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Few-cycle solitary wave formation from elliptically polarized ultrashort laser pulse in a medium with frequency dispersion

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OPTICS COMMUNICATIONS 2015年 339卷 228-235页

作者： Makarov, V. A. Perezhogin, I. A. Potravkin, N. N. Moscow MV Lomonosov State Univ Fac Phys Moscow 119991 Russia Moscow MV Lomonosov State Univ Int Laser Ctr Moscow 119991 Russia Technol Inst Superhard & Novel Carbon Mat Moscow Russia

In this work we study numerically the quasi-solitary propagation of ultrashort elliptically polarized laser pulses in isotropic medium with cubic nonlinearity, under condition, when the frequency spectrum of the propagating light does not overlap with one-photon resonances and multi-photon non-Raman resonances. For that we use the modification of finite-difference time-domain method with auxiliary differential equation. It is shown that proper choice of initial conditions results in the formation of elliptically polarized solitary wave, which propagates then for a long distance. For the few-oscillation incident pulse its shape and the oscillation character practically do not change at distances of the order of hundreds of wavelengths, and the direction of the oscillations uniformly rotates in the course of propagation. The retardation of the nonlinear response of the medium limits the possibility of the solitary wave formation for few-cycle elliptically polarized pulses, and affects the carrier frequency shift of the incident elliptically polarized pulse. It is established that for any polarization state of the pulse its carrier frequency shift is almost proportional to the reciprocal duration of the pulse in forth degree. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Solitary wave finite-difference time-domain method Polarization Ultrashort pulse Cubic nonlinearity

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Unconditionally Stable FDTD Algorithm Based on Split-Step Scheme for the Analysis of Oblique Incident Plane Wave on Periodic Structures

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FREQUENZ 2015年第9-10期69卷 427-434页

作者： Qu, Xinbo Zhou, Bihua Zhang, Nan Shi, Wei Xiang, Yang PLA Univ Sci & Technol Nanjing Jiangsu Peoples R China CESEC Nanjing Telecommun Technol Res Inst Nanjing Jiangsu Peoples R China Changchun Univ Technol Changchun Peoples R China

In this paper, an unconditionally stable finite-difference time-domain (FDTD) algorithm is presented for solving the problems of oblique incident wave on 2-D periodic structures. By expressing the extra time derivatives caused by the field transformation technique as the form of the coefficient matrix, and applying the split-step scheme (2, 2) (SS2) to the transformed Maxwell's equations, the update at each time step is subdivided into three sub-step implementations. The proposed method has second-order accuracy both in time and space, and the time step size of which is not limited by the Courant-Friedrich-Levy (CFL) stability condition. Compared with the previous approaches of the field transformation method, this technique does not need to introduce additional field components and is more efficient and accurate especially at the large incident angle.

关键词： unconditionally stable finite-difference time-domain method periodic structure oblique incidence

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Study of Extended Focal Segment Formation by Conic Axicons and Layered Lenses

Study of Extended Focal Segment Formation by Conic Axicons a...

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International Conference on Transparent Optical Networks

作者： Dmitry Savelyev Svetlana Khonina Samara State Aerospace University Moskovskoye Shosse 34 Samara 443086 Russia

ISBN: (纸本)9781509014682

It is known that the axicon forms focal segment with a large depth of focus, which is useful in many applications. One advantage is due to the weak requirements for alignment of optical components in systems. However in some cases, such as fibers couplers for optical telecommunication, axicon shape is inconvenient. Therefore, we consider the possibility of replacing the conical axicon by gradient lens with a linear variation of the refractive index. We write analytical expressions, allowing to agree the parameters of the conical axicons and gradient lenses. We also study numerically diffraction of Gaussian beam by conical micro-axicons and gradient microlenses consisting of layers with sub-wavelength thickness using finite-difference time-domain method (FDTD). We estimate characteristics of focal segments generated by both types of considered elements and compare by the depth of focus (DOF) and by transverse dimension (full width at half maximum, FWHM). Studies have shown that a layered lens with linear variation of the refractive index has advantages over the conical axicon with the same numerical aperture, as it allows to form more long and more narrow focal segments.

