Backscattering of electromagnetic waves by large-scale inhomogeneities in a periodically inhomogeneous medium

It is shown that backscattering of electromagnetic waves is possible in a periodically inhomogeneous medium by random inhomogeneities whose scale is greater than the wavelength. A small scattered field emerges in the case of appearance of the Bragg cavity when the periodic layer is a matching system for the incident wave. Scattering is effective even for inhomogeneities whose scale is much greater than the Fresnel radius of the inhomogeneous layer. The correlation radius of the scattered field can also be that large. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 10, pp. 1230–1240, October, 1997.     

非均匀量子等离子体中的非线性波

本文探讨具有温度和密度梯度的非均匀量子等离子体系统, 获得了该系统在离子与中子碰撞频率较低情况下的二维非线性流体动力学方程． 求得了非均匀量子等离子体中的电势的冲击、爆炸和旋涡解．分析讨论了在致密天体物理环境中静电势的变化, 结果表明电势的冲击波的幅度和爆炸波的宽度,都随密度的增大(即随无维量子参量的减小)而增大, 但随漂移速度的增大(即随密度和温度梯度的增大)而减小; 静电势随时空相位的增大而趋向于稳定值, 系统最后达到稳定的状态． 旋涡解表明,旋涡静电势的时空分布呈现稳定的周期性的旋涡流．     

Nonlinear waves guided by graded-index films

We derive both the dispersion relation and the power flow for waves guided by a linear graded-index film in contact with an arbitrary nonlinear cladding. For an exponential-like graded-index profile and a Kerr-like nonlinearity we present numerical results and compare them with those familar from the step-index profile.     

Nonlinear resonant two-wave interaction in an inhomogeneous medium

A one-dimensional steady-state nonlinear resonant two-wave interaction in a lossless periodically inhomogeneous medium is investigated. It is shown that the amplitudes and the phases of the waves vary in a stochastic manner.     

非均匀等离子体对平面电磁波的衰减

利用荧光灯排列形成非均匀等离子体层（面积约60 cm×52 cm,消耗功率约400 W）,研究了其对1～8 GHz E波（电矢量方向平行于灯轴方向的入射波）的反射和透射的影响。结果表明,该等离子体对1～4 GHz的E波具有强吸收和弱反射的特性,单程衰减最高可达8 dB。利用2维分段线性电流密度递归卷积时域有限差分计算式,模拟了E波传播及其在非均匀等离子体内推进的瞬态过程,计算了等离子体对电磁波的反射和透射衰减,并与实验结果拟合,得到等离子体电子数密度峰值约9.72×1016 m-3-3,电子与中性粒子碰撞频率约4 GHz。     

非均匀等离子体对平面电磁波的衰减

利用荧光灯排列形成非均匀等离子体层(面积约60cm×52cm,消耗功率约400W),研究了其对1～8GHzE波(电矢量方向平行于灯轴方向的入射波)的反射和透射的影响。结果表明,该等离子体对1～4GHz的E波具有强吸收和弱反射的特性,单程衰减最高可达8dB。利用2维分段线性电流密度递归卷积时域有限差分计算式,模拟了E波传播及其在非均匀等离子体内推进的瞬态过程,计算了等离子体对电磁波的反射和透射衰减,并与实验结果拟合,得到等离子体电子数密度峰值约9.72×1016m-3,电子与中性粒子碰撞频率约4GHz。     

On electromagnetic waves by an accelerated charged particle in medium

We have investigated the effects of acceleration of a charged particle on its Cerenkov emission and ionization-losses. We have considered the accelerated motion of a charged particle in an infinite medium with the acceleration parallel to the direction of its motion. We have used the method of Fourier transforms to solve the Maxwell's equations with appropriate current and charge-densities to find electromagnetic fields and hence the force experienced by the incident charge due to its interaction with the medium (dielectric or plasma). The results obtained are general and applicable to any acceleration. In the approximations of ‘small acceleration’ and ‘small interaction time’, we have solved the wave equations and determined electromagnetic potentials. It is found that the acceleration of the charged particle strongly changes both its ionization-loss and Cerenkov emission.     

Diffraction of electromagnetic waves by ultrasonic waves in an anisotropic medium. I

Summary The theory of diffraction of electromagnetic waves by an ultrasonic wave in a crystal is discussed above. Expressions are obtained for the diffraction field in the near and the far zones. In the near zone the system is shown to be describable by the scattering matrix S of a 2(N+1)-pole, thus enabling the matrix method of network theory to be used for in vestigating different kinds of cascade connection of such systems. The expressions obtained contain the classical formulas of scalar diffraction in an isotropic layer as particular cases.Izvestiya VUZ. Radiofizika, Vol. 9, No. 1, pp. 16–32, 1966     

Calculation of nonlinear waves guided by optical fibers with an inhomogeneous nonlinear core

A circular optical fiber consisting of an inhomogeneous nonlinear core bounded by a linear cladding medium is considered here. In this case, the calculation of the nonlinear modes is of practical importance because of the joint effects of nonlinearity and inhomogeneity on the field concentration and the achievable optical confinement. Numerical results indicate that the combination of this type of inhomogeneity along with the characteristics of nonlinearity may play a significant role towards the optical confinement in the core.     

Nonlinear waves guided by a dielectric slab

An exact solution of Maxwell's equations is found for TM-polarized nonlinear guided waves which are guided by a linear dielectric slab embedded between two nonlinear uniaxial media. Additional waves in comparison with the linear case arise. Some of these waves have no counterpart in linear systems. Similarities and differences with respect to TE-polarized nonlinear guided waves are pointed out.     

Nonlinear waves guided by a dielectric slab

We consider dispersion relations and field structure of TE-polarized guided waves travelling along an asymmetric dielectric slab surrounded by two different nonlinear media. For a given configuration there are four types of guided waves. Three of this four types possess at least one field maximum outside the slab region and have no counterpart in linear waveguide optics. The solutions of the dispersion relations depend now on an additional parameter making them more flexible with respect to the linear limit.