光在两单轴晶体间界面的反射和透射

根据位相匹配条件和应该满足的边界方程,在光轴取向任意的条件下,得到了光在两单轴晶体界面的反射和折射的理论表达式,给出了更普遍的公式计算光能量损失以及两束折射光的能量比。数值模拟表明所得结果满足能量守恒,光轴的取向和入射角大小对晶体中折射的o光、e光的能量比有重大影响,但是对反射率影响很小。只要知道了晶体的有关参数及入射条件,利用所给表达式可以计算各光束光能量比,为晶体器件特性研究提供了有力的工具。由于对光轴取向和入射角度没有任何限制,公式具有普遍性。     

光在光轴取向任意条件下的晶体表面透射率

为了分析一束光在晶体表面的能量损失以及两束折射光的能量比,给出了一种求解反射率和透射率的方法。讨论了光从各向同性介质入射到单轴晶体表面时的折射和反射,注意到了e光线与e光波方向的不同,e光折射率与e光波法线折射率的不同,得出了在界面处应该满足的边界方程。在晶体光轴取向任意的条件下,给出了表明各光束间能量关系的折射率和反射率的理论表达式,为晶体器件特性的研究提供了有力的理论工具。数值模拟表明:得到的结果满足能量守恒;反射到各向同性介质中的光的电场(或磁场)与原入射光的电场(或磁场)不再平行;光轴的取向和入射角的大小对折射的o光、e光的能量比有很大的影响。     

光轴方向任意的晶体连续双折射双反射

根据惠更斯定理,研究了单轴晶体光轴任意方向的双折射与全内双反射,给出了光线方向和光波法线方向的普遍公式.讨论了在晶体内沿多个面的连续双折射双反射,分析了前一界面输出量和后一界面输入量之间的联系,得到多次双折射双反射后的光线方向和光波法线方向.在此基础上,适当地选取晶体的界面参数,相当于选取光轴方向,可以使o光和e光的分离角Δoe更大.光轴方向任意的晶体连续双折射双反射对晶体器件的最优化设计非常有帮助.最后给出了改变斜入射2×2电光开关的出射面参数使Δoe优化的实例.     

傍轴光束在单轴晶体中传输的矢量性质

研究了垂直光轴入射的傍轴光束在单轴晶体中传输的矢量性质.通过角谱的方法得到了寻常光（o光）和非常光（e光）在晶体中传输的严格解，并得到了傍轴近似下的矢量传输模型.利用这一模型，分析得到了垂直光轴偏振的入射光束在晶体中只激发o光，而平行光轴偏振的入射光束在晶体中同时激发e光和二阶小量的o光. 关键词： 傍轴传输 单轴晶体 矢量效应     

双折射晶体激光传输的热光效应与电调制机理

本文基于多物理场数值仿真平台COMSOL的RF射频模块,通过有限元法求解电磁场频域分析方程,求解了高斯激光在双折射晶体中的传输问题,重点分析了波长,温度和外加电场强度对o光e光离散角和e光波形的影响。研究结果表明温度升高使得离散角变小,接收屏上e光波形向左偏移,而Z方向外加电场强度正向增大则会使o光e光离散角增大,接收屏上e光波形向右偏移。上述研究结果验证了通过改变外加电场来调节温度影响的可行性,为设计一种消除温度效应的光信号调制装置提供了理论依据和基础。     

Ce∶BaTiO_3中光折变光栅衍射效率上升现象及分析

在对Ce∶BaTi O3晶体进行双光束干涉光折变光栅暗衰减特性的实验研究中,发现了暗条件下光折变光栅归一化衍射效率长时间上升的异常现象:在e光偏振、大入射角度产生光折变光栅的实验中,衍射效率在长逾8 h的时间内持续上升.而在e光干涉、小入射角度和o光干涉时均未出现衍射效率长时间上升的现象.分析认为:由于自泵浦位相共轭光的产生和晶体中的两个深能级参与了光折变过程,形成了衰减速度不同、光栅方向垂直的两个光栅,导致了暗衰减时衍射效率的长时间上升.     

