20 MeV. From existing experimental bounds, a strength of $2 \\pm 10$ keV is deduced for the real and imaginary parts of the five-fold term, which implies an upper bound of order $10^{-4}$ on the relative $T$-odd strength when compared to the central real optical potential.
AeroCom INSITU Project: Comparing modeled and measured aerosol optical properties
Andrews, Elisabeth; Schmeisser, Lauren; Schulz, Michael; Fiebig, Markus; Ogren, John; Bian, Huisheng; Chin, Mian; Easter, Richard; Ghan, Steve; Kokkola, Harri; Laakso, Anton; Myhre, Gunnar; Randles, Cynthia; da Silva, Arlindo; Stier, Phillip; Skeie, Ragnehild; Takemura, Toshihiko; van Noije, Twan; Zhang, Kai
2016-04-01
AeroCom, an open international collaboration of scientists seeking to improve global aerosol models, recently initiated a project comparing model output to in-situ, surface-based measurements of aerosol optical properties. The model/measurement comparison project, called INSITU, aims to evaluate the performance of a suite of AeroCom aerosol models with site-specific observational data in order to inform iterative improvements to model aerosol modules. Surface in-situ data has the unique property of being traceable to physical standards, which is an asset in accomplishing the overall goal of bettering the accuracy of aerosols processes and the predicative capability of global climate models. Here we compare dry, in-situ aerosol scattering and absorption data from ~75 surface, in-situ sites from various global aerosol networks (including NOAA, EUSAAR/ACTRIS and GAW) with a simulated optical properties from a suite of models participating in the AeroCom project. We report how well models reproduce aerosol climatologies for a variety of time scales, aerosol characteristics and behaviors (e.g., aerosol persistence and the systematic relationships between aerosol optical properties), and aerosol trends. Though INSITU is a multi-year endeavor, preliminary phases of the analysis suggest substantial model biases in absorption and scattering coefficients compared to surface measurements, though the sign and magnitude of the bias varies with location. Spatial patterns in the biases highlight model weaknesses, e.g., the inability of models to properly simulate aerosol characteristics at sites with complex topography. Additionally, differences in modeled and measured systematic variability of aerosol optical properties suggest that some models are not accurately capturing specific aerosol behaviors, for example, the tendency of in-situ single scattering albedo to decrease with decreasing aerosol extinction coefficient. The endgoal of the INSITU project is to identify specific
Modeling and compensation of transmitter nonlinearity in coherent optical OFDM.
Amiralizadeh, Siamak; Nguyen, An T; Rusch, Leslie A
2015-10-05
We present a comprehensive study of nonlinear distortions from an optical OFDM transmitter. Nonlinearities are introduced by the combination of effects from the digital-to-analog converter (DAC), electrical power amplifier (PA) and optical modulator in the presence of high peak-to-average power ratio (PAPR). We introduce parameters to quantify the transmitter nonlinearity. High input backoff avoids OFDM signal compression from the PA, but incurs high penalties in power efficiency. At low input backoff, common PAPR reduction techniques are not effective in suppressing the PA nonlinear distortion. A bit error distribution investigation shows a technique combining nonlinear predistortion with PAPR mitigation could achieve good power efficiency by allowing low input backoff. We use training symbols to extract the transmitter nonlinear function. We show that piecewise linear interpolation (PLI) leads to an accurate transmitter nonlinearity characterization. We derive a semi-analytical solution for bit error rate (BER) that validates the PLI approximation accurately captures transmitter nonlinearity. The inverse of the PLI estimate of the nonlinear function is used as a predistorter to suppress transmitter nonlinearity. We investigate performance of the proposed scheme by Monte Carlo simulations. Our simulations show that when DAC resolution is more than 4 bits, BER below forward error correction limit of 3.8 × 10(-3) can be achieved by using predistortion with very low input power backoff for electrical PA and optical modulator.
Computer Modeling and Simulation Evaluation of High Power LED Sources for Secondary Optical Design
Institute of Scientific and Technical Information of China (English)
SU Hong-dong; WANG Ya-jun; DONG Ji-yang; CHEN Zhong
2007-01-01
Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with its spatial and angular distribution. Merits and non-merits of traditional modeling methods when applied to high power LEDs based on secondary optical design are discussed. Two commercial high power LEDs are simulated using the proposed computer modeling method. Correlation coefficient is proposed to compare and analyze the simulation results and manufacturing specifications. The source model is precisely demonstrated by obtaining above 99% in correlation coefficient with different surface incident angle intervals.
Aden, Abdirahman; Anthony, Arthi; Brigi, Carel; Merchant, Muhammad Sabih; Siraj, Huda; Tomlins, Peter H.
2017-07-01
Dental enamel mineral loss is multifactorial and is consequently explored using a variety of in vitro models. Important factors include the presence of acidic pH and its specific ionic composition, which can both influence lesion characteristics. Optical coherence tomography (OCT) has been demonstrated as a promising tool for studying dental enamel demineralization. However, OCT-based characterization and comparison of demineralization model dynamics are challenging without a consistent experimental environment. Therefore, an automated four-dimensional OCT system was integrated with a multispecimen flow cell to measure and compare the optical properties of subsurface enamel demineralization in different models. This configuration was entirely automated, thus mitigating any need to disturb the specimens and ensuring spatial registration of OCT image volumes at multiple time points. Twelve bovine enamel disks were divided equally among three model groups. The model demineralization solutions were citric acid (pH 3.8), acetic acid (pH 4.0), and acetic acid with added calcium and phosphate (pH 4.4). Bovine specimens were exposed to the solution continuously for 48 h. Three-dimensional OCT data were obtained automatically from each specimen at a minimum of 1-h intervals from the same location within each specimen. Lesion dynamics were measured in terms of the depth below the surface to which the lesion extended and the attenuation coefficient. The net loss of surface enamel was also measured for comparison. Similarities between the dynamics of each model were observed, although there were also distinct characteristic differences. Notably, the attenuation coefficients showed a systematic offset and temporal shift with respect to the different models. Furthermore, the lesion depth curves displayed a discontinuous increase several hours after the initial acid challenge. This work demonstrated the capability of OCT to distinguish between different enamel demineralization
Progress in modeling polarization optical components for the Daniel K. Inouye Solar Telescope
Sueoka, Stacey Ritsuyo; Harrington, David M.
2016-07-01
The DKIST will have a suite of first-light polarimetric instrumentation requiring precise calibration of a complex articulated optical path. The optics are subject to large thermal loads caused by the 300Watts of collected solar irradiance across the 5 arc minute field of view. The calibration process requires stable optics to generate known polarization states. We present modeling of several optical, thermal and mechanical effects of the calibration optics, the first transmissive optical elements in the light path, because they absorb substantial heat. Previous studies showed significant angle of incidence effects from the f/13 converging beam and the 5 arc minute field of view, but were only modeled at a single nominal temperature. New thermal and polarization modeling of these calibration retarders shows heating causes significant stability limitations both in time and with field caused by the bulk temperature rise along with depth and radial thermal gradients. Modeling efforts include varying coating and material absorption, Mueller matrix stability estimates and mitigation efforts.
Internal model control of a fast steering mirror for electro-optical fine tracking
Xia, Yun-xia; Bao, Qi-liang; Wu, Qiong-yan
2010-11-01
The objective of this research is to develop advanced control methods to improve the bandwidth and tracking precision of the electro-optical fine tracking system using a fast steering mirror (FSM). FSM is the most important part in this control system. The model of FSM is established at the beginning of this paper. Compared with the electro-optical fine tracking system with ground based platform, the electro-optical fine tracking system with movement based platform must be a wide bandwidth and a robustness system. An advanced control method based on internal model control law is developed for electro-optical fine tracking system. The IMC is an advanced algorithm. Theoretically, it can eliminate disturbance completely and make sure output equals to input even there is model error. Moreover, it separates process to the system dynamic characteristic and the object perturbation. Compared with the PID controller, the controller is simpler and the parameter regulation is more convenient and the system is more robust. In addition, we design an improved structure based on classic IMC. The tracking error of the two-port control system is much better than which of the classic IMC. The simulation results indicate that the electro-optical control system based on the internal model control algorithm is very effective. It shows a better performance at the tracing precision and the disturbance suppresses. Thus a new method is provided for the high-performance electro-optical fine tracking system.
Numerical Modelling of Spontaneous Emission in Optical Parametric Amplifiers
DEFF Research Database (Denmark)
Friis, Søren Michael Mørk; Andersen, Ulrik Lund; Rottwitt, Karsten
2013-01-01
Fiber optical parametric processes offer a wide range of applications including phase sensitive as well as phase insensitive amplification, wavelength conversion and signal regeneration. One of the difficult challenges is any of these applications is to predict their associated noise performance....... However, it is well accepted that one contribution to the noise performance originates from vacuum fluctuations. In this work we show a novel approach to predict the spontaneous radiation from a parametric amplifier. In the approach the propagating fields are treated as a sum of a classical mean field...
Directory of Open Access Journals (Sweden)
Q. Xin
2015-02-01
Full Text Available Modeling vegetation photosynthesis is essential for understanding carbon exchanges between terrestrial ecosystems and the atmosphere. The radiative transfer process within plant canopies is one of the key drivers that regulate canopy photosynthesis. Most vegetation cover consists of discrete plant crowns, of which the physical observation departs from the underlying assumption of a homogenous and uniform medium in classic radiative transfer theory. Here we advance the Geometric Optical Radiative Transfer (GORT model to simulate photosynthesis activities for discontinuous plant canopies. We separate radiation absorption into two components that are absorbed by sunlit and shaded leaves, and derive analytical solutions by integrating over the canopy layer. To model leaf-level and canopy-level photosynthesis, leaf light absorption is then linked to the biochemical process of gas diffusion through leaf stomata. The canopy gap probability derived from GORT differs from classic radiative transfer theory, especially when the leaf area index is high, due to leaf clumping effects. Tree characteristics such as tree density, crown shape, and canopy length affect leaf clumping and regulate radiation interception. Modeled gross primary production (GPP for two deciduous forest stands could explain more than 80% of the variance of flux tower measurements at both near hourly and daily time scales. We also demonstrate that the ambient CO2 concentration influences daytime vegetation photosynthesis, which needs to be considered in state-of-the-art biogeochemical models. The proposed model is complementary to classic radiative transfer theory and shows promise in modeling the radiative transfer process and photosynthetic activities over discontinuous forest canopies.
Simulation and experimental results of optical and thermal modeling of gold nanoshells.
Ghazanfari, Lida; Khosroshahi, Mohammad E
2014-09-01
This paper proposes a generalized method for optical and thermal modeling of synthesized magneto-optical nanoshells (MNSs) for biomedical applications. Superparamagnetic magnetite nanoparticles with diameter of 9.5 ± 1.4 nm are fabricated using co-precipitation method and subsequently covered by a thin layer of gold to obtain 15.8 ± 3.5 nm MNSs. In this paper, simulations and detailed analysis are carried out for different nanoshell geometry to achieve a maximum heat power. Structural, magnetic and optical properties of MNSs are assessed using vibrating sample magnetometer (VSM), X-ray diffraction (XRD), UV-VIS spectrophotometer, dynamic light scattering (DLS), and transmission electron microscope (TEM). Magnetic saturation of synthesized magnetite nanoparticles are reduced from 46.94 to 11.98 emu/g after coating with gold. The performance of the proposed optical-thermal modeling technique is verified by simulation and experimental results.
Benchaabane, Aida; Ben Hamed, Zied; Kouki, Fayçal; Abderrahmane Sanhoury, Mohamed; Zellama, Kacem; Zeinert, Andreas; Bouchriha, Habib
2014-04-01
The effective medium model is applied to investigate the optical properties of hybrid nanocomposite layers of Polyvinylcarbazole (PVK) and nanoparticles of Zinc Selenide (ZnSe). Thin films of PVK:ZnSe nanocomposites show a porous microstructure with pore diameters of 500 nm. Numerical calculations led to the determination of optical constants such as the refractive index n, the extinction coefficient k, the dielectric permittivity ɛ, and absorption coefficient α. Using common theoretical models, we have determined the Cauchy parameters of the refractive index, namely, static ɛs and lattice ɛ∞ dielectric constants as well as the plasma frequency ωp, carrier density to effective mass ratio N/me*, and the optical conductivity σoc. We show that the optical band gap energy Eg of the nanocomposite structure decreases slightly upon the increase of the nanoparticles volume fraction and is in good agreement with the Vegard law.
Microscopic modeling of the effect of phonons on the optical properties of solid-state emitters
Norambuena, Ariel; Reyes, Sebastián A.; Mejía-Lopéz, José; Gali, Adam; Maze, Jerónimo R.
2016-10-01
Understanding the effect of vibrations in optically active nanosystems is crucial for successfully implementing applications in molecular-based electro-optical devices, quantum information communications, single photon sources, and fluorescent markers for biological measurements. Here, we present a first-principles microscopic description of the role of phonons on the isotopic shift presented in the optical emission spectrum associated to the negatively charged silicon-vacancy color center in diamond. We use the spin-boson model and estimate the electron-phonon interactions using a symmetrized molecular description of the electronic states and a force-constant model to describe molecular vibrations. Group theoretical arguments and dynamical symmetry breaking are presented in order to explain the optical properties of the zero-phonon line and the isotopic shift of the phonon sideband.
Dispersion model for optical thin films applicable in wide spectral range
Franta, Daniel; Nečas, David; Ohlídal, Ivan; Giglia, Angelo
2015-09-01
In the optics industry thin film systems are used to construct various interference devices such as antireflective coatings, high-reflectance mirrors, beam splitters and filters. The optical characterization of complex optical systems can not be performed by measurements only in the short spectral range in which the interference devices will be employed because the measured data do not contain sufficient information about all relevant parameters of these systems. The characterization of film materials requires the extension of the spectral range of the measurements to the IR region containing phonon absorption and to the UV region containing the electronic excitations. However, this leads to necessity of a dispersion model suitable for the description of the dielectric response in the wide spectral range. Such model must respect the physical conditions following from theory of dispersion, particularly Kramers-Kronig relations and integrability imposed by sum rules. This work presents the construction of a universal dispersion model composed from individual contributions representing both electronic and phonon excitations. The efficiency of presented model is given by the fact that all the contributions are described by analytical expressions. It is shown that the model is suitable for precise modeling of spectral dependencies of optical constants of a broad class of materials used in the optical industry for thin film systems such as MgF2, SiO2, Al2O3, HfO2, Ta2O5 and TiO2 in the spectral range from far IR to vacuum UV.
Cereal Yield Modeling in Finland Using Optical and Radar Remote Sensing
Directory of Open Access Journals (Sweden)
Jouko Kleemola
2010-09-01
Full Text Available During 1996–2006, the Ministry of Agriculture and Forestry in Finland (MAFF, MTT Agrifood Research and the Finnish Geodetic Institute performed a joint remote sensing satellite research project. It evaluated the applicability of optical satellite (Landsat, SPOT data for cereal yield estimations in the annual crop inventory program. Four Optical Vegetation Indices models (I: Infrared polynomial, II: NDVI, III: GEMI, IV: PARND/FAPAR were validated to estimate cereal baseline yield levels (yb using solely optical harmonized satellite data (Optical Minimum Dataset. The optimized Model II (NDVI yb level was 4,240 kg/ha (R2 0.73, RMSE 297 kg/ha for wheat and 4390 kg/ha (R2 0.61, RMSE 449 kg/ha for barley and Model I yb was 3,480 kg/ha for oats (R2 0.76, RMSE 258 kg/ha. Optical VGI yield estimates were validated with CropWatN crop model yield estimates using SPOT and NOAA data (mean R2 0.71, RMSE 436 kg/ha and with composite SAR/ASAR and NDVI models (mean R2 0.61, RMSE 402 kg/ha using both reflectance and backscattering data. CropWatN and Composite SAR/ASAR & NDVI model mean yields were 4,754/4,170 kg/ha for wheat, 4,192/3,848 kg/ha for barley and 4,992/2,935 kg/ha for oats.
Model-based defect detection on structured surfaces having optically unresolved features.
O'Connor, Daniel; Henning, Andrew J; Sherlock, Ben; Leach, Richard K; Coupland, Jeremy; Giusca, Claudiu L
2015-10-20
In this paper, we demonstrate, both numerically and experimentally, a method for the detection of defects on structured surfaces having optically unresolved features. The method makes use of synthetic reference data generated by an observational model that is able to simulate the response of the selected optical inspection system to the ideal structure, thereby providing an ideal measure of deviation from nominal geometry. The method addresses the high dynamic range challenge faced in highly parallel manufacturing by enabling the use of low resolution, wide field of view optical systems for defect detection on surfaces containing small features over large regions.
Lin, Alexander J.; Konecky, Soren D.; Rice, Tyler B.; Green, Kim N.; Choi, Bernard; Durkin, Anthony J.; Tromberg, Bruce J.
2012-02-01
Early neurovascular coupling (NVC) changes in Alzheimer's disease can potentially provide imaging biomarkers to assist with diagnosis and treatment. Previous efforts to quantify NVC with intrinsic signal imaging have required assumptions of baseline optical pathlength to calculate changes in oxy- and deoxy-hemoglobin concentrations during evoked stimuli. In this work, we present an economical spatial frequency domain imaging (SFDI) platform utilizing a commercially available LED projector, camera, and off-the-shelf optical components suitable for imaging dynamic optical properties. The fast acquisition platform described in this work is validated on silicone phantoms and demonstrated in neuroimaging of a mouse model.
A Novel Model of Resolving Contention in Optical Burst Switched Networks
Institute of Scientific and Technical Information of China (English)
Huang Anpeng(黄安鹏); Xie Linzhen; Li Jingcong; Li Zhengbin; Xu Anshi
2004-01-01
A Novel segmentation and feedback model (SFM) applied to resolve collision has been proposed. The SFM is featured with Burst Segmentation and Prioritized Feedback (BSPF) that are used to provide quality of service (QoS) and realize high throughput and faster switching in the optical burst switched networks. Simulation and performance analyses show that the SFM effectively avoid collision in optical burst switching (OBS). Long delay time of deflection routing and immature technology of wavelength converter and optical buffer are not employed in the SFM. The SFM not only realizes quick switching but also allows preemption for higher priority bursts.
Mouse mtDNA mutant model of Leber hereditary optic neuropathy.
Lin, Chun Shi; Sharpley, Mark S; Fan, Weiwei; Waymire, Katrina G; Sadun, Alfredo A; Carelli, Valerio; Ross-Cisneros, Fred N; Baciu, Peter; Sung, Eric; McManus, Meagan J; Pan, Billy X; Gil, Daniel W; Macgregor, Grant R; Wallace, Douglas C
2012-12-04
An animal model of Leber hereditary optic neuropathy (LHON) was produced by introducing the human optic atrophy mtDNA ND6 P25L mutation into the mouse. Mice with this mutation exhibited reduction in retinal function by elecroretinogram (ERG), age-related decline in central smaller caliber optic nerve fibers with sparing of larger peripheral fibers, neuronal accumulation of abnormal mitochondria, axonal swelling, and demyelination. Mitochondrial analysis revealed partial complex I and respiration defects and increased reactive oxygen species (ROS) production, whereas synaptosome analysis revealed decreased complex I activity and increased ROS but no diminution of ATP production. Thus, LHON pathophysiology may result from oxidative stress.
Performance evaluation of generalized M-modeled atmospheric optical communications links
DEFF Research Database (Denmark)
Lopez-Gonzalez, Francisco J.; Garrido-Balsellss, José María; Jurado-Navas, Antonio;
2016-01-01
, the behavior of the atmospheric optical channel is treated as a superposition of a finite number of Generalized-K distributed sub-channels, controlled by a discrete Negative-Binomial distribution dependent on the turbulence parameters. Unlike other studies, here, the closed-form mathematical expressions......In this paper, the performance analysis of atmospheric optical communications links is analyzed in terms of the average bit error rate. To this end, the optical irradiance scintillation due to the turbulence effects is modeled by a generalization of the M´alaga or M distribution. In particular...
Theoretical model of the modulation transfer function for fiber optic taper
Wang, Yaoxiang; Tian, Weijian; Bin, XiangLi
2005-02-01
Fiber optic taper has been used more and more widely as a relay optical component in the integrated taper assembly image intensified sensors for military and medical imaging application. In this paper, the transmission characteristic of energy in the taper is analyzed, and following the generalized definition of the modulation transfer function for sampled imaging system, a spatial averaged impulse response and a corresponding MTF component that are inherent in the sampling process of taper are deduced, and the mathematical model for evaluating the modulation transfer function of fiber optic taper is built. Finally, the dynamic and static modulation transfer function curves simulated by computer have been exhibited.
Institute of Scientific and Technical Information of China (English)
戈迪; 蔡阳健; 林强
2005-01-01
By use of a tensor method, the transform formulae for the beam coherence-polarization matrix of the partially polarized Gaussian Schell-model (GSM) beams through aligned and misaligned optical systems are derived. As an example, the propagation properties of the partially polarized GSM beam passing through a misaligned thin lens are illustrated numerically and discussed in detail. The derived formulae provide a convenient way to study the propagation properties of the partially polarized GSM beams through aligned and misaligned optical systems.
2012-09-30
1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Flocculation , Optics and Turbulence in the Community...www.phys.ocean.dal.ca/~phill LONG-TERM GOALS The goal of this research is to develop greater understanding of how the flocculation of fine-grained sediment...COVERED - 4. TITLE AND SUBTITLE Flocculation , Optics and Turbulence in the Community Sediment Transport Model System: Application of Oasis
2011-09-30
1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Flocculation , Optics and Turbulence in the Community...www.phys.ocean.dal.ca/~phill LONG-TERM GOALS The goal of this research is to develop greater understanding of how the flocculation of fine-grained...DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Flocculation , Optics and Turbulence in the Community Sediment Transport Model System
Liu, Na; Giessen, Harald
2008-12-22
In this paper, we demonstrate that metamaterials represent model systems for longitudinal and transverse magnetic coupling in the optical domain. In particular, such coupling can lead to fully parallel or antiparallel alignment of the magnetic dipoles at the lowest frequency resonance. Also, we present the design scheme for constructing three-dimensional metamaterials with solely magnetic interaction. Our concept could pave the way for achieving rather complicated magnetic materials with desired arrangements of magnetic dipoles at optical frequencies.
Effective-mass model and magneto-optical properties in hybrid perovskites
Yu, Z. G.
2016-01-01
Hybrid inorganic-organic perovskites have proven to be a revolutionary material for low-cost photovoltaic applications. They also exhibit many other interesting properties, including giant Rashba splitting, large-radius Wannier excitons, and novel magneto-optical effects. Understanding these properties as well as the detailed mechanism of photovoltaics requires a reliable and accessible electronic structure, on which models of transport, excitonic, and magneto-optical properties can be effici...
Lackovic, Marko; Bungarzeanu, Cristian
2006-01-01
The article analyzes the influence of the Internet Protocol (IP) access interface on the packet loss probability and delay times in the optical packet switched network. The network and node model have been proposed, and the structure of the IP access interface, including assembler and holder, have been included in the analysis. It has been shown that the increase of the maximum optical packet sizes, as well as use of the holding feature as contention resolution mechanism, decrease the packet ...
Algebraic approach to electro-optic modulation of light: Exactly solvable multimode quantum model
Miroshnichenko, George P; Trifanov, Alexander I; Gleim, Artur V
2016-01-01
We theoretically study electro-optic light modulation based on the quantum model where the linear electro-optic effect and the externally applied microwave field result in the interaction between optical cavity modes. The model assumes that the number of interacting modes is finite and effects of the mode overlapping coefficient on the strength of the intermode interaction can be taken into account through dependence of the coupling coefficient on the mode characteristics. We show that, under certain conditions, the model is exactly solvable and, in the semiclassical approximation where the microwave field is treated as a classical mode, can be analyzed using the technique of the Jordan mappings for the su(2) Lie algebra. Analytical results are applied to study effects of light modulation on the frequency dependence of the photon counting rate. We also establish the conditions of validity of the semiclassical approximation by applying the methods of polynomially deformed Lie algebras for analysis of the model...
Optical modeling and physical performances evaluations for the JT-60SA ECRF antenna
Energy Technology Data Exchange (ETDEWEB)
Platania, P., E-mail: platania@ifp.cnr.it; Figini, L.; Farina, D.; Micheletti, D.; Moro, A.; Sozzi, C. [Istituto di Fisica del Plasma “P. Caldirola”, Consiglio Nazionale delle Ricerche, Via R. Cozzi 53, 20125, Milano (Italy); Isayama, A.; Kobayashi, T.; Moriyama, S. [Japan Atomic Energy Agency, 801-1 Mukoyama, Naka, Ibaraki 311-0193 (Japan)
2015-12-10
The purpose of this work is the optical modeling and physical performances evaluations of the JT-60SA ECRF launcher system. The beams have been simulated with the electromagnetic code GRASP® and used as input for ECCD calculations performed with the beam tracing code GRAY, capable of modeling propagation, absorption and current drive of an EC Gaussion beam with general astigmatism. Full details of the optical analysis has been taken into account to model the launched beams. Inductive and advanced reference scenarios has been analysed for physical evaluations in the full poloidal and toroidal steering ranges for two slightly different layouts of the launcher system.
Assessment of some optical model potentials in predicting neutron cross sections
Energy Technology Data Exchange (ETDEWEB)
Kumar, A.; Young, P.G.; Chadwick, M.B.
1998-03-01
Optical model potential parameters play an important role in the evaluation of nuclear data for applied purposes. The IAEA Coordinated Research Program on {open_quotes}Reference Input Parameter Library for Evaluation of Nuclear Data for Application in Nuclear Technology{close_quotes} aims to release a reference input file of various types of parameters for the evaluation of nuclear cross sections using nuclear model codes. Included in the parameter files are a collection of optical model potentials that are available in the literature to evaluate these cross sections. As part of this research program we assess the applicability of these potentials over a range of target mass and projectile energy.
Red tide optical index: in situ optics and remote sensing models
Cetinic, I.; Karp-Boss, L.; Boss, E.; Ragan, M. A.; Jones, B. H.
2007-05-01
Harmful Algal Blooms (HABs) are recurring events in the coastal ocean, and local economies that depend on beach and coastal use are often adversely affected by these events. Inherent optical properties (absorption and backscattering) of the HAB dinoflagellate Lingulodinium polyedrum were measured in order to develop specific index that would enable easier detection of this HAB organism in the field. It has been noticed that red to blue and red to green ratio of absorption in this species is much lower then other measured species. A red tide ratio was tested in the field during a red tide episode in the San Pedro Channel, using a Wetlabs acS flow-through system. The red tide index gave a distinguishable signal in areas where L.polyedrum was present. Remote sensing reflectance was calculated from field and laboratory IOP measurements, using reverse Quasi-Analythical Alghoritm and Hydrolight to evaluate if the red tide index can be detected in the remote sensing ocean color measurements.
Directory of Open Access Journals (Sweden)
Paula COPĂESCU
2009-12-01
Full Text Available Preliminary results obtained in developing a numerical model of laser light intensity transversedistribution into undeformed/deformed step index optical fiber are presented. The main purpose ofthe presented preliminary numerical modelling results consists in developing a simple method offiber optical sensors interrogation, especially concerning strain and pressure measurements. It is apotential important matter for aeronautical research and industry because of the more extendeduse of fibre optic sensors in aircraft manufacturing. The developed numerical model relies onsolving the equations of electromagnetic waves propagation into optical fibers by using the finiteelement method technique (FEM. The results of numerical simulation obtained by consideringsingle mode or multimode and various laser wavelengtsh are presented. One importantachievement reported in this paper consists in preliminary experimental results concerning themodification of laser intensity transverse distribution observed for multimode optical fiber with andwithout perpendicular mechanical load. The reported preliminary experimental results confirm tosome extent the predictions of numerical simulations regarding laser intensity distribution underlow and medium transverse mechanical load. One important conclusion of this paper consists inthe future development of fiber optic sensor interrogation techniques based on the reportedpreliminary experimental and numerical simulation results.
Ruley, John D.
1986-01-01
In the design of spacecraft for proper thermal balance, accurate information on the long-term optical behavior of the spacecraft outer skin materials is necessary. A phenomenological model for such behavior is given. The underlying principles are explained and some examples are given of the model's fit to actual measurements under simulated Earth-orbit conditions. Comments are given on the applicability of the model to materials testing and thermal modelling.
Model-based optical metrology and visualization of 3-D complex objects
Institute of Scientific and Technical Information of China (English)
LIU Xiao-li; LI A-meng; ZHAO Xiao-bo; GAO Peng-dong; TIAN Jin-dong; PENG Xiang
2007-01-01
This letter addresses several key issues in the process of model-based optical metrology, including three dimensional (3D) sensing, calibration, registration and fusion of range images, geometric representation, and visualization of reconstructed 3D model by taking into account the shape measurement of 3D complex structures,and some experimental results are presented.
Zeng, Y.; Schaepman, M.E.; Wu, B.; Clevers, J.G.P.W.; Bregt, A.K.
2009-01-01
The physical-based geometric-optical Li-Strahler model can be inverted to retrieve forest canopy structural variables. One of the main input variables of the inverted model is the fractional component of sunlit background (K g). K g is calculated by using pure reflectance spectra (endmembers) of the
Optical and Acoustical Frequencies in a Nonlinear Helicoidal Model of DNA Molecules
Institute of Scientific and Technical Information of China (English)
ZDRAVKOVI(C) S.; SATARI(C) M.V.
2005-01-01
@@ We compare optical and acoustical frequencies in the Peyrard-Bishop-Dauxois model, i.e.an extended Peyrard-Bishop model, of DNA molecules.We discuss how ratio of those frequencies depends on a value of the harmonic constant of the helicoidal spring K.Also, we suggest that the most favourable mode could be a resonance mode.
Model independent optical potential for protons at 155 MeV
Brissaud, I.
1981-06-01
Using the model independent procedure, 155 MeV proton optical potentials are deduced from the elastic scattering data. The nuclear interior of these potentials are less attractative than predicted by a phenomenological potentials. A comparison is done with a self consistent meson model.
Scully, S.; Burke, D.; O'Sullivan, C.; Gayer, D.; Gradziel, M.; Murphy, J. A.; De Petris, M.; Buzi, D.; Zannoni, M.; Mennella, A.; Gervasi, M.; Tartari, A.; Maffei, B.; Aumont, J.; Banfi, S.; Battaglia, P.; Battistelli, E. S.; Baó, A.; Bélier, B.; Bennet, D.; Bergé, L.; Bernard, J.-Ph.; Bersanelli, M.; Bigot-Sazy, M.-A.; Bleurvacq, N.; Bordier, G.; Brossard, J.; Bunn, E. F.; Cammileri, D.; Cavaliere, F.; Chanial, P.; Chapron, C.; Coppolecchia, A.; Couchot, F.; D'Alessandro, G.; De Bernardis, P.; Decourcelle, T.; Del Torto, F.; Dumoulin, L.; Franceschet, C.; Gault, A.; Ghribi, A.; Giard, M.; Giraud-Héraud, Y.; Grandsire, L.; Hamilton, J. C.; Haynes, V.; Henrot-Versillé, S.; Holtzer, N.; Kaplan, J.; Korotkov, A.; Lande, J.; Lowitz, A.; Marnieros, S.; Martino, J.; Masi, S.; McCulloch, Mark; Melhuish, Simon; Montier, L.; Néel, D.; Ng, M. W.; Pajot, F.; Passerini, A.; Perbost, C.; Perdereau, O.; Piacentini, F.; Piat, M.; Piccirillo, L.; Pisano, G.; Prêle, D.; Puddu, R.; Rambaud, D.; Rigaut, O.; Salatino, M.; Schillaci, A.; Stolpovskiy, M.; Timbie, P.; Tristram, M.; Tucker, G.; Viganò, D.; Voisin, F.; Watson, B.
2016-07-01
Big Bang cosmologies predict that the cosmic microwave background (CMB) contains faint temperature and polarisation anisotropies imprinted in the early universe. ESA's PLANCK satellite has already measured the temperature anisotropies1 in exquisite detail; the next ambitious step is to map the primordial polarisation signatures which are several orders of magnitude lower. Polarisation E-modes have been measured2 but the even-fainter primordial B-modes have so far eluded detection. Their magnitude is unknown but it is clear that a sensitive telescope with exceptional control over systematic errors will be required. QUBIC3 is a ground-based European experiment that aims to exploit the novel concept of bolometric interferometry in order to measure B-mode polarisation anisotropies in the CMB. Beams from an aperture array of corrugated horns will be combined to form a synthesised image of the sky Stokes parameters on two focal planes: one at 150 GHz the other at 220 GHz. In this paper we describe recent optical modelling of the QUBIC beam combiner, concentrating on modelling the instrument point-spread-function and its operation in the 220-GHz band. We show the effects of optical aberrations and truncation as successive components are added to the beam path. In the case of QUBIC, the aberrations introduced by off-axis mirrors are the dominant contributor. As the frequency of operation is increased, the aperture horns allow up to five hybrid modes to propagate and we illustrate how the beam pattern changes across the 25% bandwidth. Finally we describe modifications to the QUBIC optical design to be used in a technical demonstrator, currently being manufactured for testing in 2016.
Remote sensing reflectance model of optically active components of turbid waters
Kutser, Tiit; Arst, Helgi
1994-12-01
A mathematical model that simulates the spectral curves of remote sensing reflectance is developed. The model is compared to measurements obtained from research vessel or boat in the Baltic Sea and Estonian lakes. The model simulates the effects of light backscattering from water and suspended matter, and the effects of its absorption due to water, phytoplankton, suspended matter and yellow substance. Measured by remote sensing spectral curves are compared by multiple of spectra obtained from model calculations to find the theoretical spectrum which is closest to experimental. It is assumed that in case of coincidence of the spectral curves concentrations of optically active substances in the model correspond to real ones. Preliminary testing of the model demonstrates that this model is useful for estimation of concentration of optically active substances in the waters of the Baltic Sea and Estonian lakes.
Modeling simulation of the thermal radiation for high-speed flight vehicles' aero-optical windows
Chen, Lei; Zhang, Liqin; Guo, Mingjiang
2015-10-01
When high-speed flight vehicles fly in the atmosphere, they can generate serious aero-optical effect. The optical window temperature rises sharply because of aerodynamic heating. It will form radiation interference that can lead infrared detectors to producing non-uniform radiation backgrounds, decreasing system SNR and detection range. Besides, there exits temperature difference due to uneven heating. Under the thermo-optical and elastic-optical effects, optical windows change into inhomogeneous mediums which influence the ray propagation. In this paper, a model of thermal radiation effect was built by a finite element analysis method. Firstly, the optical window was divided into uniform grids. Then, radiation distribution on the focal planes at different angles of the window's normal line and optical axis was obtained by tracing light rays of each grid. Finally, simulation results indicate that radiation distribution reflects the two directions-the length and width-of temperature distribution, and the change of angle causes the center of radiation distribution to shift to one direction of the image surface under the same window temperature.
Modeling the Stability of Topological Matter in Optical Lattices
2013-05-18
is of the same order as the Heisenberg coupling constant, J. (II) We study the phase diagram of the effective spin model using classical Monte Carlo ...I will construct and analyze a model using a combination of mean field theory and quantum Monte Carlo . The proposed work will foster new...construct and analyze a model using a com- bination of mean field theory and quantum Monte Carlo . The proposed work will foster new directions in
Gustafson, S. C.
1985-12-01
The technical contributions were as follows: (1) Optical parallel 2-D neighborhood processor and optical processor assessment technique; (2) High accuracy with moderately accurate components and optical fredkin gate architectures; (3) Integrated optical threshold computing, pipelined polynomial processor, and all optical analog/digital converter; (4) Adaptive optical associative memory model with attention; (5) Effectiveness of parallelism and connectivity in optical computers; (6) Optical systolic array processing using an integrated acoustooptic module; (7) Optical threshold elements and networks, holographic threshold processors, adaptive matched spatial filtering, and coherence theory in optical computing; (8) Time-varying optical processing for sub-pixel targets, optical Kalman filtering, and adaptive matched filtering; (9) Optical degrees of freedom, ultra short optical pulses, number representations, content-addressable-memory processors, and integrated optical Givens rotation devices; (10) Optical J-K flip flop analysis and interfacing for optical computers; (11) Matrix multiplication algorithms and limits of incoherent optical computers; (12) Architecture for machine vision with sensor fusion, pattern recognition functions, and neural net implementations; (13) Optical computing algorithms, architectures, and components; and (14) Dynamic optical interconnections, advantages and architectures.
