新型液晶光学相控阵的特性研究

将液晶作为平板光波导的上包层,构建了液晶光学相控阵器件.根据Frank-Oseen液晶连续体弹性形变理论与光栅衍射理论,研究分析了基于这种新型结构下液晶光学相控阵的传输特性,输出衍射特性和其它性能特性.研究结果表明,器件的传输电控相位延迟可以实现更大的光程差;阵列电极周期数目、电极宽度、电极间隔宽度等结构参量对器件的输出衍射光束的光强分布和半峰值全宽度影响很大,同时光束扫描的可行性得到论证;器件的响应时间提高了一个数量级,且其色散性能获得改善.为以后研制新型液晶光学相控阵提供了理论基础与技术设计依据.     

紫外光诱导液晶相位光栅

使用紫外光诱导取向技术制作了可转换的液晶相位光栅,通过光掩模两次曝光的方法形成光栅条纹.这种光栅制作工艺较为简单,不需要上下基板精确的对准,驱动电压较低.采用He-Ne激光器和光探测器进行测试,结果表明,衍射效率具有电场调制性并出现同预测一致的衍射条纹.对液晶光栅的偏振特性进行了研究,利用琼斯矩阵和衍射理论对液晶相位光栅衍射强度进行了分析和模拟计算.     

纳米银掺杂的高效率全息聚合物分散液晶光栅制备

报道了一种基于掺杂纳米银聚合物分散液晶(PDLC)材料的高衍射率全息电控光栅的制备及特性。通过在原有聚合物分散液晶材料体系中添加适量的纳米银颗粒以制备体全息光栅,实验研究了掺杂不同质量比的纳米银颗粒对全息聚合物分散液晶(H-PDLC)体光栅的衍射效率、驱动阈值电压、响应时间的影响。实验结果表明,通过掺杂纳米银材料,能够优化聚合物和液晶两相分离结构,使聚合物与液晶分离更加彻底,显著提高H-PDLC体光栅的一级衍射效率,同时能改善体光栅的电光特性,缩短响应时间。初步分析表明,由于纳米银颗粒的表面等离子体效应和体系折射率匹配的优化改善了H-PDLC光栅的特性。     

二元光学液晶闪耀光栅的特性分析

在二元光学理论的基础上,结合波动光学理论和液晶指向矢的计算提出一种新的二元光学液晶闪耀光栅设计.对液晶光栅电极施加阶梯分布的电压使之形成相位阶梯形分布,推导出液晶闪耀光栅的衍射效率.结果表明,通过改变周期单元光栅电极数日而改变光栅常数,可以改变光衍射角度,一级衍射角度调节范围0°～10°;调节电极电压可以使特定级次衍射光效率达到90%以上,使该级次得到闪耀.     

新型聚合物分散液晶材料研制的电控体全息光栅

报道了聚合物分散液晶材料全息光栅元件的研制，并研究了聚合物分散液晶材料光栅的衍射特性及电控开关特性。该光栅结合了聚合物分散液晶材料的电控光开关特性和全息光栅的优点，在光通信器件、可调窗口、液晶显示等领域具有广泛的应用前景和巨大的潜在生产力。     

一种液晶相位调制特性的测量方法

提出一种基于衍射光栅的液晶相位调制特性测量方法.该方法利用液晶构建相位分别为0和φ的二值光栅,通过傅里叶光学的方法推导衍射光栅第0级衍射光斑光强和调制相位φ之间的关系,然后实测光强和液晶驱动电压之间的对应关系来得到相位和液晶驱动电压之间的对应关系,即液晶相位光栅的相位调制特性.最后利用测量相位调制特性结果构建液晶相控阵,用光束偏转误差验证调制特性测量结果,相位测量误差小于1×10~(-3)rad.     

具有可变电控光栅常数的液晶光栅

针对现有液晶光栅器件存在的光栅常数不能变化、电极尖端放电、边缘效应等缺点,设计了一种可转换光栅常数的液晶光栅。通过控制不同导电区的通断电,使液晶光栅不同区域产生透光与不透光,实现光栅常数的转换;液晶光栅梳状电极端部的圆弧状设计,避免了尖端放电现象,减小了边缘效应的影响。以He-Ne激光为光源,用WGD-8A型组合式多功能光栅光谱仪对所设计的液晶光栅器件进行了测量,结果表明：通过控制导电区的变化实现了光栅常数的转变,在2～3.4 V电压驱动下,具有3种不同光栅常数的液晶光栅的1级衍射光强逐渐增强,且其衍射光强的差值不断增大,达到了预期设计目的。设计的液晶光栅在视差栅栏、光栅尺等方面有好的应用前景。     

不同电极对α-LiIO3离子输运特征的影响的光学显微观测

介绍了用偏光显微镜对α-LiIO₃特性的观察.研究了五种不同电极界面状态的八块晶体样品在c向静电场作用下晶体的电导、空间电荷的沉积和分布.观察到由于α-LiIO₃的空间电荷的输运形成的彩色准直条纹.此彩色条纹与光折变型光栅的衍射带之间有对应关系.而不同的电极界面状态对α-LiIO₃晶体的电导和离子输运有明显的影响. 关键词：     

电控聚合物分散液晶全息透镜及特性研究

报道位相型电控聚合物分散液晶(H-PDLC)全息衍射透镜的研制及特性研究,理论上,根据耦合波理论,研究了不同的相分离程度系数下,理想位相型电控聚合物分散液晶(H-PDLC)全息衍射透镜在可见光波长(400—800nm)的衍射特性.实验研制了衍射效率最高为70%的电控H-PDLC变焦透镜样品,研究表明H-PDLC透镜具有优良的成像特性,和快速响应的电控开关特性,在光学成像系统,光通信系统中具有良好的应用前景.     

