ON FREE WAVE PROPAGATION IN ANISOTROPIC LAYERED MEDIA

The method of reverberation-ray matrix （MRRM） is extended and modified for the analysis of free wave propagation in anisotropic layered elastic media. A general, numerically stable formulation is established within the state space framework. The compatibility of physical variables in local dual coordinates gives the phase relation, from which exponentially growing functions are excluded. The interface and boundary conditions lead to the scattering relation, which avoids matrix inversion operation. Numerical examples are given to show the high accuracy of the present MRRM.

Anisotropic optical and electronic properties of two- dimensional layered germanium sulfide

Two-dimensional （2D） layered materials, transition-metal dichalcogenides, and black phosphorus have attracted considerable interest from the viewpoints of fundamental physics and device applications. The establishment of new functionalities in anisotropic layered 2D materials is a challenging but rewarding frontier, owing to the remarkable optical properties of these materials and their prospects for new devices. Herein, we report the anisotropic and thickness- dependent optical properties of a 2D layered monochalcogenide of germanium sulfide （GeS）. Three Raman-scattering peaks corresponding to the B3g,, A1g, and A2g modes with a strong polarization dependence are demonstrated in the GeS flakes, which validates polarized Raman spectroscopy as an effective method for identifying the crystal orientation of anisotropic layered GeS. Photoluminescence （PL） is observed with a peak at -1.66 eV that originates from the direct optical transition in GeS at room temperature. The polarization-dependent characteristics of the PL, which are revealed for the first time, along with the demonstration of anisotropic absorption, indicate an obvious anisotropic optical transition near the band edge of GeS, which is supported by density functional theory calculations. The significantly thickness-dependent PL is observed and discussed. This anisotropic layered GeS presents opportunities for the discovery of new physical phenomena and will find applications that exploit its anisotropic properties, such as polarization-sensitive photodetectors.

The propagation of Lamb waves in an anisotropic plate bordered with liquid layers

Based on elastic wave propagation theory, the dispersion equation for a thin anisotropic plate (such as commonly used Zinc okide in micro-transducers) bordered with liquid layers is derived. Higher symmetry crystals, such as orthorhombic, tetragonal, cubic, isotropic, are included in this analysis as well. For the case of one liquid layer loading, numerical calcu- lations show that the phase velocity changes periodically with the thickness of the liquld layer. When the thickness 2d of the anisotropic plate is very small, mass sensing application of Ao mode Lamb wave is also discussed.

Absorption of electromagnetic wave by inhomogeneous,unmagnetized plasma

In this article,a novel and normalized Ztransform finite-difference time-domain(ZTFDTD)method is presented.This method uses a more general form of Maxwell’s equations using the E,H,D fields.The iterative model of D-E-H-D can be obtained by using the Z-transform resulted frequency-dependent formula between D and E.The advantages of the ZTFDTD consist in that the discrete equations are simple,the results are precise,easy to program and capable of dealing with the key technologies of finite-difference time-domain(FDTD),such as absorbing boundary conditions(uniaxial anisotropic perfectly matched layer,UPML)and near-to-farfield transformation.The ZTFDTD method is then used to simulate the interaction of electromagnetic wave with plasma.Using a simplified two-dimensional model,the stealth effect of inhomogeneous,unmagnetized plasma is studied both in different electron densities of plasma,different electromagnetic wave frequencies and different plasma collision frequencies.The numerical results indicate that plasma stealth is effective in theory and a reasonable selection with the plasma parameters that can greatly enhance the effectiveness of plasma stealth.