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。     

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。     

光在双轴晶体中的传播

单轴晶体中光的传播情况已为人们所熟知.它的物理图象简单清晰,也便于定量计算.双轴晶体中光的传播要复杂得多,且不便于定量计算.本文的分析表明,单色平面波在双轴晶体中传播时,相应的两光振动是处在这样两个平面内,即由波法线分别和两个晶体光轴所成平面的两个平分平面内.与单轴晶体相类似,我们定义这两个平分平面为两光的主平面,相应的两光线也分别处在这两个主平面内,其方向与波法线方向之间有明确的关系.在晶体界面上的双折射中,两光波法线都满足折射定律,两光线方向也可随之确定. 一、一般描述 若单色平面波在晶体中的波法线为S,两个…     

单轴晶体光学公式的系统推导

引言 光在各向异性晶体中的传播行为是复杂的,问题的分析将涉及若干线和若干面.尤其是对于描述晶体光学各向异性的波面、光线面、法线面、折射率椭球面等,由于在基础光学中缺乏对它们的系统推导,使人往往不能正确地清晰地理解这些面之间的联系和区别.就笔者所见到的国内外一批光学书籍看,对这些面的阐述方式大致分两类. 第一类的处理要点是,开宗明义提到惠更斯在《论光》中的基本假设,晶体中的点源同时激发两个波前,一个是球面波前,另一个是旋转椭球面波前,并将此模型应用于晶体中的惠更斯作图法,对双折射现象作出定性说明.但是,书中没有利…     

基于混合导光型光子晶体光纤的波分解复用器研究

设计了一种基于混合导光型光子晶体光纤的波分解复用器,该波分解复用器同时具有折射率导光型光子晶体光纤和带隙导光型光子晶体光纤的特点,可用于稀疏型波分复用系统中.设计的稀疏型波分解复用器由一段三芯光子晶体光纤组成,通过填充不同折射率的材料.形成了混合导光型光子晶体光纤.根据耦合模原理,在临近的波导中,当传播常数相等时,模式之间发生强烈耦合.能量在波导之间交替.由于填充的材料折射率不同,使得光功率在两个小同的波长上发生耦合,构成了两个不同响应波长的光滤波器.通过选择合适的光纤长度,使得在光纤的输出端,不同波长的光从不同的波导输出,实现波分解复用的功能.采用全矢量有限元法分析了光纤传输特性,计算了不同波长光的耦合长度.采用光束传播法仿真发现,长度为4.3 mm的光纤能实现波长为1.31μm和1.55μm光的解复用.     

一维光子晶体反常折射的数值分析

分析了一维光子晶体中产生反常折射的原因,根据波向量图对光在其中传播的方式做了定性的分析.根据一维光子晶体中具有波频率与波向量之间明确解析表达式的特点,指出利用此关系式能方便地对光在其中的传播方式进行深入的分析.利用这种方法,文中分析了光在其中传播的一些性质.指出光的偏移性质与角度和频率密切相关.     

光扇效应对Ce：KNSBN记录偏振组态的影响

在非同时读出条件下 ,采用Ar+ 5 14 .5nm单色激光为光源。以信号光为非寻常偏振光 (e光 ) ,通过改变抽运光的偏振态 ,研究不同写入光偏振组态下Ce∶KNSBN晶体的两波耦合特性。结果表明 :由于光扇效应的影响 ,信号光和抽运光同为e光时并非如预测的那样为最佳记录偏振组态。在信号光和抽运光与晶体表面法线呈θ =11°角对称入射下 ,当抽运光的偏振方向与e光偏振方向呈 30°角时 ,光扇噪声得到明显抑制 ,两波耦合增益最大。其原因是抽运光的o光分量对光扇散射光起到了非相干擦除 ,使两波有效耦合得到提高。     

