基于金属-介质-金属结构的反射式彩色滤光片特性研究

研究了金属-介质-金属结构在可见光波段的反射滤光特性。该结构由柔性透明基底、金属层、介质-金属纳米光栅结构组成。利用严格耦合波分析法(RCWA)模拟了TM偏振光入射时,亚波长介质-金属光栅的占宽比、周期和厚度等结构参数对反射光谱特性的影响。理论模拟结果表明:光栅的结构参数变化可改变反射波段,进而调节滤光颜色。在此基础上,进一步优化结构参数,得到了基于减色法的彩色滤光片结构,获得了青色、品红色和黄色三原色。该结构的主要优点是,当入射角在0～45范围内变化时,反射光谱谷值位置和反射带宽基本不变。本文所提出的结构特别适合用于反射式彩色显示。     

缓冲层对导模共振滤光片反射光谱截止特性的影响

提出将均质多层膜系设计中的缓冲层概念71入到反射导模共振(GMR)滤光片的设计中,通过严格的耦合波理论精确计算,研究了加入缓冲层对改善导模共振滤光片反射峰边带截止深度及截止宽度的作用.双层导模共振滤光片结构中,入射光为TE偏振光时,设计增加97.5 nm缓冲层后,能够明显地展宽反射光谱范围.由原来的192.4 nm展宽到345.6 nm,并且在650～1250 nm波长范围内的边带截止度均比不含缓冲层结构的要深.入射光为TM偏振光,以类似TE结构的滤光片在布儒斯特角入射时,在700~1300 nm波长范围内,较不含缓冲层的结构,也能够获得更宽的截止带反射光谱和更深的截止度.在提出的膜系结构中,经过优化膜系、选择合适的光栅参数等,可以使反射光谱具有更好的截止特性,同时保证设计的共振峰位置不变.     

基于金属狭缝阵列的各向异性偏振分束器

在金属-电介质结构的基础上提出了一种基于金属狭缝阵列的各向异性偏振分束器,并采用有限元法研究了横磁(TM)和横电(TE)偏振光入射后结构所表现出的负反射和镜面反射等特性.计算结果表明,当偏振光的入射角设定在20?—70?时,入射的TM光发生强烈的负反射,而TE光的负反射很弱,并随着波长的增加而急剧下降.分析可得偏振分束光栅的理想负反射点和反射面的完美对称响应效果.通过仿真得到了理想负反射点的取值范围.结合严格耦合波法软件,计算不同偏振光入射时负反射和镜面反射条件下的反射率,其消光比高达10~6.     

应用于VCSEL的GaAs/AlOx高折射率对比度亚波长光栅反射镜的设计和制备

基于严格耦合波理论,分析GaAs/AlO_x高折射率对比度亚波长光栅(HCG)反射镜的偏振和反射特性,设计了横电(TE)偏振的HCG。当入射光由衬底垂直入射时,HCG在940 nm附近的最高反射率接近1。分析了光栅形貌误差和入射角偏差对其反射特性的影响。采用金属有机化合物气相沉积技术进行外延生长,通过电子束曝光、干法刻蚀、湿法刻蚀以及湿法氧化等方法制备出HCG,并进行理论与实验结果的对比分析。实验测试了入射光由光栅表面垂直入射的反射率,其中TE偏振光的最高反射率达到84.9%,与86.5%的理论值比较接近,且横磁(TM)偏振光的反射率低于40%,反射谱的变化规律也与理论结果基本一致,这验证了理论结果的合理性。该反射镜可以作为垂直腔面发射激光器的超薄反射器,具有低损耗、偏振稳定和单模工作的特性。     

基于RCWA的太阳能电池抗反射膜分析研究

利用严格耦合波分析法（RCWA）分别计算了五种不同形貌的亚波长浮雕结构的太阳能电池抗反射膜性能,分别从占空比、光栅高度和周期等结构参数以及入射光角度进行模拟。研究结果表明：周期为200rim,高度为400nm,占空比为1的金字塔型浮雕结构的抗反射效果令人满意,且平均反射率低于1％;光波的入射角对光栅的反射率影响较大,光波在光栅法线的角度控制在40°以下合适。通过对亚波长浮雕结构的反射特性模拟和分析,为太阳能电池抗反射膜设计与制作提供理论支持。     

