等离子体的SO-FDTD算法和对电磁波反射系数的计算分析

将一类色散介质的介电常数写成有理分式函数形式，进而导出FDTD中电位移矢量D和电场强度E之间的关系，形成SO-FDTD方法. 应用该方法计算了冷等离子体平板对电磁波的反射系数，通过与解析结果的比较，验证了该算法的高效性和高精度，同时，应用SO-FDTD方法，计算了等离子体层对垂直入射电磁波的反射系数，结果表明：等离子体厚度、电子密度、电子密度的分布形式和入射波频率是影响反射系数的重要因素. 关键词： 等离子体 电磁波 FDTD方法     

FDTD Simulation of Electromagnetic Reflection of Conductive Plane Covered with Imhomogeneous Time-Varying Plasma

A finite-difference time-domain (FDTD) algorithm is applied to study the electromagnetic reflection of conduction plane covered with inhomogeneous, collision, warm, time-varying plasma. The collision frequency of plasma is a function of electron density and plasma temperature. Under the one-dimensional case, transient electromagnetic propagation through various plasmas have been obtained, and the reflection coefficient of EM wave through inhomogeneous time-varying plasma (ITVP), homogeneous time-varying plasma (HTVP) and inhomogeneous plasma (IP) are calculated under different conditions. The results illustrate that a plasma cloaking system can successfully absorb the incident EM wave.     

Modeling and simulation of multiple resonant Lorentz dispersive materials for integrated optics

Complex materials are of increasing interest in Finite-Difference Time-Domain (FDTD) modeling. For example, when the particle density becomes large, collisional fluid models of plasmas are an attractive alternative to particle in cell methods. Further, frequency dispersive meta-materials are of increasing interest. Thus, Finite-Difference Time-Domain (FDTD) models are derived for magnetized plasmas and for the Lorentz and Drude material models. This paper models the Lorentz material using the FDTD tool. The modal analysis and various types of simulation results are also presented for these materials.     

用FDTD计算各向异性磁化等离子体涂敷二维目标的RCS

采用z变换方法把时域有限差分方法(FDTD)推广应用于二维各向异性色散介质—磁化等离子 体中，该算法同时解决了电磁波在各向异性和频率色散介质中传播的计算问题，给出了各向 异性磁化等离子体中FDTD迭代公式.计算了各向异性磁化等离子体涂敷导体圆柱前后其雷达 散射截面(RCS)的变化情况，分析了等离子体碰撞频率和电子回旋频率对其RCS的影响. 关键词： 时域有限差分方法 各向异性磁化等离子体     

一维等离子体光子晶体的带隙研究

采用时域有限差分方法(FDTD),结合等离子体计算中的分段线性电流密度卷积技术(PLJERC)对一维等离子体光子晶体(1D-PPC)进行了数值模拟,给出了微分高斯脉冲在一维等离子体光子晶体中的传播过程。计算得到的带隙结构与K-P模型方法的结果一致。计算并分析了等离子体频率、介质介电常数、等离子体-介质层的厚度比以及周期厚度对一维等离子体光子晶体带隙结构的影响。     

FDTD Analysis of Electromagnetic Reflection by Conductive Plane Covered with Magnetized Inhomogeneous Plasmas

A novel finite-difference time-domain (FDTD) methodology which incorporates both anisotropy and frequency dispersion at the same time is developed for electromagnetic wave propagation in anisotropic magnetoactive plasmas in this paper. The numerical verification of the method are confirmed by computing the reflection and transmission of right-handed/left-handed circularly polarized (RCP/LCP) wave through a magnetized plasma layer, with the direction of propagation parallel to the direction of the biasing field. And, the right-handed / left-handed polarized wave reflection coefficients for electromagnetic signals normally incident upon a conductive plane covered with a layer of magnetized plasma are computed using the new FDTD method. The parabolic electron-number density profile varies only in the direction perpendicular to the plane. The function dependence of reflection coefficients on the number density, collision frequency and external magnetic field is studied.     

一种高效计算各向异性磁化等离子体的时域有限差分算法

利用电流密度和电场强度的卷积关系,引入电流密度和电场强度分段线性近似,导出一种适合各向异性磁化等离子体介质的FDTD算法的计算公式.计算各向异性碰撞磁化等离子体平板对平行于磁场传播的电磁波的反射和透射系数,与解析结果比较,验证该算法的高效性和高精度,与电流密度卷积(JEC)算法和分段线性电流密度卷积(PLCDRC)算法相比,计算精度及计算效率显著提高.此外,用该算法验证了法拉第旋转效应.     

