广义传播矩阵法分析分层各向异性材料对电磁波的反射与透射

在实验室坐标系下由Maxwell旋度方程出发构造了横向场的状态矢量和耦合矩阵,讨论了各 向异性介质中的特征波.通过引入横向场的传播矩阵,进而得到分层各向异性介质的反射系数和透射系数的解析表达式.该式可以适用于一般情况,包括分层单轴各向异性材料和回旋介质,以及半空间各向异性介质的反射和透射问题. 关键词： 广义传播矩阵 各向异性介质 反射与透射     

Reflection and transmission of acoustic waves on multilayered porous media

Based on the Boit theory of acoustic wave propagation in fluid-satu-rated porous medium we have studied in this paper the acoustic reflection andtransmission on multilayered porous media,in which the adequate boundaryconditions across the interfaces are taken into account.Numerical calculationsof the reflection and transmission coefficients at different incident angles andfrequencies of the fast compressional wave incident on porous media with threeor four layers are presented.The results indicate that the maximum or mini-mum reflection and transmission coefficients appear at certain ratios of thewavelength to the thickness.The acoustic incident angle and porous mediumproperties are shown to affect significantly these coefficients.As an example,the measured transmission coefficients in a water-saturated fused glass beadsample are in good agreement with theoretical prediction.     

Bulk heterogeneous plane waves propagation through viscoelastic plates and stratified media with large values of frequency domain

This paper introduces the bulk heterogeneous waves concept into the well known Thomson-Haskell method for computing transmission/reflection coefficients through stratified media. If one of the layers is absorbing, bulk heterogeneous waves are generated at interfaces with other layers and the generalized Snell's laws for heterogeneous modes have to be used. This method was reported to be unstable for large values of frequency domain (FD), the product of the frequency and the medium thickness. The new expression for the matrix transfer between interfaces given in this paper is tested with large values of FD, without showing instability. Large values of FD imply significant effects of attenuation, which is frequency dependent. One particular effect is the interface transmission of modes beyond the limit angle if it is defined with the homogeneous waves concept. This is shown with acquired and simulated waveforms, after transmission through an epoxy layer. Waveforms transmitted by adhesive joints are also presented.     

Electromagnetic wave propagation through frequency-dispersive and lossy double-negative slab

This study presents the electromagnetic wave propagation through the frequency-dispersive and lossy double-negative slab embedded between two different semi-infinite media. The double-negative slab is realized by using two models, the Lorentz and Drude medium models. The properties and the required equations for the frequency-dispersive and lossy double-negative slab, the Lorentz medium and Drude medium are given in detail. After the construction of the problem, the reflection and transmission coefficients are derived for both TE and TM waves. Then, the reflected, transmitted and loss powers are determined using these coefficients. Finally, in the numerical results, the mentioned powers for TE and TM waves are computed and illustrated as a function of the incidence angle, the frequency and the slab thickness when the damping frequency changes.     

Reflection and refraction of elastic wave at VTI-TTI media interface

We explore the physical phenomenon of acoustic waves induced at the interface between two different anisotropic rock media.Specifically,one medium is a transversely isotropic medium with a vertical axis of symmetry(VTI medium)and the other one is a transversely isotropic medium with a tilt axis of symmetry(TTI medium).By solving the Kelvin-Christoffel equation,an eighth-order polynomial is established for reflection and refraction angles,which is confirmed from SnelFs law.Three types of analytical expressions of the polarization coefficients of the induced waves are obtained corresponding to different incident angle regions.An effective algorithm has been developed for numerical analysis of the polarization coefficients.Applying characteristic anisotropic parameters reported in the literature,the influencing factors on reflection and refraction coefficients are analyzed,e.g.,the anisotropy,the tilt-angle of rock-layer,and the incident-angle.The calculated reflection and refraction coefficients have been rechecked for energy conservation.     

