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.     

法-珀干涉绝对距离测量中的声光移频器双通道配置方法

为在能量天平动圈位移测量中实现大范围纳米精度法-珀干涉绝对距离测量, 提出了声光移频器双通道配置, 实现了调谐范围为200 MHz的可调谐频差. 通过分析声光移频器调制带宽与衍射效率的平衡与入射光束聚焦透镜的关系, 确定透镜的最佳焦距范围; 利用零级光斑分布特点准确定位入射光束, 保证一级衍射光束质量. 声光移频器在调制带宽内的实验单通道和双通道峰值衍射效率分别为79.54%, 61.41%; 声光移频器双通道配置输出的一级衍射光束与入射本征光束的拍频范围为440-640 MHz, 是单通道调制带宽输出220-320 MHz的两倍, 信噪比好. 理论分析表明, 声光移频器双通道配置方法实现的可调谐频差可测量腔长变化范围约为53 mm的折叠法-珀腔.     

偏振敏感材料中具有圆各向异性的偏振全息光栅

在向列相液晶中掺杂质量分数约0.2%的偶氮侧链型聚合物制成偏振敏感材料,使用正交圆偏振光记录了具有圆各向异性的一维偏振全息光栅,用线偏振光探测偏振全息光栅,得到正,负一级衍射光也为线偏振光,且偏振态与探测光和零级偏振态相互正交,可以运用琼斯矩阵理论加以解释.偏振全息光栅可由外加电场控制衍射级的变化,即在外加电场作用下,正、负一级衍射产生了90°的相位差.在频率6.05 Hz、电压2.2 V的外场作用下,衍射级的极值振荡变化.     

嵌入式镀膜光栅的数值模拟研究

嵌入式镀膜光栅是将平行四边形的介质膜层,以亚波长量级的周期嵌入波导中.针对该光栅在不同偏振态、不同角度入射下的各级衍射效率问题,本文基于严格耦合波分析理论,对该光栅进行建模与数值分析.结果表明,在TE模入射时,该光栅的一级衍射效率可随膜厚在[0,37％]内变化,其余非零级次的衍射效率低于2％.衍射特性可以满足平视器成像的效率递增要求,同时可以减少能量的损失与杂散成像光线.当入射光束的角度在纵向[45°,70°]、横向[-15°,15°]内变化时,一级衍射效率的变化平稳,可以保持平视器不同视场的成像能量均匀.针对入射光偏振态、光栅材料、嵌入膜层倾角、光栅周期对衍射特性的影响,给出了相应的数值分析,可为波导全息平视器中衍射元件的制作提供理论指导.     

偏振全息光栅衍射光场的理论分析

利用介质的光致各向异性和可记录偏振全息光栅,从偏振全息的透射琼斯矩阵出发,运用傅里叶展开法,对记录光不同的偏振态组合情况下,衍射光场的可能出现的衍射级次及其偏振特性进行了理论分析.并以甲基橙掺杂聚乙烯醇膜为例,对各阶衍射光的衍射效率进行了理论计算.     

偏振全息光栅衍射光场的理论分析

利用介质的光致各向异性和可记录偏振全息光栅,从偏振全息的透射琼斯矩阵出发,运用傅里叶展开法,对记录光不同的偏振态组合情况下,衍射光场的可能出现的衍射级次及其偏振特性进行了理论分析.并以甲基橙掺杂聚乙烯醇膜为例,对各阶衍射光的衍射效率进行了理论计算.     

嵌入式镀膜光栅的数值模拟研究

嵌入式镀膜光栅是将平行四边形的介质膜层,以亚波长量级的周期嵌入波导中.针对该光栅在不同偏振态、不同角度入射下的各级衍射效率问题,本文基于严格耦合波分析理论,对该光栅进行建模与数值分析.结果表明,在TE模入射时,该光栅的一级衍射效率可随膜厚在[0, 37%]内变化,其余非零级次的衍射效率低于2%.衍射特性可以满足平视器成像的效率递增要求,同时可以减少能量的损失与杂散成像光线.当入射光束的角度在纵向[45 °,70 °]、横向[-15 °,15 °]内变化时,一级衍射效率的变化平稳,可以保持平视器不同视场的成像能量均匀.针对入射光偏振态、光栅材料、嵌入膜层倾角、光栅周期对衍射特性的影响,给出了相应的数值分析,可为波导全息平视器中衍射元件的制作提供理论指导.     

