高效全偏振矩形闪耀光栅的设计(英文)

入射光在光栅内传输时将激发产生离散模.本文采用模态法调节光栅内离散模的传输特性,使TE和TM偏振光所激发的0、1模为传输模,其余高阶模为消逝模.通过调控0模和1模间的累积相位差,对衍射光进行调控,实现了-1级近100%的高效衍射.采用模态法分三部设计了共振域的矩形全偏振闪耀光栅:1)根据光栅的共振条件给出光栅周期,光栅周期越大槽深越小;2)根据特征模方程计算出光栅占空比;3)根据耦合模条件计算机光栅槽深.实验结果表明,该光栅的TE和TM偏振光同时具备近100%的-1级衍射效率.给出了633nm波长-1级矩形石英全偏振闪耀光栅的典型设计实例,计算结果表明:所设计的全偏振闪耀光栅对TE和TM偏振入射光的-1级衍射效率分别高达96.7%和98.1%,且具有较宽的入射角及入射波长的变化适应范围,较大的制作容差.     

用耦合波方法研究取样光栅的衍射特性

介绍了利用耦合波理论编写计算光栅衍射特性程序的基本思想和主要步骤.利用编写的程序计算并分析了一种用于激光取样光栅TE波和TM波的衍射特性.     

用耦合波方法研究取样光栅的衍射特性

 介绍了利用耦合波理论编写计算光栅衍射特性程序的基本思想和主要步骤。利用编写的程序计算并分析了一种用于激光取样光栅TE波和TM波的衍射特性。     

红外波段高效率低偏振相关损耗光栅的设计

衍射效率高、偏振相关损耗低的衍射光栅是集成波分复用/解复用器件的一种核心元件,在光通信中具有很重要的应用价值。通过利用严格的耦合波理论计算光栅衍射效率的方法,分别编制出了计算TE波和TM波的衍射效率程序。通过改变光栅的面形来进行计算,最终得到了衍射效率高和偏振相关损耗小的光栅面形。     

一维TiO2亚波长光栅的衍射异常现象及其结构设计

研究了一维TiO₂亚波长光栅（SWG）的衍射异常现象,具体表现为泄漏模共振效应和瑞利异常。研究表明,一定参数条件下的横磁波（TM偏振）和横电波（TE偏振）入射均会出现瑞利异常和泄漏模共振效应。在TM偏振光情况下,会出现传统的窄带、高衍射效率泄漏模共振效应,而在TE偏振光情况下,由于多个接近的泄漏模共振峰相互叠加,故会形成宽带、高衍射效率的反射谱。采用严格耦合波理论计算了一维TiO₂ SWG的衍射效率,研究了光栅周期、高度和占空比对光栅反射率的影响。当光栅周期为0.49μm,高度为0.25μm,占空比为0.34时,SWG具有TE偏振选择性,在0.52μm波段处的反射率接近1,且高反带（反射率达到99.9%以上）宽度为26 nm。优化各结构参数,得到光栅周期、占空比、高度的制作容差分别为1.6%、8.3%、2.0%,故SWG理论上可以作为垂直腔面发射激光器的反射镜。     

高密度相位光栅的偏振选择性

高密度光栅具有与传统光栅不同的性质,其衍射特性往往是偏振相关的。本文针对1550nm波长TE/TM偏振入射光和0.5的光栅占空比,利用严格耦合波分析数值计算了不同光栅周期下0级及-1级的衍射效率。研究表明,相比周期为1550nm的光栅,当周期为1200nm时,偏振相关衍射效应明显增强,当光栅周期为890nm时,TE偏振光的衍射效率随着光栅深度呈正余弦变化,而TM偏振光的衍射效率始终集中在0级,具有偏振选择性。通过模式方法,利用模式中的有效折射率概念,研究了不同周期下被入射光所激发的两种光波模式通过光栅区域传播所累积的相位差;基于双光束干涉,模拟了0级和-1级的衍射效率。结果表明,利用严格耦合波分析的数值计算结果符合模式方法的理论预期,对于高密度相位光栅的偏振选择性给予了合理的物理机制解释。     

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.     