关键词： microaxicon layered lens finite-difference time-domain method extended focal segment

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Numerical and experimental study on noise shielding effect of eaves/louvers attached on building facade

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BUILDING AND ENVIRONMENT 2015年第Part2期94卷 773-784页

作者： Sakamoto, Shinichi Aoki, Ami Univ Tokyo Inst Ind Sci Meguro Ku Tokyo 1538505 Japan Nikken Sekkei LTD Chiyoda Ku Tokyo 1340088 Japan

Recently, high-rise buildings located in urban area of Japan have eaves on their facade. The eaves are regarded as an efficient measure for mitigating environmental loads by solar radiation heat. The eaves are also utilized to introduce sunlight into the rooms and they contribute energy saving. Besides that, the eaves can be an efficient countermeasure for reduction of traffic noise. On the noise reduction effects by eaves/louvers attached on building facade, numerical analyses and a scale model experiment were performed. Three dimensional numerical analysis of outdoor sound propagation generally takes huge computational costs. To relieve the computational costs, 2-D to 3-D Fourier-like transformation technique based on 2-D finite-difference time-domain analysis was employed in this study. Comparison between flat type eaves, inclined type eaves and louvers consisting of short fins revealed that the inclined type eaves are effective as a noise reduction measure. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Eaves and louvers Noise reduction Road traffic noise finite-difference time-domain method Scale model experiment

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Optical filtering properties of subwavelength Tai-chi-shaped metal hole arrays

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OPTICS COMMUNICATIONS 2015年 340卷 56-62页

作者： Wang, Xinlin Liu, Hui Luo, Hu Zhu, Weihua Chen, Zhiyong Liu, Jun Guo, Wei Univ South China Sch Elect Engn Hengyang 421001 Peoples R China

finite-difference time-domain (FDTD) method is employed to study the optical properties of a novel kind of periodic subwavelength hole arrays composed of Tai-chi-shaped holes in silver film, and the optical transmission properties of femtosecond optical pulse excitation is numerically calculated. We find that this Tai-chi-shaped device has better optical band-pass filtering properties, such as narrower pass band and higher transmissivity in visible wavelengths range, than other devices under consideration. Based on the generation of surface plasmons resonance mode in the dielectric-metal interface, the center wavelength of transmission can be tuned by changing the array periodicities. We observe that the tune ability mainly depends on the space period along the direction parallel to that of the incident pulse polarization. It is also found that both the strength and the wavelength of the transmission peaks of rectangularly distributed metal hole arrays are determined by the polarization of incident light. Additionally, we demonstrate the typical band-pass filtering properties of this Tai-Chi-shaped holes structure. The full-width at half-maximum (FWHM) of the narrow pass band is about 20 nm in visible wavelengths range. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Surface plasmons Subwavelength hole arrays Tai-Chi-shaped structure Wavelength-filtering device finite-difference time-domain method

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Accurate transmittance analysis of liquid crystal displays using a rational fraction approach in the time domain

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OPTICS COMMUNICATIONS 2015年 351卷 155-159页

作者： Kang, Dong-Wan Ahn, Hyeongjin Kim, Heetae Lee, Jong-Kwon Daou InCube Display Business Unit Yongin 448547 Gyeonggi Do South Korea Inst for Basic Sci Korea Rare Isotope Sci Project Taejon 305811 South Korea Seoul Natl Univ Global Frontier Ctr Multiscale Energy Syst Seoul 151744 South Korea

Transmittance of liquid crystal display (LCD) is accurately characterized by using a rational fraction approach to extract complex multi-poles corresponding to a modified Drude-Lorentz dispersive model in the time-domain simulation. Here, the multi-pole fitting accuracy to the measured complex refractive indices of color filters and polarizers with low absorption coefficients and high noise levels is significantly improved with the suggested multi-pole fitting algorithm. Then, the transmittance and power distribution of LCD for oblique incidence are analyzed with high angle accuracy, and the color shift arising from the misalignment between the color filter and thin-film transistor substrates is effectively evaluated. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Liquid crystal display finite-difference time-domain method Rational fraction approach Multi-pole fitting

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Optical switch based on the liquid-crystal-modulated self-collimating photonic crystals

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MATERIALS RESEARCH INNOVATIONS 2015年第Sup1期19卷 S219-S221页

作者： Wu, Z. H. Zhang, Q. Tang, B. Qiu, Y. Luo, Q. Southwest Petr Univ Sch Sci Chengdu 610500 Peoples R China

In this paper, a compact optical switch for self-collimated light beams in a liquid-crystal-modulated photonic crystal is proposed. The designed optical switch is working at 1550 nm. The equifrequency contours and band diagram of the structure are calculated by using plane wave expansion method. The transmission spectra for different liquid crystal rotation angle are computed with finite-difference time-domain method. Meanwhile, the steady-state field distributions of the light propagation in the structure are presented. The designed optical switch may find important applications in the photonic integrated circuits.

