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Simulations of light scattering from a biconcave red blood cell using the finite-difference time-domain method

JOURNAL OF BIOMEDICAL OPTICS 2005年第2期10卷 024022页

作者： Lu, JQ Yang, P Hu, XH E Carolina Univ Dept Phys Greenville NC 27858 USA Texas A&M Univ Dept Atmospher Sci College Stn TX USA

Numerical simulations of light scattering by a biconcave shaped human red blood cell (RBC) are carried out using the finite-difference time-domain (FDTD) method. A previously developed FDTD code for the study of light scattering by ice crystals is modified for the current purpose and it is validated against Mie theory using a spherically shaped RBC. Numerical results for the angular distributions of the Mueller scattering matrix elements of an RBC and their dependence on shape, orientation, and wavelength are presented. Also calculated are the scattering and absorption efficiencies. The implication of these results on the possibility of probing RBC shape changes is discussed. (c) 2005 Society of Photo-Optical instrumentation Engineers.

关键词： red blood cell cell scattering finite-difference time-domain method Mueller scattering matrix

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Analysis of femtosecond optical pulse propagation in one-dimensional nonlinear photonic crystals using finite-difference time-domain method

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OPTIK 2005年第10期116卷 486-492页

作者： Shokooh-Saremi, M Mirsalehi, MM Ferdowsi Univ Mashhad Fac Engn Dept Elect Engn Mashhad 1111 Iran Univ Sydney Sch Phys CUDOS Sydney NSW 2006 Australia

In this paper, we have used the finite-difference time-domain (FDTD) method to analyze the optical pulse propagation in a nonlinear, one-dimensional photonic crystal (1DPC). Hyperbolic secant pulses with various carrier wavelengths are utilized in this study. In a nonlinear regime, a 1DPC introduces a photonic band-gap whose central wavelength and width depend on the input pulse intensity. In the present work, three different cases are considered. These correspond to the carrier wavelengths of the incident pulses being out of, near to, and partially in the band-gap. For each case, the effect of nonlinearity on pulse propagation is investigated. Also, we have analyzed the two-frequency regime, in which each of the two pulses has a different carrier frequency (wavelength). This kind of study can be done directly with FDTD without any further computational burden but it is somewhat complicated using nonlinear coupled-mode equations (NLCME) and nonlinear Schrodinger equation (NLSE), which require separate treatments for each carrier wavelength. (c) 2005 Elsevier GmbH. All rights reserved.

关键词： nonlinear photonic crystals optical pulse propagation finite-difference time-domain method

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Calculation of diffraction characteristics of subwavelength conducting gratings using a high accuracy nonstandard finite-difference time-domain method

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OPTICAL REVIEW 2005年第4期12卷 274-280页

作者： Banerjee, S Cole, JB Yatagai, T Univ Tsukuba Inst Appl Phys Tsukuba Ibaraki 3058573 Japan Univ Tsukuba Dept Syst & Informat Engn Tsukuba Ibaraki 3058573 Japan

Gratings with subwavelength groove depth and period are frequently used in optics for various purposes. The polarization dependent diffraction characteristics of subwavelength (high frequency) gratings can only be calculated by solving Maxwell's equations of electromagnetism. In this paper, we calculate the classical diffraction characteristics of subwavelength conducting gratings numerically, using a new high accuracy version of nonstandard finite-difference time-domain (NS-FDTD) algorithm. For the purpose of analysis, we employ a gold sinusoidal grating with light incident at a large angle. We have compared high accuracy NS-FDTD simulation results with those obtained from standard finite-difference time-domain (S-FDTD), and the finite element method (FEM) simulations. (c) 2005 The Optical Society of Japan.