带缓冲层的导模共振滤光片反射光谱特性

将均质多层膜系设计中的缓冲层概念引入到反射导模共振滤光片的设计中,以研究缓冲层的增加对导模共振滤光片反射光谱特性的影响.设计并通过严格的耦合波理论计算了一、二、三、四通道导模共振反射滤光片光谱特性.在膜系设计中增加缓冲层后.随着其厚度的逐渐增加.反射光谱中依次出现二、三、四个窄带反射峰;缓冲层厚度为796.35 nm时.当滤光片光栅层占空比在0.2～O.9范围内、光栅深度在100～200 nm变化时,共振峰的位置、反射率峰值高度几乎不变,保持了很好的多通道滤光片特性.     

入射角对Al0.5Ga0.5As-AlAs分布布拉格反射器反射光谱的影响

采用传输矩阵法对Al0.5Ga0.5As-AlAs材料的发光二极管分布布拉格反射器进行入射角的反射光谱研究,计算发现反射偏振光p和s随入射角的增大呈“V”形变化,在49.8°处有最小反射值。不同入射介质[以空气和限制层(Al0.7Ga0.3)0.5In0.5P材料]下的反射光谱受入射角的影响差异很大,其中入射角对空气入射介质的反射谱影响较小,由0°入射的反射率88.13%降至45°的84.94%,反射峰值波长蓝移仅10 nm;但入射角对(Al0.7Ga0.3)0.5In0.5P入射介质的反射谱影响很大,仅从0°到45°入射,反射率降幅就超过45%,反射峰值波长蓝移超过127 nm。为了减缓这种影响,提出了多波长布拉格反射器结构设计。计算表明多波长分布布拉格反射器在0ο~45°的入射角内比传统的分布布拉格反射器有更好的光谱特性,这对提高发光二极管的出光效率有现实意义。     

亚波长金属偏振分束光栅设计分析

结合有效介质理论和薄膜光学的抗反射设计方法,设计了基于0.65μm工作波长的亚波长金属偏振分束光栅,给出了光栅的优化设计参数,采用严格耦合波理论分析了光栅的偏振分束特性.结果表明,亚波长金属光栅对TE偏振表现为金属膜特性,具有高反射,对TM偏振表现为介质膜特性,具有高透射,在-30°<θ<30°的大入射角范围和0.47μm<λ<0.80μm的宽入射波谱内,该光栅的透射光和反射光均具有高偏振消光比和低插入损耗的特点. 关键词： 亚波长金属偏振分束光栅 有效介质理论 薄膜光学 严格耦合波理论     

激光斜入射窄带滤光片的热力效应

基于麦克斯韦方程组及热力学理论,分析了脉冲强激光在不同入射角、不同偏振态下辐照10.6μm窄带滤光片的热力效应,研究了不同入射角及偏振态下的温度场、应力场,计算了激光辐照下热力效应给窄带滤光片带来的通带漂移效应,比较讨论了不同入射角下的损伤阈值.结果表明:随着入射角度的增大,温升峰值的幅值与位置都有了较大的变化;P偏振光与S偏振光辐照引起的温升峰值都随着入射角度的增大逐渐下降;温升峰值的位置随着入射角的增大逐渐靠近滤光片与空气的界面;P偏振光与S偏振光引起的热力效应差异性越来越明显.在激光能量相同的情况下对比了不同激光入射角下的通带漂移特性,小角度入射时滤光片中心波长偏移超过200nm,10.6μm处透射率下降到6%以下.随着入射角的增大,滤光片熔融损伤阈值越来越大,而且在小角度入射时,P偏振光与S偏振光熔融损伤的阈值差别很小;当入射角大于30°时,P偏振光与S偏振光的熔融损伤阈值差别越来越大.以较小的功率实现激光对窄带滤光片的损伤需要考虑激光的入射角及偏振态.     