Modelling and prediction of non-stationary optical turbulence behaviour
Doelman, Niek; Osborn, James
2016-07-01
There is a strong need to model the temporal fluctuations in turbulence parameters, for instance for scheduling, simulation and prediction purposes. This paper aims at modelling the dynamic behaviour of the turbulence coherence length r0, utilising measurement data from the Stereo-SCIDAR instrument installed at the Isaac Newton Telescope at La Palma. Based on an estimate of the power spectral density function, a low order stochastic model to capture the temporal variability of r0 is proposed. The impact of this type of stochastic model on the prediction of the coherence length behaviour is shown.
Simulation and experimental results of optical and thermal modeling of gold nanoshells
Energy Technology Data Exchange (ETDEWEB)
Ghazanfari, Lida; Khosroshahi, Mohammad E., E-mail: khosrom@mie.utoronto.ca
2014-09-01
This paper proposes a generalized method for optical and thermal modeling of synthesized magneto-optical nanoshells (MNSs) for biomedical applications. Superparamagnetic magnetite nanoparticles with diameter of 9.5 ± 1.4 nm are fabricated using co-precipitation method and subsequently covered by a thin layer of gold to obtain 15.8 ± 3.5 nm MNSs. In this paper, simulations and detailed analysis are carried out for different nanoshell geometry to achieve a maximum heat power. Structural, magnetic and optical properties of MNSs are assessed using vibrating sample magnetometer (VSM), X-ray diffraction (XRD), UV–VIS spectrophotometer, dynamic light scattering (DLS), and transmission electron microscope (TEM). Magnetic saturation of synthesized magnetite nanoparticles are reduced from 46.94 to 11.98 emu/g after coating with gold. The performance of the proposed optical–thermal modeling technique is verified by simulation and experimental results. - Highlights: • Proposing a generalized method for optical and thermal modeling of nanoshells • Verification of the proposed modeling technique by simulation and experimental results • Simulations for different nanoshell geometry to achieve a maximum heat power • Synthesis and characterization of magneto-optical nanoshells.
Leavesley, Silas; Bayraktar, Bülent; Venkatapathi, Murugesan; Hirleman, E. Dan; Bhunia, Arun K.; Robinson, J. Paul; Hassler, Richard; Smith, Linda; Rajwa, Bartek
2007-02-01
Traditional biological and chemical methods for pathogen identification require complicated sample preparation for reliable results. Optical scattering technology has been used for identification of bacterial cells in suspension, but with only limited success. Our published reports have demonstrated that scattered light based identification of Listeria colonies growing on solid surfaces is feasible with proper pattern recognition tools. Recently we have extended this technique to classification of other bacterial genera including, Salmonella, Bacillus, and Vibrio. Our approach may be highly applicable to early detection and classification of pathogens in food-processing industry and in healthcare. The unique scattering patterns formed by colonies of different species are created through differences in colony microstructure (on the order of wavelength used), bulk optical properties, and the macroscopic morphology. While it is difficult to model the effect on scatter-signal patterns owing to the microstructural changes, the influence of bulk optical properties and overall shape of colonies can be modeled using geometrical optics. Our latest research shows that it is possible to model the scatter pattern of bacterial colonies using solid-element optical modeling software (TracePro), and theoretically assess changes in macro structure and bulk refractive indices. This study allows predicting the theoretical limits of resolution and sensitivity of our detection and classification methods. Moreover, quantification of changes in macro morphology and bulk refractive index provides an opportunity to study the response of colonies to various reagents and antibiotics.
Dong, Erbao; Zhao, Zuhua; Wang, Minjie; Xie, Yanjun; Li, Shidi; Shao, Pengfei; Cheng, Liuquan; Xu, Ronald X.
2015-12-01
Biomedical optical devices are widely used for clinical detection of various tissue anomalies. However, optical measurements have limited accuracy and traceability, partially owing to the lack of effective calibration methods that simulate the actual tissue conditions. To facilitate standardized calibration and performance evaluation of medical optical devices, we develop a three-dimensional fuse deposition modeling (FDM) technique for freeform fabrication of tissue-simulating phantoms. The FDM system uses transparent gel wax as the base material, titanium dioxide (TiO2) powder as the scattering ingredient, and graphite powder as the absorption ingredient. The ingredients are preheated, mixed, and deposited at the designated ratios layer-by-layer to simulate tissue structural and optical heterogeneities. By printing the sections of human brain model based on magnetic resonance images, we demonstrate the capability for simulating tissue structural heterogeneities. By measuring optical properties of multilayered phantoms and comparing with numerical simulation, we demonstrate the feasibility for simulating tissue optical properties. By creating a rat head phantom with embedded vasculature, we demonstrate the potential for mimicking physiologic processes of a living system.
Modeling an Electrically Driven Graphene-Nanoribbon Laser for Optical Interconnects
Shan, Guangcun
2012-01-01
Graphene has two very important optical properties of population inversion of electrons, and broadband optical gain. As a result, graphene has potential for use in lasers and amplifiers. In this work, we presented a quantum master model and analyzed the properties for the electrically pumped single-AGNR vertical-cavity surface-emitting lasers (VCSELs) to investigate the lasing action and laser properties for realistic experimental parameters. A semiclassical approximation for the output power and laser linewidth is also derived. The laser threshold power was several orders of magnitude lower than that currently achievable with semiconductor microlasers. Our results have demonstrated that a single-AGNR VCSEL can serve as a nanolaser with ultralow lasing threshold. Implementation of such a GNR-based VCSEL is especially promising for optical interconnection systems since VCSELs emit low optical power and single longitudinal mode over a wide wavelength spectral range through tailoring GNRs.
Drude Weight,Optical Conductivity of Two-Dimensional Hubbard Model at Half Filling
Institute of Scientific and Technical Information of China (English)
XU Lei; ZHANG Jun
2008-01-01
We study the Drude weight D and optical conductivity of the two-dimensional (2D) Hubbard model at half filling with staggered magnetic flux (SMF).When SMF being introduced,the hopping integrals are modulated by the magnetic flux.The optical sum rule,which is related to the mean kinetic energy of band electrons,is evaluated for this 2D Hubbard Hamiltonian.Our present result gives the dependence of the kinetic energy,D and the optical conductivity on SMF and U.At half filling D vanishes exponentially with system size.We also find in the frequency dependence of the optical conductivity,there is &function peak at ω≈2|m|U and the incoherent excitations begin to present themselves extended to a higher energy region.
Propagation of Coherent Gaussian Schell-Model Beam Array in a Misaligned Optical System
Institute of Scientific and Technical Information of China (English)
ZHOU Pu; WANG Xiao-Lin; MA Yan-Xing; MA Hao-Tong; XU Xiao-Jun; LIU Ze-Jin
2011-01-01
@@ Based on a generalized Collins formula,the analytical formula for the propagation property of coherent Gaussian Schell-rnodel(GSM) beam array through a misaligned optical system is derived.As numerical examples,the propagation of a coherent GSM beam array in a typical misaligned optical system with a thin lens is evaluated.The influence of different misalignment parameters is calculated and the normalized-intensity distribution is graphically illustrated.%Based on a generalized Collins formula, the analytical formula for the propagation property of coherent Gaussian Schell-model (GSM) beam array through a misaligned optical system is derived. As numerical examples, the propagation of a coherent GSM beam array in a typical misaligned optical system with a thin lens is evaluated.The influence of different misalignment parameters is calculated and the normalized-intensity distribution is graphically illustrated.
Numerical Modeling of a Near-Field Scanning Optical System
Kann, Joshua Louis
A near-field scanning optical (NFO) system utilizes a subwavelength sized aperture to illuminate a sample. The aperture raster scans the sample. During the scan, the aperture is held in proximity to the sample. At each sampling point, the integrated far-zone energy distribution is stored. This collection of data is used to generate an image of the sample's surface. The main advantage of NFO systems is their very high spatial resolution. In this dissertation a hybrid finite-difference-time-domain (FDTD)/angular spectrum code is used to study the electromagnetic and imaging properties of a NFO scanning system. In addition, a finite-difference thermal (FD-thermal) code is used to calculate the thermal properties of a NFO system. Various aperture/sample geometries are studied numerically using both TE and TM polarization within a two-dimensional metallic waveguide that forms the aperture. The spatial properties of the electric field emitted by the aperture with no sample present are greatly influenced by the polarization. In particular, the electric field with TM polarization exhibits sharp peaks near the corners of the aperture, while the field with TE polarization is smooth and peaked at the center of the aperture. For both polarizations, the electric field remains collimated for a distance comparable to the aperture size. The electric field for both polarizations is altered when a dielectric sample is placed in proximity to the aperture. It is shown that the most representative image of the sample's topography is obtained using TE polarization and the resulting total far-zone energy as the sampled data. It is also shown that simpler scalar methods do not accurately predict the imaging behavior of a NFO system. Under certain circumstances the relationship between the sample's topography and the detected image is nearly linear. Under these conditions a system transfer function is calculated. Using the transfer function, it is shown that the spatial resolution of a NFO
Case study of modeled aerosol optical properties during the SAFARI 2000 campaign.
Kuzmanoski, Maja; Box, Michael A; Schmid, Beat; Russell, Philip B; Redemann, Jens
2007-08-01
We present modeled aerosol optical properties (single scattering albedo, asymmetry parameter, and lidar ratio) in two layers with different aerosol loadings and particle sizes, observed during the Southern African Regional Science Initiative 2,000 (SAFARI 2,000) campaign. The optical properties were calculated from aerosol size distributions retrieved from aerosol layer optical thickness spectra, measured using the NASA Ames airborne tracking 14-channel sunphotometer (AATS-14) and the refractive index based on the available information on aerosol chemical composition. The study focuses on sensitivity of modeled optical properties in the 0.3-1.5 microm wavelength range to assumptions regarding the mixing scenario. We considered two models for the mixture of absorbing and nonabsorbing aerosol components commonly used to model optical properties of biomass burning aerosol: a layered sphere with absorbing core and nonabsorbing shell and the Maxwell-Garnett effective medium model. In addition, comparisons of modeled optical properties with the measurements are discussed. We also estimated the radiative effect of the difference in aerosol absorption implied by the large difference between the single scattering albedo values (approximately 0.1 at midvisible wavelengths) obtained from different measurement methods for the case with a high amount of biomass burning particles. For that purpose, the volume fraction of black carbon was varied to obtain a range of single scattering albedo values (0.81-0.91 at lambda=0.50 microm). The difference in absorption resulted in a significant difference in the instantaneous radiative forcing at the surface and the top of the atmosphere (TOA) and can result in a change of the sign of the aerosol forcing at TOA from negative to positive.
Alliss, R.; Felton, B.
Optical turbulence (OT) acts to distort light in the atmosphere, degrading imagery from large astronomical telescopes and possibly reducing data quality of air to air laser communication links. Some of the degradation due to turbulence can be corrected by adaptive optics. However, the severity of optical turbulence, and thus the amount of correction required, is largely dependent upon the turbulence at the location of interest. Therefore, it is vital to understand the climatology of optical turbulence at such locations. In many cases, it is impractical and expensive to setup instrumentation to characterize the climatology of OT, so simulations become a less expensive and convenient alternative. The strength of OT is characterized by the refractive index structure function Cn2, which in turn is used to calculate atmospheric seeing parameters. While attempts have been made to characterize Cn2 using empirical models, Cn2 can be calculated more directly from Numerical Weather Prediction (NWP) simulations using pressure, temperature, thermal stability, vertical wind shear, turbulent Prandtl number, and turbulence kinetic energy (TKE). In this work we use the Weather Research and Forecast (WRF) NWP model to generate Cn2 climatologies in the planetary boundary layer and free atmosphere, allowing for both point-to-point and ground-to-space seeing estimates of the Fried Coherence length (ro) and other seeing parameters. Simulations are performed using the Maui High Performance Computing Centers Jaws cluster. The WRF model is configured to run at 1km horizontal resolution over a domain covering the islands of Maui and the Big Island. The vertical resolution varies from 25 meters in the boundary layer to 500 meters in the stratosphere. The model top is 20 km. We are interested in the variations in Cn2 and the Fried Coherence Length (ro) between the summits of Haleakala and Mauna Loa. Over six months of simulations have been performed over this area. Simulations indicate that
Perera, M. Nilusha M. N.; Schmidt, Daniel; Gibbs, W. E. Keith; Juodkazis, Saulius; Stoddart, Paul R.
2016-09-01
Surface-enhanced Raman scattering (SERS) is drawing increasing interest in fields such as chemical and biomolecular sensing, nanoscale plasmonic engineering and surface science. In addition to the electromagnetic and chemical enhancements in SERS, several studies have reported a "back-side" enhancement when nanostructures are excited through a transparent base rather than directly through air. This additional enhancement has been attributed to a local increase in the electric field for propagation from high to low refractive index media. In this study, Mueller matrix ellipsometry was used to derive the effective optical constants of Ag nanostructures fabricated by thermal evaporation at oblique angles. The results confirm that the effective optical constants of the nanostructured Ag film depart substantially from the bulk properties. Detailed analysis suggests that the optical constants of the nano-island Ag structures exhibit uniaxial optical properties with the optical axis inclined from the substrate normal towards the deposition direction of the vapour flux. The substrates were functionalized with thiophenol and used to measure the wavelength dependence of the additional SERS signal. Further, a model based on the Fresnel equations was developed, using the Ag film optical constants and thickness as determined by ellipsometry. Both experimental data and the model show a significant additional enhancement in the back-side SERS, blue shifted from the plasmon resonance of the nanostructures. This information will be useful for a range of applications where it is necessary to understand the effective optical behaviour of thin films and in designing miniaturized optical fibre sensors for remote sensing applications.
An optical flow-based state-space model of the vocal folds
DEFF Research Database (Denmark)
Granados, Alba; Brunskog, Jonas
2017-01-01
. A linear and Gaussian nonstationary state-space model is proposed and thoroughly discussed. The evolution model is based on a self-sustained three-dimensional finite element model of the vocal folds, and the observation model involves a dense optical flow algorithm. The results show that the method is able......High-speed movies of the vocal fold vibration are valuable data to reveal vocal fold features for voice pathology diagnosis. This work presents a suitable Bayesian model and a purely theoretical discussion for further development of a framework for continuum biomechanical features estimation...... to capture different deformation patterns between the computed optical flow and the finite element deformation, controlled by the choice of the model tissue parameters....
Modelling and Observation of Mineral Dust Optical Properties over Central Europe
Chilinski, Michał T.; Markowicz, Krzysztof M.; Zawadzka, Olga; Stachlewska, Iwona S.; Kumala, Wojciech; Petelski, Tomasz; Makuch, Przemysław; Westphal, Douglas L.; Zagajewski, Bogdan
2016-12-01
This paper is focused on Saharan dust transport to Central Europe/Poland; we compare properties of atmospheric Saharan dust using data from NAAPS, MACC, AERONET as well as observations obtained during HyMountEcos campaign in June 2012. Ten years of dust climatology shows that long-range transport of Saharan dust to Central Europe is mostly during spring and summer. HYSPLIT back-trajectories indicate airmass transport mainly in November, but it does not agree with modeled maxima of dust optical depth. NAAPS model shows maximum of dust optical depth ( 0.04-0.05, 550 nm) in April-May, but the MACC modeled peak is broader ( 0.04). During occurrence of mineral dust over Central-Europe for 14% (NAAPS) / 12% (MACC) of days dust optical depths are above 0.05 and during 4% (NAAPS) / 2.5% (MACC) of days dust optical depths exceed 0.1. The HyMountEcos campaign took place in June-July 2012 in the mountainous region of Karkonosze. The analysis includes remote sensing data from lidars, sun-photometers, and numerical simulations from NAAPS, MACC, DREAM8b models. Comparison of simulations with observations demonstrates the ability of models to reasonably reproduce aerosol vertical distributions and their temporal variability. However, significant differences between simulated and measured AODs were found. The best agreement was achieved for MACC model.
Modelling and Observation of Mineral Dust Optical Properties over Central Europe
Directory of Open Access Journals (Sweden)
Chilinski Michał T.
2016-12-01
Full Text Available This paper is focused on Saharan dust transport to Central Europe/Poland; we compare properties of atmospheric Saharan dust using data from NAAPS, MACC, AERONET as well as observations obtained during HyMountEcos campaign in June 2012. Ten years of dust climatology shows that long-range transport of Saharan dust to Central Europe is mostly during spring and summer. HYSPLIT back-trajectories indicate airmass transport mainly in November, but it does not agree with modeled maxima of dust optical depth. NAAPS model shows maximum of dust optical depth (~0.04-0.05, 550 nm in April-May, but the MACC modeled peak is broader (~0.04. During occurrence of mineral dust over Central-Europe for 14% (NAAPS / 12% (MACC of days dust optical depths are above 0.05 and during 4% (NAAPS / 2.5% (MACC of days dust optical depths exceed 0.1. The HyMountEcos campaign took place in June-July 2012 in the mountainous region of Karkonosze. The analysis includes remote sensing data from lidars, sun-photometers, and numerical simulations from NAAPS, MACC, DREAM8b models. Comparison of simulations with observations demonstrates the ability of models to reasonably reproduce aerosol vertical distributions and their temporal variability. However, significant differences between simulated and measured AODs were found. The best agreement was achieved for MACC model.
Meneses, Domingos De Sousa; Rousseau, Benoit; Echegut, Patrick; Matzen, Guy
2007-06-01
A new expression of dielectric function model based on piecewise polynomials is introduced. Its association with spline and more recent shape preserving interpolation algorithms allows easy reproduction of every kind of experimental spectra and thus retrieval of all the linear optical functions of a material. Based on a pure mathematical framework, the expression of the model is always applicable and does not necessitate any knowledge of the microscopic mechanisms of absorption responsible for the optical response. The potential of piecewise polynomial dielectric functions is shown through synthetic examples and the analysis of experimental spectra.
Analogical optical modeling of the asymmetric lateral coherence of betatron radiation.
Paroli, B; Chiadroni, E; Ferrario, M; Potenza, M A C
2015-11-16
By exploiting analogical optical modeling of the radiation emitted by ultrarelativistic electrons undergoing betatron oscillations, we demonstrate peculiar properties of the spatial coherence through an interferometric method reminiscent of the classical Young's double slit experiment. The expected effects due to the curved trajectory and the broadband emission are accurately reproduced. We show that by properly scaling the fundamental parameters for the wavelength, analogical optical modeling of betatron emission can be realized in many cases of broad interest. Applications to study the feasibility of future experiments and to the characterization of beam diagnostics tools are described.
Different models of gravitating Dirac fermions in optical lattices
Celi, Alessio
2017-07-01
In this paper I construct the naive lattice Dirac Hamiltonian describing the propagation of fermions in a generic 2D optical metric for different lattice and flux-lattice geometries. First, I apply a top-down constructive approach that we first proposed in [Boada et al., New J. Phys. 13, 035002 (2011)] to the honeycomb and to the brickwall lattices. I carefully discuss how gauge transformations that generalize momentum (and Dirac cone) shifts in the Brillouin zone in the Minkowski homogeneous case can be used in order to change the phases of the hopping. In particular, I show that lattice Dirac Hamiltonian for Rindler spacetime in the honeycomb and brickwall lattices can be realized by considering real and isotropic (but properly position dependent) tunneling terms. For completeness, I also discuss a suitable formulation of Rindler Dirac Hamiltonian in semi-synthetic brickwall and π-flux square lattices (where one of the dimension is implemented by using internal spin states of atoms as we originally proposed in [Boada et al., Phys. Rev. Lett. 108, 133001 (2012)] and [Celi et al., Phys. Rev. Lett. 112, 043001 (2014)]).
Optical spectroscopic studies of animal skin used in modeling of human cutaneous tissue
Drakaki, E.; Makropoulou, M.; Serafetinides, A. A.; Borisova, E.; Avramov, L.; Sianoudis, J. A.
2007-03-01
Optical spectroscopy and in particular laser-induced autofluorescence spectroscopy (LIAFS) and diffuse reflectance spectroscopy (DRS), provide excellent possibilities for real-time, noninvasive diagnosis of different skin tissue pathologies. However, the introduction of optical spectroscopy in routine medical practice demands a statistically important data collection, independent from the laser sources and detectors used. The scientists collect databases either from patients, in vivo, or they study different animal models to obtain objective information for the optical properties of various types of normal and diseased tissue. In the present work, the optical properties (fluorescence and reflectance) of two animal skin models are investigated. The aim of using animal models in optical spectroscopy investigations is to examine the statistics of the light induced effects firstly on animals, before any extrapolation effort to humans. A nitrogen laser (λ=337.1 nm) was used as an excitation source for the autofluorescence measurements, while a tungsten-halogen lamp was used for the reflectance measurements. Samples of chicken and pig skin were measured in vitro and were compared with results obtained from measurements of normal human skin in vivo. The specific features of the measured reflectance and fluorescence spectra are discussed, while the limits of data extrapolation for each skin type are also depicted.
Directory of Open Access Journals (Sweden)
Corrado Caudek
Full Text Available We measured perceived depth from the optic flow (a when showing a stationary physical or virtual object to observers who moved their head at a normal or slower speed, and (b when simulating the same optic flow on a computer and presenting it to stationary observers. Our results show that perceived surface slant is systematically distorted, for both the active and the passive viewing of physical or virtual surfaces. These distortions are modulated by head translation speed, with perceived slant increasing directly with the local velocity gradient of the optic flow. This empirical result allows us to determine the relative merits of two alternative approaches aimed at explaining perceived surface slant in active vision: an "inverse optics" model that takes head motion information into account, and a probabilistic model that ignores extra-retinal signals. We compare these two approaches within the framework of the bayesian theory. The "inverse optics" bayesian model produces veridical slant estimates if the optic flow and the head translation velocity are measured with no error; because of the influence of a "prior" for flatness, the slant estimates become systematically biased as the measurement errors increase. The bayesian model, which ignores the observer's motion, always produces distorted estimates of surface slant. Interestingly, the predictions of this second model, not those of the first one, are consistent with our empirical findings. The present results suggest that (a in active vision perceived surface slant may be the product of probabilistic processes which do not guarantee the correct solution, and (b extra-retinal signals may be mainly used for a better measurement of retinal information.
MILES extended: Stellar population synthesis models from the optical to the infrared
Röck, B.; Vazdekis, A.; Ricciardelli, E.; Peletier, R. F.; Knapen, J. H.; Falcón-Barroso, J.
2016-05-01
We present the first single-burst stellar population models, which covers the optical and the infrared wavelength range between 3500 and 50 000 Å and which are exclusively based on empirical stellar spectra. To obtain these joint models, we combined the extended MILES models in the optical with our new infrared models that are based on the IRTF (Infrared Telescope Facility) library. The latter are available only for a limited range in terms of both age and metallicity. Our combined single-burst stellar population models were calculated for ages larger than 1 Gyr, for metallicities between [ Fe / H ] = - 0.40 and 0.26, for initial mass functions of various types and slopes, and on the basis of two different sets of isochrones. They are available to the scientific community on the MILES web page. We checked the internal consistency of our models and compared their colour predictions to those of other models that are available in the literature. Optical and near infrared colours that are measured from our models are found to reproduce the colours well that were observed for various samples of early-type galaxies. Our models will enable a detailed analysis of the stellar populations of observed galaxies.
REFINED MODEL OF THE OPTICAL SYSTEM FOR SPACE MINI-VEHICLES WITH LASER PROPULSION
Directory of Open Access Journals (Sweden)
M. S. Egorov
2015-09-01
Full Text Available Simulation results for on-board optical system of a space mini-vehicle with laser propulsion are presented. This system gives the possibility for receiving theremote laser radiation power independently of a system telescope mutual orientation to the vehicle orbiting direction. The on-board optical system is designed with the use of such optical elements as optical hinges and turrets. The system incorporates the optical switch that is a special optical system adapting optically both receiving telescope and laser propulsion engines. Modeling and numerical simulation of the system have been performed with the use of ZEMAX software (Radiant Ltd. The object matter of calculations lied in size definition of system optical elements, requirements to accuracy of their manufacturing and reciprocal adjusting to achieve an efficient radiation energy delivery to laser propulsion engine. Calculations have been performed with account to the limitations on the mini-vehicle mass, its overall dimensions, and radiation threshold density of the optical elements utilized. The requirements to the laser beam quality at the entrance aperture of laser propulsion engine have been considered too. State-of-the-art optical technologies make it possible to manufacture space reflectors made of CO-115M glassceramics with weight-reducing coefficient of 0.72 and the radiation threshold of 5 J/cm2 for the radiation with a 1.064 microns wavelength at 10-20 ns pulse duration. The optimal diameter of a receiving telescope primary mirror has been 0.5 m when a coordinated transmitting telescope diameter is equal to 1 m. This provides the reception of at least 84% of laser energy. The main losses of radiation energy are caused by improper installation of receiving telescope mirrors and by in-process errors arising at manufacturing the telescope mirrors with a parabolic surface. It is shown that requirements to the in-process admissible errors for the on-board optical system elements
Energy Technology Data Exchange (ETDEWEB)
Moro, Erik A [Los Alamos National Laboratory; Puckett, Anthony D [Los Alamos National Laboratory; Todd, Michael D [UCSD
2011-01-24
The intensity distribution of a transmission from a single mode optical fiber is often approximated using a Gaussian-shaped curve. While this approximation is useful for some applications such as fiber alignment, it does not accurately describe transmission behavior off the axis of propagation. In this paper, another model is presented, which describes the intensity distribution of the transmission from a single mode optical fiber. A simple experimental setup is used to verify the model's accuracy, and agreement between model and experiment is established both on and off the axis of propagation. Displacement sensor designs based on the extrinsic optical lever architecture are presented. The behavior of the transmission off the axis of propagation dictates the performance of sensor architectures where large lateral offsets (25-1500 {micro}m) exist between transmitting and receiving fibers. The practical implications of modeling accuracy over this lateral offset region are discussed as they relate to the development of high-performance intensity modulated optical displacement sensors. In particular, the sensitivity, linearity, resolution, and displacement range of a sensor are functions of the relative positioning of the sensor's transmitting and receiving fibers. Sensor architectures with high combinations of sensitivity and displacement range are discussed. It is concluded that the utility of the accurate model is in its predicative capability and that this research could lead to an improved methodology for high-performance sensor design.
Experience at Los Alamos with use of the optical model for applied nuclear data calculations
Energy Technology Data Exchange (ETDEWEB)
Young, P.G.
1994-10-01
While many nuclear models are important in calculations of nuclear data, the optical model usually provides the basic underpinning of analyses directed at data for applications. An overview is given here of experience in the Nuclear Theory and Applications Group at Los Alamos National Laboratory in the use of the optical model for calculations of nuclear cross section data for applied purposes. We consider the direct utilization of total, elastic, and reaction cross sections for neutrons, protons, deuterons, tritons, {sup 3}He and alpha particles in files of evaluated nuclear data covering the energy range of 0 to 200 MeV, as well as transmission coefficients for reaction theory calculations and neutron and proton wave functions direct-reaction and Feshbach-Kerman-Koonin analyses. Optical model codes such as SCAT and ECIS and the reaction theory codes COMNUC, GNASH FKK-GNASH, and DWUCK have primarily been used in our analyses. A summary of optical model parameterizations from past analyses at Los Alamos will be given, including detailed tabulations of the parameters for a selection of nuclei.
Thermodynamic Modeling and Analysis of an Optical Electric-Field Sensor
Directory of Open Access Journals (Sweden)
Xia Xiao
2015-03-01
Full Text Available The stability of the optical electric field sensor (OEFS in actual operation is affected by environmental factors such as temperature and SF6 (sulfur hexafluoride. To analyze the operational environment parameters affecting the optical properties of crystals, a thermodynamic model of the OEFS in which the optical properties of the crystal are changed by the first-order effects and the second-order effects was established. The intensity parameters such as electric, stress and temperature fields were introduced. The theoretical analysis results show that under temperature, stress and electric field conditions, the optical properties of the sensing crystals are no longer changed only by the electro-optic effect, but also by the temperature and the stress fields. Further synthesis suggests the expected optical property changes under the effect of the environment fields. OEFS tests show that the accuracy of OEFS is dependent on temperature with a ratio error of −0.8%~1.5% in the temperature range from −25 °C to +40 °C.
Teaching Algebra and Geometry Concepts by Modeling Telescope Optics
Siegel, Lauren M.; Dickinson, Gail; Hooper, Eric J.; Daniels, Mark
2008-01-01
This article describes preparation and delivery of high school mathematics lessons that integrate mathematics and astronomy through The Geometer's Sketchpad models, traditional proof, and inquiry-based activities. The lessons were created by a University of Texas UTeach preservice teacher as part of a project-based field experience in which high…
Information Model for Connection Management in Automatic Switched Optical Network
Institute of Scientific and Technical Information of China (English)
Xu Yunbin(徐云斌); Song Hongsheng; Gui Xuan; Zhang Jie; Gu Wanyi
2004-01-01
The three types of connections (Permanent Connection, Soft Permanent Connection and Switched Connection) provided by ASON can adapt the requirement of different network services. Management and maintenance of these three connections are the most important aspect of ASON management. The information models proposed in this paper are used for the purpose of ASON connection management. Firstly a new information model is proposed to meet the requirement for the control plane introduced by ASON. In this model, a new class ControlNE is given, and the relationship between the ControlNE and the transport NE (network element) is also defined. Then this paper proposes information models for the three types of connections for the first time, and analyzes the relationship between the three kinds of connections and the basic network transport entities. Finally, the paper defines some CORBA interfaces for the management of the three connections. In these interfaces, some operations such as create or release a connection are defined, and some other operations can manage the performance of the three kinds of connections, which is necessary for a distributed management system.
Modelling a singly resonant, intracavity ring optical parametric oscillator
DEFF Research Database (Denmark)
Buchhave, Preben; Tidemand-Lichtenberg, Peter; Wei, Hou;
2003-01-01
We study theoretically and experimentally the dynamics of a single-frequency, unidirectional ring laser with an intracavity nonlinear singly resonant OPO-crystal in a coupled resonator. We find for a range of operating conditions good agreement between model results and measurements of the laser ...
Optical Test of Local Hidden-Variable Model
Institute of Scientific and Technical Information of China (English)
WU XiaoHua; ZONG HongShi; PANG HouRong
2001-01-01
An inequality is deduced from local realism and a supplementary assumption. This inequality defines an experiment that can be actually performed with the present technology to test local hidden-variable models, and it is violated by quantum mechanics with a factor 1.92, while it can be simplified into a form where just two measurements are required.``
MILES extended: Stellar population synthesis models from the optical to the infrared
Röck, B; Ricciardelli, E; Peletier, R F; Knapen, J H; Falcon-Barroso, J
2016-01-01
We present the first single-burst stellar population models which covers the optical and the infrared wavelength range between 3500 and 50000 Angstrom and which are exclusively based on empirical stellar spectra. To obtain these joint models, we combined the extended MILES models in the optical with our new infrared models that are based on the IRTF (Infrared Telescope Facility) library. The latter are available only for a limited range in terms of both age and metallicity. Our combined single-burst stellar population models were calculated for ages larger than 1 Gyr, for metallicities between [Fe/H] = -0.40 and 0.26, for initial mass functions of various types and slopes, and on the basis of two different sets of isochrones. They are available to the scientific community on the MILES web page. We checked the internal consistency of our models and compared their colour predictions to those of other models that are available in the literature. Optical and near infrared colours that are measured from our models...
Optical modeling of nickel-base alloys oxidized in pressurized water reactor
Energy Technology Data Exchange (ETDEWEB)
Clair, A. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Universite de Bourgogne, 9 avenue Alain Savary, BP 47870, 21078 Dijon cedex (France); Foucault, M.; Calonne, O. [Areva ANP, Centre Technique Departement Corrosion-Chimie, 30 Bd de l' industrie, BP 181, 71205 Le Creusot (France); Finot, E., E-mail: Eric.Finot@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Universite de Bourgogne, 9 avenue Alain Savary, BP 47870, 21078 Dijon cedex (France)
2012-10-01
The knowledge of the aging process involved in the primary water of pressurized water reactor entails investigating a mixed growth mechanism in the corrosion of nickel-base alloys. A mixed growth induces an anionic inner oxide and a cationic diffusion parallel to a dissolution-precipitation process forms the outer zone. The in situ monitoring of the oxidation kinetics requires the modeling of the oxide layer stratification with the full knowledge of the optical constants related to each component. Here, we report the dielectric constants of the alloys 600 and 690 measured by spectroscopic ellipsometry and fitted to a Drude-Lorentz model. A robust optical stratification model was determined using focused ion beam cross-section of thin foils examined by transmission electron microscopy. Dielectric constants of the inner oxide layer depleted in chromium were assimilated to those of the nickel thin film. The optical constants of both the spinels and extern layer were determined. - Highlights: Black-Right-Pointing-Pointer Spectroscopic ellipsometry of Ni-base alloy oxidation in pressurized water reactor Black-Right-Pointing-Pointer Measurements of the dielectric constants of the alloys Black-Right-Pointing-Pointer Optical simulation of the mixed oxidation process using a three stack model Black-Right-Pointing-Pointer Scattered crystallites cationic outer layer; linear Ni-gradient bottom layer Black-Right-Pointing-Pointer Determination of the refractive index of the spinel and the Cr{sub 2}O{sub 3} layers.
Simple method of modelling of digital holograms registering and their optical reconstruction
Evtikhiev, N. N.; Cheremkhin, P. A.; Krasnov, V. V.; Kurbatova, E. A.; Molodtsov, D. Yu; Porshneva, L. A.; Rodin, V. G.
2016-08-01
The technique of modeling of digital hologram recording and image optical reconstruction from these holograms is described. The method takes into account characteristics of the object, digital camera's photosensor and spatial light modulator used for digital holograms displaying. Using the technique, equipment can be chosen for experiments for obtaining good reconstruction quality and/or holograms diffraction efficiency. Numerical experiments were conducted.
DEFF Research Database (Denmark)
Jurado-Navas, Antonio
2015-01-01
Recently, a new and generalized statistical model, called Málaga or simply M distribution, has been proposed to characterize the irradiance fluctuations of an unbounded optical wavefront (plane and spherical waves) propagating through a turbulent medium under all irradiance fluctuation conditions...
A semitransparency-based optical-flow method with a point trajectory model for particle-like video.
Sakaino, Hidetomo
2012-02-01
This paper proposes a new semitransparency-based optical-flow model with a point trajectory (PT) model for particle-like video. Previous optical-flow models have used ranging from image brightness constancy to image brightness change models as constraints. However, two important issues remain unsolved. The first is how to track/match a semitransparent object with a very large displacement between frames. Such moving objects with different shapes and sizes in an outdoor scene move against a complicated background. Second, due to semitransparency, the image intensity between frames can also violate a previous image brightness-based optical-flow model. Thus, we propose a two-step optimization for the optical-flow estimation model for a moving semitransparent object, i.e., particle. In the first step, a rough optical flow between particles is estimated by a new alpha constancy constraint that is based on an image generation model of semitransparency. In the second step, the optical flow of a particle with a continuous trajectory in a definite temporal interval based on a PT model can be refined. Many experiments using various falling-snow and foggy scenes with multiple moving vehicles show the significant improvement of the optical flow compared with a previous optical-flow model.