Ce∶BaTiO3中光折变光栅衍射效率上升现象及分析

在对Ce∶BaTiO3晶体进行双光束干涉光折变光栅暗衰减特性的实验研究中,发现了暗条件下光折变光栅归一化衍射效率长时间上升的异常现象：在e光偏振、大入射角度产生光折变光栅的实验中,衍射效率在长逾8 h的时间内持续上升.而在e光干涉、小入射角度和o光干涉时均未出现衍射效率长时间上升的现象.分析认为：由于自泵浦位相共轭光的产生和晶体中的两个深能级参与了光折变过程,形成了衰减速度不同、光栅方向垂直的两个光栅,导致了暗衰减时衍射效率的长时间上升.     

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。     

单轴各向异性晶体纤芯偏振光传播特性分析

提出了一种光纤芯为单轴各向异性晶体、光轴方向为x轴、包层为各向同性材料的新型光纤模型。应用波导方程近似地求出光纤内场强分布,利用数值模拟分析了o光和e光的传播常数β随归一化频率V变化的色散曲线。进一步分析了光纤芯半径对o光和e光的色散方程的影响,结果表明光纤芯半径对o光和e光截止频率没有影响。基于以上特性,分别讨论了o光和e光传播常数β随光纤芯半径变化的曲线。通过分析光纤介电常数对色散曲线的影响,表明当入射光的归一化频率在一定范围内时,通过改变x方向和y方向介电常数的比值可以改变光纤内传播光的偏振方向。研究结果为设计偏振光纤提供了理论依据。     

惠更斯作图法分析双折射中e光的反常现象

在单轴晶体双折射中,e光会发生一些反常的折射现象如负折射、e光离散角、全反射现象等.与文献中普遍所采用的基于平面光波在晶体中传播的电磁理论特性求解的过程不同,本文则以更为直观的惠更斯作图法为出发点,利用几何求解,得出负反射临界角、e光离散角、全反射临界角,并加以说明和讨论.     

光轴与光线轴夹角的数学表示

利用二轴晶的光波面,对光轴与光线轴的关系进行了研究.计算出了光轴与光线轴夹角的具体表达式,把它应用到黄玉与堇青石中,发现夹角远小于1度.这给光学器件的设计提供了重要的依据.最后对一轴晶进行了讨论,结果表明此时光轴方向与光线轴方向一致.     

失调多腔镜型环形谐振腔共轭光轴位置精度分析

为了详细分析由多个反射镜构成的谐振腔内的闭合光轴(共轭光轴)的特性以及存在条件, 首先从光束传输坐标变换的角度, 分析了由多个平面镜所构成的谐振腔的共轭光轴存在条件, 得出了奇数平面镜谐振腔仅当平面镜间具有高精度的相同垂直度时才存在闭合光轴, 而偶数平面镜谐振腔总是存在闭合光轴的结论, 并给出了腔共轭轴随腔镜方向失调而产生的角度变化关系. 然后从矩阵光学的角度分析包含球面镜的谐振腔的共轭光轴在腔镜间传输时的方向变换问题, 具体分析了由两个平面镜和一个球面镜构成的三角形环形谐振腔的闭合共轭光轴存在的问题. 结果表明, 当不同的镜子出现角度偏差时, 腔内仍然存在闭合的共轭光轴, 并给出了对应的腔轴变化以及新谐振面的位置及方向. 由此表明由于球面镜的加入降低了谐振腔共轭轴存在性对平面镜间高精度平行度的要求, 为基于高品质光学无源腔的光谱测量技术的高精度装调工作提供了理论指导.     

Influence of the polarization and optical axis on the transmission behavior in a one dimensional photonic crystal containing uniaxial metamaterial

In this letter, we introduce a one-dimensional photonic crystal (1DPC) structure with a uniaxial metamaterial defect layer. It is proposed to control the transmitted wave of the defect mode by adjusting the orientation of the optical axis and incidence angle for both polarization states. The 4 × 4 transfer matrix method was employed to calculate the transmittance spectrum of the proposed structure. It is shown that the photonic band gaps, the intensity and the peak wavelength of the defect mode depends on the polarization, the orientation of the optical axis and the incidence angle of the wave, due to the strong anisotropy of the metamaterial. The transmittance spectrum curves at different optical axes of the uniaxial metamaterial and the distinct incidence angles are illustrated graphically. It is shown that the defect mode appears as a peak in the transmission spectrum. Pronounced contrasts in the intensity, wavelength positions of the defect mode and photonic band gap were demonstrated depending on the incidence angle and the orientation of the optical axis of the uniaxial metamaterial defect layer for both polarizations. Our structure offers a great variety of possibilities for designing and controlling the transmitted intensity of the defect mode.     