Reflection and transmission of plane waves at the interface of pyroelectric bi-materials

A simple reflection and transmission theory of plane waves at the interface of pyroelectric media is studied in this paper. In an infinite homogeneous pyroelectric medium, there are four bulk wave modes: quasi-longitudinal (QL), two quasi-transversal (QT) and one temperature (T) waves, whose velocities depend on the frequency and incident angle. Simultaneously, a quasi-surface (QS) wave on each side of the interface of pyroelectric bi-materials will appear in the general reflection and transmission problem. The quasi-surface wave has the same wave vector component with the incident waves along the interface plane. So, the reflection and transmission problem is different with the propagation wave in the infinite homogeneous space, but it is still solvable. In the reflection and transmission problem, there are ten complex continuous conditions on the interface, which are satisfied by the bulk and quasi-surface waves together. Numerical calculations are performed for bi-material PZT-6B/BaTiO₃. Incidences of the quasi-longitudinal and quasi-transversal waves from the side of PZT-6B or BaTiO₃ medium are discussed. The reflection and transmission amplitude coefficients and energy flow ratios varying with the incident angle are examined.     

Deformation Features on the Free Surface and Rigid Interface during Elastic Wave Reflection

Analytical expressions defining the reflection coefficients have been derived in the framework of the known problem of elastic wave reflection from the free surface and rigid interface. The found reflection coefficients are used to analyze the dependences of different strain and rotation components during elastic wave reflection from the free surface and rigid interface in the case of ideal contact and possible slip on the wave incidence angle and elastic parameters of the medium. Deformation features of elastic media at the studied interfaces are considered for incident longitudinal and transverse waves.     

Reflection and refraction of bulk acoustic waves in piezoelectrics under uniaxial stress

Basic equations that describe the conditions of reflection and refraction of bulk acoustic waves at the boundary between acentric crystalline media under uniaxial stress are presented. The effect of uniaxial stress on the anisotropy of reflection and refraction of bulk acoustic waves is numerically analyzed for boundaries of the crystal-vacuum, piezoelectric crystal-piezoelectric crystal, and piezoelectric crystal-elastic isotropic medium types.     

正交各向异性板液/固界面的声反射与声透射

采用Legendre正交多项式法,对液/固界面声波反射和透射系数进行求解。利用Legendre正交多项式对正交各向异性板中的位移解进行展开,推导出板中的应力和波动控制方程。联立液/固界面的边界条件和波动控制方程,建立线性无关方程组,用以计算液/固界面的反射和透射系数及Legendre多项式的展开系数,计算所得铝板液/固界面的反射和透射系数与传递矩阵法的计算结果吻合良好。以单向纤维增强复合材料板为例,在不同的方位角下,分析了反射和透射系数随斜入射角度、入射波频率的变化关系,以及板中声场的位移分布。所取Legendre正交多项式截止阶数越大,可用来计算的频厚积范围越大。研究拓展了Legendre正交多项式法的适用范围,为材料力学性能的声学测量提供了理论基础。      

Floquet-bloch waves in bound one-dimensional photonic crystals

Floquet-Bloch waves in a bound one-dimensional photonic crystal are considered. It is shown that a single Floquet-Bloch wave can be excited in a one-dimensional photonic crystal located between two homogeneous media. An exact solution of the wave equation corresponding to this case is represented in the form of a set of heterogeneous waves. For the case of incidence of the plane wave from a homogeneous medium on a bounded one-dimensional photonic crystal, the functions for the reflection and transmission coefficients are obtained based on the exact solution of the wave equation. It is shown that the transmission function for the one-dimensional photonic crystal has a form similar to that for the traditional Fabri-Perot interferometer and is determined by the interference of the Floquet-Bloch waves excited in the crystal. The evolution of the amplitude profile of the decaying Floquet-Bloch waves and the reflection spectrum of the bounded one-dimensional photonic crystal are considered in the first-order forbidden band.     

Anomalous postcritical refraction behavior for certain transversely isotropic media

Snell's law at the boundary between two transversely isotropic media with a vertical axis of symmetry (VTI media) can be solved by setting up a fourth order polynomial for the sine of the reflection/transmission angles. This approach reveals the possible presence of an anomalous postcritical angle for certain transversely isotropic media. There are thus possibly three incident angle regimes for the reflection/refraction of longitudinal or transverse waves incident upon a VTI medium: precritical, postcritical/preanomalous, and postanomalous. The anomalous angle occurs for certain strongly anisotropic media where the required root to the phase velocity equation must be switched in order to obey Snell's law. The reflection/transmission coefficients, polarization directions, and the phase velocity are all affected by both the anisotropy and the incident angle. The incident critical angles are also effected by the anisotropy.     