Gokul, Elamurugu Alias; Shanmugam, Palanisamy; Sundarabalan, Balasubramanian; Sahay, Arvind; Chauhan, Prakash
2014-08-01
Retrieval of the inherent optical properties and estimation of the constituents' concentrations from satellite ocean colour data in turbid and eutrophic waters are important as these products provide innovative opportunities for the study of biological and biogeochemical properties in such optically complex waters. This paper intends to develop models to retrieve absorption coefficients of phytoplankton, suspended sediments and coloured dissolved organic matter and describe vertical profiles of chlorophyll and suspended sediments from satellite ocean colour data. These models make use of the relationships between remote sensing reflectance ratios Rrs (555)/Rrs (443) and Rrs (620)/Rrs (490) versus aph (443) and aph (555), and acdom (443), and ad (443) to derive the model parameters. Validation with the in-situ data obtained from coastal waters around India and other regional waters (e.g., NASA bio-Optical Marine Algorithm Data-Set, NOMAD) shows that the new models are more accurate in terms of producing the spectral absorption coefficients (aph, ad, acdom across the entire visible wavelengths 400-700 nm) in a wide variety of waters. Further comparison with existing models shows advantage of the new models that have important implications for remote sensing of turbid coastal and eutrophic waters. The retrieved absorption coefficients of phytoplankton and suspended sediments (non-algal matter) are also found to relate better to chlorophyll and total suspended sediments. Taking advantages of this, we derive models to determine and describe the vertical profiles of chlorophyll and suspended sediment concentrations along the depth. The model parameters are derived empirically. These new parameterizations show potential in estimating the vertical profiles of chlorophyll and suspended sediments with good accuracy. These results suggest robustness and suitability of the new models for studying the ecologically important components of optically complex turbid and eutrophic
Optical bandgap modeling of thermal annealed ZnO:Ga thin films using neural networks
Energy Technology Data Exchange (ETDEWEB)
Kim, Chang Eun; Moon, Pyung; Yun, Ilgu [School of Electrical and Electronic Engineering, Yonsei University, 262 Seongsanno, Seodaemoon-gu, Seoul 120-749 (Korea); Kim, Sungyeon; Myoung, Jae-Min [Department of Materials Science and Engineering, Yonsei University, 262 Seongsanno, Seodaemoon-gu, Seoul 120-749 (Korea); Jang, Hyeon Woo; Bang, Jungsik [LG Chem, Ltd., Research Park, 104-1 Moonji-Dong, Yuseng-Gu, Daejeon 305-380 (Korea)
2010-07-15
In this paper, the thermal annealing process modeling for the optical bandgap of ZnO:Ga thin films for transparent conductive oxide was presented using neural network (NNets) based on error backpropagation (BPNN) algorithm and multilayer perceptron (MLP). The thermal annealing process of ZnO:Ga thin films were analyzed by general factorial experimental design. The annealing temperature and film thickness were considered as input factors. To model the nonlinear annealing process, 6 experiments were trained by BPNN which has 2-4-1 structures and 2 additional samples were experimented to verify the predicted models. The output response model on optical bandgap and carrier concentration of ZnO:Ga thin films trained by BPNN was represented by surface plot of response surface model. Based on the modeling results, NNets can provide sufficient correspondence between the predicted output values and the measured. The optical bandgap variation of ZnO:Ga thin films by annealing is due to increased carrier concentration and explained by Burstein-Moss effect. The thermal annealing process is nonlinear and complex but the output response can be predicted by the NNets model. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Artificial topological models based on a one-dimensional spin-dependent optical lattice
Zheng, Zhen; Pu, Han; Zou, Xubo; Guo, Guangcan
2017-01-01
Topological matter is a popular topic in both condensed matter and cold-atom research. In the past decades, a variety of models have been identified with fascinating topological features. Some, but not all, of the models can be found in materials. As a fully controllable system, cold atoms trapped in optical lattices provide an ideal platform to simulate and realize these topological models. Here we present a proposal for synthesizing topological models in cold atoms based on a one-dimensional spin-dependent optical lattice potential. In our system, features such as staggered tunneling, staggered Zeeman field, nearest-neighbor interaction, beyond-near-neighbor tunneling, etc. can be readily realized. They underlie the emergence of various topological phases. Our proposal can be realized with current technology and hence has potential applications in quantum simulation of topological matter.
Constraints on Disks Models of The Big Blue Bump from UV/Optical/IR Observations
Antonucci, R
1998-01-01
Optical/UV observations provide many constraints on accretion disk models of AGN which aren't always appreciated by modelers of the X-ray emission (or sometimes even of the optical/UV emission). The spectral behavior at the Ly edge, the polarization, the continuum slopes and breaks, and the variability timescales and phasing all conflict with simple models and strongly constrain the more Baroque ones. Partial-covering absorbers and microlensing data suggest that the radiation is not released simply according to where the potential drop (modified by standard viscous transport) takes place. On the other hand, the orientation-based unified model is in accord with the K-\\alpha inclination distributions for the AGN spectral classes, basing the latter on the limited existing data and theoretical understanding.
Causality issues of particle detector models in QFT and Quantum Optics
Martin-Martinez, Eduardo
2015-01-01
We analyze the constraints that causality imposes on some of the particle detector models employed in quantum field theory in general, and in particular on those used in quantum optics (or superconducting circuits) to model atoms interacting with light. Namely, we show that disallowing faster-than-light communication can impose severe constraints on the applicability of particle detector models in three different common scenarios: 1) when the detectors are spatially smeared, 2) when a UV cutoff is introduced in the theory and 3) under one of the most typical approximations made in quantum optics: the rotating-wave approximation. We identify in which scenarios the models' causal behaviour can be cured and in which it cannot.
Modeling the spectral optical properties of ammonium sulfate and biomass burning aerosols
Energy Technology Data Exchange (ETDEWEB)
Grant, K.E.; Chuang, C.C.; Grossman, A.S.; Penner, J.E. [Michigan Univ., Ann Arbor, MI (United States)
1997-09-01
The importance of including the global and regional radiative effects of aerosols in climate models has increasingly been realized. Accurate modeling of solar radiative forcing due to aerosols from anthropogenic sulfate and biomass burning emissions requires adequate spectral resolution and treatment of spatial and temporal variability. The variation of aerosol spectral optical properties with local relative humidity and dry aerosol composition must be considered. Because the cost of directly including Mie calculations within a climate model is prohibitive, parameterizations from offline calculations must be used. Starting from a log-normal size distribution of dry ammonium sulfate, we developed optical properties for tropospheric sulfate aerosol at 15 relative humidities up to 99 percent. The resulting aerosol size distributions were then used to calculate bulk optical properties at wavelengths between 0.175 {micro}m and 4 {micro}m. Finally, functional fits of optical properties were made for each of 12 wavelength bands as a function of relative humidity. Significant variations in optical properties occurred across the total solar spectrum. Relative increases in specific extinction and asymmetry factor with increasing relative humidity became larger at longer wavelengths. Significant variation in single-scattering albedo was found only in the longest near-IR band. This is also the band with the lowest albedo. A similar treatment was done for aerosols from biomass burning. In this case, size distributions were taken as having two carbonaceous size modes and a larger dust mode. The two carbonaceous modes were considered to be humidity dependent. Equilibrium size distributions and compositions were calculated for 15 relative humidities and five black carbon fractions. Mie calculations and Chandrasekhar averages of optical properties were done for each of the resulting 75 cases. Finally, fits were made for each of 12 spectral bands as functions of relative humidity
AlQuwaiee, Hessa
2016-11-01
One of the potential solutions to the radio frequency (RF) spectrum scarcity problem is optical wireless communications (OWC), which utilizes the unlicensed optical spectrum. Long-range outdoor OWC are usually referred to in the literature as free-space optical (FSO) communications. Unlike RF systems, FSO is immune to interference and multi-path fading. Also, the deployment of FSO systems is flexible and much faster than optical fibers. These attractive features make FSO applicable for broadband wireless transmission such as optical fiber backup, metropolitan area network, and last mile access. Although FSO communication is a promising technology, it is negatively affected by two physical phenomenon, namely, scintillation due to atmospheric turbulence and pointing errors. These two critical issues have prompted intensive research in the last decade. To quantify the effect of these two factors on FSO system performance, we need effective mathematical models. In this work, we propose and study a generalized pointing error model based on the Beckmann distribution. Then, we aim to generalize the FSO channel model to span all turbulence conditions from weak to strong while taking pointing errors into consideration. Since scintillation in FSO is analogous to the fading phenomena in RF, diversity has been proposed too to overcome the effect of irradiance fluctuations. Thus, several combining techniques of not necessarily independent dual-branch free-space optical links were investigated over both weak and strong turbulence channels in the presence of pointing errors. On another front, improving the performance, enhancing the capacity and reducing the delay of the communication link has been the motivation of any newly developed schemes, especially for backhauling. Recently, there has been a growing interest in practical systems to integrate RF and FSO technologies to solve the last mile bottleneck. As such, we also study in this thesis asymmetric an RF-FSO dual-hop relay
Human tissue optical properties measurements and light propagation modelling
CSIR Research Space (South Africa)
Dam, JS
2006-07-01
Full Text Available measurements and light propagation modelling J. S. Dam , A. Singh , and A. E. Karsten Biophotonics Group, National Laser Centre, CSIR, Pretoria. www.csir.co.za/biophotonics SAIP 2006 Slide 2 © CSIR 2006 www... and µ’s S a m p l e S a m p l e S a m p l e Integrating Sphere measurements “Measurements of the total transmittance and reflectance of a thin slab-shaped multiple scattering sample can yield the absorption- and the reduced...
Modeling Graphene Contrast on Copper Surfaces Using Optical Microscopy
2014-10-01
Determining whether graphene has been successfully synthesized often requires transfer to a support substrate such as glass or SiO2 . During the transfer... SiO2 thickness from Blake et al.23 In comparison, Fig. 6b shows the same graphene contrast calculations using an in-house Matlab model. 7... graphene : interference colors of ultrathin graphite on SiO2 . Nano Letters. 2007;7(9):2707–2710. 11 26. Jung I, Pelton M, Piner R, Dikin DA
Energy Technology Data Exchange (ETDEWEB)
Mani, G.S.; Melkanoff, M.A.; Iori, I. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1963-07-01
The neutron penetrabilities and reaction cross-sections are presented in these tables for the case of an optical model potential for the nucleus, for nuclei up to mass 230. (authors) [French] Les penetrabilites et les sections efficaces de reaction pour les neutrons sont donnees dans ces tables en utilisant le modele du potentiel optique, pour les noyaux cibles jusqu'a la masse 230. (auteurs)
Improved analytical model for the field of index-guiding microstructured optical fibers
Sharma, Dinesh Kumar; Sharma, Anurag
2016-05-01
We present an improved version of our earlier developed analytical field model for the fundamental mode of index-guiding microstructured optical fibers (MOFs), to obtain better accuracy in the simulated results. Using this improved field model, we have studied the splice losses between an MOF and a traditional step-index single-mode fiber (SMF). Comparisons with available experimental and numerical simulation results have also been included.
1980-12-01
models by comparing model results to optical measurements made over Monterey Bay off the Central California coast of the U.S. Commanding Officer COPY...FPO SAN FRANCISCO 96654 OFFICER IN CHARGE NAVOCEANCOM OET MONTEREY, CA 93940 COMMANDING OFFICER OFFICE OF NAVAL RESEARCH EASTERN/ CENTRAL ...TECHNICIAN CITY, HAIFA ISRAEL 32000 INSTITUTO OE GEOFISICA U.N.A.M. BIBLIOTECA TORRE DE CIENCIAS, 3ER PISO CIUDAD UNIVERSITARIA MEXICO 20, D.F
Linear and nonlinear optics of surface plasmon toy-models of black holes and wormholes
Smolyaninov, I I
2003-01-01
Experimental and theoretical studies of linear and nonlinear optics of surface plasmon toy wormholes and black holes have been performed. These models are based on dielectric microdroplets on the metal surfaces and on nanoholes drilled in thin metal films. Toy surface plasmon black holes and wormholes are shown to exhibit strongly enhanced nonlinear optical behavior in the frequency range near the surface plasmon resonance of a metal-liquid interface. Various possibilities to emulate such nontrivial gravitation theory effects as Hawking radiation and Cauchy horizons are discussed.
Design of nanostructured solar cells using coupled optical and electrical modeling.
Deceglie, Michael G; Ferry, Vivian E; Alivisatos, A Paul; Atwater, Harry A
2012-06-13
Nanostructured light trapping has emerged as a promising route toward improved efficiency in solar cells. We use coupled optical and electrical modeling to guide optimization of such nanostructures. We study thin-film n-i-p a-Si:H devices and demonstrate that nanostructures can be tailored to minimize absorption in the doped a-Si:H, improving carrier collection efficiency. This suggests a method for device optimization in which optical design not only maximizes absorption, but also ensures resulting carriers are efficiently collected.
Empirical model of optical sensing via spectral shift of circular Bragg phenomenon
Mackay, Tom G
2009-01-01
Setting up an empirical model of optical sensing to exploit the circular Bragg phenomenon displayed by chiral sculptured thin films (CSTFs), we considered a CSTF with and without a central twist defect of $\\pi/2$ radians. The circular Bragg phenomenon of the defect-free CSTF, and the spectral hole in the co-polarized reflectance spectrum of the CSTF with the twist defect, were both found to be acutely sensitive to the refractive index of a fluid which infiltrates the void regions of the CSTF. These findings bode well for the deployment of CSTFs as optical sensors.
Indian Academy of Sciences (India)
Dhairya A Dholakia; G K Solanki; S G Patel; M K Agarwal
2001-06-01
The optical energy gaps of WS2 single crystal were determined from the analysis of the absorption spectrum near the fundamental absorption edge at room temperature using light parallel to -axis incident normally on the basal plane. On the basis of two- and three-dimensional models it was found that both direct and indirect band transitions took place in WS2 and the indirect transition was of the allowed type. The optical energy gaps corresponding to both transitions were determined and the phonon energies associated with the indirect transitions estimated. The implications of the results have been discussed.
Directory of Open Access Journals (Sweden)
Congrong Li
2015-08-01
Full Text Available Forest canopy leaf area index (LAI inversion based on remote sensing data is an important method to obtain LAI. Currently, the most widely-used model to achieve forest canopy structure parameters is the Li-Strahler geometric-optical bidirectional reflectance model, by considering the effect of crown shape and mutual shadowing, which is referred to as the GOMS model. However, it is difficult to retrieve LAI through the GOMS model directly because LAI is not a fundamental parameter of the model. In this study, a gap probability model was used to obtain the relationship between the canopy structure parameter nR2 and LAI. Thus, LAI was introduced into the GOMS model as an independent variable by replacing nR2 The modified GOMS (MGOMS model was validated by application to Dayekou in the Heihe River Basin of China. The LAI retrieved using the MGOMS model with optical multi-angle remote sensing data, high spatial resolution images and field-measured data was in good agreement with the field-measured LAI, with an R-square (R2 of 0.64, and an RMSE of 0.67. The results demonstrate that the MGOMS model obtained by replacing the canopy structure parameter nR2 of the GOMS model with LAI can be used to invert LAI directly and precisely.
Improved Reduced Models for Single-Pass and Reflective Semiconductor Optical Amplifiers
Dúill, Seán P Ó
2014-01-01
We present highly accurate and easy to implement, improved lumped semiconductor optical amplifier (SOA) models for both single-pass and reflective semiconductor optical amplifiers (RSOA). The key feature of the model is the inclusion of the internal losses and we show that a few subdivisions are required to achieve an accuracy of 0.12 dB. For the case of RSOAs, we generalize a recently published model to account for the internal losses that are vital to replicate observed RSOA behavior. The results of the improved reduced RSOA model show large overlap when compared to a full bidirectional travelling wave model over a 40 dB dynamic range of input powers and a 20 dB dynamic range of reflectivity values. The models would be useful for the rapid system simulation of signals in communication systems, i.e. passive optical networks that employ RSOAs, signal processing using SOAs and for implementing digital back propagation to undo amplifier induced signal distortions.
Radar model fusion of asteroid (4179) Toutatis via its optical images observed by Chang'e-2 probe
Zhao, Wei; Xiao, Ting; Liu, Peng; Sun, Lei; Huang, Jiangchuan; Tang, Xianglong
2016-06-01
Asteroid (4179) Toutatis has been modeling by ground-based radar observations until Dec 13th, 2012, when distinct optical images of Toutatis were captured during the Chang'e-2 flyby at the shortest distance for the first time. The surface details on Toutatis in the optical images are abundant enough to reinforce the radar model descriptions. Under this context, we customized a method of frequency domain data fusion, which combines the topography information of radar model and the 3rd dimension information estimated from optical image by shape from shading algorithm, and gave out a new Toutatis' radar model. A model with abundant surface characteristics had been resulted.
Probabilistic Model for Free-Space Optical Links Under Continental Fog Conditions
Directory of Open Access Journals (Sweden)
Marzuki
2010-09-01
Full Text Available The error characteristics of a free-space optical (FSO channel are signiﬁcantly different from the ﬁber based optical links and thus require a deep physical understanding of the propagation channel. In particular different fog conditions greatly inﬂuence the optical transmissions and thus a channel model is required to estimate the detrimental fog effects. In this paper we shall present the probabilistic model for radiation fog from the measured data over a 80 m FSO link installed at Graz, Austria. The fog events are classiﬁed into thick fog, moderate fog, light fog and general fog based on the international code of visibility range. We applied some probability distribution functions (PDFs such as Kumaraswamy, Johnson SB and Logistic distribution, to the actual measured optical attenuations. The performance of each distribution is evaluated by Q-Q and P-P plots. It is found that Kumaraswamy distribution is the best ﬁt for general fog, while Logistic distribution is the optimum choice for thick fog. On the other hand, Johnson SB distribution best ﬁts the moderate and light fog related measured attenuation data. The difference in these probabilistic models and the resultant variation in the received signal strength under different fog types needs to be considered in designing an efﬁcient FSO system.
Numerical Model for the Deformation of Nucleated Cells by Optical Stretchers
Sraj, Ihab; Marr, David W M; Eggleton, Charles D
2015-01-01
In this paper, we seek to model the deformation of nucleated cells by single diode-laser bar optical stretchers. We employ a recently developed computational model, the Dynamic Ray-Tracing method, to determine the stress distribution induced by the applied optical forces on a capsule encapsulating a nucleus of different optical properties. These forces are shape dependent and can deform real non-rigid objects; thus resulting in a dynamically changing optical stress distribution with cell and nucleus deformation. Chinese hamster ovary cell is a common biological cell that is of interest to the biomedical community because of their use in recombinant protein therapeutics and is an example of a nucleated cell. To this end, we model chinese hamster ovary cells as two three-dimensional elastic capsules of variable inner capsule size immersed in a fluid where the hydrodynamic forces are calculated using the Immersed Boundary Method. Our results show that the presence of a nucleus has a major effect on the force dis...
Modeling and experimental verification for a broad beam light transport in optical tomography.
Janunts, Edgar; Pöschinger, Thomas; Eisa, Fabian; Langenbucher, Achim
2010-01-01
This paper describes a general theoretical model for computing a broad beam excitation light transport in a 3D diffusion medium. The model is based on the diffusion approximation of the radiative transport equation. An analytical approach for the light propagation is presented by deriving a corresponding Green's function. A finite cylindrical domain with a rectangular cross section was considered as a 3D homogeneous phantom model. The results of the model are compared with corresponding experimental data. The measurements are done on solid and liquid phantoms replicating tissue-like optical properties.
Integrated Model of the Eye/Optic Nerve Head Biomechanical Environment
Ethier, C. R.; Feola, A.; Myers, J. G.; Nelson, E.; Raykin, J.; Samuels, B.
2017-01-01
Visual Impairment and Intracranial Pressure (VIIP) syndrome is a concern for long-duration space flight. Previously, it has been suggested that ocular changes observed in VIIP syndrome are related to the cephalad fluid shift that results in altered fluid pressures [1]. We are investigating the impact of changes in intracranial pressure (ICP) using a combination of numerical models, which simulate the effects of various environment conditions, including finite element (FE) models of the posterior eye. The specific interest is to understand how altered pressures due to gravitational changes affect the biomechanical environment of tissues of the posterior eye and optic nerve sheath. METHODS: Additional description of the numerical modeling is provided in the IWS abstract by Nelson et al. In brief, to simulate the effects of a cephalad fluid shift on the cardiovascular and ocular systems, we utilized a lumped-parameter compartment model of these systems. The outputs of this lumped-parameter model then inform boundary conditions (pressures) for a finite element model of the optic nerve head (Figure 1). As an example, we show here a simulation of postural change from supine to 15 degree head-down tilt (HDT), with primary outcomes being the predicted change in strains at the optic nerve head (ONH) region, specifically in the lamina cribrosa (LC), retrolaminar optic nerve, and prelaminar neural tissue (PLNT). The strain field can be decomposed into three orthogonal components, denoted as the first, second and third principal strains. We compare the peak tensile (first principal) and compressive (third principal) strains, since elevated strain alters cell phenotype and induces tissue remodeling. RESULTS AND CONCLUSIONS: Our lumped-parameter model predicted an IOP increase of c. 7 mmHg after 21 minutes of 15 degree HDT, which agreed with previous reports of IOP in HDT [1]. The corresponding FEM simulations predicted a relative increase in the magnitudes of the peak tensile
Polarization modeling for the main optics of Chinese Giant Solar Telescope
Yuan, Shu; Fu, Yu; Jin, Zhenyu
2016-07-01
Chinese Giant Solar Telescope, which has a 8m diameter segmented primary mirror, is a plan for the next generation ground-based large solar telescope in China. A major scientific requirement for this telescope is the high accuracy polarimetry. In this paper, the instrumental polarization of the main optics is analyzed by polarization modeling, which is caused by off-axial field of view, spider asymmetry, nonuniform segment gap and segment coating. The result shows that the net polarization is sensitive to the asymmetrical spider leg widening and the uniformity of the segment optical property. For meeting the accuracy requirement, the extinction ratio and retardence error for each segment should be less than 0.3% and 0.8 degree, respectively. Generally, the ring segmented primary mirror have advantage in controlling the instrumental polarization for large main optics.
Modeling of semiconductor devices for high-speed all-optical signal processing
DEFF Research Database (Denmark)
Bischoff, Svend; Højfeldt, Sune; Mørk, Jesper
2001-01-01
The all-optical signal processing performance of devices based on active semiconductor waveguides is investigated. A large signal model is used to analyse the physical mechanisms limiting the high-speed performance of both semiconductor optical amplifiers (SOAs) and electro-absorption modulators...... (EAMs). Wavelength conversion and signal regeneration in EAMs is discussed at 10 and 40 Gbit/s. The finite carrier sweep-out time is shown to limit the EAM performance. Four-wave mixing (FWM) in SOAs is almost instantaneous. However, with increasing bit rates and advanced processing functionalities some...... limitations arise. These limitations are elucidated by studying bi-directional simultaneous clear and drop (de-multiplexing) for a 4x40 Gbit/s signal. The simultaneous clearing and de-multiplexing (drop) of an optical time division multiplexing signal channel for an 8x40 Gbit/s signal is investigated...
Optical modeling of organic solar cells based on CuPc and C60.
Monestier, Florent; Simon, Jean-Jacques; Torchio, Philippe; Escoubas, Ludovic; Ratier, Bernard; Hojeij, Wassim; Lucas, Bruno; Moliton, André; Cathelinaud, Michel; Defranoux, Christophe; Flory, François
2008-05-01
We have investigated the influence of the poly(3,4-ethylenedioxythiophene)-blend-poly(styrene-sulfonate) (PEDOT:PSS) layer on the short-circuit current density (J(sc)) of single planar heterojunction organic solar cells based on a copper phthalocyanine (CuPc)-buckminsterfullerene (C(60)) active layer. Complete optical and electrical modeling of the cell has been performed taking into account optical interferences and exciton diffusion. Comparison of experimental and simulated external quantum efficiency has allowed us to estimate the exciton diffusion length to be 37 nm for the CuPc and 19 nm for the C(60). The dependence of short-circuit current densities versus the thickness of the PEDOT:PSS layer is analyzed and compared with experimental data. It is found that the variation in short-circuit current densities could be explained by optical interferences.
Modelling optical scattering artefacts for varying pathlength in a gel dosimeter phantom.
Bosi, Stephen G; Brown, Saxby; Sarabipour, Sarvenaz; De Deene, Yves; Baldock, Clive
2009-01-21
A gelatin phantom containing an optically scattering funnel-shaped region of elevated optical density (OD) was used to examine light-scattering-induced artefacts in a cone-beam optical CT scanner used for gel dosimetry. To simulate polymer gel dosimeters, the opacity was introduced by adding a colloidal scatterer to the gelatin. Scatter results in an underestimate of OD (hence dose). In line profiles of OD taken from 3D reconstructions of the funnel, those profiles with a long pathlength through high OD regions exhibited a 'dishing' (or 'cupping') artefact, while those of short pathlength exhibited the opposite effect-'doming'. These phenomena are accounted for by a model that includes the effect of stray, scattered light.
Modelling optical scattering artefacts for varying pathlength in a gel dosimeter phantom
Energy Technology Data Exchange (ETDEWEB)
Bosi, Stephen G [Department of Radiation Oncology, Prince of Wales Hospital, Randwick, NSW 2031 (Australia); Brown, Saxby; Sarabipour, Sarvenaz; Baldock, Clive [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia); De Deene, Yves [Division of Radiotherapy, University Hospital of Ghent, de Pintelaan 185, 9000 Ghent (Belgium)], E-mail: s.bosi@physics.usyd.edu.au
2009-01-21
A gelatin phantom containing an optically scattering funnel-shaped region of elevated optical density (OD) was used to examine light-scattering-induced artefacts in a cone-beam optical CT scanner used for gel dosimetry. To simulate polymer gel dosimeters, the opacity was introduced by adding a colloidal scatterer to the gelatin. Scatter results in an underestimate of OD (hence dose). In line profiles of OD taken from 3D reconstructions of the funnel, those profiles with a long pathlength through high OD regions exhibited a 'dishing' (or 'cupping') artefact, while those of short pathlength exhibited the opposite effect-'doming'. These phenomena are accounted for by a model that includes the effect of stray, scattered light.
Li, Hui; Fu, Zhida; Liu, Liying; Lin, Zhili; Deng, Wei; Feng, Lishuang
2017-01-03
An improved temperature-insensitive optical voltage sensor (OVS) with a reciprocal dual-crystal sensing method is proposed. The inducing principle of OVS reciprocity degradation is expounded by taking the different temperature fields of two crystals and the axis-errors of optical components into consideration. The key parameters pertaining to the system reciprocity degeneration in the dual-crystal sensing unit are investigated in order to optimize the optical sensing model based on the Maxwell's electromagnetic theory. The influencing principle of axis-angle errors on the system nonlinearity in the Pockels phase transfer unit is analyzed. Moreover, a novel axis-angle compensation method is proposed to improve the OVS measurement precision according to the simulation results. The experiment results show that the measurement precision of OVS is superior to ±0.2% in the temperature range from -40 °C to +60 °C, which demonstrates the excellent temperature stability of the designed voltage sensing system.
Modeling of Distributed Sensing of Elastic Waves by Fiber-Optic Interferometry
Directory of Open Access Journals (Sweden)
Just Agbodjan Prince
2016-09-01
Full Text Available This paper deals with the transduction of strain accompanying elastic waves in solids by firmly attached optical fibers. Stretching sections of optical fibers changes the time required by guided light to pass such sections. Exploiting interferometric techniques, highly sensitive fiber-optic strain transducers are feasible based on this fiber-intrinsic effect. The impact on the actual strain conversion of the fiber segment’s shape and size, as well as its inclination to the elastic wavefront is studied. FEM analyses show that severe distortions of the interferometric response occur when the attached fiber length spans a noticeable fraction of the elastic wavelength. Analytical models of strain transduction are presented for typical transducer shapes. They are used to compute input-output relationships for the transduction of narrow-band strain pulses as a function of the mechanical wavelength. The described approach applies to many transducers depending on the distributed interaction with the investigated object.
Xu, H; Toth, J; Tokesi, K; Ding, Z J
2016-01-01
We present an absolute extraction method of optical constants of metal from the measured reflection electron energy loss (REELS) spectra by using the recently developed reverse Monte Carlo (RMC) technique. The method is based on a direct physical modeling of electron elastic and electron inelastic scattering near the surface region where the surface excitation becomes important to fully describe the spectrum loss feature intensity in relative to the elastic peak intensity. An optimization procedure of oscillator parameters appeared in the energy loss function (ELF) for describing electron inelastic scattering due to the bulk- and surface-excitations was performed with the simulated annealing method by a successive comparison between the measured and Monte Carlo simulated REELS spectra. The ELF and corresponding optical constants of Fe were obtained from the REELS spectra measured at incident energies of 1000, 2000 and 3000 eV. The validity of the present optical data has been verified with the f- and ps-sum r...
Optical modeling of plasma-deposited ZnO films: Electron scattering at different length scales
Energy Technology Data Exchange (ETDEWEB)
Knoops, Harm C. M., E-mail: H.C.M.Knoops@tue.nl; Loo, Bas W. H. van de; Smit, Sjoerd; Ponomarev, Mikhail V.; Weber, Jan-Willem; Sharma, Kashish [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Kessels, Wilhelmus M. M.; Creatore, Mariadriana, E-mail: M.Creatore@tue.nl [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands and Solliance, High Tech Campus 5, 5656 AE Eindhoven (Netherlands)
2015-03-15
In this work, an optical modeling study on electron scattering mechanisms in plasma-deposited ZnO layers is presented. Because various applications of ZnO films pose a limit on the electron carrier density due to its effect on the film transmittance, higher electron mobility values are generally preferred instead. Hence, insights into the electron scattering contributions affecting the carrier mobility are required. In optical models, the Drude oscillator is adopted to represent the free-electron contribution and the obtained optical mobility can be then correlated with the macroscopic material properties. However, the influence of scattering phenomena on the optical mobility depends on the considered range of photon energy. For example, the grain-boundary scattering is generally not probed by means of optical measurements and the ionized-impurity scattering contribution decreases toward higher photon energies. To understand this frequency dependence and quantify contributions from different scattering phenomena to the mobility, several case studies were analyzed in this work by means of spectroscopic ellipsometry and Fourier transform infrared (IR) spectroscopy. The obtained electrical parameters were compared to the results inferred by Hall measurements. For intrinsic ZnO (i-ZnO), the in-grain mobility was obtained by fitting reflection data with a normal Drude model in the IR range. For Al-doped ZnO (Al:ZnO), besides a normal Drude fit in the IR range, an Extended Drude fit in the UV-vis range could be used to obtain the in-grain mobility. Scattering mechanisms for a thickness series of Al:ZnO films were discerned using the more intuitive parameter “scattering frequency” instead of the parameter “mobility”. The interaction distance concept was introduced to give a physical interpretation to the frequency dependence of the scattering frequency. This physical interpretation furthermore allows the prediction of which Drude models can be used in a specific
MODELING AND EXPERIMENTAL STUDY OF A FIBER OPTIC HYDROPHONE SENSING ELEMENT
Directory of Open Access Journals (Sweden)
Mikhail E. Efimov
2014-09-01
Full Text Available A model of the fiber-optic hydrophone sensor is suggested. Hydrophone construction comprises a malleable core made of a polymeric material with regulated elastic properties to which the optical fiber is wound. The built-in module of Comsol Multiphysics - Acoustic Solid Interaction is used in the simulation; it evaluates the impact of the acoustic field of different frequencies and amplitudes on the value of the sensor surface deformation. The proposed model gives the possibility for simulating the hydrophone in various environments; materials and dimensions of sensor are selected at the design stage to ensure the required performance: frequency response and sensitivity of fiber optic hydrophone. Correctness of the model construction was verified by results comparison of the computer simulation and experimental study in the acoustic pool. The prototype was represented as the phase interferometric fiber-optic hydrophone on the Bragg gratings. The sensing element is formed as a cylindrical core round which the optical fiber is wound. Core characteristics are: the material attenuation (damping – 0.1, Young's modulus of the core - 6 MPa, Poisson’s ratio - 0.49. The prototype was tested in the experimental pool, which design makes it possible to carry out measurements at frequencies above 3 kHz in the absence of reflections of the acoustic signal. The impact assessment of the acoustic field is carried out by means of an approved piezoelectric hydrophone: the amplitude of the acoustic field of a plane wave is 0.5 and 1 Pa, frequencies of the acoustic impact are 3000 - 8000 Hz. According to the findings fabricated prototype sensitivity was equal to 0.1 rad / Pa at the frequency of 3 kHz. Studies have shown that the sensitivity of the simulated fiber optic hydrophone will decrease with increasing frequency of hydroacoustic exposure. At 8 kHz frequency the sensitivity is decreased to 0.01 rad / Pa. Prototype testing results have confirmed the adequacy
Chang, Shengqian; Liu, Siqi; Yuan, Fei; Zheng, Zhenrong
2017-01-01
Since optical distortion has been a big trouble for various kinds of imaging systems, finding a simple correction method with wide applications is of significant importance. In this paper, we propose a unified and simple correction method, performing well for both photographic and projective imaging systems. The basic idea is regarding the optical distortion as geometrical deformation between the object and image, without considering the specific features of an optical system. First of all, a calibration template is employed to establish the geometrical transformation model (GTM) for the distortion of a built optical system. Two alternative algorithms are given to estimate the GTM in algebraic form. The computation is very simple because no intrinsic parameters of the optical system are needed to establish the GTM. Besides, the errors introduced by the fabricating and assembling process can be eliminated. Then, the corrected image of the photographic system or the pre-distorted image of the projective systems can be obtained accordingly utilizing the GTM. Experiments are conducted to demonstrate the effectiveness of our method with wide applications.
Optic neuritis and retinal ganglion cell loss in a chronic murine model of multiple sclerosis
Directory of Open Access Journals (Sweden)
Thomas eQuinn
2011-08-01
Full Text Available Multiple sclerosis (MS and its animal model experimental autoimmune encephalomyelitis (EAE are neurodegenerative diseases with characteristic inflammatory demyelination in the central nervous system, including the optic nerve. Neuronal and axonal damage is considered to be the main cause of long-term disability in patients with MS. Neuronal loss, including retinal ganglion cell (RGC apoptosis in eyes with optic neuritis, also occurs in EAE. However, there is significant variability in the clinical course and level of neuronal damage in MS and EAE. The current studies examine the mechanisms and kinetics of RGC loss in C57BL/6 mice immunized with myelin oligodendrocyte glycoprotein to induce a chronic EAE disease. Clinical progression of EAE was scored daily and vision was assessed by optokinetic responses. At various time points, RGCs were counted and optic nerves were examined for inflammatory cell infiltration. Almost all EAE mice develop optic neuritis by day 15 post-immunization; however, RGC loss is delayed in these mice. No RGC loss is detected 25 days post-immunization, whereas RGC numbers in EAE mice significantly and progressively decrease compared to controls from 35-50 days post-immunization. The delayed time course of RGC loss is in stark contrast to that reported in relapsing EAE, as well as in rats with chronic EAE. Results suggest that different clinical disease courses of optic nerve inflammation may trigger distinct mechanisms of neuronal damage, or RGCs in different rodent strains may have variable resistance to neuronal degeneration.
Vogel, Curtis R; Tyler, Glenn A; Wittich, Donald J
2014-07-01
We introduce a framework for modeling, analysis, and simulation of aero-optics wavefront aberrations that is based on spatial-temporal covariance matrices extracted from wavefront sensor measurements. Within this framework, we present a quasi-homogeneous structure function to analyze nonhomogeneous, mildly anisotropic spatial random processes, and we use this structure function to show that phase aberrations arising in aero-optics are, for an important range of operating parameters, locally Kolmogorov. This strongly suggests that the d5/3 power law for adaptive optics (AO) deformable mirror fitting error, where d denotes actuator separation, holds for certain important aero-optics scenarios. This framework also allows us to compute bounds on AO servo lag error and predictive control error. In addition, it provides us with the means to accurately simulate AO systems for the mitigation of aero-effects, and it may provide insight into underlying physical processes associated with turbulent flow. The techniques introduced here are demonstrated using data obtained from the Airborne Aero-Optics Laboratory.
Another model for a multiexcitonic quantum dot in an optical microcavity
Institute of Scientific and Technical Information of China (English)
SHAN Guang-cun; HUANG Wei; BAO Shu-ying
2007-01-01
Very recently, a multiexcitonic quantum dot in an optical microcavity have been theoretically studied [Herbert Vincka, Boris A. Rodriguez, and Augusto Gonzalez, Physica E, 2006, 35: 99-102]. However, due to the inevitable damping losses through the microcavity, in this work, we will present a more precise and sound model in the Lindblad form master equation to investigate the photonic properties of a single quantum dot (QD) in an optical microcavity system, in which the QD may confine the multiexcitons and be in resonant interaction with a single photonic mode of an optical microcavity. The excitation energies, and the properties of the emission photon from the QD microcavity are computed as functions of the exciton-photon coupling strength, detuning, and pump rate. We further compare our results with their results, and find that the calculated intensity of the emitted photon and the spectra crucially depend on the exciton-photon coupling strength g, the photon detuning, and the number of excitons in the QD. Finally, we will give a physical mechanism of the dressed-state picture for the strong coupling between the single mode of an optical microcavity and the QD emitters to explain the details of the emission photon spectra. Our study establishes useful guidelines for the experimental study of such multiexcitonic quantum dot in an optical microcavity system.