红宝石晶体的双散射

一、引 言 红宝石晶体是掺Cr3+的a-Al2O3单晶体,空间群为D3d-R3C,在光学性质上为单光轴晶体.根据晶体光学原理,一束具有各种振动的自然光进入单光轴晶体后.一般情况下,将分成两种互相垂直振动的偏振光:寻常光和反常光.二者在晶体内以不同的速度传播,因而晶体有两种不同的折射率(分别记为n 和 ),称为晶体的双折射.通常,定义 为双折射系数。红宝石为负单轴晶,即n ,而且 在晶体内,两种偏振光被吸收的情况也不相同.有两种吸收系数.吸收系数k可以按以下建议的定义[2]进行测定计算: 对寻常光, 对反常光,其中,几为光的波长,t为样品通光厚度,I0为…     

用光纤白光干涉技术测量晶体的弹光系数

运用折射率椭球分析晶体的弹光效应,给出了三方晶系沿光轴方向的应力与折射率的变化关系.针对晶体的各向异性和折射率随应力变化很小的因素,利用白光干涉技术空间分辨率高的特点,将白光干涉技术拓展到研究各向异性材料的光学性质. 并对测量群折射率的光纤迈克尔逊白光干涉技术进行了改进.采用光栅位移传感器和全保偏光纤提高反射扫描镜的位移准确度.通过测量石英晶体在不同外力下折射率的变化情况,确定了晶体的弹光系数. 石英晶体的弹光系数P33和P13分别为0.110和0.279,其准确度达到0.001.     

白光在LiNbO_3∶Fe晶体中写入的任意折射率分布光波导

在理论分析Li NbO3∶Fe晶体中光致折射率变化分布与写入光的强度分布之间关系的基础上,提出了一种在该晶体中写入具有任意折射率分布光波导的新方法.利用由白光经电寻址空间光调制器得到的强度分布不同的片光辐照晶体,分别写入了折射率呈误差函数分布和平方律分布的光波导结构.采用干涉法测量了晶体中的光致折射率变化,并用推导出的折射率变化分布解析表达式很好地拟合了测量数据.实验结果表明,该方法是可行的.利用白光光源结合高分辨率的空间光调制器有望在多种光折变材料中制备出具有任意折射率分布的高质量光波导.     

光在双轴晶体表面的反射与折射

介绍了光在双轴晶体表面反射、折射问题的求解方法.用该方法可以方便精确地计算晶体任意取向下光从任意方向入射时折射光的折射率、偏振态、波矢方向、能流方向. 推导了反射光、折射光的振幅和能量的计算公式. 并以KTP晶体为例，给出了数值计算的结果. 关键词： 双轴晶体 双折射 菲涅耳公式 布儒斯特角     

Conical refraction of elastic waves in absorbing crystals

The absorption-induced acoustic-axis splitting in a viscoelastic crystal with an arbitrary anisotropy is considered. It is shown that after “switching on” absorption, the linear vector polarization field in the vicinity of the initial degeneracy point having an orientation singularity with the Poincaré index n = ±1/2, transforms to a planar distribution of ellipses with two singularities n = ±1/4 corresponding to new axes. The local geometry of the slowness surface of elastic waves is studied in the vicinity of new degeneracy points and a self-intersection line connecting them. The absorption-induced transformation of the classical picture of conical refraction is studied. The ellipticity of waves at the edge of the self-intersection wedge in a narrow interval of propagation directions drastically changes from circular at the wedge ends to linear in the middle of the wedge. For the wave normal directed to an arbitrary point of this wedge, during movement of the displacement vector over the corresponding polarization ellipse, the wave ray velocity s runs over the same cone describing refraction in a crystal without absorption. In this case, the end of the vector moves along a universal ellipse whose plane is orthogonal to the acoustic axis for zero absorption. The areal velocity of this movement differs from the angular velocity of the displacement vector on the polarization ellipse only by a constant factor, being delayed by π/2 in phase. When the wave normal is localized at the edge of the wedge in its central region, the movement of vector s along the universal ellipse becomes drastically nonuniform and the refraction transforms from conical to wedge-like.     