水平极化光在单轴吸收晶体中的传播

根据光在各向同性吸收介质中传播的分析方法,引入了波法线矢量传播常量,讨论了水平极化光在单轴吸收晶体中的传播规律,得到了波法线折射率、光线折射率、吸收系数等描述吸收晶体性质和光传播性质的物理量的表达式,推导出透明晶体的相应公式.数值计算表明,由该法得到的晶体表面的反射和透射系数与用复折射率表示法得到的结论一致.     

Reflection and transmission of phonons at a planar interface between two dissimilar solids

Two semi-infinite dissimilar crystals with, however, the same crystal structure and lattice parameter are in contact at a planar interface. Using a simple force constant model, restricted to near-neighbour interaction reflection and transmission coefficients for sound waves propagating along one solid are calculated. At low frequencies the reflection and transmission coefficients are determined solely by the force constants and the atomic masses in the two media. At high frequencies the transmission coefficient becomes small if the force constant at the interface between the two media is weak. Information of the local force constant in the interface region can be gained at least in principle, by measuring the reflection and transmission coefficients at high frequencies.     

On the propagation of linear transverse acoustic waves in isotropic media with mechanical relaxation phenomena due to viscosity and a tensorial internal variable: II. Some cases of special interest (Poynting-Thomson,Jeffreys, Maxwell,Kelvin-Voigt,Hooke and Newton media)

The propagation of linear transverse acoustic waves in isotropic media in which mechanical relaxation phenomena occur was considered in a previous paper. In particular expressions for the velocity and attenuation of the waves were obtained and the limiting cases of waves with high and low frequencies were discussed. In the present paper we investigate the propagation of linear transverse acoustic waves in Poynting-Thomson, Jeffreys, Maxwell, Kelvin-Voigt, Hooke and Newton media. We show that the dispersion relations for these waves may be considered as degeneracies of the dispersion relation which we derived in the general case of a viscoanelastic medium with memory. In particular we investigate the explicit dependence of the dispersion relations on the thermodynamic parameters and the phenomenological coefficients.     

One-sided omnidirectional constant transmission between two isotropic media

In this paper, the reflection and transmission at the planar interface between an isotropic achiral medium (IAM) and an isotropic chiral medium (ICM) are theoretically studied. For one of the circularly polarized (CP) waves fullfilling the wavenumber matching condition incident from IAM with incident angle from 0 to π/2, the amplitude reflection and transmission coefficients are constant. The phenomenon is called the omnidirectional constant transmission (OCT). In the situation of CP waves incident from ICM, OCT will not occur, but the absolute values of the amplitude reflection and transmission coefficients can be constants in a range of incident angle under certain conditions. It is suggested that for OCT to occur, both the wavenumber matching condition and the mode matching condition should be satisfied.     

Study of reflection and transmission on the moving interface of medium

The laws of refection and transimission on a moving interface between two nonvacuum medium are studied and the new method, which can be used for handling reflection and transimission on the moving interfaces between the vacuum-nonvacuum media and between two nonvacuum medium is suggested. The formula of reflection and transmission coefficients that suitable for both cases are derived. The present paper not only enriches electrodynamical theory, but also laies the foundation of optical waveguide modulators and other similar device.     

等离子体的分段线性电流密度递推卷积FDTD算法

给出了一种新的色散介质的时域有限差分(FDTD)算法，称为分段线性电流密度递推卷积FDTD算法.利用电流密度和电场强度的卷积关系，给出了该算法的计算公式.通过计算碰撞冷均匀等离子体平板对电磁波的反射系数和透射系数，验证了该算法的高效性和高精度. 关键词： 色散介质 FDTD算法 电磁波     

Study of reflection and transmission on the moving interface of medium

The laws of refection and transimission on a moving interface between two nonvacuum medium are studied and the new method, which can be used for handling reflection and transimission on the moving interfaces between the vacuum-nonvacuum media and between two nonvacuum medium is suggested. The formula of reflection and transmission coefficients that suitable for both cases are derived. The present paper not only enriches electrodynamical theory, but also laies the foundation of optical waveguide modulators and other similar device.     

平面电磁波在任意方向运动的介质-介质界面上的反射和透射

研究平面电磁波从一种介质入射到另一种以任意方向运动的介质时,在介质界面上发生的反射和透射现象,从Maxwell方程组、运动界面的边值关系和运动介质的本构关系出发,得到了反射波和透射波电磁场矢量与入射波电磁场矢量的关系的表达式、反射和透射系数,讨论了反射波、透射波与入射波之间的能量关系,电磁波对运动介质作用力的性质,并得出一些新的结论． 关键词：