Loyd, Jody; Gregory, Don; Gaskin, Jessica
2016-01-01
This presentation discusses work done to assess the design of a focusing column in a miniaturized Scanning Electron Microscope (SEM) developed at the NASA Marshall Space Flight Center (MSFC) for use in-situ on the Moon-in particular for mineralogical analysis. The MSFC beam column design uses purely electrostatic fields for focusing, because of the severe constraints on mass and electrical power consumption imposed by the goals of lunar exploration and of spaceflight in general. The resolution of an SEM ultimately depends on the size of the focused spot of the scanning beam probe, for which the stated goal here is a diameter of 10 nanometers. Optical aberrations are the main challenge to this performance goal, because they blur the ideal geometrical optical image of the electron source, effectively widening the ideal spot size of the beam probe. In the present work the optical aberrations of the mini SEM focusing column were assessed using direct tracing of non-paraxial rays, as opposed to mathematical estimates of aberrations based on paraxial ray-traces. The geometrical ray-tracing employed here is completely analogous to ray-tracing as conventionally understood in the realm of photon optics, with the major difference being that in electron optics the lens is simply a smoothly varying electric field in vacuum, formed by precisely machined electrodes. Ray-tracing in this context, therefore, relies upon a model of the electrostatic field inside the focusing column to provide the mathematical description of the "lens" being traced. This work relied fundamentally on the boundary element method (BEM) for this electric field model. In carrying out this research the authors discovered that higher accuracy in the field model was essential if aberrations were to be reliably assessed using direct ray-tracing. This led to some work in testing alternative techniques for modeling the electrostatic field. Ultimately, the necessary accuracy was attained using a BEM
Rigorous bounds on aerosol optical properties from measurement and/or model constraints
McGraw, Robert; Fierce, Laura
2016-04-01
Sparse-particle aerosol models are an attractive alternative to sectional and modal methods for representation of complex, generally mixed particle populations. In the quadrature method of moments (QMOM) a small set of abscissas and weights, determined from distributional moments, provides the sparse set. Linear programming (LP) yields a generalization of the QMOM that is especially convenient for sparse particle selection. In this paper we use LP to obtain rigorous, nested upper and lower bounds to aerosol optical properties in terms of a prescribed Bayesian-like sequence of model or simulated measurement constraints. Examples of such constraints include remotely-sensed light extinction at different wavelengths, modeled particulate mass, etc. Successive reduction in bound separation with each added constraint provides a quantitative measure of its contextual information content. The present study is focused on univariate populations as a first step towards development of new simulation algorithms for tracking the physical and optical properties of multivariate particle populations.
Magnetic properties of the α -T3 model: Magneto-optical conductivity and the Hofstadter butterfly
Illes, E.; Nicol, E. J.
2016-09-01
The α -T3 model interpolates between the pseudospin S =1 /2 honeycomb lattice of graphene and the pseudospin S =1 dice lattice via parameter α . We present calculations of the magnetic properties of this hybrid pseudospin model, namely the absorptive magneto-optical conductivity and the Hofstadter butterfly spectra. In the magneto-optics curves, signatures of the hybrid system include a doublet structure present in the peaks, resulting from differing Landau level energies in the K and K' valleys. In the Hofstadter spectra, we detail the evolution of the Hofstadter butterfly as it changes its periodicity by a factor of three as we vary between the two limiting cases of the α -T3 model.
A hybridizable discontinuous Galerkin method for solving nonlocal optical response models
Li, Liang; Mortensen, N Asger; Wubs, Martijn
2016-01-01
We propose Hybridizable Discontinuous Galerkin (HDG) methods for solving the frequency-domain Maxwell's equations coupled to the Nonlocal Hydrodynamic Drude (NHD) and Generalized Nonlocal Optical Response (GNOR) models, which are employed to describe the optical properties of nano-plasmonic scatterers and waveguides. Brief derivations for both the NHD model and the GNOR model are presented. The formulations of the HDG method are given, in which we introduce two hybrid variables living only on the skeleton of the mesh. The local field solutions are expressed in terms of the hybrid variables in each element. Two conservativity conditions are globally enforced to make the problem solvable and to guarantee the continuity of the tangential component of the electric field and the normal component of the current density. Numerical results show that the proposed HDG methods converge at optimal rate. We benchmark our implementation and demonstrate that the HDG method has the potential to solve complex nanophotonic pro...
Doxaran, David; Cherukuru, Nagur; Lavender, Samantha J.
2006-04-01
Spectral measurements of remote-sensing reflectance (Rrs) and absorption coefficients carried out in three European estuaries (Gironde and Loire in France, Tamar in the UK) are presented and analyzed. Typical Rrs and absorption spectra are compared with typical values measured in coastal waters. The respective contributions of the water constituents, i.e., suspended sediments, colored dissolved organic matter, and phytoplankton (characterized by chlorophyll-a), are determined. The Rrs spectra are then reproduced with an optical model from the measured absorption coefficients and fitted backscattering coefficients. From Rrs ratios, empirical quantification relationships are established, reproduced, and explained from theoretical calculations. These quantification relationships were established from numerous field measurements and a reflectance model integrating the mean values of the water constituents' inherent optical properties. The model's sensitivity to the biogeochemical constituents and to their nature and composition is assessed.
Jiang, Runhua; Zhou, Zhenqiao; Lv, Xiaohua; Zeng, Shaoqun; Huang, Zhifeng; Zhou, Huaichun
2012-07-01
Thermal effects greatly influence the optical properties of the acousto-optic deflectors (AODs). Thermal analysis plays an important role in modern AOD design. However, the lack of an effective method of analysis limits the prediction in the thermal performance. In this paper, we propose a finite element analysis model to analyze the thermal effects of a TeO(2)-based AOD. Both transducer heating and acoustic absorption are considered as thermal sources. The anisotropy of sound propagation is taken into account for determining the acoustic absorption. Based on this model, a transient thermal analysis is employed using ANSYS software. The spatial temperature distributions in the crystal and the temperature changes over time are acquired. The simulation results are validated by experimental results. The effect of heat source and heat convection on temperature distribution is discussed. This numerical model and analytical method of thermal analysis would be helpful in the thermal design and practical applications of AODs.
Duan, Jinming; Tench, Christopher; Gottlob, Irene; Proudlock, Frank; Bai, Li
2015-11-21
Optical coherence tomography (OCT) imaging plays an important role in clinical diagnosis and monitoring of diseases of the human retina. Automated analysis of optical coherence tomography images is a challenging task as the images are inherently noisy. In this paper, a novel variational image decomposition model is proposed to decompose an OCT image into three components: the first component is the original image but with the noise completely removed; the second contains the set of edges representing the retinal layer boundaries present in the image; and the third is an image of noise, or in image decomposition terms, the texture, or oscillatory patterns of the original image. In addition, a fast Fourier transform based split Bregman algorithm is developed to improve computational efficiency of solving the proposed model. Extensive experiments are conducted on both synthesised and real OCT images to demonstrate that the proposed model outperforms the state-of-the-art speckle noise reduction methods and leads to accurate retinal layer segmentation.
Energy Technology Data Exchange (ETDEWEB)
Kohler, Christian [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2012-04-01
Complex glazing systems such as venetian blinds, fritted glass and woven shades require more detailed optical and thermal input data for their components than specular non light-redirecting glazing systems. Various methods for measuring these data sets are described in this paper. These data sets are used in multiple simulation tools to model the thermal and optical properties of complex glazing systems. The output from these tools can be used to generate simplified rating values or as an input to other simulation tools such as whole building annual energy programs, or lighting analysis tools. I also describe some of the challenges of creating a rating system for these products and which factors affect this rating. A potential future direction of simulation and building operations is model based predictive controls, where detailed computer models are run in real-time, receiving data for an actual building and providing control input to building elements such as shades.
Demidov, Valentin; Vitkin, I. Alex; Doronin, Alexander; Meglinski, Igor
2017-03-01
We report on the development of a unified Monte-Carlo based computational model for exploring speckle pattern formation in swept-source optical coherence tomography (OCT). OCT is a well-established optical imaging modality capable of acquiring cross-sectional images of turbid media, including biological tissues, utilizing back scattered low coherence light. The obtained OCT images include characteristic features known as speckles. Currently, there is a growing interest to the OCT speckle patterns due to their potential application for quantitative analysis of medium's optical properties. Here we consider the mechanisms of OCT speckle patterns formation for swept-source OCT approaches and introduce further developments of a Monte-Carlo based model for simulation of OCT signals and images. The model takes into account polarization and coherent properties of light, mutual interference of back-scattering waves, and their interference with the reference waves. We present a corresponding detailed description of the algorithm for modeling these light-medium interactions. The developed model is employed for generation of swept-source OCT images, analysis of OCT speckle formation and interpretation of the experimental results. The obtained simulation results are compared with selected analytical solutions and experimental studies utilizing various sizes / concentrations of scattering microspheres.
Comparing analytical and Monte Carlo optical diffusion models in phosphor-based X-ray detectors
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.
Semi-coherent optical modelling of thin film silicon solar cells
Energy Technology Data Exchange (ETDEWEB)
Walder, Cordula; Lacombe, Juergen; Maydell, Karsten von; Agert, Carsten [EWE-Forschungszentrum fuer Energietechnologie e.V., Carl-von-Ossietzky-Strasse 15, 26129 Oldenburg (Germany)
2011-07-01
At NEXT ENERGY the experimental investigation of thin film silicon solar cells is combined with numerical simulations using the software Sentaurus TCAD from Synopsys. We present the results of optical modelling with Sentaurus TCAD based on the one-dimensional semi-coherent optical model by Janez Krc. The idea of this model is that after interacting with a rough interface the incident light is split into a direct coherent part treated as electromagnetic waves and in a diffuse incoherent part treated as light beams. The proportion of either direct or diffuse part is determined by the haze parameter which can be obtained from spectrometer data. In order to describe the scattering effects at rough interfaces the intensities of the diffuse light are scaled with angular distribution functions. These functions are obtained from angle resolved scattering measurements. The optical model will be verified by experimental data and compared to the Raytracer and the Transfer Matrix Model. Furthermore the influence of different angles of incidence and of the spectral dependency on the solar cell performance will be investigated.
Bakry, A.; Abdulrhmann, S.; Ahmed, M.
2016-06-01
We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding the second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.
Numerical model for the deformation of nucleated cells by optical stretchers
Sraj, Ihab
2015-07-01
In this paper, we seek to numerically study the deformation of nucleated cells by single diode-laser bar optical stretchers. We employ a recently developed computational model, the dynamic ray-tracing method, to determine the force distribution induced by optical stretchers on a cell encapsulating a nucleus of different optical properties. These optical forces are shape dependent and can deform real non-rigid objects; thus resulting in dynamically changing distributions with cell and nucleus deformation. A Chinese hamster ovary (CHO) cell is a common biological cell that is of interest to the biomedical community because of its use in recombinant protein therapeutics and is an example of a nucleated cell. To this end, we model CHO cells as two concentric three-dimensional elastic capsules immersed in a fluid where the hydrodynamic forces are calculated using the immersed boundary method. We vary the inner capsule size to simulate different nucleus sizes. Our results show that the presence of a nucleus has a major effect on the force distribution on the cell surface and consequently on its net deformation. Scattering and gradient forces are reported for different nucleus sizes and the effect of nucleus size on the cell deformation is discussed quantitatively. © 2015 IOP Publishing Ltd.
Energy Technology Data Exchange (ETDEWEB)
Bakry, A. [King Abdulaziz University, 80203, Department of Physics, Faculty of Science (Saudi Arabia); Abdulrhmann, S. [Jazan University, 114, Department of Physics, Faculty of Sciences (Saudi Arabia); Ahmed, M., E-mail: mostafa.farghal@mu.edu.eg [King Abdulaziz University, 80203, Department of Physics, Faculty of Science (Saudi Arabia)
2016-06-15
We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding the second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.
Model of laser-induced temperature changes in solid-state optical refrigerators
Patterson, W. M.; Sheik-Bahae, M.; Epstein, R. I.; Hehlen, M. P.
2010-03-01
We present an efficient and numerically stable method to calculate time-dependent, laser-induced temperature distributions in solids and provide a detailed description of the computational procedure and its implementation. This study combines the two-dimensional heat equation with laser-induced heat generation and temperature-dependent luminescence. The time-dependent optical response of a system is obtained numerically by the Crank-Nicolson method. This general model is applied to the specific case of optical refrigeration in ytterbium (Yb3+) doped fluorozirconate glass (ZBLAN). The laser-induced temperature change upon optical pumping and the respective transient luminescence response are calculated and compared to experimental data. The model successfully predicts the zero-crossing temperature, the net quantum efficiency, and the functional shape of the transients. We find that the laser-cooling transients have a fast and a slow component that are determined by the excited-state lifetime of the luminescent ion and the thermal properties of the bulk, respectively. The tools presented here may find application in the design of a wide range of optical and optoelectronic devices.
A two-habit model for the microphysical and optical properties of ice clouds
Directory of Open Access Journals (Sweden)
C. Liu
2014-07-01
Full Text Available To provide a better representation of natural ice clouds, a novel ice cloud model containing two particle habits is developed. The microphysical and optical properties of the two-habit model (THM are compared with both laboratory and in situ measurements, and its performance in downstream satellite remote sensing applications is tested. The THM assumes an ice cloud to be an ensemble of hexagonal columns and twenty-element aggregates, and to have specific habit fractions at each particle size. The ice water contents and median mass diameters calculated based on the THM closely agree with in situ measurements made during 11 field campaigns. In this study, the scattering, absorption, and polarization properties of ice crystals are calculated with a combination of the invariant imbedding T-matrix, pseudo-spectral time domain, and improved geometric-optics methods over an entire range of particle sizes. The phase functions, calculated based on the THM, show excellent agreement with counterparts from laboratory and in situ measurements and from satellite retrievals. For downstream applications in the retrieval of cloud microphysical and optical properties from MODIS observations, the THM presents excellent spectral consistency; specifically, the retrieved cloud optical thicknesses based on the visible/near infrared bands and the thermal infrared bands agree quite well. Furthermore, a comparison between the polarized reflectivities observed by the PARASOL satellite and from theoretical simulations illustrates that the THM can be used to represent ice cloud polarization properties.
Dutkiewicz, S.; Hickman, A. E.; Jahn, O.; Gregg, W. W.; Mouw, C. B.; Follows, M. J.
2015-02-01
We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem in a dynamic three-dimensional physical framework. The radiative transfer component resolves spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (the phytoplankton community, detrital particles, and coloured dissolved organic matter, CDOM). The model is evaluated against in situ observed and satellite derived products. In particular we compare to concurrently measured biogeochemical, ecosystem and optical data along a north-south transect of the Atlantic Ocean. The simulation captures the patterns and magnitudes of these data, and estimates surface upwelling irradiance analogous to that observed by ocean colour satellite instruments. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, and the crucial feedbacks between the light field and the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at short wavelengths and in more productive waters, phytoplankton absorption is especially important at the deep chlorophyll a (Chl a) maximum, and absorption by water molecules is relatively most important in the highly oligotrophic gyres. Sensitivity experiments in which absorption by any of the optical constituents was increased led to a decrease in the size of the oligotrophic regions of the subtropical gyres: lateral nutrient supplies were enhanced as a result of decreasing high latitude productivity. Scattering does not as strongly affect the ecosystem and biogeochemistry fields within the water column but is important for setting the surface upwelling irradiance, and hence sea surface reflectance. Having a model capable of capturing bio-optical feedbacks will be important for
Assimilation of remotely-sensed optical properties to improve marine biogeochemistry modelling
Ciavatta, Stefano; Torres, Ricardo; Martinez-Vicente, Victor; Smyth, Timothy; Dall'Olmo, Giorgio; Polimene, Luca; Allen, J. Icarus
2014-09-01
In this paper we evaluate whether the assimilation of remotely-sensed optical data into a marine ecosystem model improves the simulation of biogeochemistry in a shelf sea. A localized Ensemble Kalman filter was used to assimilate weekly diffuse light attenuation coefficient data, Kd(443) from SeaWiFs, into an ecosystem model of the western English Channel. The spatial distributions of (unassimilated) surface chlorophyll from satellite, and a multivariate time series of eighteen biogeochemical and optical variables measured in situ at one long-term monitoring site were used to evaluate the system performance for the year 2006. Assimilation reduced the root mean square error and improved the correlation with the assimilated Kd(443) observations, for both the analysis and, to a lesser extent, the forecast estimates, when compared to the reference model simulation. Improvements in the simulation of (unassimilated) ocean colour chlorophyll were less evident, and in some parts of the Channel the simulation of this data deteriorated. The estimation errors for the (unassimilated) in situ data were reduced for most variables with some exceptions, e.g. dissolved nitrogen. Importantly, the assimilation adjusted the balance of ecosystem processes by shifting the simulated food web towards the microbial loop, thus improving the estimation of some properties, e.g. total particulate carbon. Assimilation of Kd(443) outperformed a comparative chlorophyll assimilation experiment, in both the estimation of ocean colour data and in the simulation of independent in situ data. These results are related to relatively low error in Kd(443) data, and because it is a bulk optical property of marine ecosystems. Assimilation of remotely-sensed optical properties is a promising approach to improve the simulation of biogeochemical and optical variables that are relevant for ecosystem functioning and climate change studies.
Review on optical constants of Titan aerosols: Experimental results and modeling/observational data
Brassé, Coralie; Muñoz, Olga; Coll, Patrice; Raulin, François
2014-05-01
During the last years many studies have been performed to improve the experimental database of optical constants of Titan aerosols. Indeed, the determination of the optical constants of these particles is essential to quantify their capacity to absorb and to scatter solar radiation, and thus to evaluate their role on Titan's radiative balance and climate. The study of optical properties is also crucial to analyze and to better interpret many of Titan's observational data, in particular those acquired during the Cassini-Huygens mission. One way to determine Titan aerosols optical constant is to measure the optical constants of analogues of Titan complex organic material synthesized in the laboratory, usually named Titan's tholins (Sagan and Khare, 1979). But the optical constants depend on the chemical composition, the size and the shape of particles (Raulin et al., 2012). Those three parameters result from the experimental conditions such as energy source, gas mixing ratio, gas pressure, flow rate and irradiation time (Cable et al., 2012). Besides the determination of the refractive index in the laboratory, there are others methods using theoretical models or observational data. Nevertheless, theoretical models are based on laboratory data or/and observational data. The visible - near infrared spectral region of optical constants has been widely studied with laboratory analogues. Comparison of the obtained results suggest that tholins synthesized by Tran et al. (2003) and Majhoub et al. (2012) are the best representative of Titan aerosols with regards to their refractive indexes in this spectral region. The mid-infrared spectral range has been studied only by Imanaka et al. (2012) and slightly by Tran et al. (2003). In that spectral range, Titan tholins do not exhibit the features displayed by Kim and Courtin (2013) from Titan's observations. For spectral region of wavelengths smaller than 0.20µm or higher than 25µm, only the data from Khare et al. (1984) are
Coe, Ryan L; Seibel, Eric J
2012-12-01
We present a method for modeling image formation in optical projection tomographic microscopy (OPTM) using high numerical aperture (NA) condensers and objectives. Similar to techniques used in computed tomography, OPTM produces three-dimensional, reconstructed images of single cells from two-dimensional projections. The model is capable of simulating axial scanning of a microscope objective to produce projections, which are reconstructed using filtered backprojection. Simulation of optical scattering in transmission optical microscopy is designed to analyze all aspects of OPTM image formation, such as degree of specimen staining, refractive-index matching, and objective scanning. In this preliminary work, a set of simulations is performed to examine the effect of changing the condenser NA, objective scan range, and complex refractive index on the final reconstruction of a microshell with an outer radius of 1.5 μm and an inner radius of 0.9 μm. The model lays the groundwork for optimizing OPTM imaging parameters and triaging efforts to further improve the overall system design. As the model is expanded in the future, it will be used to simulate a more realistic cell, which could lead to even greater impact.
Poole, Kristin M.; Sit, Wesley W.; Tucker-Schwartz, Jason M.; Duvall, Craig L.; Skala, Melissa C.
2013-03-01
Peripheral arterial disease (PAD) leads to an increased risk of myocardial infarction and stroke, increased mortality, and reduced quality of life. The mouse hind limb ischemia (HLI) model is the most commonly used system for studying the mechanisms of collateral vessel formation and for testing new PAD therapies, but there is a lack of techniques for acquiring physiologically-relevant, quantitative data intravitally in this model. In this work, non-invasive, quantitative optical imaging techniques were applied to the mouse HLI model over a time course. Optical coherence tomography (OCT) imaged changes in blood flow (Doppler OCT) and microvessel morphology (speckle variance OCT) through the skin of haired mice with high resolution. Hyperspectral imaging was also used to quantify blood oxygenation. In ischemic limbs, blood oxygenation in the footpad was substantially reduced after induction of ischemia followed by complete recovery by three weeks, consistent with standard measures. Three dimensional images of the vasculature distal to vessel occlusion acquired with speckle variance OCT revealed changes in OCT flow signal and vessel morphology. Taken together, OCT and hyperspectral imaging enable intravital acquisition of both functional and morphological data which fill critical gaps in understanding structure-function relationships that contribute to recovery in the mouse HLI model. Therefore, these optical imaging methods hold promise as tools for studying the mechanisms of vascular recovery and evaluating novel therapeutic treatments in preclinical studies.
Multi-scale analysis of optic chiasmal compression by finite element modelling.
Wang, Xiaofei; Neely, Andrew J; McIlwaine, Gawn G; Lueck, Christian J
2014-07-18
The precise mechanism of bitemporal hemianopia (a type of partial visual field defect) is still not clear. Previous work has investigated this problem by studying the biomechanics of chiasmal compression caused by a pituitary tumour growing up from below the optic chiasm. A multi-scale analysis was performed using finite element models to examine both the macro-scale behaviour of the chiasm and the micro-scale interactions of the nerve fibres within it using representative volume elements. Possible effects of large deflection and non-linear material properties were incorporated. Strain distributions in the optic chiasm and optic nerve fibres were obtained from these models. The results of the chiasmal model agreed well with the limited experimental results available, indicating that the finite element modelling can be a useful tool for analysing chiasmal compression. Simulation results showed that the strain distribution in nasal (crossed) nerve fibres was much more nonuniform and locally higher than in temporal (uncrossed) nerve fibres. This strain difference between nasal and temporal nerve fibres may account for the phenomenon of bitemporal hemianopia.
Oubei, Hassan M.
2017-06-16
In this Letter, we use laser beam intensity fluctuation measurements to model and describe the statistical properties of weak temperature-induced turbulence in underwater wireless optical communication (UWOC) channels. UWOC channels with temperature gradients are modeled by the generalized gamma distribution (GGD) with an excellent goodness of fit to the measured data under all channel conditions. Meanwhile, thermally uniform channels are perfectly described by the simple gamma distribution which is a special case of GGD. To the best of our knowledge, this is the first model that comprehensively describes both thermally uniform and gradient-based UWOC channels.
Stramski, Dariusz; Mitchell, B. Greg; Marra, John W. (Technical Monitor)
2001-01-01
This project was a collaboration between two Principal Investigators, Dr. Dariusz Stramski and Dr. Greg Mitchell of Scripps Institution of Oceanography, University of California San Diego. Our overall goal was to conduct optical measurements and modeling to estimate concentrations of organic matter in the Southern Ocean in support of the U.S. JGOFS Process Study in this region. Key variables and processes of high relevance to accomplish the JGOFS goals include time and space resolution of phytoplankton pigments, particulate organic carbon, and the formation and export of organic carbon. Our project focused on establishing the fundamental relationships for parameterization of these variables and processes in terms of the optical properties of seawater, and developing understanding of why the Southern Ocean differs from other low-latitude systems, or has differentiation within. Our approach builds upon historical observations that optical properties provide a useful proxy for key reservoirs of organic matter such as chlorophyll alpha (Chl) and particulate organic carbon (POC) concentrations, which are of relevance to the JGOFS objectives. We carried out detailed studies of in situ and water sample optical properties including spectral reflectance, absorption, beam attenuation, scattering, and backscattering coefficients. We evaluated the ability to estimate Chl from the spectral reflectance (ocean color) in the Southern Ocean. We examined relationships between the ocean optical properties and particulate organic carbon. We developed, for the first time, an algorithm for estimating particulate organic carbon concentration in the surface ocean from satellite imagery of ocean color. With this algorithm, we obtained maps of POC distribution in the Southern Ocean showing the seasonal progression of POC in the austral spring-summer season. We also developed a semianalytical reflectance model for the investigated polar waters based on our field measurements of absorption
Nucleon scattering on actinides using a dispersive optical model with extended couplings
SoukhovitskiÄ©, E. Sh.; Capote, R.; Quesada, J. M.; Chiba, S.; Martyanov, D. S.
2016-12-01
The Tamura coupling model [Rev. Mod. Phys. 37, 679 (1965), 10.1103/RevModPhys.37.679] has been extended to consider the coupling of additional low-lying rotational bands to the ground-state band. Rotational bands are built on vibrational bandheads (even-even targets) or single-particle bandheads (odd-A targets) including both axial and nonaxial deformations. These additional excitations are introduced as a perturbation to the underlying axially symmetric rigid-rotor structure of the ground-state rotational band. Coupling matrix elements of the generalized optical model are derived for extended multiband transitions in even-even and odd-A nuclei. Isospin symmetric formulation of the optical model is employed. A coupled-channels optical-model potential (OMP) containing a dispersive contribution is used to fit simultaneously all available optical experimental databases including neutron strength functions for nucleon scattering on 232Th,233,235,238U, and 239Pu nuclei. Quasielastic (p ,n ) scattering data on 232Th and 238U to the isobaric analog states of the target nucleus are also used to constrain the isovector part of the optical potential. Lane consistent OMP is derived for all actinides if corresponding multiband coupling schemes are defined. For even-even (odd-A ) actinides almost all low-lying collective levels below 1 MeV (0.5 MeV) of excitation energy are coupled. OMP parameters show a smooth energy dependence and energy-independent geometry. A phenomenological optical-model potential that couples multiple bands in odd-A actinides is published for a first time. Calculations using the derived OMP potential reproduce measured total cross-section differences between several actinide pairs within experimental uncertainty for incident neutron energies from 50 keV up to 150 MeV. The importance of extended coupling is studied. Multiband coupling is stronger in even-even targets owing to the collective nature of the coupling; the impact of extended coupling on
A simple model for fibre optics: planar dielectric waveguides in rotation
Energy Technology Data Exchange (ETDEWEB)
Perez-Ocon, F [Departamento de Optica, Universidad de Granada, 18071 Granada (Spain); Pena, A [Valeo Iluminacion, 23600 Martos, Jaen (Spain); Jimenez, J R [Departamento de Optica, Universidad de Granada, 18071 Granada (Spain); Diaz, J A [Departamento de Optica, Universidad de Granada, 18071 Granada (Spain)
2006-05-01
In planar dielectric waveguides, there is only one type of propagated ray: the one that crosses the waveguide axis after each total internal reflection. According to the model of geometrical optics, there are two types of guided ray in fibre optics: meridional and skew. Each one is formulated by a suitable mathematical treatment. In this work, we demonstrate that the complex mathematical treatment for the skew rays can be avoided by considering a planar waveguide (with the same refractive index profile as the fibre and thickness equal to its diameter) that rotates around the direction of the axis with angular velocity {omega}. A section of this fibre is inscribed in the hypothetical slab. This model has been successfully introduced to students of engineering and physics.
Lachaume, Régis
2012-01-01
Bandwidth smearing is a chromatic aberration due to the finite frequency bandwidth. In long-baseline optical interferometry terms, it is when the angular extension of the source is greater than the coherence length of the interferogram. As a consequence, separated parts of the source will contribute to fringe packets that are not fully overlapping; it is a transition from the classical interferometric regime to a double or multiple fringe packet. While studied in radio interferometry, there has been little work on the matter in the optical, where observables are measured and derived in a different manner, and are more strongly impacted by the turbulent atmosphere. We provide here the formalism and a set of usable equations to model and correct for the impact of smearing on the fringe contrast and phase, with the case of multiple stellar systems in mind. The atmosphere is briefly modeled and discussed.
Detailed Theoretical Model for Adjustable Gain-Clamped Semiconductor Optical Amplifier
Directory of Open Access Journals (Sweden)
Lin Liu
2012-01-01
Full Text Available The adjustable gain-clamped semiconductor optical amplifier (AGC-SOA uses two SOAs in a ring-cavity topology: one to amplify the signal and the other to control the gain. The device was designed to maximize the output saturated power while adjusting gain to regulate power differences between packets without loss of linearity. This type of subsystem can be used for power equalisation and linear amplification in packet-based dynamic systems such as passive optical networks (PONs. A detailed theoretical model is presented in this paper to simulate the operation of the AGC-SOA, which gives a better understanding of the underlying gain clamping mechanics. Simulations and comparisons with steady-state and dynamic gain modulation experimental performance are given which validate the model.
Blocking probability in the hose-model optical VPN with different number of wavelengths
Roslyakov, Alexander V.
2017-04-01
Connection setup with guaranteed quality of service (QoS) in the optical virtual private network (OVPN) is a major goal for the network providers. In order to support this we propose a QoS based OVPN connection set up mechanism over WDM network to the end customer. The proposed WDM network model can be specified in terms of QoS parameter such as blocking probability. We estimated this QoS parameter based on the hose-model OVPN. In this mechanism the OVPN connections also can be created or deleted according to the availability of the wavelengths in the optical path. In this paper we have considered the impact of the number of wavelengths on the computation of blocking probability. The goal of the work is to dynamically provide a best OVPN connection during frequent arrival of connection requests with QoS requirements.
Modeling chiral sculptured thin films as platforms for surface-plasmonic-polaritonic optical sensing
Mackay, Tom G
2010-01-01
Biomimetic nanoengineered metamaterials called chiral sculptured thin films (CSTFs) are attractive platforms for optical sensing because their porosity, morphology and optical properties can be tailored to order. Furthermore, their ability to support more than one surface-plasmon-polariton (SPP) wave at a planar interface with a metal offers functionality beyond that associated with conventional SPP--based sensors. An empirical model was constructed to describe SPP-wave propagation guided by the planar interface of a CSTF--infiltrated with a fluid which supposedly contains analytes to be detected--and a metal. The inverse Bruggeman homogenization formalism was first used to determine the nanoscale model parameters of the CSTF. These parameters then served as inputs to the forward Bruggeman homogenization formalism to determine the reference relative permittivity dyadic of the infiltrated CSTF. By solving the coresponding boundary-value problem for a modified Kretschmann configuration, the characteristics of t...
Computer modelling of the optical properties of transition-metal ions in solids
Energy Technology Data Exchange (ETDEWEB)
Bartram, R.H. [Univ. of Connecticut, Storrs, CT (United States)
1994-12-31
Computational methods for modeling the optical properties of substitutional transition-metal impurities in insulating solids, potentially applicable to some scintillator and phosphor materials, are reviewed. Methods considered include crystal-field and semiempirical ligand-field models; SCF-X{alpha}-SW, SCF-RHF-LCAO, SCF-UHF-LCAO and CI ab initio methods; and ICECAP and HADESR embedded-cluster methods with lattice relaxation. A detailed example of the application of the HADESR method to crystal-field spectra of Cr{sup 3+} in halide elpasolites is described. In this method, ab initio molecular-orbital calculations with effective core potentials are performed for selected ionic configurations. Simultaneous relaxation of the cluster and surrounding lattice, with mutual pair-potential interactions, is accomplished by a modified lattice statics program. properties include pressure-dependent optical transition energies, vibration frequencies and radiationless transition rates.
AN EFFECTIVE MODEL TO EVALUATE BLOCKING PROBABILITY OF TIME-SLOTTED OPTICAL BURST SWITCHED NETWORKS
Institute of Scientific and Technical Information of China (English)
Yang Zongkai; Ou Liang; Tan Xiansi
2006-01-01
Time-slotted optical burst switched network is a potential technique to support IP over Wavelength Division Multiplexing (WDM) by introduce Time Division Multiplexing (TDM) channel to Optical Burst Switching (OBS) technology. This paper presents a framework to evaluate blocking performance of time-slotted OBS networks with multi-fiber wavelength channels. The proposed model is efficient for not only single class traffic such as individual circuit switch traffics or best-effort traffics but also mixed multi-class traffics.The effectiveness of the proposed model is validated by simulation results. The study shows that blocking performance of multi-fiber TS-OBS network is acceptable for future Internet services.
Simulink models for performance analysis of high speed DQPSK modulated optical link
Sharan, Lucky; Rupanshi, Chaubey, V. K.
2016-03-01
This paper attempts to present the design approach for development of simulation models to study and analyze the transmission of 10 Gbps DQPSK signal over a single channel Peer to Peer link using Matlab Simulink. The simulation model considers the different optical components used in link design with their behavior represented initially by theoretical interpretation, including the transmitter topology, Mach Zehnder Modulator(MZM) module and, the propagation model for optical fibers etc. thus allowing scope for direct realization in experimental configurations. It provides the flexibility to incorporate the various photonic components as either user-defined or fixed and, can also be enhanced or removed from the model as per the design requirements. We describe the detailed operation and need of every component model and its representation in Simulink blocksets. Moreover the developed model can be extended in future to support Dense Wavelength Division Multiplexing (DWDM) system, thereby allowing high speed transmission with N × 40 Gbps systems. The various compensation techniques and their influence on system performance can be easily investigated by using such models.
Simulink models for performance analysis of high speed DQPSK modulated optical link
Energy Technology Data Exchange (ETDEWEB)
Sharan, Lucky, E-mail: luckysharan@pilani.bits-pilani.ac.in; Rupanshi,, E-mail: f2011222@pilani.bits-pilani.ac.in; Chaubey, V. K., E-mail: vkc@pilani.bits-pilani.ac.in [EEE Department, BITS-Pilani, Rajasthan, 333031 (India)
2016-03-09
This paper attempts to present the design approach for development of simulation models to study and analyze the transmission of 10 Gbps DQPSK signal over a single channel Peer to Peer link using Matlab Simulink. The simulation model considers the different optical components used in link design with their behavior represented initially by theoretical interpretation, including the transmitter topology, Mach Zehnder Modulator(MZM) module and, the propagation model for optical fibers etc. thus allowing scope for direct realization in experimental configurations. It provides the flexibility to incorporate the various photonic components as either user-defined or fixed and, can also be enhanced or removed from the model as per the design requirements. We describe the detailed operation and need of every component model and its representation in Simulink blocksets. Moreover the developed model can be extended in future to support Dense Wavelength Division Multiplexing (DWDM) system, thereby allowing high speed transmission with N × 40 Gbps systems. The various compensation techniques and their influence on system performance can be easily investigated by using such models.
Modeling the land surface reflectance for optical remote sensing data in rugged terrain
Institute of Scientific and Technical Information of China (English)
2008-01-01
A model for topographic correction and land surface reflectance estimation for optical remote sensing data in rugged terrian is presented.Considering a directional-directional reflectance that is used for direct solar irradiance correction and a hemispheric-directional reflectance that is used for atmospheric diffuse irradiance and terrain background reflected irradiance correction respectively,the directional reflectance-based model for topographic effects removing and land surface reflectance calculation is developed by deducing the directional reflectance with topographic effects and using a radiative transfer model.A canopy reflectance simulated by GOMS model and Landsat/TM raw data covering Jiangxi rugged area were taken to validate the performance of the model presented in the paper.The validation results show that the model presented here has a remarkable ability to correct topography and estimate land surface reflectance and also provides a technique method for sequently quantitative remote sensing application in terrain area.
An Optical Model for Estimating the Underwater Light Field from Remote Sensing
Liu, Cheng-Chien; Miller, Richard L.
2002-01-01
A model of the wavelength-integrated scalar irradiance for a vertically homogeneous water column is developed. It runs twenty thousand times faster than simulations obtained using full Hydrolight code and limits the percentage error to less than 3.7%. Both the distribution of incident sky radiance and a wind-roughened surface are integrated in the model. Our model removes common limitations of earlier models and can be applied to waters with any composition of the inherent optical properties. Implementation of this new model, as well as the ancillary information required for processing global-scale satellite data, is discussed. This new model is fast, accurate, and flexible and therefore provides important information of the underwater light field from remote sensing.
