二维光栅光调制器阵列的光学分析与实验

基于标量衍射理论分析了二维光栅光调制器的衍射特性,提出了投影系统的光学处理方法,利用Matlab软件进行了仿真分析.分析结果表明,二维光栅光调制器的衍射光强分布是单个像素衍射光强的干涉叠加,其分布趋势与单个光调制器的衍射光强分布类似;通过反傅里叶变换可将各个调制器的衍射光重新分开而成像.如果用±1级衍射光的成像,相位为2kπ的调制器在投影面得到一个明亮的像,而相位为(2k-1)π的调制器在投影像面上得到一个黑暗的像.通过一个基于静态微光电系统光栅光调制器的投影光学系统得到了一幅明暗调制的像,证明了光栅光调制器用于投影显示的可行性.     

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.     

High-efficiency electrically tunable phase diffraction grating based on a transparent lead magnesium niobate-lead titanite electro-optic ceramic

An electrically tunable high-efficiency phase diffraction grating using the transparent lead magnesium niobate-lead titanite (PMNT) electro-optic ceramic is proposed. A photomask technique is used for fabricating the grating with the Ti/Pt/Au interdigital electrodes. With the variation of the equivalent phase face induced by the quadratic electro-optic effect of the PMNT ceramic, the diffraction patterns of the light beam will be changed in which the diffraction efficiency may be controlled by an applied DC voltage. When the applied voltages are 41, 80, and 139 V, the zero-order, first-order, or second-order diffraction lights will disappear in turn with about 100% diffraction efficiency. The proposed grating can be used as an electrically controlled switch in the laser beam modulation and scanning, especially for the application of the high-power laser systems.     

种电热驱动法布里 珀罗光调制器

提出了一种用于显示基于微机电系统的电热驱动法布里 珀罗光调制器.利用多光束干涉理论分析了该调制器的原理及光学特性.分析表明:当腔长为(2k+1)λ/4时,反射光强取极大值|当腔长为2kλ/4时,反射光强取极小值|通过改变腔长可以实现显示.光源谱宽越窄,衬比度越高|干涉级次越低,衬比度越高|衬比度随反射率的增加而减小.借助Ansys软件仿真分析了调制器的驱动特性.加工了器件并搭建实验装置进行了动态响应特性测试实验.结果表明,该调制器具有驱动电压低至3.2 V,响应速度约为5 kHz的良好驱动特性.实验结果初步验证了该结构的可行性.     

High Efficiency Electrically-Addressable Phase-Only Spatial Light Modulator

To realize a high efficiency electrically addressable phase-only modulator, we have coupled a liquid crystal display (LCD) to an optically addressed parallel-aligned nematic liquid crystal spatial light modulator (PAL-SLM) with a set of lenses. Phase modulation exceeding 3ϖ at 532 nm wavelength was obtained. We obtained linear transfer characteristics for phase modulation at various desired phase levels after calibration and adjustment of the transfer characteristics of the PAL-SLM and the LCD. Diffraction efficiency of 40% for binary phase grating and of 90% for 8-level blazed phase grating, which were very close to the simulation values, were observed. The power loss of the readout light was caused when passed through a half mirror, therefore, we examined a setup using an oblique readout light at the modulator. Very high diffraction efficiency was obtained from the setup by optimizing the polarization direction and optical path for this light, and the orientation of liquid crystals. Since the modulator can perform at better than 90% diffraction efficiency and at nearly 100% reflectivity, various high efficiency systems utilizing such modulators are expected.     

一维非厄密光子晶格中分叉可调无衍射光传输

理论计算和数值模拟了一维周期性复式光子晶格中光的分叉无衍射传输现象.当晶格满足退化的SSH模型时,波矢为±π的入射光将分裂为两束完全相同的对称无衍射光,且分叉夹角可通过耦合系数J来调节;在此基础上,通过微扰波导作用引入了调制相位?,当微扰满足宇称时间对称时,只要入射光波矢k与调制相位?之和为±π便能实现任意入射光波的无...     

光栅光阀的光学特性分析和仿真

光栅光阀是一种基于微型机电系统（MEMS）工艺的光调制器,利用其表面具有的可选择的变形部分（可动光阀）,提供衍射光栅,被应用于投影显示等领域。光栅光阀的光学性能决定其在投影显示系统中应用的成败。依据多光束干涉理论和衍射理论对光栅光阀工作状态的光学特性进行了详细的理论分析和计算机仿真。结果说明,光栅光阀在工作中处于“开”态时,可动光阀下降的距离应该是入射波长的1／4倍;设计时选择h=λ0／2,δ=Aλ0／4;当间隙处的反射率不同时,占空比对光栅光阀的光学特性有着不同的影响,给出了占空比与反射率的最佳组合值。     

