Refraction of light in two-dimensional photonic crystals

Refraction of light at an interface between a homogeneous dielectric and a two-dimensional photonic crystal is studied. Using the isofrequency method, various cases of refraction, including a change in the magnitude and direction of the wave vector of the incident wave, in the refractive indices of the media, and in the mutual orientation of the interface and the translation vectors of the photonic crystal, are investigated. Different types of refraction and the possibilities for realizing negative and multiwave refraction are considered.     

Ultrasonic diffraction of Bessel light beams in uniaxial gyrotropic crystals

Specific features of the acousto-optic diffraction of Bessel light beams propagating in the vicinity of the optical axis of a uniaxial gyrotropic crystal have been investigated. The dependences of the diffraction efficiency on the acousto-optic interaction length, ultrasound power, and polarization state of the incident Bessel light beam have been analyzed using the coupled-wave equations and the overlap-integral method. It is shown that polarization-independent diffraction of Bessel light beams is observed in paratellurite crystals, when the Bragg diffraction efficiency is independent of the polarization state of the incident beam. The physical reason for this diffraction has been established (both theoretically and experimentally) to be simultaneous implementation of two processes of anisotropic scattering, at which the Bragg synchronism conditions are satisfied for orthogonal polarized Bessel beams with elliptical polarization.     

Wideband light diffraction on bulk acoustic waves in uniaxial crystals

We study diffraction of light on ultrasonic waves, excited by a system of interdigitial transducers, in uniaxial crystals. We show that wideband acoustooptical diffraction in trigonal crystals in the presence of additional anisotropy differs significantly from the isotropy of diffraction on a shear ultrasonic wave in the absence of it. We establish that an exact Bragg angle correction in a wide frequency retuning range is achieved owing to electrically induced anisotropy in the external electric field.     

对单轴晶体中光的性质和双折射问题的几点讨论

指出了关于光在单轴晶体中的传播、偏振及双折射问题中的几个模糊概念或论点;证明了在单轴晶体中属同一波矢的两个线偏振光光矢量的偏振方向也是相互垂直的,而且此两光的主平面是相互重合的;分析了在双折射教学中尚存的不足之处和个别欠妥的提法;指出在讨论双折射问题时必须加入适当的基础理论,而仅用定性作图法将对理解掌握该部分内容带来某些弊端．     

光在介质中的折射

研究了光的磁场在光与介质相互作用中的行为,建立了电子云导体模型,即介质中一个电子的电子云可以看作是一个微小导体,光变化的磁场与电子云导体间的电磁感应作用导致光与电子云导体之间的能量交换。光在介质中速度减慢起因于这种能量交换。应用电子云导体模型和能量守恒原理,导出了介质折射率表达式,并利用这个表达式计算了几种介质的折射率,计算结果与实测值符合得很好。解释了折射率的各向异性,以及静电场或静磁场对介质折射率的影响。     

Refraction of light in media

The roles of the magnetic field and electric field of the light are investigated when the light is refracted in the medium. The model of the electron cloud conductor is presented. Electron cloud in a molecule is treated as a conductor and the Faraday’s Law is applied to this conductor that is in the alternating magnetic field of the light. dB _M/dt of the light gives rise to an alternating induced current on the electron cloud conductor, and the light exchanges energy, i.e. the refractive energy, with the electron cloud conductor. Formulas of refractive index, which is the ratio of light speed in vacuum to that in the medium, are derived with this model. These formulas are tested with several mediums and Langevin’s diamagnetic susceptibility of helium gas, and the results are in good agreement with the measured data. The anisotropy and the nonlinearity of the refractive index are explained with the theory described in this work. Supported by Beijing Science and Technology New Star Program (Grant No. 952870400), the Beijing Municipal Commission of Education and the Excellent Young Teachers Program of Ministry of Education of China     

The effectiveness of mixing differently polarized light waves at uniaxial nonlinear crystals

General expressions for the nonlinear interaction coefficients are obtained for three methods of mixing light waves at uniaxial crystals in the phase matching directions. Comparison of these coefficients enables one to choose the most effective method of mixing waves. Such a comparison is carried out for the generation of the difference frequency at a lithium niobate crystal and of the sum frequency at a KDP crystal in mixing the radiations of ruby and neodymium lasers.     

Optical breathers in uniaxial crystals

Anisotropic crystals are shown to have three different mechanisms of the formation of breathers depending on the direction of the extraordinary wave propagation and on the symmetry of the medium. All uniaxial crystals with quadratic susceptibilities can be divided into three different groups, according to the crystal classes (CC). Each group is characterized by a universal structure of the breather zones (SBZ). The SBZ of the media with cubic susceptibilities does not depend neither on the crystal systems nor on the CC and coincides with the SBZ of the crystals with quadratic susceptibilities and the CC 3, 3m, 4, 4mm, 6, 6mm.     