Modeling the land surface reflectance for optical remote sensing data in rugged terrain
Institute of Scientific and Technical Information of China (English)
WEN JianGuang; LIU QinHuo; XIAO Qing; LIU Qiang; LI XiaoWen
2008-01-01
A model for topographic correction and land surface reflectance estimation for optical remote sensing data in rugged terrian is presented. Considering a directional-directional reflectance that is used for direct solar irradiance correction and a hemispheric-directional reflectance that is used for atmospheric diffuse irradiance and terrain background reflected irradiance correction respectively, the directional reflectance-based model for topographic effects removing and land surface reflectance calculation is developed by deducing the directional reflectance with topographic effects and using a radiative transfer model. A canopy reflectance simulated by GOMS model and Landsat/TM raw data covering Jiangxi rugged area were taken to validate the performance of the model presented in the paper. The validation results show that the model presented here has a remarkable ability to correct topography and estimate land surface reflectance and also provides a technique method for sequently quantitative remote sensing application in terrain area.
Energy Technology Data Exchange (ETDEWEB)
Utrillas, M.P.; Martinez-Lozano, J.A.; Tena, F. [Universitat de Valencia, Dept. de Termodinamica, Valencia (Spain); Cachorro, V.E. [Universidad de Valladolid, Dept. de Fisica Aplicada 1, Valladolid (Spain); Hernandez, S. [Universidad de Valladolid, Dept. de Ingenieria Agricola y Forestal, Valladolid (Spain)
2000-07-01
The spectral values of the aerosol optical thickness {tau}{sub a{lambda}} in the 400-670 nm band have been determined from 500 solar direct irradiance spectra at normal incidence registered at Valencia (Spain) in the period from July 1993 to March 1997. The {tau}{sub a{lambda}} values obtained from experimental measurements have been compared with the boundary layer aerosol models implemented in the radiative transfer codes ZD-LOA and LOWTRAN 7. For the ZD-LOA code, the continental and maritime models have been considered and for the LOWTRAN 7 code the rural, maritime, urban and tropospheric models have been used. The obtained results show that the aerosol model that best represents the average turbidity of the boundary layer for the urban area of Valencia (Spain) is the continental model when the ZD-LOA code is used and the urban model when the LOWTRAN 7 code is used. (Author)
Directory of Open Access Journals (Sweden)
G.S. Vorobjov
2010-01-01
Full Text Available The experimental plant and the general method of modeling of electromagnetic wave processes in multicoupled quasi-optical systems are described. Examples of choosing the optimum regimes of modeling and basic parameters of the investigated electrodynamic systems are shown. The functional scheme of the experimental plant is also described. The general method of modeling of electromagnetic phenomena in resonant and waveguide multicoupled quasi-optical systems is presented for the first time.
B-spline image model for energy minimization-based optical flow estimation.
Le Besnerais, Guy; Champagnat, Frédéric
2006-10-01
Robust estimation of the optical flow is addressed through a multiresolution energy minimization. It involves repeated evaluation of spatial and temporal gradients of image intensity which rely usually on bilinear interpolation and image filtering. We propose to base both computations on a single pyramidal cubic B-spline model of image intensity. We show empirically improvements in convergence speed and estimation error and validate the resulting algorithm on real test sequences.
de Zutter, D.; Lagasse, P.; Buus, J.; Young, T. P.; Dillon, B. M.
1989-10-01
In order to compare various modeling techniques for the eigenmode analysis of integrated optical waveguides, twelve different methods are applied to the analysis of two typical III-V rib waveguides. Both a single and a coupled waveguide case are considered. Results focus on the effective refractive index value for the lowest order TE-mode in the case of the single waveguide, and on the coupling length between the lowest order symmetric and antisymmetric TE-modes of the coupled waveguides.
Mathematic models for a ray tracing method and its applications in wireless optical communications.
Zhang, Minglun; Zhang, Yangan; Yuan, Xueguang; Zhang, Jinnan
2010-08-16
This paper presents a new ray tracing method, which contains a whole set of mathematic models, and its validity is verified by simulations. In addition, both theoretical analysis and simulation results show that the computational complexity of the method is much lower than that of previous ones. Therefore, the method can be used to rapidly calculate the impulse response of wireless optical channels for complicated systems.
Introducing the concept of anisotropy at different scales for modeling optical turbulence.
Toselli, Italo
2014-08-01
In this paper, the concept of anisotropy at different atmospheric turbulence scales is introduced. A power spectrum and its associated structure function with inner and outer scale effects and anisotropy are also shown. The power spectrum includes an effective anisotropic parameter ζ(eff) to describe anisotropy, which is useful for modeling optical turbulence when a non-Kolmogorov power law and anisotropy along the direction of propagation are present.
Grivet, Pierre; Bertein, F; Castaing, R; Gauzit, M; Septier, Albert L
1972-01-01
Electron Optics, Second English Edition, Part I: Optics is a 10-chapter book that begins by elucidating the fundamental features and basic techniques of electron optics, as well as the distribution of potential and field in electrostatic lenses. This book then explains the field distribution in magnetic lenses; the optical properties of electrostatic and magnetic lenses; and the similarities and differences between glass optics and electron optics. Subsequent chapters focus on lens defects; some electrostatic lenses and triode guns; and magnetic lens models. The strong focusing lenses and pris
DEFF Research Database (Denmark)
Tycho, Andreas; Jørgensen, Thomas Martini; Andersen, Peter E.
2002-01-01
A Monte Carlo (MC) method for modeling optical coherence tomography (OCT) measurements of a diffusely reflecting discontinuity emb edded in a scattering medium is presented. For the first time to the authors' knowledge it is shown analytically that the applicability of an MC approach to this opti......A Monte Carlo (MC) method for modeling optical coherence tomography (OCT) measurements of a diffusely reflecting discontinuity emb edded in a scattering medium is presented. For the first time to the authors' knowledge it is shown analytically that the applicability of an MC approach...... to this optical geometry is firmly justified, because, as we show, in the conjugate image plane the field reflected from the sample is delta-correlated from which it follows that the heterodyne signal is calculated from the intensity distribution only. This is not a trivial result because, in general, the light...... focused beam, and it is shown that in free space the full three-dimensional intensity distribution of a Gaussian beam is obtained. The OCT signal and the intensity distribution in a scattering medium have been obtained for several geometries with the suggested MC method; when this model and a recently...
Moro, Erik A; Todd, Michael D; Puckett, Anthony D
2011-12-10
A variety of intensity-modulated optical displacement sensor architectures have been proposed for use in noncontacting sensing applications, with one of the most widely implemented architectures being the bundled displacement sensor. To the best of the authors' knowledge, the arrangement of measurement fibers in previously reported bundled displacement sensors has not been configured with the use of a validated optical transmission model. Such a model has utility in accurately describing the sensor's performance a priori and thereby guides the arrangement of the fibers within the bundle to meet application-specific performance needs. In this paper, a recently validated transmission model is used for these purposes, and an optimization approach that employs a genetic algorithm efficiently explores the design space of the proposed bundle sensor architecture. From the converged output of the optimization routine, a bundled displacement sensor configuration is designed and experimentally tested, offering linear performance with a sensitivity of -0.066 μm(-1) and displacement measurement error of 223 μm over the axial displacement range of 6-8 mm. It is shown that this optimization approach may be generalized to determine optimized bundle configurations that offer high-sensitivity performance, with an acceptable error level, over a variety of axial displacement ranges. This document has been approved by Los Alamos National Laboratory for unlimited public release (LA-UR 11-03413). © 2011 Optical Society of America
Local and global nucleon optical models from 1 keV to 200 MeV
Köning, A J
2003-01-01
We present new phenomenological optical model potentials (OMPs) for neutrons and protons with incident energies from 1 keV up to 200 MeV, for (near-)spherical nuclides in the mass range 24<=A<=209. They are based on a smooth, unique functional form for the energy dependence of the potential depths, and on physically constrained geometry parameters. For the first time, this enables one to predict basic scattering observables over a broad mass range and over an energy range that covers several orders of magnitude in MeV. Thereby, the necessity of using different OMPs in different energy regions has been removed. Using extensive grid searches and a new computational steering technique, we have obtained optical model parameters for many isotopes separately. We recommend that the resulting, so-called local, optical models be used in theoretical analyses of nuclear data. From these parameterizations, we have also constructed asymmetry-dependent neutron and proton global OMPs that are superior to all other exi...
Lo, Patrick; Crouzet, Christian; Vasilevko, Vitaly; Choi, Bernard
2016-03-01
Cerebral amyloid angiopathy (CAA) is a neurovascular disease that is strongly associated with an increase in the number and size of spontaneous microhemorrhages. Conventional methods, such as magnetic resonance imaging (MRI), can detect microhemorrhages while positron emission tomography (PET) with Pittsburgh Compound B can detect amyloid deposits. MRI and PET can separately demonstrate the presence of microhemorrhages and CAA in affected brains in vivo; however, there is still a lack of strong evidence for the direct involvement of CAA in the presence of microhemorrhage formation. In this study, we use optical histology, a method which combines histochemical staining, chemical optical clearing, and optical imaging, in a Tg2576 mouse model of Alzheimer's disease to enable simultaneous, co-registered three-dimensional visualization of cerebral microvasculature, microhemorrhages, and amyloid deposits. Our data strongly suggest that microhemorrhages are localized within the brain regions affected by amyloid deposits. All but two observed microhemorrhages (n=18) were closely localized with vessels affected by CAA whereas no microhemorrhages or amyloid deposits were observed in wild type mouse brain sections. Our data also suggest that the predominant type of CAA-related microhemorrhage is associated with leaky or ruptured hemorrhagic microvasculature within the hippocampus and cerebral cortex rather than occluded ischemic microvasculature. The proposed optical histology method will allow future studies about the relationship between CAA and microhemorrhages during disease development and in response to treatment strategies.
Online to offline teaching model in optics education: resource sharing course and flipped class
Li, Xiaotong; Cen, Zhaofeng; Liu, Xiangdong; Zheng, Zhenrong
2016-09-01
Since the platform "Coursera" is created by the professors of Stanford University Andrew Ng and Daphne Koller, more and more universities have joined in it. From the very beginning, online education is not only about education itself, but also connected with social equality. This is especially significant for the economic transformation in China. In this paper the research and practice on informatization of optical education are described. Online to offline (O2O) education activities, such as online learning and offline meeting, online homework and online to offline discussion, online tests and online to offline evaluation, are combined into our teaching model in the course of Applied Optics. These various O2O strategies were implemented respectively in the autumn-winter small class and the spring-summer middle class according to the constructivism and the idea of open education. We have developed optical education resources such as videos of lectures, light transmission or ray trace animations, online tests, etc. We also divide the learning procedure into 4 steps: First, instead of being given a course offline, students will learn the course online; Second, once a week or two weeks, students will have a discussion in their study groups; Third, students will submit their homework and study reports; Fourth, they will do online and offline tests. The online optical education resources have been shared in some universities in China, together with new challenges to teachers and students when facing the revolution in the e-learning future.
Surface error modeling of mounted large optics in high power laser system
Wang, Hui; Xiong, Zhao; Yuan, Xiaodong
2016-10-01
The surface form of mounted large optics has a very important impact on the laser beam performance in high power laser system. To make the surface form to the minimized distortion and keep with the design specifications is always a difficult challenge in China's SG-III laser system which is made up of thousands meter-sized large optical units and requires to focus all 48 laser beams into nearly 600 μm-diameter spot better than 50 μm (RMS) within a few picoseconds. In this paper, a methodology integrated both 3D finite elements modeling method and nanometer-level precision metrology is proposed to evaluate the surface performance. According to various spatial frequencies, the wavefront characters of large aperture optical component are measured and provided to analyze its mounted surface characters. Assembly and mounting process will be adjusted to meet for the surface wavefront requirements both of with the data both of measured when pre-alignment and predicted for installation. By a case study of large transport mirror, the proposed approach has shown a good performance on obtaining precise surface features and guiding the optical mounting.
Guo, Xiaoli; Namekata, Kazuhiko; Kimura, Atsuko; Noro, Takahiko; Azuchi, Yuriko; Semba, Kentaro; Harada, Chikako; Yoshida, Hiroshi; Mitamura, Yoshinori; Harada, Takayuki
2015-04-10
Optic neuritis is inflammation of the optic nerve and is strongly associated with multiple sclerosis (MS), an inflammatory demyelinating syndrome of the central nervous system. It leads to retinal ganglion cell (RGC) death and can cause severe vision loss. Brimonidine (BMD) is a selective α2-adrenergic receptor agonist that is used clinically for the treatment of glaucoma. BMD lowers intraocular pressure, but recent evidence suggests that its therapeutic efficacy may also mediate through mechanisms independent of modulation of intraocular pressure. In this study, we examined the effects of topical administration of BMD on retinal degeneration during optic neuritis in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. EAE was induced with MOG35-55 in C57BL/6J mice and BMD eyedrops were applied daily. In the EAE retina, the number of RGCs was significantly decreased and this effect was suppressed with BMD treatment. Consistent with histological analyses, the visual impairment observed in EAE mice was inhibited with BMD treatment, indicating the functional significance of the neuroprotective effect of BMD. Furthermore, BMD increased the expression level of basic fibroblast growth factor in the EAE retina, particularly in Müller glial cells and RGCs. Our findings suggest that topical administration of BMD may be available for RGC protection during optic neuritis, as well as for glaucoma.
Enola Gay: an integrated modelling optical toolbox applied to a wide-field telescope
Schipani, P.; Perrotta, F.
2008-07-01
The integrated modelling approach is fundamental in telescopes design where it is necessary to merge different disciplines together. This paper describes the integration of optical ray-tracing capabilities within the Matlab computational environment. This approach allows to write automatic procedures to implement a huge number of computations, that are very unpractical to perform in interactive mode by ray tracing software packages. Data produced by computations are stored and automatically analyzed. One of the main benefits from this approach comes from the traceability of the work, that is intrinsically impossible when the optical designer works in interactive mode. The right procedure is built and tuned just the first time and the computation software is available for inspection and check. Furthermore computations and results are easily reproducible simply re-running Matlab scripts. An automatic approach is especially helpful in wide-field telescope projects where the optical quality has to be studied over a wide field of view. This leads to repeat the same computations many times in a number of fields. In interactive mode this would cause a significant waste of optical designer time to repeat many times the same manual procedures. The solution proposed here allows to save time and prevent occasional mistakes.
Energy Technology Data Exchange (ETDEWEB)
Chang, Jong Hwa; Lee, Jeong Yeon; Lee, Young Ouk; Sukhovitski, Efrem Sh. [Korea Atomic Energy Research Institute, Taejeon (Korea)
2000-01-01
Programs SHEMMAN and OPTMAN (Version 6) have been developed for determinations of nuclear Hamiltonian parameters and for optical model calculations, respectively. The optical model calculations by OPTMAN with coupling schemes built on wave functions functions of non-axial soft-rotator are self-consistent, since the parameters of the nuclear Hamiltonian are determined by adjusting the energies of collective levels to experimental values with SHEMMAN prior to the optical model calculation. The programs have been installed at Nuclear Data Evaluation Laboratory of KAERI. This report is intended as a brief manual of these codes. 43 refs., 9 figs., 1 tabs. (Author)
Mitochondrial optic neuropathy: In vivo model of neurodegeneration and neuroprotective strategies
Directory of Open Access Journals (Sweden)
Julio C Rojas
2010-03-01
Full Text Available Julio C Rojas, Francisco Gonzalez-LimaDepartments of Psychology, Pharmacology and Toxicology, University of Texas at Austin, Austin, TX, USAAbstract: This review summarizes the characteristics of a rodent toxicologic model of optic neuropathy induced by the mitochondrial complex I inhibitor rotenone. This model has been developed to fulfill the demand for a drug-screening tool providing a sound mechanistic context to address the role of mitochondrial dysfunction in the pathogenesis of neurodegenerative disorders. It features biochemical, structural, and functional retinal deficits that resemble those of patients with Leber’s hereditary optic neuropathy, a mitochondrial disease characterized by selective degeneration of retinal ganglion cells, and for which an environmental component is believed to play a major triggering role. The available data support the efficiency, sensitivity, and versatility of the model for providing insights into the mechanisms of neurodegeneration, including mitochondrial dysfunction, oxidative stress and excitotoxicity. Screening work with this model has provided proof-of-principle that interventions targeting the electron transport chain, such as USP methylene blue and near-infrared light therapy, are effective at preventing neurodegeneration induced by mitochondrial dysfunction in vivo. Prospective developments of this model include the use of neuronal reporter genes for in vivo non-invasive assessment of retinal degeneration at different time points, and its combination with genetic approaches to elucidate the synergism of environmental and genetic factors in neurodegeneration.Keywords: animal model, neuroprotection, mitochondrial dysfunction, visual function, oxidative stress, cytochrome oxidase
A physical model eye with 3D resolution test targets for optical coherence tomography
Hu, Zhixiong; Liu, Wenli; Hong, Baoyu; Hao, Bingtao; Wang, Lele; Li, Jiao
2014-09-01
Optical coherence tomography (OCT) has been widely employed as non-invasive 3D imaging diagnostic instrument, particularly in the field of ophthalmology. Although OCT has been approved for use in clinic in USA, Europe and Asia, international standardization of this technology is still in progress. Validation of OCT imaging capabilities is considered extremely important to ensure its effective use in clinical diagnoses. Phantom with appropriate test targets can assist evaluate and calibrate imaging performance of OCT at both installation and throughout lifetime of the instrument. In this paper, we design and fabricate a physical model eye with 3D resolution test targets to characterize OCT imaging performance. The model eye was fabricated with transparent resin to simulate realistic ophthalmic testing environment, and most key optical elements including cornea, lens and vitreous body were realized. The test targets which mimic USAF 1951 test chart were fabricated on the fundus of the model eye by 3D printing technology. Differing from traditional two dimensional USAF 1951 test chart, a group of patterns which have different thickness in depth were fabricated. By measuring the 3D test targets, axial resolution as well as lateral resolution of an OCT system can be evaluated at the same time with this model eye. To investigate this specialized model eye, it was measured by a scientific spectral domain OCT instrument and a clinical OCT system respectively. The results demonstrate that the model eye with 3D resolution test targets have the potential of qualitatively and quantitatively validating the performance of OCT systems.
The rate equation based optical model for phosphor-converted white light-emitting diodes
Du, Kang; Li, Haokai; Guo, Keqin; Wang, Heng; Li, Dacheng; Zhang, Wending; Mei, Ting; Chua, Soo Jin
2017-03-01
An optical model based on the rate equation was developed to calculate the emission spectrum of a phosphor-converted white light-emitting diode (pc-WLED) taking into consideration the phosphor weight percentage, film thickness, and optical properties of phosphor, viz. absorption spectrum, quantum efficiency spectrum and fluorescent emission spectrum. Films containing a mixture of phosphor and silicone elastomer encapsulant were investigated using this model. A linear relationship was found between the peak absorption coefficient and the phosphor weight percentage with slopes of 66.76 ± 0.52 mm‑1 and 29.66 ± 2.05 mm‑1 for a red phosphor CaAlSiN3:Eu2+ and a yellow phosphor Y3Al5O12:Ce3+, respectively. With these parameters, the model predicted emission spectra which are in good agreement with measurement, thus verifying the validity of the model. The model correctly predicts redshift and spectral width reduction of the emission peak for increasing phosphor weight percentage or film thickness, as expected from the phenomenon of photon reabsorption by the phosphors. This model does not require the use of Monte Carlo simulation and Mie theory.
Wang, Haibo; Swee Poo, Gee
2004-08-01
We study the provisioning of virtual private network (VPN) service over WDM optical networks. For this purpose, we investigate the blocking performance of the hose model versus the pipe model for the provisioning. Two techniques are presented: an analytical queuing model and a discrete event simulation. The queuing model is developed from the multirate reduced-load approximation technique. The simulation is done with the OPNET simulator. Several experimental situations were used. The blocking probabilities calculated from the two approaches show a close match, indicating that the multirate reduced-load approximation technique is capable of predicting the blocking performance for the pipe model and the hose model in WDM networks. A comparison of the blocking behavior of the two models shows that the hose model has superior blocking performance as compared with pipe model. By and large, the blocking probability of the hose model is better than that of the pipe model by a few orders of magnitude, particularly at low load regions. The flexibility of the hose model allowing for the sharing of resources on a link among all connections accounts for its superior performance.
Cao, Zhenggang; Ding, Zengqian; Hu, Zhixiong; Wen, Tao; Qiao, Wen; Liu, Wenli
2016-10-01
Optical coherence tomography (OCT) has been widely applied in diagnosis of eye diseases during the last 20 years. Differing from traditional two-dimension imaging technologies, OCT could also provide cross-sectional information of target tissues simultaneously and precisely. As well known, axial resolution is one of the most critical parameters impacting the OCT image quality, which determines whether an accurate diagnosis could be obtained. Therefore, it is important to evaluate the axial resolution of an OCT equipment. Phantoms always play an important role in the standardization and validation process. Here, a standard model eye with micro-scale multilayer structure was custom designed and manufactured. Mimicking a real human eye, analyzing the physical characteristic of layer structures of retina and cornea in-depth, appropriate materials were selected by testing the scattering coefficient of PDMS phantoms with difference concentration of TiO2 or BaSO4 particles. An artificial retina and cornea with multilayer-films which have a thickness of 10 to 60 micrometers for each layer were fabricated using spin coating technology. Considering key parameters of the standard model eye need to be traceable as well as accurate, the optical refractive index and layer structure thicknesses of phantoms were verified by utilizing Thickness Monitoring System. Consequently, a standard OCT model eye was obtained after the retinal or corneal phantom was embedded into a water-filled model eye which has been fabricated by 3D printing technology to simulate ocular dispersion and emmetropic refraction. The eye model was manufactured with a transparent resin to simulate realistic ophthalmic testing environment, and most key optical elements including cornea, lens and vitreous body were realized. By investigating with a research and a clinical OCT system respectively, the OCT model eye was demonstrated with similar physical properties as natural eye, and the multilayer film measurement
Dutkiewicz, S.; Hickman, A. E.; Jahn, O.; Gregg, W. W.; Mouw, C. B.; Follows, M. J.
2015-07-01
We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem component in a dynamic three-dimensional physical framework. The radiative transfer component resolves the penetration of spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (different phytoplankton functional types; detrital particles; and coloured dissolved organic matter, CDOM). The model is evaluated against in situ-observed and satellite-derived products. In particular we compare to concurrently measured biogeochemical, ecosystem, and optical data along a meridional transect of the Atlantic Ocean. The simulation captures the patterns and magnitudes of these data, and estimates surface upwelling irradiance analogous to that observed by ocean colour satellite instruments. We find that incorporating the different optically important constituents explicitly and including spectral irradiance was crucial to capture the variability in the depth of the subsurface chlorophyll a (Chl a) maximum. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, as well as the crucial feedbacks between the light field, the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at attenuating light at short wavelengths and in more productive waters, phytoplankton absorption is relatively more important at the subsurface Chl a maximum, and water molecules have the greatest contribution when concentrations of other constituents are low, such as in the oligotrophic gyres. Scattering had less effect on attenuation, but since it is important for the amount and type of upwelling irradiance, it is crucial for setting sea surface reflectance. Strikingly, sensitivity experiments in which absorption by any of the
Implications for GCM Modeling of MARCI/TES ACB Optical Depth Differences
Klassen, David R.; Kahre, Melinda A.; Wolff, Michael J.; Haberle, Robert; Hollingsworth, Jeffery L.
2016-10-01
The Aphelion Cloud Belt (ACB) is a well-studied phenomenon of Mars. HST violet images and microwave observations [e.g. 1–3] helped characterize its seasonal morphology and measure typical optical depths. Follow up, long-term studies by orbiting instruments [e.g. 4–6] characterized the growth and decline of the ACB as well as a baseline set of zonally averaged optical depths as a function of latitude and season. All this work provided ground-truth for the assessment and modification of Mars GCMs and current models provide good agreement with observations [e.g. 7–8].We will present recent analyses of MARCI and TES ACB optical depths that show a wavelength dependance on the timing of the peak zonal-average optical depth that implies a possible evolution in average effective radius of ACB cloud particles as the ACB ages. As we will show, this difference in timing of the optical depth peak between short and long wavelength bands is not seen in the Ames MGCM. In order to begin understanding these differences, we will present retrieved ACB cloud particle sizes from the Ames MGCM to compare to the optical depth observations and calculations and discuss possible model adjustments that may lead to better fits. Aligning model and observation results should lead to a better understanding of what is physically driving the particle size evolution.[1] James, P. B., et al. 1996, JGR, 101, 18883[2] Clancy, R. T., et al. 1996, Icarus, 122, 36[3] Wolff, M. J., et al. 1999, in The Fifth International Conference on Mars, July 19-24, 1999, Pasadena, California, 6173[4] Pearl, J. C., et al. 2001, JGR, 106, 12325[5] Smith, M. D., et al. 2003, JGR-Planets, 108, 1[6] Smith, M. D. 2004, Icarus, 167, 148[7] Montmessin, F., et al. 2004, JGR-Planets, 109, E10004[8] Haberle, R. M., et al. 2010, in BAAS, 42, 1031
Protective effects of cerebrolysin in a rat model of optic nerve crush.
Huang, Tzu-Lun; Huang, Sun-Ping; Chang, Chung-Hsing; Lin, Kung-Hung; Sheu, Min-Muh; Tsai, Rong-Kung
2014-07-01
To investigate the effects of cerebrolysin (Cbl) on optic nerves (ON) and retinal ganglion cells (RGC) in a rat model of ON crush. Rats received intravitreal injection of Cbl (n = 20), intra-ON injection of Cbl (n = 20), intraperitoneal injection (IPI) of Cbl (n = 20), or phosphate buffered saline (PBS; n = 20) every day for 2 weeks after ON crush injury. At 3 weeks post-trauma, RGC density was counted by retrograde labeling with FluoroGold and visual function was assessed by flash visual-evoked potentials. Activities of microglia after insults were quantified by immunohistochemical analysis of the presence of ED1 in the optic nerve. At 3 weeks postcrush, the densities of RGCs in the Cbl-IVI group (1125 ± 166/mm(2)) and in the Cbl-IPI treatment group (1328 ± 119/mm(2)) were significantly higher than those in the PBS group (641 ± 214/mm(2)). The flash visual-evoked potential measurements showed that latency of the P1 wave was significantly shorter in the Cbl-IVI- and Cbl-IPI-treated groups (105 ± 4 ms and 118 ± 26 ms, respectively) than in the PBS-treated group (170 ± 20 ms). However, only Cbl IPI treatment resulted in a significant decrease in the number of ED1-positive cells at the lesion sites of the ON (5 ± 2 cells/vs. 30 ± 4 cells/high-power field in control eyes). Treatment with intra-ON injection of Cbl was harmful to the optic nerve in the crush model. Systemic administration of Cbl had neuroprotective effects on RGC survival and visual function in the optic nerve crush model.
Protective effects of cerebrolysin in a rat model of optic nerve crush
Directory of Open Access Journals (Sweden)
Tzu-Lun Huang
2014-07-01
Full Text Available To investigate the effects of cerebrolysin (Cbl on optic nerves (ON and retinal ganglion cells (RGC in a rat model of ON crush. Rats received intravitreal injection of Cbl (n = 20, intra-ON injection of Cbl (n = 20, intraperitoneal injection (IPI of Cbl (n = 20, or phosphate buffered saline (PBS; n = 20 every day for 2 weeks after ON crush injury. At 3 weeks post-trauma, RGC density was counted by retrograde labeling with FluoroGold and visual function was assessed by flash visual-evoked potentials. Activities of microglia after insults were quantified by immunohistochemical analysis of the presence of ED1 in the optic nerve. At 3 weeks postcrush, the densities of RGCs in the Cbl-IVI group (1125 ± 166/mm2 and in the Cbl-IPI treatment group (1328 ± 119/mm2 were significantly higher than those in the PBS group (641 ± 214/mm2. The flash visual-evoked potential measurements showed that latency of the P1 wave was significantly shorter in the Cbl-IVI- and Cbl-IPI-treated groups (105 ± 4 ms and 118 ± 26 ms, respectively than in the PBS-treated group (170 ± 20 ms. However, only Cbl IPI treatment resulted in a significant decrease in the number of ED1-positive cells at the lesion sites of the ON (5 ± 2 cells/vs. 30 ± 4 cells/high-power field in control eyes. Treatment with intra-ON injection of Cbl was harmful to the optic nerve in the crush model. Systemic administration of Cbl had neuroprotective effects on RGC survival and visual function in the optic nerve crush model.
Single-step stereolithography of complex anatomical models for optical flow measurements.
de Zélicourt, Diane; Pekkan, Kerem; Kitajima, Hiroumi; Frakes, David; Yoganathan, Ajit P
2005-02-01
Transparent stereolithographic rapid prototyping (RP) technology has already demonstrated in literature to be a practical model construction tool for optical flow measurements such as digital particle image velocimetry (DPIV), laser doppler velocimetry (LDV), and flow visualization. Here, we employ recently available transparent RP resins and eliminate time-consuming casting and chemical curing steps from the traditional approach. This note details our methodology with relevant material properties and highlights its advantages. Stereolithographic model printing with our procedure is now a direct single-step process, enabling faster geometric replication of complex computational fluid dynamics (CFD) models for exact experimental validation studies. This methodology is specifically applied to the in vitro flow modeling of patient-specific total cavopulmonary connection (TCPC) morphologies. The effect of RP machining grooves, surface quality, and hydrodynamic performance measurements as compared with the smooth glass models are also quantified.
Optical imaging as a link between cellular neurophysiology and circuit modeling
Directory of Open Access Journals (Sweden)
Walther Akemann
2009-07-01
Full Text Available The relatively simple and highly modular circuitry of the cerebellum raised expectations decades ago that a realistic computational model of cerebellar circuit operations would be feasible, and prove insightful for unraveling cerebellar information processing. To this end, the biophysical properties of most cerebellar cell types and their synaptic connections have been well characterized and integrated into realistic single cell models. Furthermore, large scale models of cerebellar circuits that extrapolate from single cell properties to circuit dynamics have been constructed. While the development of single cell models have been constrained by microelectrode recordings, guidance and validation as these models are scaled up to study network interactions requires an experimental methodology capable of monitoring cerebellar dynamics at the population level. Here we review the potential of optical imaging techniques to serve this purpose.
Modeling and Field Study of Coupled Bio-Optical Physical Processes in the Monterey Bay Area.
Shulman, I.; Arnone, R.; Teague, W.; Chavez, F.; Schofield, O.; Moline, M.; Penta, B.; Ryan, J.; Gould, R.; Anderson, S.; Jolliff, J. K.; Book, J. W.; Derada, S.; Paduan, J. D.
2008-12-01
Scientists from government, academia and non-profit organizations participated in an interdisciplinary field program in the Monterey Bay from during May-June of 2008. The experiment was a collaboration between the NRL project "Bio-Optical Studies of Predictability and Assimilation for the Coastal Environment (BIOSPACE)", Multidisciplinary University Research Initiative (MURI) project "Rapid Environmental Assessment Using an Integrated Coastal Ocean Observation-Modeling System (ESPRESSO)", the Monterey Bay Aquarium Research Institute (MBARI), the NRL project "Unattended Sea-bed Power for In-water Operations", and the U.S. Geological Survey. Objectives of the NRL BIOSPACE and MURI ESPRESSO projects are centered around developing an understanding of coupled bio-optical and physical processes in the coastal zone and improvements of predictability of coastal ocean optical properties on time scales of 1-5 days. MBARI has long-term objectives of monitoring, studying and managing the Monterey Bay ecosystem dynamics and health. The goals for the 2008 field program were to create a synoptic view of the coupled bio- optical physical conditions in the Monterey Bay and to relate satellite observed properties to their subsurface structure. The program was focused on the so-called "upwelling shadow area"(northern part of the bay), where biological processes are enhanced as a result of the slower physical dynamics. The field program deployed a wide range of assets: gliders, AUVs, ScanFish (a ship-towed platform), SEPTR, etc. This deployment was supplemented with intensive station sampling from the R/V Point Sur and satellite ocean color imagery (MODIS, MERIS). The field program was supported by a real-time modeling effort consisting of a hierarchy of different resolution, nested, data assimilating, coupled bio-optical physical models. Development of a pair of cyclonic (in the bay) and anticyclonic (outside of the bay) eddies was observed and predicted by the model during an
OPTICAL DIAGNOSTIC AND MODELING SOLUTION GROWTH PROCESS OF SODIUM CHLORATE CRYSTALS
Institute of Scientific and Technical Information of China (English)
WANG Tao; DUAN Li
2006-01-01
Both a real time optical interferometric experiment and a numerical simulation of two-dimension non-steady state model were employed to study the growth process of aqueous sodium chlorate crystals. The parameters such as solution concentration distribution, crystal dimensions, growth rate and velocity field were obtained by both experiment and numerical simulation. The influence of earth gravity during crystal growth process was analyzed. A reasonable theory model corresponding to the present experiment is advanced. The thickness of concentration boundary layer was investigated especially. The results from the experiment and numerical simulation match well.
Rosário, N. E.; Longo, K. M.; Freitas, S. R.; Yamasoe, M. A.; Fonseca, R. M.
2012-07-01
Intra-seasonal variability of smoke aerosol optical depth (AOD) and downwelling solar irradiance at the surface during the 2002 biomass burning season in South America was modeled using the Coupled Chemistry-Aerosol-Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CCATT-BRAMS). Measurements of AOD from the AErosol RObotic NETwork (AERONET) and solar irradiance at the surface from the Solar Radiation Network (SolRad-NET) were used to evaluate model results. In general, the major features associated with AOD evolution over the southern part of the Amazon Basin and cerrado ecosystem are captured by the model. The main discrepancies were found for high aerosol loading events. In the northeastern portion of the Amazon Basin the model systematically underestimated AOD. This is likely due to the cloudy nature of the region, preventing accurate detection of the fire spots used in the emission model. Moreover, measured AOD were very often close to background conditions and emissions other than smoke were not considered in the simulation. Therefore, under the background scenario, one would expect the model to underestimate AOD. The issue of high aerosol loading events in the southern part of the Amazon and cerrado is also discussed in the context of emission shortcomings. The Cuiabá cerrado site was the only one where the highest quality AERONET data were unavailable. Thus, lower quality data were used. Root-mean-square-error (RMSE) between the model and observations decreased from 0.48 to 0.17 when extreme AOD events (AOD550 nm ≥ 1.0) and Cuiabá were excluded from analysis. Downward surface solar irradiance comparisons also followed similar trends when extremes AOD were excluded. This highlights the need to improve the modelling of the regional smoke plume in order to enhance the accuracy of the radiative energy budget. Aerosol optical model based on the mean intensive properties of smoke from the southern part of the
Quantum-Dot Semiconductor Optical Amplifiers: State Space Model versus Rate Equation Model
Directory of Open Access Journals (Sweden)
Hussein Taleb
2013-01-01
Full Text Available A simple and accurate dynamic model for QD-SOAs is proposed. The proposed model is based on the state space theory, where by eliminating the distance dependence of the rate equation model of the QD-SOA; we derive a state space model for the device. A comparison is made between the rate equation model and the state space model under both steady state and transient regimes. Simulation results demonstrate that the derived state space model not only is much simpler and faster than the rate equation model, but also it is as accurate as the rate equation model.
Optical model predictions for total cross sections for scattering of neutrons from {sup 40}Ca
Energy Technology Data Exchange (ETDEWEB)
Chinn C.R.; Elster, C.; Thaler, R.M.
1993-10-01
Measurements of neutron total cross sections are both extensive and extremely accurate. Although they should place a strong constraint on theoretically constructed optical models, there are relatively few comparisons of optical model predictions with those experiments. We have calculated total cross sections for neutron scattering from {sup 40}Ca as a function of energy from 100 - 600 MeV laboratory energy with a microscopic first order optical potential derived within the framework of the Watson expansion. Although the results are already in qualitative agreement with the data, the inclusion of medium corrections to the propagator using a recently derived microscopic mean field approach, is essential for correctly predicting the energy dependence given by the experiment. In the region below 200 MeV, where our off-shell tp calculations over predict the experiment, the modification due to the nuclear medium reduces the calculated values, whereas above 200 MeV, these corrections tend to compensate for the under prediction of the off-shell t{rho} results.