斜入射分层线性各向异性等离子体电磁散射时域有限差分方法分析

提出了斜入射分层线性各向异性等离子体电磁散射的时域有限差分(FDTD)方法,通过将二维麦克斯韦方程等价地转换为一维麦克斯韦方程,避免了用二维时域有限差分方法分析该散射问题,极大地提高了计算效率.分析推导了TEz和TMz波斜入射线性分层各向异性等离子体电磁散射的FDTD方法,然后通过该方法计算不同入射角的各向异性等离子板的电磁波反射系数,并与其解析解进行比较,结果表明该方法的准确性和有效性.最后,将该算法应用于计算涂覆分层各向异性等离子体金属板在不同入射角下的反射系数,分析了不同入射角对反射系数的影响.     

一种适于1维磁等离子体电磁波传输特性的FDTD分析

 提出了一个新的分析各向异性磁等离子体中电磁波传输特性的时域有限差分（FDTD）方法。该方法是将电流密度矢量与电场强度矢量之间的本构方程基于拉普拉斯变换原理转到复频域,然后再逆变换到时域得到它们之间显式的方程,最后再结合指数差分,得到离散时域的显式的FDTD迭代方程,解决了本构方程中电流密度矢量的分量相互耦合而不易直接离散的困难。该方法在数学上具有简单明了和易于计算的特点,同时通过该方法计算各向异性等离子体板的电磁波反射和透射系数,与其解析解进行比较,结果表明了该方法的准确性和有效性。     

Determination of the dielectric constant of YBa2Cu3O7−δ single crystals in the 10 μm spectral range by SEW phase spectroscopy

Phase spectroscopy of surface electromagnetic waves was used to determine the complex dielectric constant of YBa₂Cu₃O_7−δ single crystals in the spectral range 930–1090 cm⁻¹. The value obtained (ε=−45+90i) permits one to determine, in the case when the Drude model is valid, the plasma frequency (∼15000 cm⁻¹) and the collisional frequency of free carriers (∼2000 cm⁻¹). The plasma edge in the reflection spectrum is observed at higher frequencies (∼25000 cm⁻¹). Possible reasons for the discrepancy are discussed.     

时变非磁化等离子体光子晶体缺陷态研究

采用非磁化等离子体的分段线形电流密度卷积(Current density convolution,JEC)时域有限差分(Finite-dif-ferent time-domain,FDTD)算法研究了具有单一缺陷层的一维时变非磁化等离子体光子晶体的缺陷模特性。以高斯脉冲为激励源,通过由算法公式得到的电磁波透射系数讨论了等离子体上升时间对其缺陷模的影响。结果表明,改变等离子体的上升时间和密度可以获得不同的缺陷模。     

温度、密度对磁化等离子体光子晶体缺陷模的影响

采用等温近似,用磁化等离子体的分段线形电流密度卷积(Piecewise Linear Current Density Recursive Convolution,PLCDRC)时域有限差分(Finite-differentce Time-domain,FDTD)算法研究了具有单一缺陷层的一维磁化等离子体光子晶体的缺陷模特性;以高斯脉冲为激励源,用算法公式计算所得的电磁波透射系数,讨论了温度和等离子体层密度对其缺陷模的影响。结果表明:改变温度和等离子体层密度可以获得不同的缺陷模。     

等离子体覆盖立方散射体目标雷达散射截面的时域有限差分法分析

采用分段线性电流密度递归卷积时域有限差分（PLJERC-FDTD）算法计算了均匀非磁化等离子体覆盖三维立方体目标的散射特性.分析了等离子体厚度、密度和碰撞频率对雷达散射截面（RCS）的影响.计算结果表明：等离子体包层能有效地减小雷达目标的RCS，当等离子体频率比入射电磁波频率小得多时，主要靠增大等离子体的厚度使立方散射体目标的RCS值减小，增大等离子体碰撞频率对立方散射体目标的RCS值影响不大；当等离子体频率约为入射电磁波频率的一半时，增大等离子体厚度和碰撞频率都对立方散射体目标的RCS值减小有影响；当等 关键词： FDTD算法 电磁波 等离子体隐身 雷达散射截面     

时变磁化等离子体光子晶体的禁带特性

采用磁化等离子体的分段线形电流密度卷积(Piecewise Linear Current Density Recursive Convolution,PLCDRC)时域有限差分(Finite-Different Time-Domain, FDTD)算法研究了一维时变磁化等离子体光子晶体的禁带特性。以高斯脉冲为激励源,用算法公式所得的电磁波透射系数来讨论了等离子体上升时间、密度、周期常数对其禁带特性的影响。结果表明,改变等离子体上升时间和密度可以实现对禁带的控制。     