基于修正简化模式法的熔融石英光栅分束器设计

对用于光栅优化设计初值估计的简化模式法(SMM)进行了修正。考虑介质光栅的反射对透射率的影响,从多层膜等效的角度结合模式理论,推导出介质光栅的透射效率公式,实现了对SMM的修正。计算结果表明,与SMM相比,修正后的方法与严格耦合波(RCWA)的计算偏差大大缩小,TE和TM波都小于2%。因此相对于只能提供设计参数优化初值的SMM,该方法可对光栅参数进行优化;与RCWA相比,该方法将透射光栅的衍射效率表达成模式的相位差偏移和光栅与空气导纳之差引起的反射,更直观地展示了光栅衍射的物理过程。基于此修正的简化模式法(MSMM),优化设计了一个双端口光栅分束器,该光栅在1020~1100nm波段,TE波和TM波的0级和-1级透射效率都在50%左右,具有较好的分束效果。     

Bragg反射齿型平面凹面衍射光栅性能研究

本文基于Bragg反射光栅是一维光子晶体的一种特例结构, 提出利用一维光子晶体理论进行Bragg衍射光栅的设计并对其性能进行研究分析. 根据一维光子晶体理论, 建立了罗兰圆结构的凹面椭圆Bragg蚀刻衍射光栅, 研究了TE/TM模式下器件的分光特性以及入射角度改变对器件角色散造成的影响; 同时, 文中对比了空气介质型和金属铝线型椭圆Bragg蚀刻衍射光栅的光学性能. 研究结果表明: 选择合适的器件参数, 可以实现TE/TM模式下1.465-1.615 μm范围内波长衍射效率在95% 以上, 且空气介质型结构光栅的通道均匀性要优于金属铝线型结构光栅; 入射角在30°-60°范围内变化时, 相同入射角度下, TM模式下器件角色散大于TE模式. 基于Bragg衍射光栅设计的波分复用器是一种尺寸小、衍射效率高的新型EDG 波分复用器, 为未来密集型EDG波分复用器发展提供了一种新的设计思路.     

非对称偏振分束光栅的矢量衍射优化设计

基于严格耦合波理论分析了一种非对称偏振分束光栅的设计。这种偏振分束光栅分别在1级和0级衍射级次上衍射TE和TM偏振波。介绍了利用遗传算法设计偏振分束光栅的方法,并给出了优化实例。仿真结果表明:在设计波长为1.55时,TE偏振波在1级的衍射效率大于93%,TM偏振波在0级的衍射效率大于99%,此时1级和0级的透射消光比分别达到了9914.1和46841.5。通过对设计结果的分析发现,该偏振分束光栅在设计波长附近100nm的波长范围内都具有较高的消光比(大于100),达到了较好的偏振分束效果。     

Connecting-layer-based polarizing beam splitter grating with high efficiency for both TE and TM polarizations

We describe a novel polarizing beam splitter (PBS) of transmission connecting-layer-based grating, which can show high efficiency for TE polarization in the ?1st order and TM polarization in the 0th order. According to the modal method, grating duty cycle and period are prescribed to obtain high efficiency for TM polarization. Using the rigorous coupled-wave analysis, grating depth and thickness of the connecting layer are optimized to achieve high efficiency for TE polarization. The presented PBS has advantages of wideband properties for incident wavelength and angle. Most importantly, the efficiency is improved greatly for TE polarization compared with the reported PBS based on fused-silica grating.     

基于光谱合束技术的透射光栅模拟设计

半导体激光器光谱合束技术能够实现近衍射极限的高功率激光输出,已成为当前研究热点。衍射光栅的性能直接决定光谱合束的激光输出效果。模拟设计了一种针对940 nm波长、熔融石英材料的亚波长透射光栅。基于严格耦合波理论对光栅结构进行初步设计,运用Rsoft软件依次对光栅占空比、脊高和周期等参数进行优化确定,同时分析了各个参数对光栅衍射效率的影响。所设计的透射式光栅实现第-1级衍射级次的波分复用功能,衍射效率达到91.2%(TE模式),同时压缩其他衍射级次,使其衍射效率降到1.2%以下。同时在光栅入射角度59°±3°范围内保持90%以上的衍射效率,实现高功率激光输出的同时具有较高的误差容错率,易于调节,满足光谱合束技术的要求。     

Polarizing beam splitter of a deep-etched fused-silica grating

We described a highly efficient polarizing beam splitter (PBS) of a deep-etched binary-phase fused-silica grating, where TE- and TM-polarized waves are mainly diffracted in the -1st and 0th orders, respectively. To achieve a high extinction ratio and diffraction efficiency, the grating depth and period are optimized by using rigorous coupled-wave analysis, which can be well explained based on the modal method with effective indices of the modes for TE/TM polarization. Holographic recording technology and inductively coupled plasma etching are employed to fabricate the fused-silica PBS grating. Experimental results of diffraction efficiencies approaching 80% for a TE-polarized wave in the -1st order and more than 85% for a TM-polarized wave in the 0th order were obtained at a wavelength of 1550 nm. Because of its compact structure and simple fabrication process, which is suitable for mass reproduction, a deep-etched fused-silica grating as a PBS should be a useful device for practical applications.     