Yu, Lingfeng; Nguyen, Elaine; Liu, Gangjun; Rao, Bin; Choi, Bernard; Chen, Zhongping
2010-02-01
We present a combined optical Doppler tomography/spectral Doppler imaging modality to quantitatively evaluate the dynamic blood circulation and the artery blockage before and after a localized ischemic stroke in a mouse model. Optical Doppler Tomography (ODT) combines the Doppler principle with optical coherence tomography for noninvasive localization and measurement of particle flow velocity in highly scattering media with micrometer scale spatial resolution. Spectral Doppler imaging (SDI) provides complementary temporal flow information to the spatially distributed flow information of Doppler imaging. Fast, repeated, ODT scans across an entire vessel were performed to record flow dynamic information with high temporal resolution of cardiac cycles. Spectral Doppler analysis of continuous Doppler images demonstrates how the velocity components and longitudinally projected flow-volume-rate change over time for scatters within the imaging volume using spectral Doppler waveforms. Furthermore, vascular conditions can be quantified with various Doppler-angle-independent flow indices. Non-invasive in-vivo mice experiments were performed to evaluate microvascular blood circulation of a localized ischemic stroke mouse model.
Zhang, Jianing; Bi, Lei; Liu, Jianping; Panetta, R. Lee; Yang, Ping; Kattawar, George W.
2016-07-01
Constructing an appropriate particle morphology model is essential for realistic simulation of optical properties of atmospheric particles. This paper presents a model for generating surface roughness based on a combination of methods from discrete differential geometry combined with a stochastic partial differential equation for surface evolution introduced by Edwards and Wilkinson. Scattering of light by roughened particles is simulated using the Invariant Imbedding T-Matrix (II-TM) method. The effects of surface roughness on the single-scattering properties, namely, the phase matrix, asymmetry factor, and extinction efficiency, are investigated for a single wavelength in the visible range and for a range of size parameters up to x=50. Three different smooth shapes are considered: spherical, spheroidal, and hexagonal, the latter two in just the "compact particle" case of unit aspect ratio. It is shown that roughness has negligible effects on the optical scattering properties for size parameters less than 20. For size parameters ranging from 20 to 50, the phase matrix elements are more sensitive to the surface roughness than are two important integral optical properties, the extinction efficiency and asymmetry factor. As has been seen in studies using other forms of roughening, the phase function is progressively smoothed as roughness increases. The effect on extinction efficiency is to increase it, and on asymmetry factor is to decrease it. Each of these effects is relatively modest in the size range considered, but the trend of results suggests that greater effects will be seen for size parameters larger than ones considered here.
Continuous monitoring of arthritis in animal models using optical imaging modalities
Son, Taeyoon; Yoon, Hyung-Ju; Lee, Saseong; Jang, Won Seuk; Jung, Byungjo; Kim, Wan-Uk
2014-10-01
Given the several difficulties associated with histology, including difficulty in continuous monitoring, this study aimed to investigate the feasibility of optical imaging modalities-cross-polarization color (CPC) imaging, erythema index (EI) imaging, and laser speckle contrast (LSC) imaging-for continuous evaluation and monitoring of arthritis in animal models. C57BL/6 mice, used for the evaluation of arthritis, were divided into three groups: arthritic mice group (AMG), positive control mice group (PCMG), and negative control mice group (NCMG). Complete Freund's adjuvant, mineral oil, and saline were injected into the footpad for AMG, PCMG, and NCMG, respectively. LSC and CPC images were acquired from 0 through 144 h after injection for all groups. EI images were calculated from CPC images. Variations in feet area, EI, and speckle index for each mice group over time were calculated for quantitative evaluation of arthritis. Histological examinations were performed, and the results were found to be consistent with those from optical imaging analysis. Thus, optical imaging modalities may be successfully applied for continuous evaluation and monitoring of arthritis in animal models.
Modeling Human Control of Self-Motion Direction With Optic Flow and Vestibular Motion.
Zaal, Peter M T; Nieuwenhuizen, Frank M; van Paassen, Marinus M; Mulder, Max
2013-04-01
In this paper, we investigate the effects of visual and motion stimuli on the manual control of one's direction of self-motion. In a flight simulator, subjects conducted an active target-following disturbance-rejection task, using a compensatory display. Simulating a vehicular control task, the direction of vehicular motion was shown on the outside visual display in two ways: an explicit presentation using a symbol and an implicit presentation, namely, through the focus of radial outflow that emerges from optic flow. In addition, the effects of the relative strength of congruent vestibular motion cues were investigated. The dynamic properties of human visual and vestibular motion perception paths were modeled using a control-theoretical approach. As expected, improved tracking performance was found for the configurations that explicitly showed the direction of self-motion. The human visual time delay increased with approximately 150 ms for the optic flow conditions, relative to explicit presentations. Vestibular motion, providing higher order information on the direction of self-motion, allowed subjects to partially compensate for this visual perception delay, improving performance. Parameter estimates of the operator control model show that, with vestibular motion, the visual feedback becomes stronger, indicating that operators are more confident to act on optic flow information when congruent vestibular motion cues are present.
Generalized Tensor Analysis Model for Multi-Subcarrier Analog Optical Systems
DEFF Research Database (Denmark)
Zhao, Ying; Yu, Xianbin; Zheng, Xiaoping
2011-01-01
We propose and develop a general tensor analysis framework for a subcarrier multiplex analog optical fiber link for applications in microwave photonics. The goal of this work is to construct an uniform method to address nonlinear distortions of a discrete frequency transmission system. We employ ...... a study of two multi-subcarrier systems with detailed performance discussions. We believe the tensor model provides us not only a consolidated notation, but also an alternative numerical approach to effectively analyze multi-subcarrier analog optical systems.......We propose and develop a general tensor analysis framework for a subcarrier multiplex analog optical fiber link for applications in microwave photonics. The goal of this work is to construct an uniform method to address nonlinear distortions of a discrete frequency transmission system. We employ...... details compared with series-based approaches by hiding the underlying multi-fold summation and index operation. The integrity of the proposed methodology is validated by investigating the classical intensity modulated system. Furthermore, to give an application model of the tensor formalism, we make...
Modeling the inherent optical properties of aquatic particles using an irregular hexahedral ensemble
Xu, Guanglang; Sun, Bingqiang; Brooks, Sarah D.; Yang, Ping; Kattawar, George W.; Zhang, Xiaodong
2017-04-01
A statistical approach in defining particle morphology in terms of an ensemble of hexahedra of distorted shapes is employed for modeling the Inherent Optical Properties (IOPs) of aquatic particles. The approach is inspired by the rich variability in shapes of real aquatic particles that cannot be represented by one particular shape. Two methods, the Invariant Imbedding T-matrix (II-TM) and Physical Geometric Optics Hybrid (PGOH) method, are combined to simulate the IOPs for aquatic particles of sizes ranging from the Rayleigh scattering to geometric optics regimes. Nonspherical effects on the IOPs are examined by comparing the results with predictions based on the Lorenz-Mie theory to explore the limitations of assuming the particles to be spherical. We pay special attention to backscattering-related and polarimetric scattering properties, particularly the backscattering ratio, Gordon parameter, backscattering volume scattering function and the degree of linear polarization. The simulated IOPs are compared with the in-situ measurements to assess the feasibility of using a hexahedral ensemble in modeling the IOPs of the aquatic particles.
Enhanced Doppler reflectometry power response: physical optics and 2D full wave modelling
Pinzón, J. R.; Happel, T.; Blanco, E.; Conway, G. D.; Estrada, T.; Stroth, U.
2017-03-01
The power response of a Doppler reflectometer is investigated by means of the physical optics model; a simple model which considers basic scattering processes at the reflection layer. Apart from linear and saturated scattering regimes, non-linear regimes with an enhanced backscattered power are found. The different regimes are characterized and understood based on analytical calculations. The power response is also studied with two-dimensional full wave simulations, where the enhanced backscattered power regimes are also found in qualitative agreement with the physical optics results. The ordinary and extraordinary modes are compared for the same angle of incidence, with the conclusion that the ordinary mode is better suited for Doppler reflectometry turbulence level measurements due to the linearity of its response. The scattering efficiency is studied and a first approximation to describe it is proposed. At the end, the application of the physical optics results to experimental data analysis is discussed. In particular, a formula to assess the linearity of Doppler reflectometry measurements is provided.
Magneto-optical cellular chip model for intracellular orientational-dynamic-activity detection
Miyashita, Y.; Iwasaka, M.; Kurita, S.; Owada, N.
2012-04-01
In the present study, a magneto-optical cellular chip model (MoCCM) was developed to detect intracellular dynamics in macromolecules by using magneto-optical effects. For the purpose of cell-measurement under strong static magnetic fields of up to 10 T, we constructed a cellular chip model, which was a thin glass plate with a well for a cell culture. A cell line of osteoblast MC3T3-E1 was incubated in the glass well, and the well, 0.3 mm in depth, was sealed by a cover glass when the MoCCM was set in a fiber optic system. An initial intensity change of the polarized light transmission, which dispersed perpendicular to the cell's attaching surface, was collected for 10 to 60 min, and then magnetic fields were applied parallel and perpendicular to the surface and light direction, respectively. The magnetic birefringence signals that originated from the magnetic orientation of intracellular molecules such as cytoskeletons apparently appeared when the magnetic fields were constant at 10 T. A statistical analysis with 15 experiments confirmed that the cellular components under 10 T magnetic fields caused a stronger alignment, which was transferred into polarizing light intensity that increased more than the case before exposure. Cellular conditions such as generation and cell density affected the magnetic birefringence signals.
Multilayer Markov Random Field models for change detection in optical remote sensing images
Benedek, Csaba; Shadaydeh, Maha; Kato, Zoltan; Szirányi, Tamás; Zerubia, Josiane
2015-09-01
In this paper, we give a comparative study on three Multilayer Markov Random Field (MRF) based solutions proposed for change detection in optical remote sensing images, called Multicue MRF, Conditional Mixed Markov model, and Fusion MRF. Our purposes are twofold. On one hand, we highlight the significance of the focused model family and we set them against various state-of-the-art approaches through a thematic analysis and quantitative tests. We discuss the advantages and drawbacks of class comparison vs. direct approaches, usage of training data, various targeted application fields and different ways of Ground Truth generation, meantime informing the Reader in which roles the Multilayer MRFs can be efficiently applied. On the other hand we also emphasize the differences between the three focused models at various levels, considering the model structures, feature extraction, layer interpretation, change concept definition, parameter tuning and performance. We provide qualitative and quantitative comparison results using principally a publicly available change detection database which contains aerial image pairs and Ground Truth change masks. We conclude that the discussed models are competitive against alternative state-of-the-art solutions, if one uses them as pre-processing filters in multitemporal optical image analysis. In addition, they cover together a large range of applications, considering the different usage options of the three approaches.
Rowe, T. Scott; Zawadzki, Robert J.
2012-03-01
We document our latest work in developing eye models with solid-state retinal tissue phantoms designed for demonstrating, validating and comparing ophthalmic Optical Coherence Tomography (OCT) instruments. Eye models with retina tissue phantoms can serve a variety of purposes, including demonstrating OCT functionality and performance in both the clinic and exhibit hall, validating retina layer thickness measurements from different commercial OCT instruments and as an aide for the R&D engineer and field service technician in the development and repair of instruments, respectively. The ideal eye model for OCT, the optical cross-sectional imaging modality, would have a volumetric morphology and scattering and absorption properties similar to that of normal human retina. These include a multi-layered structure of equivalent thickness to nominal human retina layers, a foveal pit that can be used to orient the image, and a RPE/OS and choroid like layers to demonstrate the depth penetration of the OCT system. A solid state tissue phantom relieves the user of constant cleaning and maintenance associated with the more common water bath model eyes. Novel processes12 have been developed to create retinal layers model that closely mimic the reflectance and scattering coefficients of the real layers of the retina, as imaged by spectral bandwidth of OCT.
Mask optimization approaches in optical lithography based on a vector imaging model.
Ma, Xu; Li, Yanqiu; Dong, Lisong
2012-07-01
Recently, a set of gradient-based optical proximity correction (OPC) and phase-shifting mask (PSM) optimization methods has been developed to solve for the inverse lithography problem under scalar imaging models, which are only accurate for numerical apertures (NAs) of less than approximately 0.4. However, as lithography technology enters the 45 nm realm, immersion lithography systems with hyper-NA (NA>1) are now extensively used in the semiconductor industry. For the hyper-NA lithography systems, the vector nature of the electromagnetic field must be taken into account, leading to the vector imaging models. Thus, the OPC and PSM optimization approaches developed under the scalar imaging models are inadequate to enhance the resolution in immersion lithography systems. This paper focuses on developing pixelated gradient-based OPC and PSM optimization algorithms under a vector imaging model. We first formulate the mask optimization framework, in which the imaging process of the optical lithography system is represented by an integrative and analytic vector imaging model. A gradient-based algorithm is then used to optimize the mask iteratively. Subsequently, a generalized wavelet penalty is proposed to keep a balance between the mask complexity and convergence errors. Finally, a set of methods is exploited to speed up the proposed algorithms.
Directory of Open Access Journals (Sweden)
S. P. Tiwari
2013-02-01
Full Text Available An optical model is developed based on the diffuse attenuation coefficient (K_{d} to estimate particulate backscattering coefficients b_{bp}(λ in clear and turbid coastal waters. A large in-situ data set is used to establish robust relationships between b_{bp}(530 and b_{bp}(555 and K_{d}(490 using an efficient nonlinear least square method which uses the Trust-Region algorithm with Bisquare weights scheme to adjust the coefficients. These relationships are obtained with good correlation coefficients (R^{2} = 0.786 and 0.790, low Root Mean Square Error (RMSE = 0.00076 and 0.00072 and 95% confidence bounds. The new model is tested with two independent data sets such as the NOMAD SeaWiFS Match-ups and OOXIX IOP algorithm workshop evaluation data set (Version 2.0w APLHA. Results show that the new model makes good retrievals of b_{bp} at all key wavelengths (from 412–683 nm, with statistically significant improvements over other inversion models. Thus, the new model has the potential to improve our knowledge of particulate matters and their optical variability in both clear and turbid coastal waters.
An optical model for deriving the spectral particulate backscattering coefficients in oceanic waters
Tiwari, S. P.; Shanmugam, P.
2013-11-01
An optical model is developed based on the diffuse attenuation coefficient (Kd) to estimate particulate backscattering coefficients bbp(λ) in oceanic waters. A large in situ data set is used to establish robust relationships between bbp(530) and bbp(555) and Kd(490) using an efficient nonlinear least-square method which uses the trust region algorithm with Bisquare weights scheme to adjust the coefficients. These relationships are obtained with good correlation coefficients (R2 = 0.786 and 0.790), low root mean square error (RMSE = 0.00076 and 0.00072) and 95% confidence bounds. The new model is tested with three independent data sets: the NOMAD SeaWiFS Match ups, OOXIX IOP algorithm workshop evaluation data set (Version 2.0w APLHA), and IOCCG simulated data set. Results show that the new model makes good retrievals of bbp at all key wavelengths (from 412-683 nm), with statistically significant improvements over other inversion models. Thus, the new model has the potential to improve our present knowledge of particulate matter and their optical variability in oceanic waters.
Energy Technology Data Exchange (ETDEWEB)
Abdolahzadeh Ziabari, Ali, E-mail: ali.abd.ziabari@gmail.com [Nano Research Lab, Lahijan Branch, Islamic Azad University, P.O. Box 1616, Lahijan (Iran, Islamic Republic of); Refahi Sheikhani, A. H. [Department of Applied Mathematics, Lahijan Branch, Islamic Azad University, Lahijan (Iran, Islamic Republic of); Nezafat, Reza Vatani [Department of Civil Engineering, Faculty of Technology, University of Guilan, Rasht (Iran, Islamic Republic of); Haghighidoust, Kasra Monsef [Department of Mechanical Engineering, Faculty of Technology, University of Guilan, Rasht (Iran, Islamic Republic of)
2015-04-07
Cadmium oxide thin films were deposited onto glass substrates by sol–gel dip-coating method and annealed in air. The normal incidence transmittance of the films was measured by a spectrophotometer. D.C electrical parameters such as carrier concentration and mobility were analyzed by Hall Effect measurements. A combination of Forouhi–Bloomer and standard Drude model was used to simulate the optical constants and thicknesses of the films from transmittance data. The transmittance spectra of the films in the visible domain of wavelengths were successfully fitted by using the result of a hybrid particle swarm optimization method and genetic algorithm. The simulated transmittance is in good accordance with the measured spectrum in the whole measurement wavelength range. The electrical parameters obtained from the optical simulation are well consistent with those measured electrically by Hall Effect measurements.
Optical conductivity and resistivity in the two-band Emery model
Minh-Tien, Tran
1994-01-01
The temperature- and frequency-dependent conductivity due to the scattering of oxygen holes by antiferromagnetic spin fluctuations of the copper spins in the two-band Emergy model is calculated. Using the dynamic spin susceptibility obtained in the mean-field Schwinger boson approach, the resistivity obeys a near linear temperature dependence at high temperatures, whereas at low temperatures a quadratic behaviour holds. At the same time, the optical conductivity contains the Drude peak around zero frequency, whereas the scattering rate of quasiparticle appears to be proportional to frequency. Our results are essentially in agreement with experiments, at least qualitatively, and support the conclusion that the normal-state basal-plane resistivity and optical conductivity of high- Tc superconductors may be explained by two-dimensional spin-fluctuation scattering in the Fermi-liquid picture.
Directory of Open Access Journals (Sweden)
S. BENHAMIDA
2012-06-01
Full Text Available Ultrasonic waves are used extensively in nondestructive testing both for characterization of material properties, in this paper, we describe a fiber optic sensor suitable for detection of ultrasonic waves. This sensor is based on an extrinsic fiber optic sagnac interferometer. The proposed sensor model can act as a conventional in-phase detector or as a narrowband detector. In this study we use methods interference of ultrasonic waves between the source of ultrasonic waves and the object under investigation is exploited. The main advantages of the proposed sensor are the ability to detect ultrasonic waves on the surface; this sensor possesses higher sensitivity and accuracy than the pulse method. The cavity resonator was very successfully used for measurement of small ultrasound velocity changes. The ultrasonic interferometric technique based on phase-locked loop is the most suitable for measurements of small displacements. This method ensures the highest sensitivity and accuracy.
Smith, Paul S.; Sitko, Michael L.
1991-01-01
Optical broad-band polarimetry and photometry of the BL Lacertae object PKS 2155 - 304 during late 1990 are presented. Variability in both flux and linear polarization was moderate during this period. The optical polarization ranged from 2 to 7 percent while photometric variations were within 0.2 mag (V = 13.2-13.4). Accurate multicolor measurements were made to study any wavelength dependence of the polarization with an eye to using these data to test the model of Wandel and Urry (1991) which proposes that the UV to soft X-ray continuum of this object arises from an accretion disk. Wavelength-dependent polarization (WDP) is observed in PKS 2155 - 304. However, the polarization is always seen to decrease with wavelength when WDP is observed. This is opposite to the expected sense of WDP if the UV continuum is dominated by an accretion disk.
Optical model calculation for the unresolved/resolved resonance region of Fe-56
Energy Technology Data Exchange (ETDEWEB)
Kawano, Toshihiko [Kyushu Univ., Fukuoka (Japan); Froehner, F.H.
1997-03-01
We have studied optical model fits to total neutron cross sections of structural materials using the accurate data base for {sup 56}Fe existing in the resolved and unresolved resonance region. Averages over resolved resonances were calculated with Lorentzian weighting in Reich-Moore (reduced R matrix) approximation. Starting from the best available optical potentials we found that adjustment of the real and imaginary well depths does not work satisfactorily with the conventional weak linear energy dependence of the well depths. If, however, the linear dependences are modified towards low energies, the average total cross sections can be fitted quite well, from the resolved resonance region up to 20 MeV and higher. (author)
A model for the optical flares from the Galactic transient SWIFT J195509+261406
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The Galactic hard X-ray transient SWIFT J195509+261406 was first observed as gamma-ray burst GRB 070610.Within 3 days after the burst,more than forty optical flares had been observed.Here,we propose that this peculiar event should be associated with a white dwarf.The hard X-ray burst itself may be triggered by a collision between two planets orbiting the white dwarf.Some cracked fragments produced in the collision then fell onto the surface of the white dwarf over several days,giving birth to the observed optical flares via cyclotron radiation.Our model can satisfactorily explain the basic features of the observations.
Quesada, José Manuel; Capote, Roberto; Soukhovitski, Efrem S.; Chiba, Satoshi
2016-03-01
An extension for odd-A actinides of a previously derived dispersive coupledchannel optical model potential (OMP) for 238U and 232Th nuclei is presented. It is used to fit simultaneously all the available experimental databases including neutron strength functions for nucleon scattering on 232Th, 233,235,238U and 239Pu nuclei. Quasi-elastic (p,n) scattering data on 232Th and 238U to the isobaric analogue states of the target nucleus are also used to constrain the isovector part of the optical potential. For even-even (odd) actinides almost all low-lying collective levels below 1 MeV (0.5 MeV) of excitation energy are coupled. OMP parameters show a smooth energy dependence and energy independent geometry.
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)
Many-Body Quantum Optics with Decaying Atomic Spin States: ($\\gamma$, $\\kappa$) Dicke model
Gelhausen, Jan; Strack, Philipp
2016-01-01
We provide a theory for quantum-optical realizations of the open Dicke model with internal, atomic spin states subject to uncorrelated, single-site spontaneous emission with rate $\\gamma$. This introduces a second decay channel for excitations to irreversibly dissipate into the environment, in addition to the photon loss with rate $\\kappa$. We compute the mean-field non-equilibrium steady states for spin and photon observables in the long-time limit, $t\\rightarrow \\infty$. Although $\\gamma$ does not conserve the total angular momentum of the spin array, we argue that our solution is exact in the thermodynamic limit, for the number of atoms $N\\rightarrow \\infty$. In light of recent and upcoming experiments realizing superradiant phase transitions using internal atomic states with pinned atoms in optical lattices, our work lays the foundation for the pursuit of a new class of open quantum magnets coupled to quantum light.
Models of few optical cycle solitons beyond the slowly varying envelope approximation
Energy Technology Data Exchange (ETDEWEB)
Leblond, H., E-mail: herve.leblond@univ-angers.fr [LUNAM University, Université d’Angers, Laboratoire de Photonique d’Angers, EA 4464, 2 Bd. Lavoisier, 49045 Angers Cedex 01 (France); Mihalache, D. [LUNAM University, Université d’Angers, Laboratoire de Photonique d’Angers, EA 4464, 2 Bd. Lavoisier, 49045 Angers Cedex 01 (France); Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania); Academy of Romanian Scientists, 54 Splaiul Independentei, 050094 Bucharest (Romania)
2013-02-15
In the past years there was a huge interest in experimental and theoretical studies in the area of few-optical-cycle pulses and in the broader fast growing field of the so-called extreme nonlinear optics. This review concentrates on theoretical studies performed in the past decade concerning the description of few optical cycle solitons beyond the slowly varying envelope approximation (SVEA). Here we systematically use the powerful reductive expansion method (alias multiscale analysis) in order to derive simple integrable and nonintegrable evolution models describing both nonlinear wave propagation and interaction of ultrashort (femtosecond) pulses. To this aim we perform the multiple scale analysis on the Maxwell–Bloch equations and the corresponding Schrödinger–von Neumann equation for the density matrix of two-level atoms. We analyze in detail both long-wave and short-wave propagation models. The propagation of ultrashort few-optical-cycle solitons in quadratic and cubic nonlinear media are adequately described by generic integrable and nonintegrable nonlinear evolution equations such as the Korteweg–de Vries equation, the modified Korteweg–de Vries equation, the complex modified Korteweg–de Vries equation, the sine–Gordon equation, the cubic generalized Kadomtsev–Petviashvili equation, and the two-dimensional sine–Gordon equation. Moreover, we consider the propagation of few-cycle optical solitons in both (1+1)- and (2+1)-dimensional physical settings. A generalized modified Korteweg–de Vries equation is introduced in order to describe robust few-optical-cycle dissipative solitons. We investigate in detail the existence and robustness of both linearly polarized and circularly polarized few-cycle solitons, that is, we also take into account the effect of the vectorial nature of the electric field. Some of these results concerning the systematic use of the reductive expansion method beyond the SVEA can be relatively easily extended to few
We demonstrate how thermal-optical transmission analysis (TOT) for refractory light-absorbing carbon in atmospheric particulate matter was optimized with empirical response surface modeling. TOT employs pyrolysis to distinguish the mass of black carbon (BC) from organic carbon (...
Thermal and optical modeling of "blackened" tips for diode laser surgery
Belikov, Andrey V.; Skrypnik, Alexei V.; Kurnyshev, Vadim Y.
2016-04-01
This paper presents the results of thermal and optical modeling of "blackened" tips (fiber-optic thermal converter) with different structures: film and volumetric. Film converter is created by laser radiation action on a cork or paper and it is a one-step process. As a result, a carbonized cork or paper adhered to the distal end of the optical fiber absorbs light that leads to heating of the distal end of the optical fiber. We considered the peculiarities of volumetric converters formed by sintering (second step) of the target material transferred to the tip, at irradiating the target with laser radiation (first step). We investigated the interaction between 980 nm laser radiation and converters in the air and water. As a result of experiments and modeling, it was obtain, that converter temperature and power of converter destruction depend on the environment in which it is placed. We found that film converter in the air at average power of laser radiation of 0.30+/-0.05 W is heated to 900+/-50°C and destructed, and volumetric converter in the air at average power of laser radiation of 1.0+/-0.1 W is heated to 1000+/-50°C and destructed at reaching of 4.0+/-0.1 W only. We found that film converter in the water at average power of laser radiation of 1.0+/-0.1 W is heated to 550+/-50°C and destructed at reaching of 4.0+/-0.1 W only. Volumetric converter at average power of laser radiation of4.0+/-0.1 W is heated to 450+/-50°C and is not destructed up to 7.5+/-0.1 W, it is heated to 500+/-50°C in this case. Thus, volumetric converter is more resistant to action of laser heating.
HEADING RECOVERY FROM OPTIC FLOW: COMPARING PERFORMANCE OF HUMANS AND COMPUTATIONAL MODELS
Directory of Open Access Journals (Sweden)
Andrew John Foulkes
2013-06-01
Full Text Available Human observers can perceive their direction of heading with a precision of about a degree. Several computational models of the processes underpinning the perception of heading have been proposed. In the present study we set out to assess which of four candidate models best captured human performance; the four models we selected reflected key differences in terms of approach and methods to modelling optic flow processing to recover movement parameters. We first generated a performance profile for human observers by measuring how performance changed as we systematically manipulated both the quantity (number of dots in the stimulus per frame and quality (amount of 2D directional noise of the flow field information. We then generated comparable performance profiles for the four candidate models. Models varied markedly in terms of both their performance and similarity to human data. To formally assess the match between the models and human performance we regressed the output of each of the four models against human performance data. We were able to rule out two models that produced very different performance profiles to human observers. The remaining two shared some similarities with human performance profiles in terms of the magnitude and pattern of thresholds. However none of the models tested could capture all aspect of the human data.
Heat Transfer Modeling and Validation for Optically Thick Alumina Fibrous Insulation
Daryabeigi, Kamran
2009-01-01
Combined radiation/conduction heat transfer through unbonded alumina fibrous insulation was modeled using the diffusion approximation for modeling the radiation component of heat transfer in the optically thick insulation. The validity of the heat transfer model was investigated by comparison to previously reported experimental effective thermal conductivity data over the insulation density range of 24 to 96 kg/cu m, with a pressure range of 0.001 to 750 torr (0.1 to 101.3 x 10(exp 3) Pa), and test sample hot side temperature range of 530 to 1360 K. The model was further validated by comparison to thermal conductivity measurements using the transient step heating technique on an insulation sample at a density of 144 kg/cu m over a pressure range of 0.001 to 760 torr, and temperature range of 290 to 1090 K.
Photonic Beamformer Model Based on Analog Fiber-Optic Links’ Components
Volkov, V. A.; Gordeev, D. A.; Ivanov, S. I.; Lavrov, A. P.; Saenko, I. I.
2016-08-01
The model of photonic beamformer for wideband microwave phased array antenna is investigated. The main features of the photonic beamformer model based on true-time-delay technique, DWDM technology and fiber chromatic dispersion are briefly analyzed. The performance characteristics of the key components of photonic beamformer for phased array antenna in the receive mode are examined. The beamformer model composed of the components available on the market of fiber-optic analog communication links is designed and tentatively investigated. Experimental demonstration of the designed model beamforming features includes actual measurement of 5-element microwave linear array antenna far-field patterns in 6-16 GHz frequency range for antenna pattern steering up to 40°. The results of experimental testing show good accordance with the calculation estimates.
Surface-mode model of the extraordinary optical transmission without plasmons.
Xie, Yunya; Liu, Haitao; Jia, Hongwei; Zhong, Ying
2015-03-09
We propose a microscopic surface-mode model for the extraordinary optical transmission (EOT) through subwavelength metallic slit array covered with a thin dielectric layer under illumination of transverse-electric (TE) polarization. Remarkably, surface plasmon polarizations (SPPs) do not exist for this polarization. It is commonly believed that the waveguide mode in the dielectric layer plays a role similar to that of the SPP in classical EOT. To check the intuitive belief, we derive a surface-mode model by considering the multiple scattering process of the fundamental waveguide mode and neglecting all other residual field in the thin dielectric layer. The model captures the main feature of EOT and provides a phase-matching condition to predict the transmission resonance. Quantitative comparison between fully-vectorial calculations and model predictions shows that besides the fundamental waveguide mode, other residual field in the thin dielectric layer also contributes to the EOT without SPP.
Analytical Model based on Green Criteria for Optical Backbone Network Interconnection
DEFF Research Database (Denmark)
Gutierrez Lopez, Jose Manuel; Riaz, M. Tahir; Pedersen, Jens Myrup
2011-01-01
to the evaluation of the environmental impact of networks from physical interconnection point of view. Networks deployment, usage, and disposal are analyzed as contributing elements to ICT’s (Information and Communications Technology) CO2 emissions. This paper presents an analytical model for evaluating...... and quantifying the CO2 emissions of optical backbone networks during their lifetime. The main goal of this work is to present the model and illustrate how to evaluate the physical interconnection of backbones from an environmental perspective. This model can be applied as a new type of decision support criteria...... for backbone’s interconnection, since minimization of CO2 emissions is becoming an important factor. In addition, two case studies are presented to illustrate the use and application of this model, and the need for de facto and international standards to reduce CO2 emissions through good network planning....
Wan, Songlin; Zhang, Xiangchao; He, Xiaoying; Xu, Min
2016-12-20
Computer controlled optical surfacing requires an accurate tool influence function (TIF) for reliable path planning and deterministic fabrication. Near the edge of the workpieces, the TIF has a nonlinear removal behavior, which will cause a severe edge-roll phenomenon. In the present paper, a new edge pressure model is developed based on the finite element analysis results. The model is represented as the product of a basic pressure function and a correcting function. The basic pressure distribution is calculated according to the surface shape of the polishing pad, and the correcting function is used to compensate the errors caused by the edge effect. Practical experimental results demonstrate that the new model can accurately predict the edge TIFs with different overhang ratios. The relative error of the new edge model can be reduced to 15%.
Selecting among competing models of electro-optic, infrared camera system range performance
Nichols, Jonathan M.; Hines, James E.; Nichols, James D.
2013-01-01
Range performance is often the key requirement around which electro-optical and infrared camera systems are designed. This work presents an objective framework for evaluating competing range performance models. Model selection based on the Akaike’s Information Criterion (AIC) is presented for the type of data collected during a typical human observer and target identification experiment. These methods are then demonstrated on observer responses to both visible and infrared imagery in which one of three maritime targets was placed at various ranges. We compare the performance of a number of different models, including those appearing previously in the literature. We conclude that our model-based approach offers substantial improvements over the traditional approach to inference, including increased precision and the ability to make predictions for some distances other than the specific set for which experimental trials were conducted.
1991-02-01
AD-A235 622 WL-TR-91-4015 THE SYNTHESIS AND EVALUATION OF THIRD-ORDER OPTICAL NONLINEARITIES OF MODEL COMPOUNDS CONTAINING BENZOTHIAZOLE ...Nonlinearities of Model Compounds Containing Benzothiazole , Benzimidazole, and Benzoxazole Moieties 12 PERSONAL AUTHOR(S) Bruce A. Reinhardt, Marilyn R...necessary and identify by block number) FIELD GROUP SUB-GROUP nonlinear optical properties benzothiazole u/ 03 degenerate four-wave mixing benzimidazole 21
A novel rat model to study the role of intracranial pressure modulation on optic neuropathies.
Directory of Open Access Journals (Sweden)
Uttio Roy Chowdhury
Full Text Available Reduced intracranial pressure is considered a risk factor for glaucomatous optic neuropathies. All current data supporting intracranial pressure as a glaucoma risk factor comes from retrospective and prospective studies. Unfortunately, there are no relevant animal models for investigating this link experimentally. Here we report a novel rat model that can be used to study the role of intracranial pressure modulation on optic neuropathies. Stainless steel cannulae were inserted into the cisterna magna or the lateral ventricle of Sprague-Dawley and Brown Norway rats. The cannula was attached to a pressure transducer connected to a computer that recorded intracranial pressure in real-time. Intracranial pressure was modulated manually by adjusting the height of a column filled with artificial cerebrospinal fluid in relation to the animal's head. After data collection the morphological appearance of the brain tissue was analyzed. Based on ease of surgery and ability to retain the cannula, Brown Norway rats with the cannula implanted in the lateral ventricle were selected for further studies. Baseline intracranial pressure for rats was 5.5 ± 1.5 cm water (n=5. Lowering of the artificial cerebrospinal fluid column by 2 cm and 4 cm below head level reduced ICP to 3.7 ± 1.0 cm water (n=5 and 1.5 ± 0.6 cm water (n=4, a reduction of 33.0% and 72.7% below baseline. Raising the cerebrospinal fluid column by 4 cm increased ICP to 7.5 ± 1.4 cm water (n=2 corresponding to a 38.3% increase in intracranial pressure. Histological studies confirmed correct cannula placement and indicated minimal invasive damage to brain tissues. Our data suggests that the intraventricular cannula model is a unique and viable model that can be used to study the effect of altered intracranial pressure on glaucomatous optic neuropathies.
Directory of Open Access Journals (Sweden)
Bardia Yousefi
2014-01-01
Full Text Available Following the study on computational neuroscience through functional magnetic resonance imaging claimed that human action recognition in the brain of mammalian pursues two separated streams, that is, dorsal and ventral streams. It follows up by two pathways in the bioinspired model, which are specialized for motion and form information analysis (Giese and Poggio 2003. Active basis model is used to form information which is different from orientations and scales of Gabor wavelets to form a dictionary regarding object recognition (human. Also biologically movement optic-flow patterns utilized. As motion information guides share sketch algorithm in form pathway for adjustment plus it helps to prevent wrong recognition. A synergetic neural network is utilized to generate prototype templates, representing general characteristic form of every class. Having predefined templates, classifying performs based on multitemplate matching. As every human action has one action prototype, there are some overlapping and consistency among these templates. Using fuzzy optical flow division scoring can prevent motivation for misrecognition. We successfully apply proposed model on the human action video obtained from KTH human action database. Proposed approach follows the interaction between dorsal and ventral processing streams in the original model of the biological movement recognition. The attained results indicate promising outcome and improvement in robustness using proposed approach.
Directory of Open Access Journals (Sweden)
Chinwe E Abosi
2010-11-01
Full Text Available The evolution of IT and network technologies has generated far-reaching opportunities for complex service innovation in future Internet. This has resulted in an increase in the heterogeneity and complexity in service provisioning. Such complex services demand efficient coordination of distributed IT resources (storage and computing interconnected by high capacity optical networks. This paper proposes a service plane architecture as an architectural enhancement promising to handle these complexities. It implements a unified service provisioning concept that can adapt to the heterogeneous, dynamic and complex nature of emerging service requirements as well as optical network and IT resource capabilities. The main elements of the proposed architecture consist of information discovery and service discovery that require a semantic modelling framework to address heterogeneity and automation. This paper focuses on a novel semantic modelling framework which is central to the proposed service plance architecture. It is used for information description in a service-oriented environment based on Web Services Modelling Ontology (WSMO. The framework describes the information model and entities needed to communicate requirements for autonomous, homogeneous service discovery, selection and composition.