偶氮液晶聚合物薄膜的二维偏振全息记录

利用偏振全息记录的方法在一种含偶氮侧链的液晶聚合物薄膜中写入了二维偏振光栅.实验采用两束正交偏振的532 nm线偏光作为写入光,在样品同一点上分别记录了相互垂直的两个一维偏振光栅,继而对所构成的二维偏振光栅的特性进行了研究.实验结果表明：二维光栅的衍射效率比一维光栅低,其偏振特性是两个一维光栅元特性的叠加;二维光栅衍射效率对入射光偏振态的依赖性和光栅的偏振转换性质来源于材料中线双折射和圆双折射的共同作用. 关键词： 偏振全息 二维光栅 偶氮液晶聚合物     

C60掺杂向列相液晶中光栅衍射选择性的分析

利用琼斯矩阵(Jones matrix) 方法对C60掺杂向列相液晶中光栅衍射选择性进行分析.给出两束p 偏振光在液晶样品中产生相位全息光栅的透射矩阵,通过探测光的矢量和光栅透射矩阵的琼斯矩阵运算,可以探测衍射光束的偏振态与入射光偏振态的关系.分析发现对于p 偏振的探测光,透射光和正、负一阶衍射光的偏振态均为p 偏振,且正、负一阶衍射效率相同;对于s 偏振的探测光只有透射光存在,可见记录的相位光栅表现出光栅衍射的选择性.     

YAG:Nd中晶体取向对热致双折射的影响

本文对几种常用棒轴的热致双折射和传输系数进行了理论计算,并用实验测定了传输系数与偏振器角度的关系以及偏振器与输出功率的关系。理论与实验相符。结果表明,在采用上述几种石榴石棒时,只要依据我们所给出的取向关系并适当放置偏振器,就可以获得最佳的偏振输出。 关键词：     

横向剪切干涉法共路测量LCSLM的相位调制特性

提出一种测量扭曲向列液晶空间光调制器的相位调制特性的新方法——横向剪切干涉法.对经扭曲向列液晶空间光调制器调制后的待测波面进行横向剪切干涉,用CCD记录其干涉图样,并用最小能量算法计算其波面的相位分布,从而测得扭曲向列液晶空间光调制器的相位调制曲线.该方法对振动、空气扰动不敏感,对测量环境要求不高.给出了TN-LCSLM不同调制状态下相位调制幅度的三维轮廓图.     

Mueller-Stokes polarimetric characterization of transmissive liquid crystal spatial light modulator

In the twisted nematic liquid crystal spatial light modulators (TN-LCSLM), distortion of uniform twist and decrease in tilt angle of liquid crystal molecules on application of an electric field lead to amplitude and phase modulations of the transmitted or reflected wavefront, respectively. The amplitude and phase modulation characterization of TN-LCSLM using Jones calculi is simple and extensively used but does not give any information about important polarimetric parameters such as diattenuation and depolarizance. On the other hand, the characterization using Mueller calculi provides all information in terms of polarimetric properties such as diattenuation, retardance (birefringence) and depolarization. In this paper, polarimetric properties of the transmissive TN-LCSLM (HOLOEYE LC2002) are characterized measuring 17 different Mueller matrices at different addressed gray scale through Mueller Matrix Imaging Polarimeter (MMIP) at 530 nm wavelength. Lu-Chipman polar decomposition for Mueller matrix is utilized to separate out three independent Mueller matrices for diattenuation, depolarization and retardance as a function of addressed gray scale. Further, Mueller-Stokes combined formulation is used to examine the effect of depolarization present in the TN-LCSLM on six different states of polarization and evaluation of eigenpolarization states for the TN-LCSLM has been presented.     

Electromagnetically induced grating in a four-level tripod-type atomic system

An electromagnetically induced grating in a four-level tripod-type atomic system is studied theoretically. By virtue of a weak standing-wave signal field, the phase modulation effectively diffracts a weak probe field into the first-order direction. By changing the weak signal field, the diffraction of the weak probe field can be modulated in real time, and a first-order diffraction efficiency of more than 32% can be obtained with proper parameters. Such a system has a potential application in an all-optical switch controlled by a weak optical signal.     

Controllable electromagnetically induced grating in a cascade-type atomic system

A controllable electromagnetically induced grating (EIG) is experimentally realized in a coherent rubidium ensemble with 5S_1/2–5P_3/2–5D_5/2 cascade configuration. In our work, a whole picture describing the relation between the first-order diffraction efficiency and the power of the coupling field is experimentally presented for the first time, which agrees well with the theoretical prediction. More important, by fine tuning the experimental parameters, the first-order diffraction efficiency of as high as 25% can be achieved and a clear three-order diffraction pattern is also observed. Such a controllable periodic structure can provide a powerful tool for studying the control of light dynamics, pave the way for realizing new optical device.     

