A Method for the Optical Characterization of Thin Uniaxial Samples

An optical characterization procedure for small fragments of uniaxial materials is described involving the simple use of crossed polarizers with one polished face of the material. The reflectance at a fluid-uniaxial slab boundary beyond, but near, the critical angle of incident light is examined for linear incidence polarization using an orthogonal output polarizer. It is found that, as the crossed incident and output polarizers are rotated together, there are, for a given angle of incidence, particular polarization angles for which the reflectivity is a minimum. These angles give information on the optical tensor of the crystal under study. Further the intensity of the reflected light, for incidence angles beyond critical with the input and output polarizers crossed, has as a function of the incident polarization angle an oscillatory form which, when fitted to theory, can also yield the full uniaxial tensor of the material under study. This is confirmed experimentally for a thin single crystal of calcite with one polished face.     

运用ASAP光学软件模拟单轴晶体的锥光干涉

为了模拟不同光轴取向、光束发散角、晶体厚度或入射波长等参数下的单轴晶体锥光干涉,在 ASAP中定义起偏器、晶体、检偏器和接收屏的几何形状和光学特性,产生一组锥状高斯光束并设置其相干性和波动性,进行光线追迹、计算并显示接收屏上的干涉场能量分布。所得模拟结果表明,光轴与晶体表面垂直时,干涉条纹是 1组以光轴为圆心且被十字分割的内疏外密、明暗相间的同心圆环;平行时,是 2组分别以光轴的平行和垂直方向为对称轴的、内疏外密、明暗相间的双曲线;既不垂直也不平行时,条纹特征因光轴取向而异;当增大发散角、晶体厚度或减小波长时,干涉条纹都向内移动且条纹数增多,反之亦然;起、检偏器正交时的干涉条纹都和它们平行时的条纹互补。     

Optical Mode Characterization of the Configuration of a Thin Ferroelectric Liquid Crystal Cell Under an Applied Electric Field

Abstract

It is possible to probe directly the optic dielectric tensor configuration within a thin (about 3·5 μm) smectic layer of a ferroelectric liquid crystal (FLC) by the propagation of prism-coupled leaky Fabry-Perot optic modes. Incident monochromatic polarized light couples into the resonant modes of the system which are then observed as sharp dips in the reflected signal at specific incident angles. This work has shown that the FLC has an optic tensor profile which is consistent with the chevron formation of the smectic layers observed in X-ray scattering measurements. Also it is shown that under the application of a low d.c. applied field the optic dielectric tensor configuration distorts in a manner consistent with the retention of the chevron structure up to fields of about 10⁶ Vm^?1.     

大尺寸Ce:Lu1.6Y0.4SiO5闪烁晶体的生长和光谱特性

采用中频感应提拉法生长出尺寸为φ60mm×110mm的Ce:Lu1.6Y0.4SiO5(LYSO)晶体,与LSO晶体相比,LYSO晶体的优势是提高了晶体质量、降低了熔点和原料成本等.在室温下测试了LYSO晶体的透过光谱、激发光谱和发射光谱,结果表明Y的加入使LSO晶体的吸收边向短波方向偏移. Ce3+的4f1→5d1跃迁吸收导致紫外区产生三个吸收带.发射光谱具有Ce3+典型的双峰特征,经Gaussian多峰值拟合,双峰395nm和418nm归属于Cel发光中心,而435nm的发光峰与Ce2发光中心有关.     

新型非线性光学晶体MnHg(SCN)4的合成、结构及表征

合成了配合物晶体ＭｎＨｇ（ＳＣＮ）４。用Ｘ射线四确定了此配合物的晶体结构。用元素分析、红外光谱、紫外一可见光谱以及ＴＧ－ＤＴＡ热分析对其进行了化学表征。测量了不同温度下此配事物晶体在纯水中的溶解度。以尿素为标准样品,用１０６４ｎｍ被劝锁模６０ｐｓ脉冲Ｎｄ：ＹＡＧ激光为入射基频光测得此晶体的倍频光强度为尿素的５０倍。因此,ＭｎＨｇ（ＳＣＮ）晶体是一种新的非线性光学材料。     

向列型热致液晶聚酰胺的结构表征

采用傅立叶红外光谱仪（IR）、广角X射线衍射仪（WAXD）、热台偏光显微镜（POM）及扫描电子显微镜（SEM）对所合成热致液晶聚酰胺进行了结构表征。IR谱图显示了该聚合物为半刚性结构,与所设计的分子结构相一致;WAXD曲线显示处于液晶态的聚合物在2θ=20°左右有一弥散的峰,表明该液晶聚合物为向列型液晶结构;POM观察...     

PbMoO4晶体光学性质的第一性原理研究

基于密度泛函理论(DFT)的广叉梯度近似(GGA)下的平面渡超软赝势法,计算了PbMoO4晶体的电子结构和光学性质.结果表明,介电函数的虚部与光电导的实部、复数折射率、光吸收谱的峰值位置有着一一对应的关系,并且可以从电子态密度图中的价带和导带间的电子跃迁得到合理解释.     