新型聚合物分散液晶相位光栅的制备

把具有光敏特性的预聚物与向列相液晶按一定比例混合 ,注入表面经过取向处理的液晶盒中。以紫外灯为光源 ,通过光掩膜法 ,使混合物在光场的引发下发生相分离 ,形成液晶 /聚合物相位光栅。由于相分离后液晶在取向膜的作用下沿液晶盒面方向旋转 180° ,克服了传统液晶光栅器件对入射光偏振方向的依赖 ,提高了光的有效利用率。采用光学显微镜和He Ne激光器进行测试 ,结果表明所制样品具有较好的栅结构 ,其衍射效率不受入射光偏振方向的影响且具有电场可调性。该光栅制作方法简便 ,驱动电压低 ,在光通信器件、衍射光学、投影显示、光开关等领域有广泛的应用前景     

聚合物分散液晶光栅的衍射特性的研究

报道了一种由聚合物分散液晶膜与具有周期性条状电极结构板结合的新型光栅器件，借助于聚合物分散液晶膜的电光特性，这种栅对入射光的散射或衍射取决于对其施加的电压，即它是电场可调的，实验结果显示出当驱动电压超过器件器件阈值电压时，衍射光的强度和衍射斑的可见级次被电场调制，而且它能入射光的线性偏振态变为椭圆偏振态。     

A method of reducing the half wave voltage (Vπ) of an electro-optic modulator by multi passing a light through the modulator

Electro-optic material has several applications in optical communication, integrated optics and in data processing. The modulator is generally used for the purpose of amplitude and phase modulation of optical wave by the electrical message signal. Again the V_π voltage of an electro-optic modulator is an important parameter for the modulator. For the application of the V_π amount of electrical signal in the modulator the phase difference between two specific orthogonally polarized light waves changes from 0 to π. Thus the increase of V_π relates with the increase of electrical power requirement for modulation. Here in this paper the authors propose a new and novel concept for reduction of V_π voltage for the modulator. To reduce the value of the V_π voltage the multi passing technique of the beam through the modulator is used. If V_π is reduced the power requirement as well as the modulation cost will be greatly reduced to achieve a faithful and a meaningful optical communication. This paper describes also the necessary optical systems required for the multi passing technique.     

Generation of nondiffracting Bessel beams by use of a spatial light modulator

A laser beam with phase singularities is an interesting object to study in optics and may have important applications in guiding atoms and molecules. We explore the characteristics of a singularity in a nondiffracting Bessel beam experimentally by use of a programmable spatial light modulator with 64-level phase holograms. The diffraction efficiency with 64-level phase holograms is greatly improved in comparison with that obtained with a binary grating. The experiments show that the size and deflection angle of the beam can be controlled in real time. The observations are in agreement with scalar diffraction theory.     

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.     

Fast generation of controllable equal-intensity four beams based on isosceles triangle multilevel phase grating realized by liquid crystal spatial light modulator

Liquid crystal spatial light modulator (LCSLM) realizing equal-intensity multiple beams often has some features, i.e., phase valley between two adjacent pixels, flyback region when phase decreases immediately from 2π to 0, and inevitable backplane curvature, which are different from those of most conventional diffractive optical elements (DOEs), such as static DOEs. For optimal intensity uniformity, equal-intensity multi-beam generation must be considered for these artifacts. We present a tunable-grating method in which the intensity uniformity can be improved by considering the LCSLM artifacts. For instance, tuning phase modulation depth of the grating, called isosceles triangle multilevel phase grating (ITMPG), can be used not only to improve the intensity uniformity, but also to fast steer four beams with narrow beamwidths, determined by the same effective aperture of ITMPG. Improved intensity uniformity and high relative diffraction efficiency are demonstrated through experiments with phase-only LCSLM.     

基于数字闪耀光栅的位相全息图光电再现优化

针对利用液晶空间光调制器（LC-SLM）进行全息图光电再现过程中,再现像面存在多级衍射像造成单一像能量利用率低的问题,提出了一种在位相全息图中加载数字闪耀光栅的方法,以提高全息图光电再现中单一衍射像的衍射效率.分析了闪耀光栅作为衍射光学元件的特性及其对光波进行位相调制的原理,并阐述了在LC-SLM中加载数字闪耀光栅对位相全息图光电再现时像面能量分布的影响.搭建了基于LC-SLM的位相全息图光电再现实验系统.理论分析表明：在其他条件不变的情况下,加载竖直（或水平）槽向周期为2 pixels的数字闪耀光栅可使 关键词： 全息光电再现 位相全息图 数字闪耀光栅 液晶空间光调制器     