相位掩模的近场衍射特性分析

用相位掩模法制造光纤光栅是一种简单、有效的方法.本文用标量衍射理论对相位掩模的近场衍射特性进行了分析,讨论了各级衍射光形成的干涉条纹的分布情况,得到了一些有益于光纤光栅制造的结论和有用公式.     

光轴方向任意时光折变晶体中体全息光栅的衍射性质

利用坐标旋转方法和Kogelnik耦合波理论,建立了光轴方向任意时单轴晶体中体光栅布拉格衍射的耦合波方程,分析了Li NbO3晶体的光轴方向对光折变体全息光栅的各向同性和各向异性布拉格衍射性质的影响。模拟计算表明,在给定光栅的结构参量时,通过适当选择光轴方向角可以使得光折变体光栅的各向同性和各向异性布拉格衍射的衍射效率达到最大,给出了相应类型的衍射效率取得最大值时晶体光轴的大致方向。这些理论分析为光折变体全息光学器件的优化设计和进一步广泛应用提供了很好的理论参考依据。     

Electro-optical switching of liquid crystal diffraction gratings by using surface relief effect in the photopolymer

Surface relief patterns are one of the promising possibilities for the fabrication of liquid crystal (LC) electro-optical devices. Optically recorded surface relief gratings in an acrylamide based photopolymer were filled with the liquid crystal to fabricate liquid crystal diffraction gratings. E49 liquid crystals were used in this work. The switching behaviour of the diffraction grating was investigated by measuring the intensity in the first order when an electric field was applied.     

Asymmetric dynamic phase holographic grating in nematic liquid crystal

A new scheme for recording a dynamic phase grating with an asymmetric profile in C60-doped homeotropically aligned nematic liquid crystal(NLC) was presented.An oblique incidence beam was used to record the thin asymmetric dynamic phase holographic grating.The diffraction efficiency we achieved is more than 40%,exceeding the theoretical limit for symmetric profile gratings.Both facts can be explained by assuming that a grating with an asymmetric saw-tooth profile is formed in the NLC.Finally,physical mechanism and mathematical model for characterizing the asymmetric phase holographic grating were presented,based on the photo-refractive-like(PR-like) effect.     

Optical vortices generated by dislocations in a cholesteric liquid crystal

We report the observation of optical vortices in a laser beam propagating through the stripe pattern of a cholesteric liquid crystal. The liquid crystal is confined in a cell with homogeneous boundary conditions and forms a diffraction phase grating. Optical vortices are produced by edge dislocations of the cholesteric grating. The vortices show up as spots of zero light intensity in the diffraction maxima. There is one spot in each +1 and -1 diffraction maximum and two spots in diffraction maxima +2 and -2.     

凹面光栅衍射效率的研究进展

凹面光栅因同时具有聚焦和色散功能而广泛应用于各类紫外、可见和红外波段的光谱分析仪器中,尤其是平场凹面光栅可以结合线阵或面阵探测器来实现即时分析。凹面光栅衍射效率的高低直接影响光谱仪器的信噪比和信号采集,其相关研究也逐渐为人们所关注。介绍了凹面光栅衍射效率的研究进展,比较了由机械刻划法和全息法制作的凹面光栅在掠入射下衍射效率的差别,分析了现有计算衍射效率方法的优缺点,并且对凹面光栅衍射效率的研究趋势做了简要预测,提出了需要同时在凹面光栅的主截面和非主截面内考虑光束对其衍射效率的影响。     

Phase Controlled Laser Interference for Tunable Phase Gratings in Dye-Doped Nematic Liquid Crystals

A phase controlled multi-beam interference is applied to excite the doped liquid crystals. Control of the phase difference between the exciting beams allows the external control of the interference pattern inside the liquid crystal. The dynamic variation of the grating is made possible with a time-dependent phase change to derive the nonlinear refractive index as well as the responding speed of the material. The induced grating structure is numerically modelled with reorientational phase gratings in the liquid crystal, and the diffraction dynamics is found to be in good agreement between theoretical and experimental results.     

Electrically tunable holographic polymer templated blue phase liquid crystal grating

In this paper,we demonstrate an alternative approach to fabricating an electrically tunable holographic polymer templated blue phase liquid crystal grating.This grating is obtained by preforming a polymer template comprised of periodic fringes,and then refilling it with a blue phase liquid crystal.Compared with conventional holographic polymer dispersed liquid crystal gratings,our grating can remarkably reduce its switching voltage from 200 V to 43 V while maintaining a sub-millisecond response time.The holographic polymer templated blue phase liquid crystal(HPTBPLC) grating is free from electrode patterning,thus leading to a lower cost and more flexible applications.