Theoretical reflective performance of a sandwiched two-layer grating polarizer

The reflective polarizer is described by a sandwiched two-layer grating with a metal slab. Such a new polarizer is aimed to improve the performance of a reflective grating-based polarizer. The grating is optimized with the usual duty cycle of 0.5, where TE and TM polarizations are reflected in the –1st and the 0th diffraction orders, respectively. With optimized grating parameters, the extinction ratio can reach 45.5 dB and 41.9 dB in two diffraction orders, which are greatly improved compared with the conventional reported surface grating polarizer with the simple structure. Attractive merits of the new design are high efficiency, high extinction ratio, wide incident wavelength bandwidth for TE polarization, and wide angular range for TM polarization. Numerical results are expected to open new opportunities for the design of a grating-based polarizer with the enhanced performance by the complicated grating configuration.     

Complete Polarization Conversion Characteristics of Dielectric Grating Composed of Left-Handed Materials

The TE/TM polarization conversion characteristics of dielectric grating composed of left-handed materials for the case of plane wave oblique incidence are carefully investigated by a method which combines the multimode network theory with the rigorous mode matching method. It is indicated that complete polarization conversion between TE and TM modes can be realized using left-handed gratings. This can hardly achieve in the conventional right-handed gratings. Comparisons of polarization conversion properties between right-handed gratings and left-handed gratings are given with physical explanations. This unique merit of left-handed periodic structure is of important significance for accurate design of new millimeter wave TE/TM polarization converters.     

基于二维结构薄膜的偏振选择相位光栅的研究

利用二维结构薄膜构建了具有偏振选择特性的新型相位光栅,借助严格耦合波分析(RCWA)方法计算了光栅各级衍射强度随入射光波长及入射角的变化,发现在垂直入射情况下,波长600—640 nm范围内,相位光栅对横向电学(TE)模主要产生0级衍射,而对横向磁学(TM)模产生±1级衍射,在波长633nm处,0级衍射光的偏振消光比为109.8,±1级衍射光的偏振消光比为334.6.利用时域有限差分方法对这种相位光栅的偏振分束现象进行了模拟,偏振分离角在玻璃基板内可以达到10°左右,最后模拟了入射角为23°时光栅对不同偏     

Polarizing beam splitter of two-layer dielectric rectangular transmission gratings in Littrow mounting

We theoretically investigated the design of polarizing beam splitters (PBS) of two-layer dielectric rectangular transmission gratings in Littrow mounting. The PBS grating is aimed to separate TE and TM polarized waves into two different transmitted orders, i.e. the 0th and −1st orders. The polarization-dependent diffraction process is analyzed by using a simplified modal method. The mode reflection and transmission at the interface of the two layers are illustrated. Design equations are given based on the average mode indices of the even and odd modes inside the grating region, which are verified by using rigorous coupled wave analysis. Moreover, with simulated annealing algorithm, two kinds of two-layer PBS gratings are optimized for operation over the C-band (1520-1570 nm). Compared with the single-layer transmission PBS gratings, such two-layer scheme exhibits a great flexibility of design. The PBSs of two-layer dielectric transmission gratings should be useful for practical applications.     

A detailed study of metallic surface-relief grating

This paper presents a more detailed interaction of an electromagnetics light with a metallic surface-relief subwavelength grating utilizing the rigorous coupled-wave analysis. The focus of this work is the accurate modeling of undetermined aspects of diffraction patterns produced by binary metallic grating structures, specially gold grating. First-order diffraction efficiency for rectangular-groove gold grating with equal groove and ridge widths are presented for various wavelengths as a function of period, groove depth, polarization and angle of incidence. We also studied diffraction efficiency of both of TE and TM polarization modes against increasing of incident angle as well as TE polarization against increment of grating period. As a result, very low reflectivity at zero-order was found out for TE and TM polarizations at the pitch of Λ = 2λ. Having been studied diffraction efficiency of metallic surface-relief gratings, we also examined polarization-dependent efficiency of diffraction orders, for different groove depths. Simulation results have been completely presented.