Ray aberrations of two-dimensional oblique lattices on the self-image plane

We extend the geometrical theory of aberration for a self-imaging system to the case of two-dimensional oblique lattices. In our approach, the fundamental translation vectors of the lattice are not restricted in both length and orientation. Evaluating the disturbance of light through the oblique lattice under coherent illumination, we find the conditions of constraint which limit the self-imaging of the oblique lattice. Various types of oblique lattices are shown to obey the self-imaging conditions. We derive the equations to trace the optical paths of self-imaging rays and then analyze the ray aberrations which arise from the difference between the optical paths of a self-imaging ray and of the corresponding actual ray. The ray aberrations are shown to disappear when the periods of the lattice are large compared with the wavelength of light. We find that the ray aberrations carried by self-imaged oblique lattices are totally undercorrected and the aberrated image patches are displaced along the direction tangent vector of a chief ray.     

5F软X光胶片响应特性研究

提出了５Ｆ软Ｘ光胶片对低能Ｘ射线结响应的数学模型，模型中部份参数由厂家提供，其余参数由在１８３ｅＶ和９３３ｅＶ两能点实验标定的胶片响应曲线确定，数学模型及参数有有效性用２８２ｅＶ能点处５Ｆ软Ｘ胶片的实验响应曲线进行了初步检验。     

球谐函数法求解辐射传输方程的假散射和射线效应

假散射和射线效应是辐射传输方程近似解法中出现的特有误差．从辐射传输方程的近似求解过程出发，在定性分析的基础上构造物理模型，通过数值模拟研究球谐函数法（P1和P3近似法）的假散射和射线效应．构造激光平行入射和倾斜入射二维半透明介质的物理模型，通过内部温度场的分布特征研究假散射．构造顶部侧面保持高温而其余侧面保持低温的二维半透明介质方案，通过对比底面边界净热流密度分析射线效应．计算结果表明球谐函数法中同时存在假散射和射线效应，P3近似比P1近似减小了射线效应．同时，球谐函数法的射线效应随光学厚度的增加而减小．     

A Method for Calculating the Ray Paths in Optical Systems Composed of Axially Symmetric Reflecting and Refracting Surfaces

A method for calculating the ray paths in optical systems composed of axially symmetric reflecting and refracting surfaces is outlined. It is assumed that there is no common symmetry axis in the system, so that the ray paths are substantially three-dimensional. For the sake of generality, both the simplest cases admitting of an analytic solution and the more intricate cases when iterative procedure has to be used are considered. Particular attention is given to the computation features which make the algorithm both universal and robust. The method proposed allows for the use of a wide range (five types of the surfaces specified) of optical elements. Furthermore, the approach suggested is universal and, as such, makes it possible also to pass on with relative ease to other cases of specifying the surfaces.     

红外导引头高速流场及其对光线传输影响的数值模拟

研究红外光线经过高速流场时由于折射产生的瞄视误差(BSE),对于红外末制导拦截弹的命中精度有重要意义。考虑高温真实气体效应,求解热化学非平衡Navier-Stokes(N-S)方程得到导引头的流场,采用光线追迹的方法,对红外光线经过流场后到达导引头光学窗口的瞄视误差进行了计算分析,研究了光线入射角、飞行马赫数、攻角、高度及红外导引头外形对瞄视误差的影响。     

Ray splitting in the reflection and refraction of surface acoustic waves in anisotropic solids

This paper examines the conditions for, and provides examples of, ray splitting in the reflection and refraction of surface acoustic waves (SAW) in elastically anisotropic solids at straight obstacles such as edges, surface breaking cracks, and interfaces between different solids. The concern here is not with the partial scattering of an incident SAW's energy into bulk waves, but with the occurrence of more than one SAW ray in the reflected and/or transmitted wave fields, by analogy with birefringence in optics and mode conversion of bulk elastic waves at interfaces. SAW ray splitting is dependent on the SAW slowness curve possessing concave regions, which within the constraint of wave vector conservation parallel to the obstacle allows multiple outgoing SAW modes for certain directions of incidence and orientation of obstacle. The existence of pseudo-SAW for a given surface provides a further channel for ray splitting. This paper discusses some typical material configurations for which SAW ray splitting occurs. An example is provided of mode conversion entailing backward reflection or negative refraction. Experimental demonstration of ray splitting in the reflection of a laser generated SAW in GaAs(111) is provided. The calculation of SAW mode conversion amplitudes lies outside the scope of this paper.