磁化等离子体光子晶体缺陷态的研究

采用磁化等离子体的分段线性电流密度卷积时域有限差分(PLCDRC-FDTD)算法研究具有单一缺陷层的一维磁化等离子体光子晶体的缺陷模特性. 从频域角度分析得到微分高斯脉冲的透射率,并讨论该光子晶体的缺陷层厚度、位置、周期常数和等离子体参数对其缺陷模的影响. 结果表明,改变位置和周期常数不会影响缺陷模的频率,改变缺陷层的厚度可以增加缺陷模数,改变等离子体参数能同时影响缺陷模的频率和峰值. 关键词： 磁化等离子体光子晶体 光子晶体 缺陷模 时域有限差分法     

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提出碰撞吸收型等离子体的等效折射指数,重新计算了折射角,并与利用常规方法得到的折射角进行了比较。分析了等离子体密度和碰撞频率对折射角的影响。考察了斜入射电磁波在吸收型等离子体中的折射特性,并以一维非均匀碰撞吸收型等离子体为例,对斜入射电磁波的反射特性进行了考察。结果表明,等效折射指数的概念涵盖了入射角度的影响,在考察斜入射时更准确、便捷。     

Treatment of metal for the FDTD analysis of terahertz devices

A terahertz stop band filter and a resonator consisting of metal gratings are analyzed using the finite-difference time-domain (FDTD) method, with special attention to the treatment of metal. Numerical results based on a perfect electric conductor (PEC) approximation are compared to those with a metal dispersion being taken into account by the Drude model. It is shown that the results of the resonator for the PEC model are favorably compared with those for the Drude model at frequencies of less than 1 THz. However, care must be taken at higher frequencies, since not only the transmittance at the resonance remarkably reduces for the Drude model, but also its resonance frequency deviates, in comparison with those for the PEC model. Metal mesh structures are also investigated using the periodic FDTD. The differences are found to be relatively small, due to the weak confinement of THz waves in metal mesh structures. The results can serve as a guideline for the FDTD analysis of THz devices consisting of metal.     

THz电磁波在时变非磁化等离子体中的传播特性研究

本文建立了时变非磁化等离子体平板的一维模型,并采用时域有限差分(FDTD)方法对太赫兹(THz)电磁波在时变等离子体中传播时的反射、透射系数及吸收率进行了计算.然后根据计算结果分析了时变等离子体的上升时间、电子密度、温度以及等离子体平板厚度等参数对不同频段THz波在等离子体中传播特性的影响.分析结果表明:THz波在时变等离子体中传播时,其反射系数受等离子体电子密度和上升时间的影响较大;而吸收率则随着上升时间的减小、电子密度及平板厚度的增加而增大;此外,THz电磁波能够穿透量级为1020m-3的高密度等离子体层,可以作为再入段飞行器通信以及高密度等离子体诊断的理想工具.     

等离子体涂覆目标散射特性SARC FDTD方法分析

基于数字信号处理中的半解析递归卷积(SARC)算法,提出一种用于色散介质电磁特性分析的通用递归卷积时域有限差分方法(SARC FDTD),不仅具有绝对稳定性和高精度、低内存、高效率等优点,而且对于常见色散介质模型,具有统一的形式,计算时只需给出色散介质模型的极点和对应系数,使用方便,通用性好.通过算例验证了方法的有效性,并对有等离子体存在的目标电磁散射截面(RCS)进行了计算和分析.     

Numerical analysis of propagation characteristics of electromagnetic wave in lossy left-handed material media

The propagation characteristics of electromagnetic wave in lossy left-handed materials (LHM) are studied using finite-difference time-domain (FDTD) method base on auxiliary differential equation (ADE) technology. The LHM medium is realized with lossy Drude models for both the negative electric permittivity and the negative magnetic permeability. The discretized ADE-FDTD equations are derived in detail. The incident wave used in the simulation is a multiple cycle m-n-m pulses source. The term of Poynting's vector E_xH_y was calculated. These numerical results demonstrate conclusively that the phase velocity direction of electromagnetic wave propagation and the direction of the Poynting vectors are anti-parallel in LHM. The amplitude of electric field is reduced with the enhancive distance of LHM slab. It is also demonstrated that the energy of electromagnetic wave in the LHM slab is obviously attenuated, and the attenuation of energy becomes stronger with the angular plasma frequency ω_p increasing. These results indicate that LHM stealth is effective in theory, and reasonable selection of the large negative index of refraction can greatly enhance its effectiveness.