Optical properties in photoelectron diffraction theory

Photoelectron diffraction effects may be strongly influenced by optical properties of the solid. Due to refraction and absorption of light at a surface, the state of polarization of light may be changed and, therefore, the corresponding photoelectron diffraction intensity. In order to include optical properties of solids in photoelectron diffraction theory, a general polarization vector of light is defined taking into account both refraction and absorption of light at the vacuum–solid boundary. In a first step, the radiation field of light inside the solid is approximated macroscopically according to classical electrodynamics. Analytical expressions are derived within a real-angle representation of Fresnel equations to reveal the influence of refraction and absorption of light on the state of polarization of light. A general refractive index in dependence on the incident angle of light is introduced which determines the refractive angle inside the solid (refraction law with real angles) and the order of influence of absorption of light. The general polarization vector is applied in the calculation of dipole transition matrix elements in a multiple-scattering cluster model of photoelectron diffraction, where the process of photoabsorption (dipole transition matrix element) and multiple scattering processes of photoelectrons (scattering path operator) are considered separately. Different analytical and numerical results of photoelectron diffraction effects are presented for light of general polarization incident at general angles taking into account the optical properties of the solid. Examples are shown and discussed in detail for Cu(001) and GaAs(110) surfaces.     

双轴晶体中平面波解在主轴坐标系下的表达

在双轴晶体中,除光轴方向外,沿任一方向只存在2个具有不同偏振方向的平面波解,每个解有各自的传播常数。运用拉格朗日乘数法并借助双轴晶体的折射率椭球的概念,在主轴坐标系下求出双轴晶体的平面波解,得到每个解的空间色散关系,并从所得平面波解出发讨论平面波沿光轴方向传输的情况。最后将所得的结果运用到单轴晶体中检验其正确性。     

远轴高斯波的矢量场理论

提出了描述远轴高斯光波的矢量场方法,推导了精确的远场传播公式,讨论了矢量场远轴高斯波的远场光波特征和传播规律,并与标量场理论作了比较,指出了标量场理论的适用范围． 关键词：     

Structure and Morphology of Carbon Nanotubes Grown on Zeolite-Supported Catalysts by Chemical Vapor Deposition

The vector theory to describe off-axial Gaussian wave is proposed, and an accurate far-field propagation formula is derived. The light wave characteristics and propagation properties are discussed in detail, and the comparison between the vector theory and the scalar theory is also made.     

Investigation of the linear and nonlinear properties of a Drude model photonic crystal

The optical transmission properties of a one-dimensional Drude model photonic crystal are investigated. The linear wave propagation is studied by the transfer matrix method. Using a delta-function approximation a nonlinear 2-d map is obtained and used to explore the global transmission properties of nonlinear wave propagation in this system. Inclusion of a frequency-dependent refractive index represented by the Drude model results in a considerable modification of the characteristics of the linear and nonlinear wave propagation of the one-dimensional photonic crystal.     

Solitary waves in a binary nonlinear waveguide array

Based on the coupled-mode theory, the propagation of light pulses is studied analytically for a system of an infinite number of tunnel-coupled parallel equidistant waveguides of optically nonlinear materials; in the considered system, waveguides with a positive refractive index alternate with waveguides with a negative refractive index. Partial solutions to a system of nonlinear equations describing the evolution of these pulses are found in the case in which fields in adjacent waveguides differ only in the phase factor. For a solitary wave formed by coupled wave packets localized each in its own waveguide, these solutions describe the stationary propagation in a definite direction. It is shown that the coupling strength between waveguides has an effect on the propagation rate of the obtained stationary pulses.     

光子晶体光纤中布里渊散射声波模式特性的分析

推导了光子晶体光纤中声波微小位移波动方程; 研究了泵浦波长以及纤芯折射率对声波模式的影响; 应用石英圆柱模型研究了小芯径光子晶体光纤中纤芯直径对布里渊声波模式色散的影响. 结果表明在光子晶体光纤中, 纵向声波和横向声波共同作用产生质点声场, 两者相互耦合将产生混合声波模式; 可以通过改变泵浦波长或光子晶体光纤纤芯折射率来改变参与布里渊散射(BS) 过程的声波模式的传播常数; 随着光子晶体光纤(PCF) 纤芯直径的增大, 声波模式耦合程度得到加强, 相速度呈减小趋势, 且同一传播常数下, 声波模式数呈增多趋势; 随着泵浦波频率的增大, 声波相速度减小.