双折射消偏振膜的设计和制备

基于倾斜沉积薄膜材料的双折射特性,采用单一TiO2设计和制备了中心波长为632 nm的双折射消偏振膜。首先以60°和70°的沉积角度镀制了TiO2单层膜,通过单层膜的透射光谱分别拟合出两种沉积角度下薄膜对s和p偏振光的等效折射率nPH,nSH和nPL,nSL。通过对折射率的组合,实现正入射时s偏振光透射率大于p偏振光,而入射角度增大会使两者透射率差值减小,基于这一思想设计并制备了消偏振膜。分别测量了消偏振薄膜在400~800 nm波段范围内正入射及倾斜入射条件下s和p偏振光的透射光谱。入射角为60°时,s偏振光反射带宽基本与p偏振光反射带宽重合,在波长632 nm左右基本实现消偏振。结果表明,利用材料的双折射特性,可以设计和制备出倾斜入射条件下消偏振薄膜。     

Design of high-efficiency diffraction gratings based on total internal reflection for pulse compressor

We present designs of high-efficiency compression grating based on total internal reflection (TIR) for picosecond pulse laser at 1053 nm. The setup is devised by directly etching gratings into the bottom side of a prism so that light can successfully enter (or exit) the compression grating. Dependence of the −1 order diffraction efficiencies on the constructive parameters is analyzed for TE- and TM-polarized incident light at Littrow angle by using Fourier modal method in order to obtain optimal grating structure. The electric field enhancement within the high-efficiency TIR gratings is regarded as another criterion to optimize the structure of the TIR gratings. With the criterion of high diffraction efficiency, low electric field enhancement and sufficient manufacturing latitude, TIR compression gratings with optimized constructive parameters are obtained for TE- and TM-polarized incident light, respectively. The grating for TE-polarized light exhibits diffraction efficiencies higher than 0.95 within 23 nm bandwidth and relatively low square of electric field enhancement ratio of 5.7. Regardless of the internal electric field enhancement, the grating for TM-polarized light provides diffraction efficiencies higher than 0.95 within 42 nm bandwidth. With compact structure, such TIR compression gratings made solely of fused silica should be of great interest for application to chirped pulse amplification (CPA) systems.     

Design of High-Efficiency Diffraction Gratings Based on Rigorous Coupled-Wave Analysis for 800nm Wavelength

We report on the design of a high diffraction efficiency multi-layer dielectric grating with wide incident angle and broad bandwidth for 80Ohm. The optimized grating can achieve 〉 95% diffraction efficiency in the first order at an incident angle of 5° from Littrow and a wavelength from 77Ohm to 83Ohm, with peak diffraction efieieney of 〉 99.5% at 80Ohm. The electric field distribution of the optimized multi-layer dielectric grating within the gratings ridge is 1.3 times enhancement of the incidence light, which presents potential high laser resistance ability. Because of its high-effieieney, wide incident, broad bandwidth and potential high resistance ability, the multi-layer dielectric grating should have practical application in Ti：sapphire laser systems.     

大角带宽高衍射效率体全息光栅的设计和制备

高性能体全息光栅是全息波导的重要耦合元件,角带宽小、平均衍射效率不高是制约体全息光栅性能的重要因素。以不对称倾斜记录为出发点,设计并制备了大角带宽高衍射效率的体全息光栅。首先讨论在横电模式光和横磁模式光下体全息光栅的记录参数与其衍射效率的关系,找到平均衍射效率较高的记录参数范围,随后进一步分析在此范围内的记录参数与体全息光栅的角带宽的关系,从而确定获得大角带宽高衍射效率体全息光栅的最佳记录参数。实验结果表明:在参考光入射角度为25°、信号光入射角度为30°时,制备的体全息光栅的角带宽达到±14°,衍射效率为82%。     

Narrow-bandwidth tunable bandstop filters with circularly cylindrical self-suspended silicon gratings