关键词： grating diffraction subwavelength diffractive optical elements conducting gratings microoptics electromagnetic theory finite-difference time-domain method

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finite-difference time-domain model for the feeding gap of coaxial probe driven antennas

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IET MICROWAVES ANTENNAS & PROPAGATION 2009年第3期3卷 501-506页

作者： Hyun, S. -Y. Kim, S. -Y. Kim, Y. -S. Korea Inst Sci & Technol Imaging Media Res Ctr Seoul 136791 South Korea Korea Univ Dept Radio Sci & Engn Seoul 136701 South Korea

In the finite-difference time-domain (FDTD) method, a simple and realistic feed model for coaxial probe driven antennas is proposed here. The feed zone of the antenna may be considered as an equivalent source in view of the antenna theory and a load port in view of the transmission line theory. The proposed feed model is constructed by combining the infinitesimal-gap source condition of the antenna and the equivalent load condition of the feed line. It leads to perform no additional FDTD cell modelling of the line. The transient reflected voltage and the input impedance of cylindrical monopole antennas fed by coaxial lines are calculated numerically and then compared with the accurate measurement and a full fine-grid. The FDTD results of the proposed model have a good agreement with the measured data and the fine-grid results.

关键词： antenna feed zone Other numerical methods cylindrical monopole antennas infinitesimal-gap source condition Antenna accessories Antenna theory input impedance transient reflected voltage antenna theory Transmission line theory equivalent load condition monopole antennas finite difference time-domain analysis coaxial probe driven antennas Single antennas coaxial cables transmission line theory antenna feeds finite-difference time-domain method coaxial lines

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Electromagnetic method for sample-induced resistance calculation of magnetic resonance coils

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INTERNATIONAL JOURNAL OF BIOMEDICAL ENGINEERING AND TECHNOLOGY 2010年第1期4卷 18-28页

作者： Giovannetti, Giulio Viti, Vittorio Hartwig, Valentina Liu, Yongjun Yu, Wenhua Mittra, Raj Landini, Luigi Benassi, Antonio Natl Council Res Inst Clin Physiol Via Moruzzi 1 I-56124 Pisa Italy Esaote Biomed I-16153 Genoa Italy Penn State Univ Elect Engn East 319 University Pk PA 16802 USA Univ Pisa Dept Informat Engn I-56122 Pisa Italy

Signal-to-Noise Ratio (SNR) calculation in Magnetic Resonance (MR) experiments requires the knowledge of biological sample-induced resistance value. Many authors studied sample-coil interaction by using quasi-static approach, with very simple coil and sample geometries;such method fails at high-field Magnetic Resonance Imaging (MRI). In this paper, we propose a theoretical algorithm for sample-induced resistance estimation, which uses a numerical solver based on finite-difference time-domain (FDTD) method for simulating MR systems. Comparison with experimental data demonstrated the great accuracy of the developed algorithm. The proposed method can be used as a tool to estimate sample-induced resistance values for more complex geometries.

关键词： SNR signal-to-noise ratio sample-induced resistance electromagnetic simulator finite-difference time-domain method

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Rigorous electromagnetic analysis of Talbot effect with the finite-difference time-domain method

Rigorous electromagnetic analysis of Talbot effect with the ...

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Conference on Optical Design and Testing II

作者： Lu, YQ Zhou, CH Chinese Acad Sci Shanghai Inst Opt & Fine Mech Informat Opt Lab Shanghai 201800 Peoples R China

ISBN: (纸本)0819455938

We present the electromagnetic analysis of Talbot effect with the finite-difference time-domain (FDTD) method. To our knowledge, it is the first time that FDTD method is applied to analyze the performance of a Talbot illuminator. Furthermore, self-imaging performances of a grating with different flaws are analyzed. The FDTD method can be applied to analyze this kind of diffraction. Of course it also can be analyzed with the Fourier transform method. But for this non-period grating, it will be more complex. In addition, the grating employed here is a high-density grating. The Fourier transform method is not rigorous enough. For these reasons, the FDTD method can show the exact near-field distribution of different flaws in a high-density grating, which is impossible to attain with the conventional Fourier transform method.

关键词： Talbot array illuminators finite-difference time-domain method

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Optimizing the spectral efficiency of photonic quantum well structures

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OPTIK 2009年第1期120卷 35-39页

作者： Liu, Jing Sun, Junqiang Huang, Chongqing Hu, Wenjing Huang, Dexiu Huazhong Univ Sci & Technol Wuhan Natl Lab Optoelect Wuhan 430074 Peoples R China Hunan Inst Sci & Technol Dept Phys Yueyang 414006 Hunan Peoples R China

One can construct photonic single quantum well structures by sandwiching a homogeneous medium slab as a defect between two symmetrical photonic crystals (PCs). It is shown that the number of observed resonant peaks increases with increasing slab thickness. It is found that while the slab is composed of alternatively stacked step-index films, the frequencies of these resonant peaks can be adjusted finely by changing the film thickness properly. In this case, the frequency and frequency interval of confined states can be tuned accurately, and the spectral efficiency can be greatly enhanced without increasing the volume of optical devices. Numerical simulation is based on the finite-difference time-domain (FDTD) method. (C) 2007 Elsevier GmbH. All rights reserved.