Energy Technology Data Exchange (ETDEWEB)
Han, Hwa Jeong; Kim, Beom Kyu; Park, Byung Gi [Soonchunhyang Univ., Asan (Korea, Republic of)
2016-10-15
In recent year, various fiber-optic radiation sensors using Cerenkov principle have been developed without employing any scintillators for measuring high-energy photon, electron, etc. The main advantages of the optical fibers are the remote transmission of the light signal and immunity to pressure and electromagnetic waves. Therefore, the sensors utilizing the optical fibers can be used in hazardous radiation environments, such as the high-level radiation areas of a nuclear facility. The study to be simulated a fiber-optic radiation sensor based on Cerenkov principle and to be analyzed the response characteristics of the sensor. For the aforementioned study, the GEANT simulation toolkit was used. It is able to take into all the optical properties of fibers and is found to be appropriate to realistically describe the response of fiber-optic radiation sensor. In the recently, the fiber-optic radiation sensor have been developed in nuclear industry. Because sensor can detect gamma ray in harsh nuclear environments. In this study, we analyzed response characteristics of the fiber-optic radiation sensor. We have simulated the Monte Carlo model, for detecting the Cerenkov radiation using the fiber-optic radiation sensor. And the y-axis distribution of Cerenkov photons was obtained using output file. Simulation is performed with reference to the method of the previous research, and then the simulation results exhibited a good agreement with the previous research.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Chaotic synchronization of injected multiple-quantum-well lasers of optical fiber system and a theoretical model of optical fiber chaotic secure communication system are presented by coupling a chaotic multiple-quantum-well laser synchronization system and a fiber channel. A new chaotic encoding method of chaos phase shift keying On/Off is proposed for optical fiber secure communications. Chaotic synchronization is achieved numerically in long-haul fiber system at wavelength 1.55μm. The effect of the nonlinear-phase of fiber is analyzed on chaotic signal and synchronization. A sinusoidal signal of 0.2 GHz frequency is simulated numerically with chaos masking in long-haul fiber analog communication at wavelength 1.55μm while a digital signal of 0.5 Gbit/s bit rate is simulated numerically with c1 haos masking and a rate of 0.05 Gbit/s are also simulated numerically with chaos shift keying and chaos phase shift keying On/Off in long-haul fiber digital communications at wavelength 1.55μm
Li, Hui; Fu, Zhida; Liu, Liying; Lin, Zhili; Deng, Wei; Feng, Lishuang
2017-01-01
An improved temperature-insensitive optical voltage sensor (OVS) with a reciprocal dual-crystal sensing method is proposed. The inducing principle of OVS reciprocity degradation is expounded by taking the different temperature fields of two crystals and the axis-errors of optical components into consideration. The key parameters pertaining to the system reciprocity degeneration in the dual-crystal sensing unit are investigated in order to optimize the optical sensing model based on the Maxwell's electromagnetic theory. The influencing principle of axis-angle errors on the system nonlinearity in the Pockels phase transfer unit is analyzed. Moreover, a novel axis-angle compensation method is proposed to improve the OVS measurement precision according to the simulation results. The experiment results show that the measurement precision of OVS is superior to ±0.2% in the temperature range from −40 °C to +60 °C, which demonstrates the excellent temperature stability of the designed voltage sensing system. PMID:28054951
Monitoring of shallow landslides by distributed optical fibers: insights from a physical model
Luca, Schenato; Matteo, Camporese; Luca, Palmieri; Alessandro, Pasuto; Salandin, Paolo
2017-04-01
Shallow landslides represent an extreme risk for individuals and structures due to their fast propagation and the very short time between appearance of warning signs and collapse. A lot of attention has been paid in the last decades to the analysis of activation mechanisms and to the implementation of appropriate early warning systems. Intense rainfall, stream erosion, flash floods, etc, are only few of the possible triggering factors that have been identified. All those factors may induce an increase in the forces acting and/or in the pore water pressure that eventually trigger the collapse. Due to the decrease of the shear resistance of soils, significant stresses develop at the sliding surface, determining local anomalous strain even before the collapse. This highlights the importance of monitoring the early appearance of hazardous strain fields. In light of the intrinsic lack of control and reproducibility in real cases, strain sensors have been applied in small-scale physical models and testbeds. Nonetheless, it has been observed that a reliable correlation between the landslide evolution and the strain field can be determined only by using minimally invasive sensors, while comprehensive information can be achieved at the cost of very fine spatial sampling, which represents the primary issue with small-to-medium scale physical models. It is evident how the two requirements, i.e., minimal invasiveness and high spatial resolution, are a limiting factor for standard sensor technology. In this regard, strain is one of the first variable addressed by optical fiber sensors, yet only recently for geotechnical applications and in very few case for landslide monitoring. In particular, the technology of distributed fiber optic sensors, with centimeter scale resolution, has the potential to address the aforementioned needs of small scale physical testing. In this work, for the first time, the strain field at the failure surface of a shallow landslide, reproduced in an
Vibratory response modeling and verification of a high precision optical positioning system.
Energy Technology Data Exchange (ETDEWEB)
Barraza, J.; Kuzay, T.; Royston, T. J.; Shu, D.
1999-06-18
A generic vibratory-response modeling program has been developed as a tool for designing high-precision optical positioning systems. Based on multibody dynamics theory, the system is modeled as rigid-body structures connected by linear elastic elements, such as complex actuators and bearings. The full dynamic properties of each element are determined experimentally or theoretically, then integrated into the program as inertial and stiffness matrices. Utilizing this program, the theoretical and experimental verification of the vibratory behavior of a double-multilayer monochromator support and positioning system is presented. Results of parametric design studies that investigate the influence of support floor dynamics and highlight important design issues are also presented. Overall, good matches between theory and experiment demonstrate the effectiveness of the program as a dynamic modeling tool.
Modeling and Characterization of Modified Optical Burst Switching (OBS Ring Network Using Proxy Node
Directory of Open Access Journals (Sweden)
Manoj Kumar Dutta
2012-01-01
Full Text Available This paper presents an analytical model of an optical burst switching ring network capable of handling WDM traffic intelligently. The network protocol and efficient architecture increases the data transport capability of a congested network. Here we propose an architecture to ease the traffic congestion in a ring network. The backbone of the proposed model is the use of a proxy node which is connected to a particular number of nodes, depending upon the traffic, then diverting their traffic and thereby increasing throughput. A probabilistic model for the proposed network architecture is developed employing packet queuing control to estimate the average waiting time of packets in the buffer and the average number of packets in the buffer for different incoming traffic arrival rate.
Juanes, J A; Ruisoto, P; Prats-Galino, A; Framiñán, A; Riesco, J M
2014-07-01
This study presents a computer-based tool for three-dimensional (3D) visualization of the optic pathway and oculomotor system using 3D high-resolution magnetic resonance imaging (MRI) datasets from a healthy subject. The 3D models were built as wireframe grids co-registered with MRI sections. First, 3D anatomical models were generated of the visual pathway from the eyeball to the primary visual cortex and of the cranial oculomotor nerves from the brain stem to the extrinsic eye muscles. Second, a graphical user interface allowed individual and group visualization, translation, rotation and zooming of the 3D models in different spatial positions simultaneously with MRI orthogonal cut planes. Educational and clinical applications are also discussed.
Jenny, Lee; Pang, Dan-Yang; Han, Yin-Lu; B. Tsang, M.
2014-09-01
Global phenomenological GDP08 and microscopic helium-3 optical model potentials have been recently derived. We evaluate these two potential sets by comparing the elastic scattering data of 25 MeV 3He on 16O, 18O, 19F, 23Na, 24Mg, 25Mg, 26Mg, 27Al, 28Si, 30Si, 31P, 32S, 34S, 35Cl, 37Cl, and 39K isotopes. Using the deuteron angular distributions calculated with the distorted wave Born approximation model, we extract the ground-state proton spectroscopic factors from (3He, d) reactions on the same set of nuclei. The extracted proton spectroscopic factors are compared with the large-basis shell-model calculations.
Pak, Hoyoung; Kushner, Mark J.
1990-10-01
The electron energy distribution in low-pressure pulsed power plasma switches is typically not in equilibrium with the local electric field. To simulate electron transport under these conditions a computer model has been developed and has been applied to the optically triggered pseudospark, or back-lit-thyratron (BLT). The model uses many groups of electrons divided into the ``bulk'' and the ``beam''. The bulk is represented by a fluid while the beam electrons are ballistic in nature and have not undergone significant energy-loss collisions after generation. To account for beam electrons being generated at arbitrary locations in the BLT, multiple beams are employed in the model. The commutation phase of switching in the BLT is investigated and the onset of a hollow cathode effect during switching is predicted.
Barua, Bobby; Islam, Md Rezwan
2012-01-01
Free space optics (FSO) is a promising solution for the need to very high data rate point-to point communication. FSO communication technology became popular due to its large bandwidth potential, unlicensed spectrum, excellent security and quick and inexpensive setup. Unfortunately, atmospheric turbulence-induced fading is one of the main impairments affecting FSO communications. To design a high performance communication link for the atmospheric FSO channel, it is of great importance to characterize the channel with proper model. In this paper, the modulation format is Q-ary PPM across lasers, with intensity modulation and ideal photodetectors are assumed to investigate the most efficient PDF models for FSO communication under turbulent condition. The performance results are evaluated in terms of symbol error probability (SEP) for different type of channel model and the simulation results confirm the analytical findings.
Optical modeling of sunlight by using partially coherent sources in organic solar cells.
Alaibakhsh, Hamzeh; Darvish, Ghafar
2016-03-01
We investigate the effects of coherent and partially coherent sources in optical modeling of organic solar cells. Two different organic solar cells are investigated: one without substrate and the other with a millimeter-sized glass substrate. The coherent light absorption is calculated with rigorous coupled-wave analysis. The result of this method is convolved with a distribution function to calculate the partially coherent light absorption. We propose a new formulation to accurately model sunlight as a set of partially coherent sources. In the structure with glass substrate, the accurate sunlight modeling results in the elimination of coherent effects in the thick substrate, but the coherency in other layers is not affected. Using partially coherent sources instead of coherent sources for simulations with sunlight results in a smoother absorption spectrum, but the change in the absorption efficiency is negligible.
Modeling optical and UV polarization of AGNs III. From uniform-density to clumpy regions
Marin, F; Gaskell, C M
2015-01-01
A growing body of evidence suggests that part of, if not all, scattering regions of active galactic nuclei (AGNs) are clumpy. Hence. in this paper, we run radiative transfer models in the optical/UV for a variety of AGN reprocessing regions with different distributions of clumpy scattering media. We use the latest version of the Monte Carlo code STOKES presented in the first two papers of this series to model AGN reprocessing regions of increasing morphological complexity. We replace previously uniform-density media with up to thousands of constant-density clumps. We couple a continuum source to fragmented equatorial scattering regions, polar outflows, and toroidal, obscuring dust regions and investigate a wide range of geometries. We also consider different levels of fragmentation in each scattering region to evaluate importance of fragmentation for the net polarization of the AGN. We find that, in comparison with uniform-density models, equatorial distributions of gas and dust clouds result in grayer spectr...
A Novel Statistical Channel Model for Turbulence-Induced Fading in Free-Space Optical Systems
Aminikashani, Mohammadreza; Kavehrad, Mohsen
2015-01-01
In this paper, we propose a new probability distribution function which accurately describes turbulence-induced fading under a wide range of turbulence conditions. The proposed model, termed Double Generalized Gamma (Double GG), is based on a doubly stochastic theory of scintillation and developed via the product of two Generalized Gamma (GG) distributions. The proposed Double GG distribution generalizes many existing turbulence channel models and provides an excellent fit to the published plane and spherical waves simulation data. Using this new statistical channel model, we derive closed form expressions for the outage probability and the average bit error as well as corresponding asymptotic expressions of free-space optical communication systems over turbulence channels. We demonstrate that our derived expressions cover many existing results in the literature earlier reported for Gamma-Gamma, Double-Weibull and K channels as special cases.
Sharick, Joe T.; Cook, Rebecca S.; Skala, Melissa C.
2017-02-01
Previous work has shown that cellular-level Optical Metabolic Imaging (OMI) of organoids derived from human breast cancer cell-line xenografts accurately and rapidly predicts in vivo response to therapy. To validate OMI as a predictive measure of treatment response in an immune-competent model, we used the polyomavirus middle-T (PyVmT) transgenic mouse breast cancer model. The PyVmT model includes intra-tumoral heterogeneity and a complex tumor microenvironment that can influence treatment responses. Three-dimensional organoids generated from primary PyVmT tumor tissue were treated with a chemotherapy (paclitaxel) and a PI3K inhibitor (XL147), each alone or in combination. Cellular subpopulations of response were measured using the OMI Index, a composite endpoint of metabolic response comprised of the optical redox ratio (ratio of the fluorescence intensities of metabolic co-enzymes NAD(P)H to FAD) as well as the fluorescence lifetimes of NAD(P)H and FAD. Combination treatment significantly decreased the OMI Index of PyVmT tumor organoids (padaptive immunity. Thus, this method is promising for use in humans to predict long-term treatment responses accurately and rapidly, and could aid in clinical treatment planning.
Chulhai, Dhabih V; Jensen, Lasse
2014-10-01
Raman optical activity has proven to be a powerful tool for probing the geometry of small organic and biomolecules. It has therefore been expected that the same mechanisms responsible for surface-enhanced Raman scattering may allow for similar enhancements in surface-enhanced Raman optical activity (SEROA). However, SEROA has proved to be an experimental challenge and mirror-image SEROA spectra of enantiomers have so far not been measured. There exists a handful of theories to simulate SEROA, all of which treat the perturbed molecule as a point-dipole object. To go beyond these approximations, we present two new methods to simulate SEROA: the first is a dressed-tensors model that treats the molecule as a point-dipole and point-quadrupole object; the second method is the discrete interaction model/quantum mechanical (DIM/QM) model, which considers the entire charge density of the molecule. We show that although the first method is acceptable for small molecules, it fails for a medium-sized one such as 2-bromohexahelicene. We also show that the SEROA mode intensities and signs are highly sensitive to the nature of the local electric field and gradient, the orientation of the molecule, and the surface plasmon frequency width. Our findings give some insight into why experimental SEROA, and in particular observing mirror-image SEROA for enantiomers, has been difficult.
Effective-mass model and magneto-optical properties in hybrid perovskites.
Yu, Z G
2016-06-24
Hybrid inorganic-organic perovskites have proven to be a revolutionary material for low-cost photovoltaic applications. They also exhibit many other interesting properties, including giant Rashba splitting, large-radius Wannier excitons, and novel magneto-optical effects. Understanding these properties as well as the detailed mechanism of photovoltaics requires a reliable and accessible electronic structure, on which models of transport, excitonic, and magneto-optical properties can be efficiently developed. Here we construct an effective-mass model for the hybrid perovskites based on the group theory, experiment, and first-principles calculations. Using this model, we relate the Rashba splitting with the inversion-asymmetry parameter in the tetragonal perovskites, evaluate anisotropic g-factors for both conduction and valence bands, and elucidate the magnetic-field effect on photoluminescence and its dependence on the intensity of photoexcitation. The diamagnetic effect of exciton is calculated for an arbitrarily strong magnetic field. The pronounced excitonic peak emerged at intermediate magnetic fields in cyclotron resonance is assigned to the 3D±2 states, whose splitting can be used to estimate the difference in the effective masses of electron and hole.
Bottom-Up Abstract Modelling of Optical Networks-on-Chip: From Physical to Architectural Layer
Directory of Open Access Journals (Sweden)
Alberto Parini
2012-01-01
Full Text Available This work presents a bottom-up abstraction procedure based on the design-flow FDTD + SystemC suitable for the modelling of optical Networks-on-Chip. In this procedure, a complex network is decomposed into elementary switching elements whose input-output behavior is described by means of scattering parameters models. The parameters of each elementary block are then determined through 2D-FDTD simulation, and the resulting analytical models are exported within functional blocks in SystemC environment. The inherent modularity and scalability of the S-matrix formalism are preserved inside SystemC, thus allowing the incremental composition and successive characterization of complex topologies typically out of reach for full-vectorial electromagnetic simulators. The consistency of the outlined approach is verified, in the first instance, by performing a SystemC analysis of a four-input, four-output ports switch and making a comparison with the results of 2D-FDTD simulations of the same device. Finally, a further complex network encompassing 160 microrings is investigated, the losses over each routing path are calculated, and the minimum amount of power needed to guarantee an assigned BER is determined. This work is a basic step in the direction of an automatic technology-aware network-level simulation framework capable of assembling complex optical switching fabrics, while at the same time assessing the practical feasibility and effectiveness at the physical/technological level.
Effective-mass model and magneto-optical properties in hybrid perovskites
Yu, Z. G.
2016-06-01
Hybrid inorganic-organic perovskites have proven to be a revolutionary material for low-cost photovoltaic applications. They also exhibit many other interesting properties, including giant Rashba splitting, large-radius Wannier excitons, and novel magneto-optical effects. Understanding these properties as well as the detailed mechanism of photovoltaics requires a reliable and accessible electronic structure, on which models of transport, excitonic, and magneto-optical properties can be efficiently developed. Here we construct an effective-mass model for the hybrid perovskites based on the group theory, experiment, and first-principles calculations. Using this model, we relate the Rashba splitting with the inversion-asymmetry parameter in the tetragonal perovskites, evaluate anisotropic g-factors for both conduction and valence bands, and elucidate the magnetic-field effect on photoluminescence and its dependence on the intensity of photoexcitation. The diamagnetic effect of exciton is calculated for an arbitrarily strong magnetic field. The pronounced excitonic peak emerged at intermediate magnetic fields in cyclotron resonance is assigned to the 3D±2 states, whose splitting can be used to estimate the difference in the effective masses of electron and hole.
Directory of Open Access Journals (Sweden)
Lei Zhu, Ning Guo, Quanzheng Li, Ying Ma, Orit Jacboson, Seulki Lee, Hak Soo Choi, James R. Mansfield, Gang Niu, Xiaoyuan Chen
2012-01-01
Full Text Available Purpose: The aim of this study is to determine if dynamic optical imaging could provide comparable kinetic parameters to that of dynamic PET imaging by a near-infrared dye/64Cu dual-labeled cyclic RGD peptide.Methods: The integrin αvβ3 binding RGD peptide was conjugated with a macrocyclic chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA for copper labeling and PET imaging and a near-infrared dye ZW-1 for optical imaging. The in vitro biological activity of RGD-C(DOTA-ZW-1 was characterized by cell staining and receptor binding assay. Sixty-min dynamic PET and optical imaging were acquired on a MDA-MB-435 tumor model. Singular value decomposition (SVD method was applied to compute the dynamic optical signal from the two-dimensional optical projection images. Compartment models were used to quantitatively analyze and compare the dynamic optical and PET data.Results: The dual-labeled probe 64Cu-RGD-C(DOTA-ZW-1 showed integrin specific binding in vitro and in vivo. The binding potential (Bp derived from dynamic optical imaging (1.762 ± 0.020 is comparable to that from dynamic PET (1.752 ± 0.026.Conclusion: The signal un-mixing process using SVD improved the accuracy of kinetic modeling of 2D dynamic optical data. Our results demonstrate that 2D dynamic optical imaging with SVD analysis could achieve comparable quantitative results as dynamic PET imaging in preclinical xenograft models.
The optical model potential of the $\\Sigma$ hyperon in nuclear matter
Dabrowski, J; Rozynek, J.
2009-01-01
We present our attempts to determine the optical model potential $U_\\Sigma = V_\\Sigma -iW_\\Sigma$ of the $\\Sigma$ hyperon in nuclear matter. We analyze the following sources of information on $U_\\Sigma$: $\\Sigma N$ scattering, $\\Sigma^-$ atoms, and final state interaction of $\\Sigma$ hyperons in the $(\\pi,K^+)$ and $(K^-.\\pi)$ reactions on nuclear targets. We conclude that $V_\\Sigma$ is repulsive inside the nucleus and has a shallow a tractive pocket at the nuclear surface. These features of ...
Three-body recombination at finite energy within an optical model
DEFF Research Database (Denmark)
Sørensen, Peder Klokmose; V. Fedorov, D.; S. Jensen, A.;
2013-01-01
We investigate three-boson recombination of equal mass systems as function of (negative) scattering length, mass, finite energy, and finite temperature. An optical model with an imaginary potential at short distance reproduces experimental recombination data and allows us to provide a simple...... parametrization of the recombination rate as function of scattering length and energy. Using the two-body van der Waals length as unit we find that the imaginary potential range and also the potential depth agree to within thirty percent for Lithium and Cesium atoms. As opposed to recent studies suggesting...
Modeling the Radio and Optical/NIR Afterglows of GRB 980703: a Numerical Study
Kong, S. W.; Huang, Y. F.
2008-10-01
GRB 980703 has extensive available multiband afterglow data. Especially, its radio afterglows were very bright and monitored until more than 1000 days after the trigger time. This makes GRB 980703 a precious sample in GRB research. We calculate the radio and optical/NIR afterglows of GRB 980703 numerically, by using a set of generic dynamical equations. It is found that the observations consist with the theoretical expectation of the standard fireball model well. Our result suggests that the jet opening angle is ~13°, the number density of the surrounding medium is ~30 cm-3, and the isotropic equivalent kinetic energy of the explosion is ~3.8×1052 ergs.
Modeling of nonlinear optic and ESR response of CDW MX materials
Energy Technology Data Exchange (ETDEWEB)
Saxena, A.; Gammel, J.T.; Bishop, A.R. [Los Alamos National Lab., NM (United States); Shuai, Z.; Bredas, J.L. [Center de Recherche en Electronique et Photonique Moleculaires, Universite de Mons-Hainaut (Belgium); Batistic, I. [Zagreb Univ. (Croatia). Dept. of Physics; Alouani, M. [Ohio State Univ., Columbus, OH (United States). Dept. of Physics
1994-09-01
We report results on the nonlinear optic and ESR response of the PtX MX chain materials calculated using a discrete, 3/4-filled, two-band, tight-binding Peierls-Hubbard model. We calculated electroabsorption (EA) spectra for the three PtX (X=Cl, Br, 1) charge-density-wave (CDW) materials and find good agreement with the experimental data. We also obtain EA spectra for localized defects in PtBr. In addition, the field orientation dependence of the electron spin resonance spectra associated with the spin carrying defects is calculated for PtX materials and compared with ESR data on photoinduced defects.
Directory of Open Access Journals (Sweden)
Catalina Hurtado Castano
2016-01-01
Full Text Available A detailed procedure is presented to compute analytically the acoustooptic coupling coefficient between copropagating core and lowest-order cladding modes in tapered fiber optics. Based on the effect of the local bending, the linear and nonlinear variations in the refractive index are modeled. A set of equations and parameters are presented in order to calculate the influence of acoustooptic effect in nonlinear pulse propagation. We will show that as the tapered fiber diameter decreases more energy can be transferred to the cladding and the nonlinear phenomena can compensate the coupling coefficients effects.
ABAREX -- A neutron spherical optical-statistical-model code -- A user`s manual
Energy Technology Data Exchange (ETDEWEB)
Smith, A.B. [ed.; Lawson, R.D.
1998-06-01
The contemporary version of the neutron spherical optical-statistical-model code ABAREX is summarized with the objective of providing detailed operational guidance for the user. The physical concepts involved are very briefly outlined. The code is described in some detail and a number of explicit examples are given. With this document one should very quickly become fluent with the use of ABAREX. While the code has operated on a number of computing systems, this version is specifically tailored for the VAX/VMS work station and/or the IBM-compatible personal computer.
Charrois, Luc; Cosme, Emmanuel; Dumont, Marie; Lafaysse, Matthieu; Morin, Samuel; Libois, Quentin; Picard, Ghislain
2016-05-01
This paper examines the ability of optical reflectance data assimilation to improve snow depth and snow water equivalent simulations from a chain of models with the SAFRAN meteorological model driving the detailed multilayer snowpack model Crocus now including a two-stream radiative transfer model for snow, TARTES. The direct use of reflectance data, allowed by TARTES, instead of higher level snow products, mitigates uncertainties due to commonly used retrieval algorithms.Data assimilation is performed with an ensemble-based method, the Sequential Importance Resampling Particle filter, to represent simulation uncertainties. In snowpack modeling, uncertainties of simulations are primarily assigned to meteorological forcings. Here, a method of stochastic perturbation based on an autoregressive model is implemented to explicitly simulate the consequences of these uncertainties on the snowpack estimates.Through twin experiments, the assimilation of synthetic spectral reflectances matching the MODerate resolution Imaging Spectroradiometer (MODIS) spectral bands is examined over five seasons at the Col du Lautaret, located in the French Alps. Overall, the assimilation of MODIS-like data reduces by 45 % the root mean square errors (RMSE) on snow depth and snow water equivalent. At this study site, the lack of MODIS data on cloudy days does not affect the assimilation performance significantly. The combined assimilation of MODIS-like reflectances and a few snow depth measurements throughout the 2010/2011 season further reduces RMSEs by roughly 70 %. This work suggests that the assimilation of optical reflectances has the potential to become an essential component of spatialized snowpack simulation and forecast systems. The assimilation of real MODIS data will be investigated in future works.
Loch, R A; Sobierajski, R; Louis, E; Bosgra, J; Bijkerk, F
2012-12-17
The single shot damage thresholds of multilayer optics for high-intensity short-wavelength radiation sources are theoretically investigated, using a model developed on the basis of experimental data obtained at the FLASH and LCLS free electron lasers. We compare the radiation hardness of commonly used multilayer optics and propose new material combinations selected for a high damage threshold. Our study demonstrates that the damage thresholds of multilayer optics can vary over a large range of incidence fluences and can be as high as several hundreds of mJ/cm(2). This strongly suggests that multilayer mirrors are serious candidates for damage resistant optics. Especially, multilayer optics based on Li(2)O spacers are very promising for use in current and future short-wavelength radiation sources.
Vogel, Andreas; Durant, Adam; Sytchkova, Anna; Diplas, Spyros; Bonadonna, Costanza; Scarnato, Barbara; Krüger, Kirstin; Kylling, Arve; Kristiansen, Nina; Stohl, Andreas
2016-04-01
Explosive volcanic eruptions emit up to 50 wt.% (total erupted mass) of fine ash particles (threat for aviation operations. Recent volcanic eruptions, such as the 2010 Icelandic Eyjafjallajökull event, illustrated how volcanic ash can severely impact commercial air traffic. In order to manage the threat, it is important to have accurate forecast information on the spatial extent and absolute quantity of airborne volcanic ash. Such forecasts are constrained by empirically-derived estimates of the volcanic source term and the nature of the constituent volcanic ash properties. Consequently, it is important to include a quantitative assessment of measurement uncertainties of ash properties to provide realistic ash forecast uncertainty. Currently, information on volcanic ash physicochemical and optical properties is derived from a small number of somewhat dated publications. In this study, we provide a reference dataset for physical (size distribution and shape), chemical (bulk vs. surface chemistry) and optical properties (complex refractive index in the UV-vis-NIR range) of a representative selection of volcanic ash samples from 10 different volcanic eruptions covering the full variability in silica content (40-75 wt.% SiO2). Through the combination of empirical analytical methods (e.g., image analysis, Energy Dispersive Spectroscopy, X-ray Photoelectron Spectroscopy, Transmission Electron Microscopy and UV/Vis/NIR/FTIR Spectroscopy) and theoretical models (e.g., Bruggeman effective medium approach), it was possible to fully capture the natural variability of ash physicochemical and optical characteristics. The dataset will be applied in atmospheric measurement retrievals and atmospheric transport modelling to determine the sensitivity to uncertainty in ash particle characteristics.
Jones, A P
2015-01-01
Context. The properties of hydrogenated amorphous carbon (a-C:H) dust are known to evolve in response to the local conditions. Aims. We present an adaptable model for the determination of the optical properties of low-temperature, interstellar a-C:H grains that is based on the fundamental physics of their composition. Methods. The imaginary part of the refractive index, k, for a-C:H materials, from 50 eV to cm wavelengths, is derived and the real part, n, of the refractive index is then calculated using the Kramers-Kronig relations. Results. The formulated optEC(s) model allows a determination of the complex dielectric function, epsilon, and refractive index, m(n, k), for a-C:H materials as a continuous function the band gap, Eg , which is shown to lie in the range = -0.1 to 2.7 eV. We provide expressions that enable a determination of their optical constants and tabulate m(n, k, Eg ) for 14 different values of Eg . We explore the evolution of the likely extinction and emission behaviours of a-C:H grains and ...
Li, Mengnan; Tan, Liying; Ma, Jing; Yu, Siyuan; Yang, Qingbo; Wu, Jiajie
2016-05-01
Based on the characteristics of the laser device and the inevitable error of the processing technique, a laser beam emitted from a communication terminal can be represented by the Gaussian Schell model (GSM). In space-to-ground link laser communications, the optical intensity is affected by the source coherence parameter and the zenith angle. With full consideration of these two parameters, the statistical distribution model of the optical intensity with a GSM laser in both downlink and uplink is derived. The simulation results indicate that increasing the source coherence parameter has an effect on the statistical distribution of the optical intensity; this effect is highly similar to the effect of a larger zenith angle. The optical intensity invariably degrades with increasing source coherence parameter or zenith angle. The results of this work can promote the improvement of the redundancy design of a laser communication receiver system.
Li, Jun-Bao
2012-09-01
This paper presents Gabor filter based optical image recognition using Fractional Power Polynomial model based Common Kernel Discriminant Locality Preserving Projection. This method tends to solve the nonlinear classification problem endured by optical image recognition owing to the complex illumination condition in practical applications, such as face recognition. The first step is to apply Gabor filter to extract desirable textural features characterized by spatial frequency, spatial locality and orientation selectivity to cope with the variations in illumination. In the second step we propose Class-wise Locality Preserving Projection through creating the nearest neighbor graph guided by the class labels for the textural features reduction. Finally we present Common Kernel Discriminant Vector with Fractional Power Polynomial model to reduce the dimensions of the textural features for recognition. For the performance evaluation on optical image recognition, we test the proposed method on a challenging optical image recognition problem, face recognition.
Walder, Cordula; Lacombe, Jürgen; von Maydell, Karsten; Agert, Carsten
2012-06-01
This article deals with an optical model which describes silicon thin film solar cells with rough interfaces in a fast and easy way. In order to simulate thin layer stacks with rough interfaces diffuse scattering as well as interference effects have to be taken into account. Algorithms like the Finite-Difference Time-Domain method (FDTD) solve the Maxwell Equations and therefore fulfil these demands. Yet they take up a considerable amount of simulation time and computation capacity. To overcome these drawbacks an optical model was developed which combines the Transfer- Matrix-Method (TMM) and the Raytracer algorithm. The fraction of TMM and Raytracer in the model is determined by a separating function which can be interpreted as the integral haze. In order to verify the combined optical model a series of amorphous silicon single cells with varying intrinsic layer thicknesses was produced on two different kinds of textured substrates. The results of the combined optical model are compared to measured data as well as to the simulation results of the FDTD method. It can be shown that the combined optical model yields good results at low simulation time.
Effect of RSCs combined with COP-1 on optic nerve damage in glaucoma rat model
Institute of Scientific and Technical Information of China (English)
Wei-Cai Fu; Yan Jiang; Lin Zhang
2014-01-01
Objective: To explore effect of retinal stem cells (RSCs) combined with copolymer-1 (COP-1) immunotherapy on optic nerve damage in glaucoma rat model. Methods: A total of 40 SD rats were selected for glaucoma model and were randomly divided into 4 groups to observe protective effects of RSCs transplantation combined with COP-1. Results: Brain-derived neurotrophic factor (BDNF) and insulin like growth factor-1 (IGF-1) were either positive in retina of RSCs transplanted or COP-1 immunological treated rat. Positive rate of BDNF and IGF-1 and expression of mRNA and protein were significantly higher in RSCs transplantation combined with COP-1 immunotherapy treated rats compared with the other 3 groups, in which amount of apoptotic RGCs was lowest. Conclusions: RSCs transplantation combined with COP-1 immunotherapy can promote the secretion of BDNF and IGF-1. They protect RGCs in glaucoma rats in coordination, significantly reduce the number of apoptosis RGCs so as to alleviate the optic nerve damage. It ponits a new research direction for treatment of glaucoma.
Nuclear mean field and double-folding model of the nucleus-nucleus optical potential
Khoa, Dao T; Loan, Doan Thi; Loc, Bui Minh
2016-01-01
Realistic density dependent CDM3Yn versions of the M3Y interaction have been used in an extended Hartree-Fock (HF) calculation of nuclear matter (NM), with the nucleon single-particle potential determined from the total NM energy based on the Hugenholtz-van Hove theorem that gives rise naturally to a rearrangement term (RT). Using the RT of the single-nucleon potential obtained exactly at different NM densities, the density- and energy dependence of the CDM3Yn interactions was modified to account properly for both the RT and observed energy dependence of the nucleon optical potential. Based on a local density approximation, the double-folding model of the nucleus-nucleus optical potential has been extended to take into account consistently the rearrangement effect and energy dependence of the nuclear mean-field potential, using the modified CDM3Yn interactions. The extended double-folding model was applied to study the elastic $^{12}$C+$^{12}$C and $^{16}$O+$^{12}$C scattering at the refractive energies, wher...
Placati, Silvio; Guermandi, Marco; Samore, Andrea; Franchi Scarselli, Eleonora; Guerrieri, Roberto
2015-11-26
Diffuse Optical Tomography is an imaging technique based on evaluating how light propagates within the human head to obtain functional information about the brain. Precision in reconstructing such an optical properties map is highly affected by the accuracy of the light propagation model implemented, which needs to take into account the presence of clear and scattering tissues. We present a numerical solver based on the radiosity-diffusion model integrating the anatomical information provided by a structural MRI. The solver is designed to run on parallel heterogeneous platforms based on multiple GPUs and CPUs. We demonstrate how the solver provides a 7x speed-up over an isotropic-scattered parallel Monte Carlo engine based on a Radiative Transport Equation for a domain composed of 2 millions voxels, along with a significant improvement in accuracy. The speed-up greatly increases for larger domains, allowing us to compute the light distribution of a full human head ( 3 million voxels) in 116 seconds for the platform used.
Optical model for port-wine stain skin and its Monte Carlo simulation
Xu, Lanqing; Xiao, Zhengying; Chen, Rong; Wang, Ying
2008-12-01
Laser irradiation is the most acceptable therapy for PWS patient at present time. Its efficacy is highly dependent on the energy deposition rules in skin. To achieve optimal PWS treatment parameters a better understanding of light propagation in PWS skin is indispensable. Traditional Monte Carlo simulations using simple geometries such as planar layer tissue model can not provide energy deposition in the skin with enlarged blood vessels. In this paper the structure of normal skin and the pathological character of PWS skin was analyzed in detail and the true structure were simplified into a hybrid layered mathematical model to character two most important aspects of PWS skin: layered structure and overabundant dermal vessels. The basic laser-tissue interaction mechanisms in skin were investigated and the optical parameters of PWS skin tissue at the therapeutic wavelength. Monte Carlo (MC) based techniques were choused to calculate the energy deposition in the skin. Results can be used in choosing optical dosage. Further simulations can be used to predict optimal laser parameters to achieve high-efficacy laser treatment of PWS.
Three-Dimensional Electron Optics Model Developed for Traveling-Wave Tubes
Kory, Carol L.