A circularly cylindrical self-suspended silicon grating (SSG) is proposed, and its reflectance spectrum is investigated by the rigorous coupled-wave method (RCWM). For TM incident polarization, when the grating period is tuned, numerical results by the RCWM reveal that the circularly cylindrical SSG possesses a tunable narrow reflectance bandwidth property in the optical telecommunication wavelength region. It is also demonstrated that both TM incident polarization and the circular grating cross section are easier to bring narrow reflectance bandwidth, compared with TE incident polarization and square grating cross section. Via a micro-electromechanical systems actuator, the proposed circularly cylindrical SSG is expected to serve as a narrow-bandwidth tunable bandstop filter in micro-optical telecommunication systems.     

Fabrication of ultrathin color filters for three primary colors using guided-mode resonance in silicon subwavelength gratings

We fabricate reflection color filters for three primary colors using silicon two-dimensional triangular-lattice subwavelength gratings on the same quartz substrate. The grating periods are 480, 390, and 300 nm for red, green, and blue filters, respectively. All of the color filters have the same thickness of 100 nm, which enables the simple fabrication of a color filter array. Maximum reflectances of 75 and 46% are obtained at wavelengths of 647.1 and 522.1 nm for the red and green filters, respectively. The blue filter has a double-peaked spectrum with a reflectance of 30% at the peak wavelengths of 450.0 and 502.7 nm. By rigorous coupled-wave analysis, the dimensions of each color filter are designed, and the calculated theoretical reflectance is compared with the measured one.     

双带通啁啾光纤光栅光谱特性仿真及分析

针对啁啾光纤光栅的带通滤波特性,设计了纤芯/包层复合结构的啁啾光纤光栅滤波器.基于光纤耦合模和传输矩阵理论及坐标变换方法,对其光谱特性进行仿真分析,验证了该光栅的双带通滤波特性;对周期为536、537、538nm,长度为8、10、12mm,折射率调试深度为0.0002、0.0003、0.0004,啁啾系数为0.05、0...     

多层介质膜脉冲压缩光栅近场光学特性分析

利用傅里叶模式理论分析了TE波自准直角入射的使用条件下，多层介质膜光栅的光栅区和多层膜区电场分布的特点.分别讨论了HfO₂和SiO₂为顶层光栅材料时，光栅结构参数对光栅脊峰值电场的影响，结果表明，对于不同膜厚的顶层材料，存在一个最佳膜厚度，使光栅脊峰值电场最小，并且当膜厚增大时，设计大高宽比的光栅可以降低该电场峰值.最后，在大角度条件下使用多层膜光栅也可以降低光栅脊处的峰值电场. 关键词： 衍射光学 多层介质膜光栅 模式理论 损伤阈值     

单发实验测量软X射线多层膜反射镜反射特性

 提出了一种单发实验测量软X射线波段多层膜反射镜反射特性的简易方法。实验采用激光等离子体软X射线源作为光源,用平焦场光栅谱仪分光,在光路中引入掠入射镜以消除高级次谱的影响,用软X光CCD记录,在一发激光打靶实验中,测量了设计中心波长为13.9 nm的Mo/Si多层膜反射镜的反射特性。     

Crossed gratings: A theory and its applications

We introduce a rigorous formulation for the problem of the diffraction by a finitely-conducting, bi-periodic surface. The formationon is based on a coordinate transformation which maps the grating surface onto a plane. The transformed Maxwell equations are resolved using an iterative technique. The numerical implementation is tested against a number of criteria, including a comparison with two recently developed formalisms. As well, it is shown to give results in agreement with the Reciprocity Theorem, which is derived for efficiencies of crossed gratings in unpolarized light. The method has been shown to work throughout the whole range of values of surface conductivity. We investigate the effect of a surface-corrugation on the solar absorptance of a metallic mirror. We discuss a useful equivalence property linking the behaviour of crossed gratings with that of classical gratings. We exhibit for the first time a grating in a highly-reflecting metal capable of totally absorbing unpolarized incident light. On leave from the Department of Theoretical Physics, School of Physics, University of Sydney, Sydney, N.S.W., 2006, Australia