双折射位相差的拟合表达式及其应用

探讨双折射晶体的ｏ光和ｅ光的位相差的表达式，对文献中常引用的表达式作近似展开，得到一个适用性的拟合表达式及其拟合系数与昌体或液晶双折射率之间的关系，并给出该表达式的简单应用。它可作为设计晶体旋转法测试液晶双折射和预角测试仪的原理。     

冰洲石晶体色散方程解析研究及折射率温度系数表达式

冰洲石晶体的主轴折射率随波长变化而变化。本文通过对Sellmeier方程严格求解．得出其系数表达式。经验证，折射率的计算值与实验值十分吻合。通过线性插值的方法求解出不同波长的温度系数表达式．从而得出不同温度不同波长的冰洲石晶体的主轴折射率，得到Sellmeier方程常数在各温度下的常数值。     

高斯光束菲涅耳圆孔衍射轴上的光强分布

本文从惠更斯－菲涅耳原理的数学表达式出发，在菲涅耳圆孔衍射的情况下求出了高斯光束入射时轴上光强分布的解析表达式，并对比平面波和球面波入射的情况进行了分折讨论．     

超高速分布放大光孤子传输系统分析

利用微扰理论方法推导了飞秒光孤子脉冲在具有一定带宽限制的分布放大光纤传输系统中传输时，脉冲宽度和频移的变化方程，此方程有稳态解，并得到稳定传输时，脉冲宽度及频移的解析表达式。     

固体中激光热弹超声的光穿透效应

本文从热弹性基本方程出发，理论上研究了非金属固体材料受激光热弹激励超声时，光穿透效应对所产生声波的影响。在一维模型中，通过求解热扩散方程和热弹性位移方程，得到弹性位移的一般表达式，分析了材料的光叩收性质与声波位移振幅的关系。在二维模型中，对于轴对称分布的情况，忽略热扩散的影响，采用积分变换法求解热弹性运动方程，推导出远场区中的位移解析表达式。给出了纵波和横波的指向性图案，讨论了光穿透效应对声源指向性的影响。     

X射线双晶衍射摇摆曲线本征半峰宽的理论计算

本文应用X射线衍射动力学理论,推导出Bragg衍射几何X射线双晶衍射反射率的数学表达式。多种晶体、不同衍射的摇摆曲线计算结果表明,σ偏振的摇摆曲线的峰值和积分强度均比π偏振的高。而且半峰宽较宽。同时指出,对圆偏振X射线入射或者A,B两晶体不同类或者两者的衍射级数不相同时,很多文献给出的双晶衍射摇摆曲线半峰宽的近似表达式2^1/2∞不再适用。 关键词：     

单轴晶体的光程差和Lyot型滤光器的视场

 建立了以光线入射方向和晶体光轴方向为基准的入射坐标系，利用波法线反曲面方程和电磁场在晶体折射界面处切向分量连续性的边界条件，得到了晶体中波法线方向、射线方向、波法线折射率和射线折射率的表达式。从非常光的射线方向和射线折射率出发，得到了在任意的晶体光轴方向和入射角条件下，光通过单轴晶体后寻常光、非常光的光程差表达式。对Lyot型滤光单元的透射率和视场进行了计算分析后发现，滤光单元的透射率随光线入射角的变化呈现一定的周期性，视场随光轴倾角的增大而减小。得出了透射率和视场随光轴倾角(光轴与晶体表面的夹角)和光线入射角(光线在晶体表面的入射角)的变化规律。讨论了通过改变晶体倾角实现滤光器调谐和补偿晶体厚度加工误差等技术问题。     

双轴晶体主平面上倍频的相位匹配参量

根据折射率椭球方程及双光轴晶体中光波的传播与偏振特性，分析双轴晶体在主平面内激光倍频相位匹配的特性与方法，导出光波在主平面上传播时倍频的相位失配关系；给出双轴晶体中容许相位匹配倍频的相位匹配角及混频的有效非线性系数deff的表达式。利用可相位匹配的类型、相位匹配角公式和有效非线性系数deff表达式的表，容易对任意一具体晶体在一给定波长求出实际能实现相位匹配的类型或偏振组合，算出相位匹配角，比较不同的相位匹配类型或偏振组合的有效非线性系数，选择最佳的相位匹配类型与方向。从相位失配关系可以计算晶体主平面内倍频的接收角、接收光谱宽度等特性参量。     

本体极面究竟如何打滚

本文通过对Ｉ１＝Ｉ２≠Ｉ３时欧勒－潘索情况的动力学方程的求解，分别得到角速度矢量在绝对系和固连系运动的表达式，指出了本体极面究竟如何在空间极面上打滚的正确方向．     

叉指电光布拉格衍射光栅分析

叉指电光布拉格衍射光栅能够用于制作集成光学器件。将点匹配法扩展应用于又指电光布拉格衍射光栅分析,将光栅各区域的势函数表示为该区域中满足拉普拉斯方程的一系列基函数的级数,匹配边界上有限个点的边界条件以确定出级数项的系数,从而得到叉指电傲电场分布的解析表达式,在此基础上得到了叉指电光布拉格衍射光栅的一些重要的光学与电学特性参量。将分析结果与测量值进行了对比,发现二者十分吻合。所提出的分析方法简便快捷、精度高,所导出的电场分布的解析表达式和分析结果对叉指电光衍射光栅的优化设计具有重要的意义。     

Eikonal approximation of dynamical diffraction equations for X-ray beams with two-dimensional curvature of the wave front. I. Basic formulas

Taking into account the second derivatives of amplitudes with respect to the coordinate perpendicular to the diffraction plane, the eikonal approximation of dynamical diffraction equations for X-ray beams with two-dimensional curvature is presented. The diffracted field outside the crystal, in vacuum is described by the corresponding eikonal approximation of the parabolic equation of diffraction. The corresponding eikonal equations and complete integrals are obtained in case of a perfect crystal. A method is described, by which the eikonals and trajectories inside the crystal as well as in vacuum, outside the crystal, satisfying the given boundary conditions, can be obtained. This method allows to describe diffraction using sufficiently general assumptions on the incident wave front and for the non-plane entrance and exit surfaces of the crystal.     