2000-01-01
A three-dimensional traveling-wave tube (TWT) electron beam optics model including periodic permanent magnet (PPM) focusing has been developed at the NASA Glenn Research Center at Lewis Field. This accurate model allows a TWT designer to develop a focusing structure while reducing the expensive and time-consuming task of building the TWT and hot-testing it (with the electron beam). In addition, the model allows, for the first time, an investigation of the effect on TWT operation of the important azimuthally asymmetric features of the focusing stack. The TWT is a vacuum device that amplifies signals by transferring energy from an electron beam to a radiofrequency (RF) signal. A critically important component is the focusing structure, which keeps the electron beam from diverging and intercepting the RF slow wave circuit. Such an interception can result in excessive circuit heating and decreased efficiency, whereas excessive growth in the beam diameter can lead to backward wave oscillations and premature saturation, indicating a serious reduction in tube performance. The most commonly used focusing structure is the PPM stack, which consists of a sequence of cylindrical iron pole pieces and opposite-polarity magnets. Typically, two-dimensional electron optics codes are used in the design of magnetic focusing devices. In general, these codes track the beam from the gun downstream by solving equations of motion for the electron beam in static-electric and magnetic fields in an azimuthally symmetric structure. Because these two-dimensional codes cannot adequately simulate a number of important effects, the simulation code MAFIA (solution of Maxwell's equations by the Finite-Integration-Algorithm) was used at Glenn to develop a three-dimensional electron optics model. First, a PPM stack was modeled in three dimensions. Then, the fields obtained using the magnetostatic solver were loaded into a particle-in-cell solver where the fully three-dimensional behavior of the beam
Generalized Ocean Color Inversion Model for Retrieving Marine Inherent Optical Properties
Werdell, P. Jeremy; Franz, Bryan A.; Bailey, Sean W.; Feldman, Gene C.; Boss, Emmanuel; Brando, Vittorio E.; Dowell, Mark; Hirata, Takafumi; Lavender, Samantha J.; Lee, ZhongPing; Loisel, Hubert; Maritorena, Stephane; Melin, Frederic; Moore, Timothy S.; Smyth, TImothy J.; Antoine, David; Devred, Emmanuel; Fantond'Andon, Odile Hembise; Mangin, Antoine
2013-01-01
Ocean color measured from satellites provides daily, global estimates of marine inherent optical properties (IOPs). Semi-analytical algorithms (SAAs) provide one mechanism for inverting the color of the water observed by the satellite into IOPs. While numerous SAAs exist, most are similarly constructed and few are appropriately parameterized for all water masses for all seasons. To initiate community-wide discussion of these limitations, NASA organized two workshops that deconstructed SAAs to identify similarities and uniqueness and to progress toward consensus on a unified SAA. This effort resulted in the development of the generalized IOP (GIOP) model software that allows for the construction of different SAAs at runtime by selection from an assortment of model parameterizations. As such, GIOP permits isolation and evaluation of specific modeling assumptions, construction of SAAs, development of regionally tuned SAAs, and execution of ensemble inversion modeling. Working groups associated with the workshops proposed a preliminary default configuration for GIOP (GIOP-DC), with alternative model parameterizations and features defined for subsequent evaluation. In this paper, we: (1) describe the theoretical basis of GIOP; (2) present GIOP-DC and verify its comparable performance to other popular SAAs using both in situ and synthetic data sets; and, (3) quantify the sensitivities of their output to their parameterization. We use the latter to develop a hierarchical sensitivity of SAAs to various model parameterizations, to identify components of SAAs that merit focus in future research, and to provide material for discussion on algorithm uncertainties and future ensemble applications.
An Enhanced Mathematical Model for Performance Evaluation of Optical Burst Switched Networks
Morsy, Mohamed H S; Shalaby, Hossam M H
2008-01-01
An enhanced mathematical model is introduced to study and evaluate the performance of a core node in an optical burst switched network. In the proposed model, the exact Poisson traffic arrivals to the OBS node is approximated by assuming that the maximum allowed number of arrivals to the OBS node, in a given time slot, is two (instead of infinity). A detailed state diagram is outlined to illustrate the problem, and then a mathematical model based on the equilibrium point analysis (EPA) technique is presented. The steady-state system throughput is derived from the model which is built in the absence of wavelength conversion capability. Our proposed model is aided by a simulation work which studies the performance of an OBS core node under the assumption of Poisson traffic arrivals (the exact case) and calculates the steady-state system throughput. The results obtained from the proposed mathematical model are consistent with that of simulation when assuming Poisson traffic arrivals and this consistency holds fo...
Model reduction of cavity nonlinear optics for photonic logic: a quasi-principal components approach
Shi, Zhan; Nurdin, Hendra I.
2016-11-01
Kerr nonlinear cavities displaying optical thresholding have been proposed for the realization of ultra-low power photonic logic gates. In the ultra-low photon number regime, corresponding to energy levels in the attojoule scale, quantum input-output models become important to study the effect of unavoidable quantum fluctuations on the performance of such logic gates. However, being a quantum anharmonic oscillator, a Kerr-cavity has an infinite dimensional Hilbert space spanned by the Fock states of the oscillator. This poses a challenge to simulate and analyze photonic logic gates and circuits composed of multiple Kerr nonlinearities. For simulation, the Hilbert of the oscillator is typically truncated to the span of only a finite number of Fock states. This paper develops a quasi-principal components approach to identify important subspaces of a Kerr-cavity Hilbert space and exploits it to construct an approximate reduced model of the Kerr-cavity on a smaller Hilbert space. Using this approach, we find a reduced dimension model with a Hilbert space dimension of 15 that can closely match the magnitudes of the mean transmitted and reflected output fields of a conventional truncated Fock state model of dimension 75, when driven by an input coherent field that switches between two levels. For the same input, the reduced model also closely matches the magnitudes of the mean output fields of Kerr-cavity-based AND and NOT gates and a NAND latch obtained from simulation of the full 75 dimension model.
Directory of Open Access Journals (Sweden)
A. M. Sayer
2010-11-01
Full Text Available The comparison of satellite and model aerosol optical depth (AOD fields provides useful information on the strengths and weaknesses of both. However, the sampling of satellite and models is very different and some subjective decisions about data selection and aggregation must be made in order to perform such comparisons. This work examines some implications of these decisions, using GlobAerosol AOD retrievals at 550 nm from Advanced Along-Track Scanning Radiometer (AATSR measurements, and aerosol fields from the GEOS-Chem chemistry transport model. It is recommended to sample the model only where the satellite flies over on a particular day; neglecting this can cause regional differences in model AOD of up to 0.1 on monthly and annual timescales. The comparison is observed to depend strongly upon thresholds for sparsity of satellite retrievals in the model grid cells. Requiring at least 25% coverage of the model grid cell by satellite data decreases the observed difference between the two by approximately half over land. The impact over ocean is smaller. In both model and satellite datasets, there is an anticorrelation between the proportion p of a model grid cell covered by satellite retrievals and the AOD. This is attributed to small p typically occuring due to high cloud cover and lower AODs being found in large clear-sky regions. Daily median AATSR AODs were found to be closer to GEOS-Chem AODs than daily means (with the root mean squared difference being approximately 0.05 smaller. This is due to the decreased sensitivity of medians to outliers such as cloud-contaminated retrievals, or aerosol point sources not included in the model.
Mathematical model of thermal shields for long-term stability optical resonators
Sanjuan, Josep; Braxmaier, Claus
2015-01-01
Modern experiments aiming at tests of fundamental physics, like measuring gravitational waves or testing Lorentz Invariance with unprecedented accuracy, require thermal environments that are highly stable over long times. To achieve such a stability, the experiment including typically an optical resonator is nested in a thermal enclosure, which passively attenuates external temperature fluctuations to acceptable levels. These thermal shields are usually designed using tedious numerical simulations or with simple analytical models. In this paper, we propose an accurate analytical method to estimate the performance of passive thermal shields in the frequency domain, which allows for fast evaluation and optimization. The model analysis has also unveil interesting properties of the shields, such as dips in the transfer function for some frequencies under certain combinations of materials and geometries. We validate the results by comparing them to numerical simulations performed with commercial software based on ...
Martínez, Francisco J; Márquez, Andrés; Gallego, Sergi; Francés, Jorge; Pascual, Inmaculada; Beléndez, Augusto
2014-02-15
A polarimetric method for the measurement of linear retardance in the presence of phase fluctuations is presented. This can be applied to electro-optic devices behaving as variable linear retarders. The method is based on an extended Mueller matrix model for the linear retarder containing the time-averaged effects of the instabilities. As a result, an averaged Stokes polarimetry technique is proposed to characterize both the retardance and its flicker magnitude. Predictive capability of the approach is experimentally demonstrated, validating the model and the calibration technique. The approach is applied to liquid crystal on silicon displays (LCoS) using a commercial Stokes polarimeter. Both the magnitude of the average retardance and the amplitude of its fluctuation are obtained for each gray level value addressed, thus enabling a complete phase characterization of the LCoS.
Comparing mesoscale chemistry-transport model and remote-sensed Aerosol Optical Depth
Carnevale, C; Pisoni, E; Volta, M
2010-01-01
A comparison of modeled and observed Aerosol Optical Depth (AOD) is presented. 3D Eulerian multiphase chemistry-transport model TCAM is employed for simulating AOD at mesoscale. MODIS satellite sensor and AERONET photometer AOD are used for comparing spatial patterns and temporal timeseries. TCAM simulations for year 2004 over a domain containing Po-Valley and nearly whole Northern Italy are employed. For the computation of AOD, a configuration of external mixing of the chemical species is considered. Furthermore, a parametrization of the effect of moisture affecting both aerosol size and composition is used. An analysis of the contributions of the granulometric classes to the extinction coefficient reveals the dominant role of the inorganic compounds of submicron size. For the analysis of spatial patterns, summer and winter case study are considered. TCAM AOD reproduces spatial patterns similar to those retrieved from space, but AOD values are generally smaller by an order of magnitude. However, accounting a...
Proposal for the Quantum Simulation of the CP(2) Model on Optical Lattices
Laflamme, Catherine; Dalmonte, Marcello; Gerber, Urs; Mejía-Díaz, Héctor; Bietenholz, Wolfgang; Wiese, Uwe-Jens; Zoller, Peter
2015-01-01
The 2d CP(N-1) models share a number of features with QCD, like asymptotic freedom, a dynamically generated mass gap and topological sectors. They have been formulated and analysed successfully in the framework of the so-called D-theory, which provides a smooth access to the continuum limit. In that framework, we propose an experimental set-up for the quantum simulation of the CP(2) model. It is based on ultra-cold Alkaline-Earth Atoms (AEAs) located on the sites of an optical lattice, where the nuclear spins represent the relevant degrees of freedom. We present numerical results for the correlation length and for the real time decay of a false vacuum, to be compared with such a future experiment. The latter could also enable the exploration of theta-vacua and of the phase diagram at finite chemical potentials, since it does not suffer from any sign problem.
Fabrication and comprehensive modeling of ion-exchanged Bragg optical add-drop multiplexers.
Castro, Jose M; Geraghty, David F; West, Brian R; Honkanen, Seppo
2004-11-20
Optical add-drop multiplexers (OADMs) based on asymmetric Y branches and tilted gratings offer excellent-performance in wavelength-division multiplexed systems. To simplify waveguide fabrication, ion-exchange techniques appear to be an important option in photosensitive glasses. Optimum OADM performance depends on how accurately the waveguide fabrication process and tilted Bragg grating operation are understood and modeled. Results from fabrication and comprehensive modeling are compared for ion-exchange processes that use different angles of the tilted grating. The transmission and reflection spectra for the fabricated and simulated OADMs show excellent agreement. The OADM's performance is evaluated in terms of the measured characteristics of the Y branches and tilted gratings.
A physical optics/equivalent currents model for the RCS of trihedral corner reflectors
Balanis, Constantine A.; Polycarpou, Anastasis C.
1993-07-01
The scattering in the interior regions of both square and triangular trihedral corner reflectors is examined. The theoretical model presented combines geometrical and physical optics (GO and PO), used to account for reflection terms, with equivalent edge currents (EEC), used to account for first-order diffractions from the edges. First-order, second-order, and third-order reflection terms are included. Calculating the first-order reflection terms involves integrating over the entire surface of the illuminated plate. Calculating the second- and third-order reflection terms, however, is much more difficult because the illuminated area is an arbitrary polygon whose shape is dependent upon the incident angles. The method for determining the area of integration is detailed. Extensive comparisons between the high-frequency model, Finite-Difference Time-Domain (FDTD) and experimental data are used for validation of the radar cross section (RCS) of both square and triangular trihedral reflectors.
Analytical models of icosahedral shells for 3D optical imaging of viruses
Jafarpour, Aliakbar
2014-01-01
A modulated icosahedral shell with an inclusion is a concise description of many viruses, including recently-discovered large double-stranded DNA ones. Many X-ray scattering patterns of such viruses show major polygonal fringes, which can be reproduced in image reconstruction with a homogeneous icosahedral shell. A key question regarding a low-resolution reconstruction is how to introduce further changes to the 3D profile in an efficient way with only a few parameters. Here, we derive and compile different analytical models of such an object with consideration of practical optical setups and typical structures of such viruses. The benefits of such models include 1) inherent filtering and suppressing different numerical errors of a discrete grid, 2) providing a concise and meaningful set of descriptors for feature extraction in high-throughput classification/sorting and higher-resolution cumulative reconstructions, 3) disentangling (physical) resolution from (numerical) discretization step and having a vector ...
Optical diagnostics and mathematical models of intracellular protoplasmic mobility in amoeboid cells
Romanovsky, Yury M.; Priezzhev, Alexander V.; Pavlov, Dimitry A.; Teplov, Vladimir A.
1996-05-01
A review of the optical methods designed for the study of intracellular protoplasmic streaming is presented. While in case of low streaming velocities (less than 10 mcm/s) the computer analysis of the images of moving protoplasm is effective, for higher velocities the laser Doppler microscopy has an advantage. With the help of the Doppler technique it is possible to determine the velocity profiles for nonstationary protoplasmic streamings in amoeboid cells. These data and also complex time changes of protoplasmic flow in response to external factors enable to determine and to specify parameters used for designing mathematical models of intracellular dynamics. As an example, results of experiments, modelling and simulations are presented for myxomycete plasmodium Physarum polycephalum which is a huge cell with typical amoeboid properties.
Robinson, Mitchell; Butcher, Ryan; Coté, Gerard L.
2017-02-01
Monte Carlo modeling of photon propagation has been used in the examination of particular areas of the body to further enhance the understanding of light propagation through tissue. This work seeks to improve upon the established simulation methods through more accurate representations of the simulated tissues in the wrist as well as the characteristics of the light source. The Monte Carlo simulation program was developed using Matlab. Generation of different tissue domains, such as muscle, vasculature, and bone, was performed in Solidworks, where each domain was saved as a separate .stl file that was read into the program. The light source was altered to give considerations to both viewing angle of the simulated LED as well as the nominal diameter of the source. It is believed that the use of these more accurate models generates results that more closely match those seen in-vivo, and can be used to better guide the design of optical wrist-worn measurement devices.
Test of the notch technique for determining the radial sensitivity of the optical model potential
Yang, Lei; Jia, Hui-ming; Xu, Xin-Xing; Ma, Nan-Ru; Sun, Li-Jie; Yang, Feng; Zhang, Huan-Qiao; Li, Zu-Hua; Wang, Dong-Xi
2015-01-01
Detailed investigations on the notch technique are performed on the ideal data generated by the optical model potential parameters extracted from the 16O+208Pb system at the laboratory energy of 129.5 MeV, to study the sensitivities of this technique on the model parameters as well as the experimental data. It is found that, for the perturbation parameters, a sufficient large reduced fraction and an appropriate small perturbation width are necessary to determine the accurate radial sensitivity; while for the potential parameters, almost no dependence was observed. For the experimental measurements, the number of data points has little influence for the heavy target system, and the relative inner information of the nuclear potential can be derived when the measurement extended to a lower cross section.
DEFF Research Database (Denmark)
Reck, Kasper; Almind, Ninia Sejersen; Mar, Mikkel Dysseholm;
2009-01-01
We present modeling and design of an all-optical MEMS Bragg grating (half-pitch of 125 nm) strain sensor for single-fiber distributed sensing. Low optical loss and the use of frequency modulation rather than amplitude modulation, makes this sensor better suited for distributed systems than...... mechanical amplification can be obtained if using an angled double beam micrometer scale MEMS structure, compared to conventional fiber Bragg grating sensors. An optimized design and fabrication process is presented....
Directory of Open Access Journals (Sweden)
N. E. Rosário
2013-03-01
Full Text Available Intra-seasonal variability of smoke aerosol optical depth (AOD and downwelling solar irradiance at the surface during the 2002 biomass burning season in South America was modeled using the Coupled Chemistry-Aerosol-Tracers Transport model with the Brazilian developments on the Regional Atmospheric Modeling System (CCATT-BRAMS. Measurements of total and fine mode fraction (FMF AOD from the AErosol RObotic NETwork (AERONET and solar irradiance at the surface from the Solar Radiation Network (SolRad-NET were used to evaluate model results. In general, the major features associated with AOD evolution over the southern part of the Amazon basin and cerrado ecosystem are captured by the model. The main discrepancies were found for high aerosol loading events. In the northeastern portion of the Amazon basin the model systematically underestimated total AOD, as expected, since smoke contribution is not dominant as it is in the southern portion and emissions other than smoke were not considered in the simulation. Better agreement was obtained comparing the model results with observed FMF AOD, which pointed out the relevance of coarse mode aerosol emission in that region. Likewise, major discrepancies over cerrado during high AOD events were found to be associated with coarse mode aerosol omission in our model. The issue of high aerosol loading events in the southern part of the Amazon was related to difficulties in predicting the smoke AOD field, which was discussed in the context of emissions shortcomings. The Cuiabá cerrado site was the only one where the highest quality AERONET data were unavailable for both total and FMF AOD. Thus, lower quality data were used. Root-mean-square error (RMSE between the model and observed FMF AOD decreased from 0.34 to 0.19 when extreme AOD events (FMF AOD550 nm ≥ 1.0 and Cuiabá were excluded from the analysis. Downward surface solar irradiance comparisons also followed similar trends when extreme AOD were excluded
Model Analysis of Influences of Aerosol Mixing State upon Its Optical Properties in East Asia
Institute of Scientific and Technical Information of China (English)
HAN Xiao; ZHANG Meigen; ZHU Lingyun; XU Liren
2013-01-01
The air quality model system RAMS (Regional Atmospheric Modeling System)-CMAQ (Models-3 Community Multi-scale Air Quality) coupled with an aerosol optical/radiative module was applied to investigate the impact of different aerosol mixing states (i.e.,externally mixed,half externally and half internally mixed,and internally mixed) on radiative forcing in East Asia.The simulation results show that the aerosol optical depth (AOD) generally increased when the aerosol mixing state changed from externally mixed to internally mixed,while the single scattering albedo (SSA) decreased.Therefore,the scattering and absorption properties of aerosols can be significantly affected by the change of aerosol mixing states.Comparison of simulated and observed SSAs at five AERONET (Aerosol Robotic Network) sites suggests that SSA could be better estimated by considering aerosol particles to be internally mixed.Model analysis indicates that the impact of aerosol mixing state upon aerosol direct radiative forcing (DRF) is complex.Generally,the cooling effect of aerosols over East Asia are enhanced in the northern part of East Asia (Northern China,Korean peninsula,and the surrounding area of Japan) and are reduced in the southern part of East Asia (Sichuan Basin and Southeast China) by internal mixing process,and the variation range can reach ±5 W m-2.The analysis shows that the internal mixing between inorganic salt and dust is likely the main reason that the cooling effect strengthens.Conversely,the internal mixture of anthropogenic aerosols,including sulfate,nitrate,ammonium,black carbon,and organic carbon,could obviously weaken the cooling effect.
Indian Academy of Sciences (India)
I Ahmad; M R Arafah
2006-03-01
Elastic scattering of 800 MeV/c pions by 12C has been studied in the diffraction model with a view to determine pion optical potential by the method of inversion. Finding an earlier diffraction model analysis to be deficient in some respects, we propose a Glauber model based parametrization for the elastic -matrix and show that it provides an exceedingly good fit to the pion-carbon data. The proposed elastic -matrix gives a closed expression for the pion-12C optical potential by the method of inversion in the high energy approximation.
2014-01-01
Background Although optic neuritis (ON) is a defining feature of neuromyelitis optica (NMO), appropriate animal models of NMO ON are lacking. Most NMO patients are seropositive for immunoglobulin G autoantibodies (NMO-IgG) against the astrocyte water channel aquaporin-4 (AQP4). Methods Several approaches were tested to develop a robust, passive-transfer mouse model of NMO ON, including NMO-IgG and complement delivery by: (i) retrobulbar infusion; (ii) intravitreal injection; (iii) a single intracranial injection near the optic chiasm; and (iv) 3-days continuous intracranial infusion near the optic chiasm. Results Little ON or retinal pathology was seen using approaches (i) to (iii). Using approach (iv), however, optic nerves showed characteristic NMO pathology, with loss of AQP4 and glial fibrillary acidic protein immunoreactivity, granulocyte and macrophage infiltration, deposition of activated complement, demyelination and axonal injury. Even more extensive pathology was created in mice lacking complement inhibitor protein CD59, or using a genetically modified NMO-IgG with enhanced complement effector function, including significant loss of retinal ganglion cells. In control studies, optic nerve pathology was absent in treated AQP4-deficient mice, or in wild-type mice receiving control (non-NMO) IgG and complement. Conclusion Passive transfer of NMO-IgG and complement by continuous infusion near the optic chiasm in mice is sufficient to produce ON with characteristic NMO pathology. The mouse model of NMO ON should be useful in further studies of NMO pathogenesis mechanisms and therapeutics. PMID:24468108
Balster, Sven; Wenzel, Gentiana I; Warnecke, Athanasia; Steffens, Melanie; Rettenmaier, Alexander; Zhang, Kaiyin; Lenarz, Thomas; Reuter, Guenter
2014-02-01
Optical stimulation for hearing restoration is developing as an alternative therapy to electrical stimulation. For a more frequency-specific activation of the auditory system, light-guiding fibres need to be inserted into the coiled cochlea. To enable insertion with minimal trauma, glass fibres embedded in silicone were used as models. Thus, glass fibres of varying core/cladding diameter with and without silicon coating (single as well as in bundles) were inserted into a human scala tympani (ST) model. Insertion cochlear model force measurements were performed, and the thinner glass fibres that showed low insertion forces in the model were inserted into cadaveric human temporal bones. Silicone-coated glass fibres with different core/cladding diameters and bundle sizes could be inserted up to a maximum depth of 20 mm. Fibres with a core/cladding diameter of 50/55 μm break during insertion deeper than 7-15 mm into the ST model, whereas thinner fibres (20/25 μm) could be inserted in the model without breakage and in human temporal bones without causing trauma to the inner ear structures. The insertion forces of silicone-coated glass fibres are comparable to those measured with conventional cochlear implant (CI) electrodes. As demonstrated in human temporal bones, a minimal traumatic implantation of an optical CI may be considered feasible.
Kartje, John F.
1995-10-01
I have computed the 1200-8000 A thermal continuum polarization induced by gas and dust arranged in configurations compatible with current active galactic nuclei (AGNs) unification schemes. Both uniform- density tori and stratified-density disk-driven winds were considered. A Monte Carlo radiative transfer code was developed which includes the polarization mechanisms of electron and dust scattering as well as dichroic extinction by aligned grains. A Galactic-type grain population was assumed. Based on these calculations, I propose a new interpretation of many of the observed polarization traits of Seyfert galaxies and QSOs: namely, that the polarization in these sources is induced by the same optically thick material which is assumed to obscure the central engine in unification schemes. In particular, I suggest that stratified-density winds could provide a natural explanation (and one consistent with unification models) of the polarization trends observed in Seyfert galaxies. Such winds can display polarizations (P ≲ 20%) oriented perpendicular to the axis along viewing angles inclined to the axis by θ0 ≳ 45° in well-collimated winds, this polarization shifts to smaller magnitudes (P ≲ 2%) and parallel orientations for more face-on viewing, consistent with the patterns observed in Seyfert 2 and Seyfert 1 sources, respectively. In less-collimated winds, scattering alone tends to produce parallel orientations for all viewing angles; perpendicular polarization at large θ0 can result if there is a high degree of magnetic grain alignment. The simplest torus models (i.e., uniform-density, opaque gas and dust) do not reproduce this flip in polarization position angle. Furthermore, they generally display high polarization magnitudes (P ≳ 10%) along most viewing angles θ0 > θ∞ (where θ is the torus half-opening angle) and negligible polarization along θ0 > θ∞. Unlike previous models for AGN polarization which invoke scattering by optically thin electron
Rourke, Devin; Ahn, Sungmo; Nardes, Alexandre M.; van de Lagemaat, Jao; Kopidakis, Nikos; Park, Wounjhang
2014-09-01
The nanoscale light control for absorption enhancement of organic photovoltaic (OPV) devices inevitably produces strongly non-uniform optical fields. These non-uniformities due to the localized optical modes are a primary route toward absorption enhancement in OPV devices. Therefore, a rigorous modeling tool taking into account the spatial distribution of optical field and carrier generation is necessary. Presented here is a comprehensive numerical model to describe the coupled optical and electrical behavior of plasmon-enhanced polymer:fullerene bulk heterojunction (BHJ) solar cells. In this model, a position-dependent electron-hole pair generation rate that could become highly non-uniform due to photonic nanostructures is directly calculated from the optical simulations. By considering the absorption and plasmonic properties of nanophotonic gratings included in two different popular device architectures, and applying the Poisson, current continuity, and drift/diffusion equations, the model predicts quantum efficiency, short-circuit current density, and desired carrier mobility ratios for bulk heterojunction devices incorporating nanostructures for light management. In particular, the model predicts a significant degradation of device performance when the carrier species with lower mobility are generated far from the collecting electrode. Consequently, an inverted device architecture is preferred for materials with low hole mobility. This is especially true for devices that include plasmonic nanostructures. Additionally, due to the incorporation of a plasmonic nanostructure, we use simulations to theoretically predict absorption band broadening of a BHJ into energies below the band gap, resulting in a 4.8% increase in generated photocurrent.
Palacios-Peña, Laura; Baró, Rocío; Guerrero-Rascado, Juan Luis; Alados-Arboledas, Lucas; Brunner, Dominik; Jiménez-Guerrero, Pedro
2017-01-01
The effects of atmospheric aerosol particles on the Earth's climate mainly depend on their optical, microphysical and chemical properties, which modify the Earth's radiative budget. The aerosol radiative effects can be divided into direct and semi-direct effects, produced by the aerosol-radiation interactions (ARIs), and indirect effects, produced by aerosol-cloud interactions (ACIs). In this sense the objective of this work is to assess whether the inclusion of aerosol radiative feedbacks in the online coupled WRF-Chem model improves the modelling outputs over the Iberian Peninsula (IP) and surrounding water areas. For this purpose, the methodology is based on the evaluation of modelled aerosol optical properties under different simulation scenarios. The evaluated data come from two WRF-Chem simulations for the IP differing in the inclusion/no-inclusion of ARIs and ACIs (RF/NRF simulations). The case studies cover two episodes with different aerosol types over the IP in 2010, namely a Saharan dust outbreak and a forest fire episode. The evaluation uses observational data from AERONET (Aerosol Robotic Network) stations and MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, including aerosol optical depth (AOD) and Ångström exponent (AE). Experimental data of aerosol vertical distribution from the EARLINET (European Aerosol Research Lidar Network) Granada station are used for checking the models. The results indicate that for the spatial distribution the best-represented variable is AOD and the largest improvements when including the aerosol radiative feedbacks are found for the vertical distribution. In the case of the dust outbreak, a slight improvement (worsening) is produced over the areas with medium (high/low) levels of AOD(-9 % / +12 % of improvement) when including the aerosol radiative feedbacks. For the wildfire episode, improvements of AOD representation (up to 11 %) over areas further away from emission sources are estimated, which
DEFF Research Database (Denmark)
Polat, Burak; Meincke, Peter
2004-01-01
A forward model for ground penetrating radar imaging of buried 3-D perfect electric conductors is addressed within the framework of diffraction tomography. The similarity of the present forward model derived within the physical optics approximation with that derived within the first Born...
Hansen, Anja; Géneaux, Romain; Günther, Axel; Krüger, Alexander; Ripken, Tammo
2013-06-01
In femtosecond laser ophthalmic surgery tissue dissection is achieved by photodisruption based on laser induced optical breakdown. In order to minimize collateral damage to the eye laser surgery systems should be optimized towards the lowest possible energy threshold for photodisruption. However, optical aberrations of the eye and the laser system distort the irradiance distribution from an ideal profile which causes a rise in breakdown threshold energy even if great care is taken to minimize the aberrations of the system during design and alignment. In this study we used a water chamber with an achromatic focusing lens and a scattering sample as eye model and determined breakdown threshold in single pulse plasma transmission loss measurements. Due to aberrations, the precise lower limit for breakdown threshold irradiance in water is still unknown. Here we show that the threshold energy can be substantially reduced when using adaptive optics to improve the irradiance distribution by spatial beam shaping. We found that for initial aberrations with a root-mean-square wave front error of only one third of the wavelength the threshold energy can still be reduced by a factor of three if the aberrations are corrected to the diffraction limit by adaptive optics. The transmitted pulse energy is reduced by 17% at twice the threshold. Furthermore, the gas bubble motions after breakdown for pulse trains at 5 kilohertz repetition rate show a more transverse direction in the corrected case compared to the more spherical distribution without correction. Our results demonstrate how both applied and transmitted pulse energy could be reduced during ophthalmic surgery when correcting for aberrations. As a consequence, the risk of retinal damage by transmitted energy and the extent of collateral damage to the focal volume could be minimized accordingly when using adaptive optics in fs-laser surgery.
Majumder, Apratim; Helms, Phillip L.; Andrew, Trisha L.; Menon, Rajesh
2016-03-01
Optical lithography is the most prevalent method of fabricating micro-and nano-scale structures in the semiconductor industry due to the fact that patterning using photons is fast, accurate and provides high throughput. However, the resolution of this technique is inherently limited by the physical phenomenon of diffraction. Absorbance-Modulation-Optical Lithography (AMOL), a recently developed technique has been successfully demonstrated to be able to circumvent this diffraction limit. AMOL employs a dual-wavelength exposure system in conjunction with spectrally selective reversible photo-transitions in thin films of photochromic molecules to achieve patterning of features with sizes beyond the far-field diffraction limit. We have developed a finite-element-method based full-electromagnetic-wave solution model that simulates the photo-chemical processes that occur within the thin film of the photochromic molecules under illumination by the exposure and confining wavelengths in AMOL. This model allows us to understand how the material characteristics influence the confinement to sub-diffraction dimensions, of the transmitted point spread function (PSF) of the exposure wavelength inside the recording medium. The model reported here provides the most comprehensive analysis of the AMOL process to-date, and the results show that the most important factors that govern the process, are the polarization of the two beams, the ratio of the intensities of the two wavelengths, the relative absorption coefficients and the concentration of the photochromic species, the thickness of the photochromic layer and the quantum yields of the photoreactions at the two wavelengths. The aim of this work is to elucidate the requirements of AMOL in successfully circumventing the far-field diffraction limit.
Directory of Open Access Journals (Sweden)
Apratim Majumder
2016-03-01
Full Text Available Optical lithography is the most prevalent method of fabricating micro-and nano-scale structures in the semiconductor industry due to the fact that patterning using photons is fast, accurate and provides high throughput. However, the resolution of this technique is inherently limited by the physical phenomenon of diffraction. Absorbance-Modulation-Optical Lithography (AMOL, a recently developed technique has been successfully demonstrated to be able to circumvent this diffraction limit. AMOL employs a dual-wavelength exposure system in conjunction with spectrally selective reversible photo-transitions in thin films of photochromic molecules to achieve patterning of features with sizes beyond the far-field diffraction limit. We have developed a finite-element-method based full-electromagnetic-wave solution model that simulates the photo-chemical processes that occur within the thin film of the photochromic molecules under illumination by the exposure and confining wavelengths in AMOL. This model allows us to understand how the material characteristics influence the confinement to sub-diffraction dimensions, of the transmitted point spread function (PSF of the exposure wavelength inside the recording medium. The model reported here provides the most comprehensive analysis of the AMOL process to-date, and the results show that the most important factors that govern the process, are the polarization of the two beams, the ratio of the intensities of the two wavelengths, the relative absorption coefficients and the concentration of the photochromic species, the thickness of the photochromic layer and the quantum yields of the photoreactions at the two wavelengths. The aim of this work is to elucidate the requirements of AMOL in successfully circumventing the far-field diffraction limit.
Testing and modeling of diffusion bonded prototype optical windows under ITER conditions
Energy Technology Data Exchange (ETDEWEB)
Jacobs, M. [Flemish Inst. for Technological Research, Mol (Belgium); Van Oost, G. [Dept. of Applied Physics, Ghent Univ., Ghent (Belgium); Degrieck, J.; De Baere, I. [Dept. of Materials Science and Engineering, Ghent Univ., Ghent (Belgium); Gusarov, A. [Belgian Nuclear Research Center, Mol (Belgium); Gubbels, F. [TNO, Eindhoven (Netherlands); Massaut, V. [Belgian Nuclear Research Center, Mol (Belgium)
2011-07-01
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 deg.C and fast neutron fluxes of {approx}3.10{sup 9} n/cm{sup 2}.s. At the moment, little information is available about glass-metal joints suitable for ITER. Therefore, we performed mechanical and thermal tests on some prototypes of an aluminium diffusion bonded optical window. Finite element modeling with Abaqus code was used to understand the experimental results. The prototypes were helium leaking probably due to very tiny cracks in the interaction layer between the steel and the aluminium. However, they were all able to withstand a thermal cycling test up to 200 deg. C; no damage could be seen after the tests by visual inspection. The prototypes successfully passed push-out test with a 500 N load. During the destructive push-out tests the prototypes broke at a 6-12 kN load between the aluminium layer and the steel or the glass, depending on the surface quality of the glass. The microanalysis of the joints has also been performed. The finite element modeling of the push-out tests is in a reasonable agreement with the experiments. According to the model, the highest thermal stress is created in the aluminium layer. Thus, the aluminium joint seems to be the weakest part of the prototypes. If this layer is improved, it will probably make the prototype helium leak tight and as such, a good ITER window candidate. (authors)
Modeling Laser Effects on the Final Optics in Simulated IFE Environments
Energy Technology Data Exchange (ETDEWEB)
Nasr Ghoniem
2004-08-14
When laser light interacts with a material's surface, photons rapidly heat the electronic system, resulting in very fast energy transfer to the underlying atomic crystal structure. The intense rate of energy deposition in the shallow sub-surface layer creates atomic defects, which alter the optical characteristics of the surface itself. In addition, the small fraction of energy absorbed in the mirror leads to its global deformation by thermal and gravity loads (especially for large surface area mirrors). The aim of this research was to model the deformation of mirror surfaces at multiple length and time scales for applications in advanced Inertial Fusion Energy (IFE) systems. The goal is to control micro- and macro-deformations by material system and structural design. A parallel experimental program at UCSD has been set up to validate the modeling efforts. The main objective of the research program was to develop computer models and simulations for Laser-Induced Damage (LID) in reflective and transmissive final optical elements in IFE laser-based systems. A range of materials and material concepts were investigated and verified by experiments at UCSD. Four different classes of materials were considered: (1) High-reflectivity FCC metals (e.g. Cu, Au, Ag, and Al), (2) BCC metals (e.g. Mo, Ta and W), (3) Advanced material concepts (e.g. functionally graded material systems, amorphous coatings, and layered structures), and (4) Transmissive dielectrics (e.g. fused SiO2). In this report, we give a summary of the three-year project, followed by details in three areas: (1) Characterization of laser-induced damage; (2) Theory development for LIDT; and (3) Design of IFE reflective laser mirrors.
Wu, Yu; Cheng, Tianhai; Zheng, Lijuan; Chen, Hao
2016-10-01
Light absorption enhancement of aged soot aerosols is highly sensitive to the morphologies and mixing states of soot aggregates and their non-absorbing coatings, such as organic materials. The quantification of these effects on the optical properties of thinly coated soot aerosols is simulated using an effective model with fixed volume fractions. Fractal aggregated soot was simulated using the diffusion limited aggregation (DLA) algorithm and discretized into soot dipoles. The dipoles of non-absorbing aerosols, whose number was fixed by the volume fraction, were further generated from the neighboring random edge dipoles. Their optical properties were calculated using the discrete dipole approximation (DDA) method and were compared with other commonly used models. The optical properties of thinly coated soot calculated using the fixed volume fraction model are close to (less than ~10% difference) the results of the fixed coating thickness model, except their asymmetry parameters (up to ~25% difference). In the optical simulations of thinly coated soot aerosols, this relative difference of asymmetry parameters and phase functions between these realistic models may be notable. The realizations of the fixed volume fraction model may introduce smaller variation of optical results than those of the fixed coating thickness model. Moreover, the core-shell monomers model and homogeneous aggregated spheres model with the Maxwell-Garnett (MG) theory may underestimate (up to ~20%) the cross sections of thinly coated soot aggregates. The single core-shell sphere model may largely overestimate (up to ~150%) the cross sections and single scattering albedo of thinly coated soot aggregates, and it underestimated (up to ~60%) their asymmetry parameters. It is suggested that the widely used single core-shell sphere approximation may not be suitable for the single scattering calculations of thinly coated soot aerosols.