关键词： Spectral efficiency Confined states finite-difference time-domain method Photonic quantum well

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A Study of Properties of the Photonic Band Gap of Unmagnetized Plasma Photonic Crystal

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Plasma Science and Technology 2009年第1期11卷 14-17页

作者：刘崧钟双英刘三秋 School of Sciences Nanchang University

In this study, the propagation of electromagnetic waves in one-dimensional plasma photonic crystals （PPCs）, namely, superlattice structures consisting alternately of a homogeneous unmagnetized plasma and dielectric material, is simulated numerically using the finite-difference time-domain （FDTD） algorithm. A perfectly matched layer （PML） absorbing technique is used in this simulation. The reflection and transmission coefficients of electromagnetic （EM） waves through PPCs are calculated. The characteristics of the photonic band gap （PBG） are discussed in terms of plasma density, dielectric constant ratios, number of periods, and introduced layer defect. These may provide some useful information for designing plasma photonic crystal devices.

关键词： plasma photonic crystal finite-difference time-domain method photonic band gap reflection and transmission coefficients

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FDTD Implementation and Application of High Order Impedance Boundary Condition Using Rational Functions

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2009年第8期57卷 2397-2408页

作者： Zheng, Hong-Xing Leung, Kwok Wa City Univ Hong Kong Dept Elect Engn Kowloon Hong Kong Peoples R China

An algorithm is proposed for the implementation of the high-order surface impedance boundary condition using the finite-difference time-domain method. The surface impedance function of a lossy medium is approximated by a series of rational functions in the Laplace domain, whereas the dyadic differential operator is approximated by a second-order power series. By assuming that the fields are piecewise linear, the time-domain convolution integrals are computed using a recursive formula. The impedance function of a coating layer is approximated by a third-order power series. The algorithm can be applied to scattering problems of a three-dimensional coating for both vertically and horizontally polarized waves. The advantage of the proposed method is that the result can be applied to media of arbitrary conductivities, with a wide range of incident angles from zero to graze. Some numerical examples are given to substantiate the theory.

关键词： Approximate operator expansion coating finite-difference time-domain method rational function scattering surface impedance boundary conditions

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Investigation of a slot nanoantenna in optical frequency range

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PHOTONICS AND NANOSTRUCTURES-FUNDAMENTALS AND APPLICATIONS 2009年第3期7卷 161-168页

作者： Kumar, V. Dinesh Asakawa, Kiyoshi Natl Inst Mat Sci Tsukuba Ibaraki 3050047 Japan

Following the analogy of radio frequency slot antenna and its complementary dipole, we propose the implementation of a slot nanoantenna (SNA) in the optical frequency range. Using finite-difference time-domain (FDTD) method, we investigate the electromagnetic (EM) properties of a SNA formed in a thin gold film and compare the results with the properties of a gold dipole nanoantenna (DNA) of the same dimension as the slot. It is found that the response of the SNA is very similar to the DNA, like their counterparts in the radio frequency (RF) range. The SNA can enhance the near field intensity of incident field which strongly depends on its feedgap dimension. The resonance of the SNA is influenced by its slot length;for the increasing slot length, resonant frequency decreases whereas the sharpness of resonance increases. Besides, the resonance of the SNA is found sensitive to the thickness of metal film, when the latter is smaller than the skin depth. The effect of polarization of incident field on the EM response of the SNA was examined;the field enhancement is optimum when polarization is parallel to the feedgap. Finally, we calculate the radiation patterns of the DNA and SNA and compare them with those of the RF dipole antenna. The radiation pattern of the SNA is found to be independent of its slot length when excited at resonant frequency. To the best of our knowledge, this is the first study on a slot antenna in the optical frequency. (C) 2009 Elsevier B.V. All rights reserved.

关键词： Slot nanoantenna Dipole nanoantenna Radio frequency antenna finite-difference time-domain method Surface plasmon

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