Electro-optic modulation of light propagating near the optic axis with any polarization in uniaxial crystals

The electro-optic effect in uniaxial crystals for light propagating near the optic axis with any polarization has been analyzed. The passive and the electrically induced birefringences and the rotation of polarization direction in crystals have been calculated, and the conoscopic interference figures under orthogonal polariscopes for different polarizer directions have been plotted. The extinction areas caused by the rotation of polarization direction in crystals change with the polarizer direction, but the two heads of the induced optical axes do not vary, which are always on the induced principal axis with bigger refractive index. The directions of polariscopes are always extinction, and the ±45° directions with polarizer are always complete transmission. The conoscopic interference figures for LiNbO₃ crystals have been demonstrated experimentally by rotating polariscopes directions, which accord with the theoretically calculating plots.     

Electrooptical parameters of uniaxial crystals

For the linear effect in classes 4, ¯4, 42, 4 · m, 6, 62, and 6 m, one of the optic axes always coincides with the high-order symmetry axis c when the electric field e lies in a plane perpendicular to that axis, while the other describes a circular cone around c as e rotates in that plane. The same rotation in classes 3, 32, 3 · m, 3 m, and m · 3 m causes both optic axes to deviate from c to opposite sides by equal angles, both describing circular cones. One of the optic axes always coincides with c for any direction of e in classes 42 and 62, while the other axis describes an elliptic cone around c as e rotates in a plane inclined to c. Both optic axes describe an elliptic cone in classes 3 m, 32, and m · 3 m.     

Additional beams in optically uniaxial crystals

Reasons for occurrence of additional beams are established for rays reflected from a tilted prism face and transmitted through the interface between two crystal media. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 50–53, July, 2007.     

Generation of singular beams in uniaxial crystals

The process of generation and transformation of the structure of singular beams both coherent and incoherent, in a crystal-polarization compensator-polarizer system is studied. It is shown that this system can transform the topological charge of the initial beam. The value of the transformed charge depends both on the structure of the initial beam and on its polarization. The initial singular beams, transferring topological multipoles, are shown to acquire unique properties after passing through the system. This system, in particular, makes it possible to control the position of bound optical vortices and the magnitudes of their angular momenta, which may find practical application in devices for trapping, transportation, and mutual arrangement of microparticles.     

平顶高斯光束在单轴晶体中的传输

基于光束在各向异性单轴介质中的近轴矢量传输理论，对平顶高斯光束在单轴晶体中的传输 作了研究，得到了解析的传输公式. 利用该传输公式可用一种简单的方法研究平顶高斯光束 在单轴晶体中的传输. 研究结果表明，由于晶体的各向异性特性使平顶高斯光束初始的圆对 称性在传输过程中不能保持，并且其偏振状态也随传输而变化. 用数值计算例对晶体内源于 入射平顶高斯光束的寻常光和非常光的场分布以及x和y方向的偏振分量在空间中的演化都作 了详细说明. 关键词： 平顶高斯光束 单轴晶体 各向异性 近轴矢量理论 传输公式     

单轴晶体中光折射的图解计算及会聚偏振光干涉的定量分析

介绍了用单根入射光线图解各向同性和各向异性介质中折射线的作图法,该方法可直接求得非寻常光的波法线方向,从而为利用（通常）折射率计算光程提供方便,作为实例,分析计算了单轴晶体中会聚偏振光的干涉,得到了比已有文献更为精确和简明的结果。     

Optoacoustic interaction in uniaxial gyrotropic quartz crystals

The specific features are considered of the noncollinear optoacoustic interaction in uniaxial gyrotropic quartz crystals in an intermeadiate regime of diffraction close to the Bragg regime. A system of equations of coupled waves is presented which describes the optoacoustic interaction in uniaxial gyrotropic crystals in the Raman-Nath, intermedaite, and the Bragg regimes of diffraction. The dependences of the diffraction efficiency on the ultrasonic wave intensity, the optoacoustic interaction length, and on the incident light polarization are investigated. A multispike structure of the Bragg maximum is studied that appears in accounting for the crystal gyrotropy. A good agreement between the theoretical calculations and the known experimental results for a quartz crystal is shown. Mozyr State Pedagogical Institute, 28, Studencheskaya Str., Mozyr, 247760, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 278–281, March–April, 1999.     

Waves and rays in uniaxial birefringent crystals

In this paper, we present a more elaborate and complete way of the formalism that we have developed in successive steps for ray tracing through uniaxial birefringent media in view of the optical design. With the obtained formulas we analyze in detail what we see through a cleavage calcite crystal.     

Features of acousto-optic interaction in uniaxial gyrotropic crystals

The features of noncollinear acousto-optic interaction in gyrotropic crystals in the intermediate diffraction regime and the regime of Bragg diffraction were investigated. The dependence of the efficiency of diffraction in gyrotropic paratellurite, tellurium, and quartz crystals on the intensity of the ultrasonic wave, acousto-optic interaction length, and incident-light polarization was investigated. It is shown that the gyrotropy of the crystal is responsible for the appearance of a multiple-peak structure of the Bragg maximum. It has been established that in the case of propagation of incident and diffracted waves in the vicinity of the optical axis of the crystal, the diffraction efficiency is independent of the polarization state of the incident light. The results of theoretical calculations are in agreement with the experimental results obtained for uniaxial crystals. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 105–110, January–February, 2000.