关键词： Photonic crystals Optical switch Self-collimation Liquid crystals finite-difference time-domain method

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Overview of the Three-Dimensional FDTD-Based Surge Simulation Code VSTL REV

Overview of the Three-Dimensional FDTD-Based Surge Simulatio...

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Asia-Pacific Symposium on Electromagnetic Compatibility

作者： Akiyoshi Tatematsu Electric Power Engineering Research Laboratory Central Research Institute of Electric Power Industry

ISBN: (纸本)9781467383103

The prediction of surge phenomena is required for designing effective lightning protection methodologies, and circuit-theory-based simulation techniques, which assume the transverse electromagnetic (TEM) mode, have traditionally been widely employed for lightning surge analysis. Recently, the finite-difference time-domain (FDTD) method, which is one of the full-wave numerical approaches, has become an effective tool for analyzing surge phenomena in three-dimensional structures and grounding structures thanks to the development of several techniques useful for FDTD-based surge simulations. In this study, we review a three-dimensional FDTD-based surge simulation code developed by CRIEPI, its acceleration using the general-purpose computing on graphics processing units (GPGPU) technique, and its application to surge simulations in a microwave relay station.

关键词： finite-difference time-domain method Lightning Surge analysis GPGPU Microwave relay station

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Diagnosis of Multiple Wiring Faults Using time-domain Reflectometry and Teaching-Learning-Based Optimization

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ELECTROMAGNETICS 2015年第1期35卷 10-24页

作者： Boudjefdjouf, H. Mehasni, R. Orlandi, A. Bouchekara, H. R. E. H. De Paulis, F. Smail, M. K. Univ Constantine 1 Dept Elect Engn Elect Engn Lab Constantine Constantine 25000 Algeria Univ Aquila Dept Ind & Informat Engn & Econ Electromagnet Compatibil Lab I-67100 Laquila Italy Univ Paris Est IFSTTAR F-77747 Champs Sur Marne France

time-domain reflectometry has proven to be one of the best methods for wiring network diagnosis, and it can easily be applied to the detection and localization of defects, while only requiring one access point to the wiring network. In this article, a novel approach combining the time-domain reflectometry response extracted from vector network analyzer measurements and the teaching-learning-based optimization technique is developed and applied to the diagnosis of wiring networks. The proposed approach consists of two steps. In the first step, propagation along the cables is modeled using the forward model. In the second step, teaching-learning-based optimization is used to solve the inverse problem to deduce physical information about the defects in the wiring network. The proposed approach has been successfully tested on several cases and for different configurations. Comparisons of the proposed time-domain reflectometry/teaching-learning-based optimization approach results with measurements reveal that this approach has a high potential and is very effective for wiring network diagnosis.

关键词： finite-difference time-domain method multiple wiring diagnosis time-domain reflectometry teaching-learning-based optimization

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An Improved Thin Wire Representation for FDTD Transient Simulations

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IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY 2015年第3期57卷 484-487页

作者： Asada, Takashi Baba, Yoshihiro Nagaoka, Naoto Ametani, Akihiro Doshisha Univ Dept Elect Engn Kyoto 6100321 Japan

The equivalent radius of a thin wire, which is represented by forcing the tangential electric field along the wire axis to zero in a three-dimensional finite-difference time-domain simulation, has been evaluated on the basis of a surge or characteristic impedance of a perfectly conducting horizontal wire above a perfectly conducting ground. It is 0.199 Delta s, where Delta s is the lateral side length of cubic cells employed, and is smaller than the equivalent radii, 0.230 Delta s and 0.208 Delta s, estimated by Noda and Yokoyama (2002) and by Railton et al. (2006), respectively. Further, the thin wire representation of Railton et al. with this equivalent radius, which embeds a wire having the equivalent radius in an artificial parallelepiped medium having modified relative permittivity and permeability, has been proposed, and its validity has been tested for a horizontal wire and a vertical wire.

关键词： finite-difference time-domain method thin wire transient

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