13.4nm软X射线干涉光刻透射光栅的优化设计

基于严格的矢量耦合波方法,结合纳米级光栅实际制作工艺,定量分析了在13.4 nm软X射线(TE偏振)正入射条件下,光栅材料、厚度、占空比、梯形浮雕底角大小等因素对光栅一级衍射效率的影响.结果表明,在此波段处,Si3N4、Cr、Au浮雕的相位作用对光栅衍射起重要影响,其中非金属材料Si3N4比金属材料Cr、Au的相位作用更明显.最后优化得到了用Si(或Si3N4)做衬底的si3N4、Cr、Au光栅,分析结果显示,其一级衍射效率优于目前用于13.4 nm软X射线干涉光刻的Cr、Si3N4复合光栅.     

Replicative fabrication of diffractive structure from self-assembled particles onto a glass substrate using corona-charging treatment

We have succeeded in the first fabrication of a diffractive structure replicated onto a glass substrate using a template of self-assembled polystyrene particles via corona-charging treatment. A hexagonal close-packed structure of selfassembled particles was used as the template in the structural replication. As a result, a sixfold symmetric diffraction pattern was generated from the glass substrate, on/in which the diffractive structure was replicatively fabricated. The dependence of the diffraction efficiency on processing time of corona-charging treatment was examined. It was found that the diffraction efficiency increased with treatment time up to 2 h. The observed first-order diffraction efficiency was 2.4 × 10⁻³%. In contrast, the diffraction efficiency decreased after 2 h treatment under our current experimental conditions. This trend of diffraction efficiency was discussed on the basis of structural changes of the polystyrene template.     

亚波长介质光栅的闪耀特性分析

采用严格耦合波理论与矩阵LU分解法,求解了亚波长矩形介质光栅的衍射场,给出了TE和TM偏振波的耦合波方程组及其矩阵形式.通过数值计算分析了TE和TM偏振波的入射角、刻槽深度、入射波长等参量对＋1级衍射波衍射效率的影响.结果表明,当Λ=0.5λ0,θ=55°,d=0.38λ0,λ=10.6 μm时可以实现对TE偏振波＋1级的闪耀,衍射效率达到近90%,同时具有较宽广的角度适应范围.     

光纤激光器频谱组束的理论研究

 建立了由光纤激光器阵列、薄透镜和衍射光栅组成的频谱叠加理论模型，基于高斯光束的变换和衍射理论，推导出远场光强分布的关系式，探讨了系统参量的优化设计并进行了数值模拟。结果表明：当中心波长激光器的-1级干涉主极大与槽面衍射主极大重合、零级干涉主极大刚好落在槽面衍射的+1级零值极小上、其它波长激光器的-1级干涉主极大与中心波长激光器的槽面衍射主极大重合时，输出光束的衍射效率较高；当光栅平面法线与薄透镜光轴的夹角为衍射光栅槽形角的一半时，输出光束的半角宽度较小。     

Temperature and orientation dependence of surface relief gratings based on dye-doped polymer film with the interface of nematic liquid crystals

The formation of surface relief grating on dye-doped polymer film with the interface of nematic liquid crystals has been investigated by means of the holographic technique. The first-order diffraction efficiency of surface relief grating depends on the temperature and the orientation of molecular director in the interface of nematic liquid crystals. The diffraction efficiency is roughly independent of thermal fluctuations of molecular director in the most part of nematic temperature range and apparently drops near the transition temperature. The morphology of surface relief grating demonstrates that the surface modulation is larger for molecular director parallel to the groove direction. The experimental result also shows that the first-order diffraction efficiency is dependent on the surface modulation of surface relief grating.     

基于相干粒子数囚禁的电磁诱导光栅研究

基于相干布居囚禁,提出了一种新的电磁诱导光栅物理模型, 得到了该模型下介质极化率的解析表达式. 由于相干布居囚禁引入的原子相干性, 介质极化率会形成增益、无吸收高折射率点以及暗态三个区域. 根据该理论模型, 基于⁸⁷Rb的原子能级, 提出了一种新型衍射光栅实现方案, 并进行了分析与计算. 结果表明, 在无吸收高折射率点处, 这种光栅是一种纯相位光栅, 一级衍射强度可达到0.4; 在增益区域中, 发现这种光栅是相位光栅和幅度光栅组合而成的混合型光栅, 在其最大增益点, 一级衍射效率最大可达1.26, 二级衍射效率也可增加到0.31. 关键词： 相干粒子数囚禁 电磁诱导光栅 衍射效率