Image Intensity at the Edge of a Straight Edge Object

Abstract

We consider the value of the intensity image at the geometrical position of a general, flat, straight edge object. We adopt a Fourier optical transfer function approach and obtain, rigorously, analytic expressions for the cases of coherent, incoherent and equal aperture, partially coherent imaging. Aberration-free, circular pupils are considered and the analytic results are found to agree with earlier numerical calculations. We also obtain expressions for the intensity gradient at the edge.     

纳米尺度栅线结构的线边缘粗糙度分析和表征

为了对线边缘粗糙度(LER)和线宽粗糙度(LWR)进行分析和表征,采用电子束光刻工艺和感应耦合等离子体刻蚀工艺制备了两种纳米尺度栅线结构,用扫描电子显微镜(SEM)对所制备结构进行了检测和定性分析.基于离线SEM图像分析法提取了纳米栅线结构的线边缘轮廓.将所提取的线边缘轮廓视为随机信号,分别采用均方根偏差σ、偏斜度Sk、峭度Ku、高高相关函数和功率谱密度函数表征了LER/LWR的幅度特征、形状特征和空间特征,研究了LER/LWR各参数从光刻图形到刻蚀图形的变化,实现了LER/LWR的定量分析和表征.     

Design of an Optical Absorption Cavity for Titanium Transition Edge Sensors

We have developed a TES optical photon detector with a titanium superconducting film showing a very fast response with rise time and fall times of 30 ns and 313 ns, respectively. The fast response is promising for many quantum measurement applications. Increasing the quantum efficiency of this device from the current value of ∼20% makes the detector even more suitable for these applications. Here we report on simulation and experimental results of a cavity designed to improve optical photon absorption of titanium.     

ZnO薄膜的晶体性能的分析

在硅基上制备出了c轴取向高度一致的ZnO薄膜 ,这将有可能成为新型GaN单晶薄膜的过渡层。对ZnO薄膜的晶体性能进行了分析 ,研究不同衬底和不同衬底温度对ZnO薄膜的结晶状况的影响 ,并着重用TEM研究了硅基ZnO薄膜的晶体性能。     

Determination of the Director Alignment in a Ferroelectric Liquid Crystal Device by Observation of Optical Modes

Abstract

By observing the angular dependence of the reflectivity of a ferroelectric liquid crystal (FLC) cell fabricated from glass pyramids with 60° evaporated SiO aligning layers it has been possible to sensitively probe the configuration of the optical dielectric tensor in the FLC layer. It is found that the optical data can best be explained by a uniaxial slab twisted from the alignment axis; this is consistent with the recently proposed chevron structure.     

Uniaxial compression of a circular elastic slice

We show that some asymptotic results can be derived for the deformation of a thin circular slice of an isotropic elastic material. These results are very accurate when compared to a more exact Boundary element analysis and can be used in correlating experimental data.     

一种低支化聚酯液晶的合成及性能表征

采用不同比例的4,4′-对苯二甲酰二羟苯甲酸乙二醇酯（TOBB）与偏苯三酸酐（TMA）反应,合成端基含有羧基的哑铃型聚酯液晶和低支化度的聚酯液晶。通过红外光谱（FT-IR）、差示扫描量热（DSC）、偏光显微镜（POM）、广角X射线衍射（WAXD）及热重分析（TGA）等对其结构及性能进行表征。结果表明,所合成的聚酯液晶呈...     

单模光纤模场直径（MFD）双刀口法快速测量系统的研究

本文依据标准的单模光纤模场直径（ＭＦＤ）刀口测量方法，提出了一种新颖独特的双刀口法测量方案并在实验室实现．此方法最突出的优点是：测量操作方便，简洁，可以实现全自动，测量精度相当高．     

晶体生长的边界层效应—兼论光学实时观察法晶体生长技术

晶体生长边界层模型起源于流体动力学边界层模型，但两者又不完全相同．晶体生长边界层模型有两方面的含义：（1）在固-液界面处的、垂直于界面的、由杂质和组份构成的质量流决定晶体生长速度；（2）在界面附加溶液一侧的质量浓度流，其浓度分布是决定界面稳定性的基本参数．特征扩散长度是表征垂直于界面的质量流的一个重要参数．对熔体晶体生长而言，理论估计此值在0．04～0．4cm之间．光学实时观察法晶体生长技术是一种研究晶体生长过程的新颖方法．它能有效地区分扩散-平流和扩散-对流两种不同的生长状态，其实验测得的KNbO3熔体生长的特征扩散长度值为0．01～0．1cm之间．应用此方法实时观察到胞状结构的形成和发展，也证实了界面附近的质量浓度流是决定界面稳定性的一个重要参数．     

Uniaxial Ratcheting Behaviors of Metals with Different Crystal Structures or Values of Fault Energy: Macroscopic Experiments

The uniaxial ratcheting behaviors of several metals with different crystal structures or values of fault energy were observed by the stress-controlled cyclic tests at room temperature. The prescribed metals included 316L stainless steel, pure copper, pure aluminum, and ordinary 20# carbon steel. The effects of applied mean stress, stress amplitude and stress ratio on the uniaxial ratcheting were also investigated. The observations show that different crystal structures or values of fault energy result in more or less di?erent ratcheting behaviors for the prescribed metals. The different ratcheting behaviors are partially caused by the variation of dislocation mobility.