光谱分析方法测试GMLM微间距的实验和方法推广

基于MEMS的光栅平动式光调制器(GMLM)依靠结构中可动光栅和下反射镜之间的微间距的变化来实现光的调制作用,被应用于显示领域。可动光栅和下反射镜之间的微间距是一个关键的参数,传统的测试方法如台阶仪等要破坏结构,WYKO白光干涉仪测量成本高,所以要寻求一种测试成本较低、测量精度较高的测试方法。文章采用非接触的波长扫描式光谱分析方法进行了GMLM可动光栅和下反射镜之间的微间距测试实验研究。实验表明：实验结果和理论分析吻合,验证了理论模型的正确性;对比WYKO白光干涉仪测试,该方法的相对测试误差小于1%;具有很好的重复性。对该光谱分析方法进行了推广,从理论上推导了该方法可以实现准动态测量GMLM器件吸合电压、共振频率以及其他基于衍射/干涉的MEMS器件的微小间距测试等。     

反射镜平动式光栅光调制器的光学特性分析

提出了一种反射镜平动式光栅光调制器,每个像素主要由一个可动反射镜和上面的固定光栅组成,通过控制可动反射镜和固定光栅的距离达到对入射光的调制.依据标量衍射理论对反射镜平动式光栅光调制器工作状态的光学特性进行了详细的理论分析;并仿真了光调制器的结构参量对衍射效率和对比度的影响.发现:当可动平板和光栅的距离为λ0和5λ0/4,像素表现为暗态和亮态;这种光调制器的工作原理决定了其有效面积大,具有形成面阵的潜力;固定光栅占空比为1/2时,对比度最优;同时给出了对比度随入射光带宽的关系,即带宽越大,对比度急剧下降.     

介质层充电对光栅光调制器驱动的影响

利用高斯定理分析了二氧化硅层中存在电荷时,光栅光调制器中的空间电场分布,得到了光栅光调制器在介质层存贮电荷影响下的静电力公式. 分析了调制器中二氧化硅介质的充电和放电机理,得到了光栅的位移随介质充放电的变化关系. 通过分析指出当驱动电压的周期和介质的充放电时间常数相近的时候,介质层中存贮的电荷会使得可动光栅被下拉后发生缓慢的回跳. 电压被撤消后,光栅会受到存贮电荷所产生电场的作用而被下拉. 当驱动电压的周期远小于介质的充放电时间常数的时候,随着存贮电荷的增加,光栅在有外加电场时被下拉的距离和外加电场为零时被下拉的距离逐渐相等,光调制器输出光的光强变化逐渐减弱,当存贮电荷产生的电场为外加电场的一半时,器件完全失效. 通过实验对理论分析的结果进行了验证,实验结果和理论分析一致. 文章最后提出了一种消除介质层所存贮的电荷的方法,通过实验证明了这种方法的可行性. 关键词： 微机电系统 光栅光调制器 介质层充电     

反射式液晶空间光调制器电控光束偏转

为获得较大的光束电控偏转范围,使用空间分辨力高达8 m的反射式液晶空间光调制器实现了对入射632 nm激光的电控偏转。利用双光束共焦干涉方法测量了液晶空间光调制器的电控相位延迟特性,最大相移量可达3。根据二元光学理论和器件的电控相位延迟特性,设计了周期台阶相位模式和相应的加载灰度图,以最大衍射效率实现对入射光束的闪耀电控偏转。结果表明:相位模式台阶数为8时,可以实现10 mrad的光束偏转,闪耀级次衍射效率可达46%。利用二元光学的衍射模型对影响衍射效率的关键因素进行了分析,认为器件较低的填充因子和周期台阶模式相位重置点诱导的指向矢回程区是限制光束衍射效率的主要因素。     

基于Talbot效应的掺镁铌酸锂二维六角位相阵列光栅的研究

本文系统研究了基于泰伯效应(Talbot) 的位相可调掺镁铌酸锂二维六角位相阵列光栅及其光衍射成像, 对光栅占空比D、不同位相差Δφ、及泰伯分数β条件下的光栅近场光衍射强度分布进行了理论研究, 结果表明当光栅占空比D=52%、位相差Δφ=0.75 π、 泰伯分数β=0.2时, 光栅近场衍射光图像效果最佳. 实验设计与 制备了掺镁铌酸锂二维六角位相阵列光栅, 并对其进行了Talbot衍射光成像实验研究, 得到了不同位相差和不同泰伯分数β条件下光栅近场衍射 光图像, 实验结果与理论研究结果相符. 关键词： 二维六角位相阵列光栅 掺镁铌酸锂晶体 泰伯效应     

聚合物分散液晶(PDLC)光栅的制备及其光衍射特性

聚合物分散液晶（ＰＤＬＣ）光栅的制备及其光衍射特性任洪文黄锡珉王宗凯马凯（中国科学院长春物理研究所北方液晶研究开发中心长春１３００２１）ＦａｂｒｉｃａｔｉｏｎｏｆＰＤＬＣＧｒａｔｉｎｇａｎｄＩｔｓＯｐｔｉｃａｌＤｉｆｒａｃｔｉｖｅＰｒｏｐｅｒｔｉｅｓ...