四能级增益介质光子晶体激光器的时域有限差分模型与模拟

基于Maxwell-Bloch方程和速率方程相结合的模型,模拟包括四能级增益介质光子晶体激光器的光学特性.根据FDTD法的基本原理,给出方程的Yee氏离散方程.通过计算电场的时域特性,模拟光子晶体激光器的频谱特性、阈值特性、动力学演化等过程,模拟结果和理论结论一致,检验了该模型的有效性.     

Superfluidity of a perfect quantum crystal II

This paper continues the work begun in a previous paper [Eur. Phys. J. B 71, 85 (2009)]. To treat the equations that describe a crystal with condensate that can be superfluid, a method termed the Kirkwood approximation is used. Earlier, the method was found to be rather seminal when applied to a classical crystal. In the case of a simple cubic lattice, solutions to the equations under study can be expressed in terms of the well-known Mathieu functions. A more realistic case of the face centered cubic lattice is also considered although in this case the three-dimensional equations cannot be reduced to one-dimensional ones. Condensate crystals without superfluidity are studied first and then the same crystals in a superfluid state. It is shown in particular that a crystal in which the condensate is formed is energetically preferable with respect to the same quantum crystal without condensate at absolute zero of temperature. Therefore, on lowering the temperature there must somewhere occur Bose-Einstein condensation in the crystal. In the concluding section, we discuss various physical aspects of the problem.     

Multiple-beams Mutually Pumped Phase Conjugation Generated by a Bridge Phase Conjugator in Photorefractive Ba1-xSrxTi03 Crystal

A new method generating multiple-beams mutually pumped phase conjugation (MMPPC) in a photorefractive Bat- xSrxTiO3 crystal is demonstrated, in which a pumping beam is incident upon a-face of the crystal and two signal beams are introduced into + c face of the crystal with the almost same incident angle and position. The time evolution of the phase conjugations from signal beams and the dependence of phase-conjugate reflectivities on the input-beam intensity ratios are presented. Also, the amplitude coupled-wave equations based on the model of two interaction reigns is derived. The results obtained by numerical calculation of the corresponding coupled-wave equations show qualitative agreement with the experimental results.     

Multiple-beams Mutually Pumped Phase Conjugation Generated by a Bridge Phase Conjugator in Photorefractive Ba1 - xSrxTi03 Crystal

A new method generating multiple-beams mutually pumped phase conjugation (MMPPC) in a photorefractive Bat- xSrxTiO3 crystal is demonstrated, in which a pumping beam is incident upon a-face of the crystal and two signal beams are introduced into + c face of the crystal with the almost same incident angle and position. The time evolution of the phase conjugations from signal beams and the dependence of phase-conjugate reflectivities on the input-beam intensity ratios are presented. Also, the amplitude coupled-wave equations based on the model of two interaction reigns is derived. The results obtained by numerical calculation of the corresponding coupled-wave equations show qualitative agreement with the experimental results.     

The concept of “incompatibility” for a simple model of a crystal lattice

A system of equations is derived for a simple model of a crystal lattice disturbed by a dislocation. The model is represented by two rows of atoms. The system of equations is analogous to that describing a singular dislocation in the theory of the continuous distribution of crystal imperfections. The method of solving the derived system of equations is given.     

Analytical description of the thermomechanical deformation of a crystal

A metallic single crystal is considered as a thermodynamic system interacting with a surrounding medium by mechanical and thermal forms of motion in an irreversible process. The equations determining the process are obtained, taking account of the changes in structure and thermal conductivity of the crystal, for which new concepts of mathematical expectation and additional stress are introduced.     

Coherence and saturation properties of second-harmonic generation with a nonlinear crystal inside the laser cavity

The basic equations for second-harmonic generation including noise are derived for the case that the nonlinear crystal is put inside the laser cavity. A realistic model of a (detuned) laser with two-level atoms in single-mode operation is taken using the nonlinear theory of laser noise which describes the laser saturation effects, the phase diffusion and the intensity fluctuations. The reaction of the second-harmonic field on the fundamental field is taken into account as well as the reaction of the fundamental field on the laser. The nonlinear crystal is described by microscopic anharmonic oscillator equations (without introducing nonlinear susceptibilities by perturbation theory). The saturation of the polarization of the nonlinear medium is taken into account exactly with the only assumption that the influence of third and higher harmonics should be small. The electromagnetic field is described semiclassically by stochastic equations. In all equations, the damping is introduced simultaneously with Markoffian fluctuating forces by coupling to heatbaths. The equations are solved exactly in the stationary state without noise (the time dependent solution including noise will be presented in a subsequent paper). The most important saturation effect is a frequency shift which depends on the laser intensity.     

Theory of formation of second-phase particles as a result of diffusive saturation of solid solutions

A complete system of canonical equations, which describes the precipitation of new-phase particles as a result of diffusive saturation, is formulated. An asymptotic solution of this system of equations with respect to time is obtained in the general form. The volume of the precipitated new phase and the motion of the boundary of a two-phase region at a given point in the crystal is found for sufficiently large times to be independent of the nucleation mechanism and of the mechanism of mass to the particles of the precipitated phase.