Autocollimation reflection of light from the surface of corrugated waveguides with leaky modes

The diffraction of light at the corrugated surface of a layer structure was studied. We show that the excitation of the waveguide modes in a layer structure causes a significant change in the diffraction efficiency of the corrugated structure. It is found that the diffraction efficiency of a grating in the autocollimation regime may be as much as 100% with reasonable depths of the grating. The efficiency of a waveguide-grating mirror in dye lasers is experimentally demonstrated.     

Grating amplitude effect on electroluminescence enhancement of corrugated organic light-emitting devices

We report grating amplitude dependence of electroluminescence (EL) in organic light-emitting devices with one-dimensional corrugated structure. Our proposed devices can emit light from both the top silver and bottom quartz side, and both exhibit amplitude-dependence EL enhancement. The effect of grating amplitude on the EL intensity has been studied experimentally and numerically to find out the optimal grating amplitude for the greatest EL enhancement. We deduce from the numerical simulations and experimental results that surface plasmon-polariton modes and waveguide modes are coupled out of the corrugated devices efficiently at the optimal amplitude; therefore, higher efficiency of light extraction could be realized.     

Extraordinary optical transmission through multiple corrugated metallic layers

The enhancement of light transmittance through multiple corrugated grating with double metallic layers is investigated theoretically. Our calculation of transmittance-reflectance through multiple corrugated grating is performed using the coordinate translation method, which is widely used for the calculation of various gratings. For the multiple corrugated grating with double metallic layers, it is confirmed for the first time that the physical mechanism of optical enhancement can be attributed to excitation of wave-guided modes inside the dielectric gap when an F-P like dielectric cavity is formed between two adjacent metal layers.     

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.     

Analytical model of a corrugated optical waveguide

An analytical model of the diffraction energy exchange between the radiative and the waveguide modes in a planar optical waveguide corrugated by a waveguide grating with an arbitrary form of teeth is developed on the basis of the coupled-wave method. It is shown that the mechanism of the energy exchange between the modes is determined by the partial interaction of all components of the spatial frequency spectrum of the waveguide modes with the corresponding components of the spatial frequency spectrum of the grating. It is established that gratings with an asymmetric tooth profile providing a shift of the peak of the spatial frequency spectrum toward matching are characterized by a higher diffraction efficiency α; however, at small thicknesses δ of the waveguide grating, the efficiency is almost independent of the tooth profile. It is shown that gratings with a symmetric profile give on average a decreasing dependence α(δ), while gratings with an optimized asymmetric profile yield a monotonically increasing saturating dependence α(δ).     

Design of a 50/50 splitting ratio non-polarizing beam splitter based on the modal method with fused-silica transmission gratings

The optical design of a beam splitter that has a 50/50 splitting ratio regardless of the polarization is presented. The non-polarizing beam splitter (NPBS) is based on the fused-silica rectangular transmission gratings with high intensity tolerance. The modal method has been used to estimate the effective index of the modes excited in the grating region for TE and TM polarizations. If a phase difference equals an odd multiples of π/2 for the first two modes (i.e. modes 0 and 1), the incident light will be diffracted into the 0 and ?1 orders with about 50% and 50% diffraction efficiency for TM and TE polarizations, respectively.     

共振域矩形介质光栅的逆向设计

采用模态法研究了共振域光栅分束器及闪耀光栅等光学器件的设计原理及逆向设计方法,给出了-1级非偏振闪耀光栅的典型设计示例。研究表明,自准直角入射时,光束在光栅内传输将激发产生离散模,通过调节离散模透过光栅传输时的累积相位差,可对衍射光进行调控,实现偏振(非偏振)分束、偏振(非偏振)闪耀等功能。采用严格耦合波法对基于模态法逆向设计的-1级非偏振石英闪耀光栅的几何参数进行验证,计算结果显示两者非常吻合,证明了该方法的正确性。     

Role of propagating modes in a double-groove grating with a +1st-order diffraction angle larger than the substrate-air critical angle

Here we show, analytically and numerically, that in a TiO(2) double-groove grating with two different groove widths per period attached on the SiO(2) substrate, the normally incident light couples to the +1st-order transmission with 96.9% efficiency and with a 50° diffraction angle that is larger than the SiO(2)-air interface critical angle. Modal analysis reveals that three propagating modes for the +1st diffraction order reach the grating back end in phase, while the corresponding propagating modes for the -1st and zeroth orders are added destructively at the grating end. Four optical devices based on this grating characteristic are numerically demonstrated.     

Planar anisotropic Mikaelian lens on the basis of EBG-structure

The problem on the synthesis of a planar Mikaelian lens in the form of layered metal?dielectric waveguide with a nonuniform anisotropic dielectric layer is solved. The problem is reduced to solution of the dispersion equations for E and H modes of a homogeneous layered waveguide. As an example of implementation of the solution obtained, the synthesis and analysis of the Mikaelian lens is carried out on the basis of the EBG structure in the form of a planar corrugated open and closed layered metal?dielectric waveguide. For a special case of the closed waveguide, the solution of the problem of synthesis for both polarizations is obtained explicitly.     

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.     

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.     

飞秒激光用多层介质膜脉宽压缩光栅的设计

以薄膜光学的干涉理论和衍射光学的傅里叶模式理论为基础，给出了0.8μm飞秒激光器用多层介质膜脉宽压缩光栅的理论设计；设计采用H3L(HL)^9H0.5L2.4H的多层介质膜为基底，当刻蚀后表面浮雕结构的占宽比为0.35，线密度为1480线/mm，槽深为0.2μm，顶层HfO₂的剩余厚度为0.15μm时，对于Littrow角度(36.7°)和TE波模式入射的衍射光栅其-1级衍射效率达到95％以上. 关键词： 飞秒激光 脉宽压缩光栅 多层介质膜     

Diffraction efficiency and electron microscopy of large amplitude holographic gratings

The diffraction efficiency of Ag coated holographic gratings was measured as a function of the grating amplitude, H, for a He-Ne laser incident at 30° and 70° in the plane perpendicular to the grating grooves. The grating amplitude was determined using a scanning electron microscope. It was found that the diffraction efficiency of s polarized light increased monotonically with increasing H for H < 250 nm. In contrast, for the same amplitude range, the diffraction efficiency of p polarized light oscillated through two maxima at H = 90 nmand 220 nm. These results were compared to the theoretical calculations of Heitmann and found to agree within 10% for H < 60 nm in the s polarization case and for H < 15 nm in the p polarization case. For larger H, the data deviated significantly, presumably due to a breakdown of the small amplitude assumption on which the calculations were based.     

用于彩色液晶显示器的色分离光栅的优化设计

利用光栅实现液晶显示器中的色分离可以提高液晶显示器对光能的利用率。为了提高光能利用率,对光栅台阶数进行了优化设计,经矢量衍射理论计算,优化后的多台阶色分离光栅的能量利用率达到了65.3%,与采用滤色片的方法相比,光能利用率提高了近一倍;与三台阶相比,光能利用率提高了9.3%。     

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...     

基于傅里叶光学原理的新型凹面光栅衍射效率测量方法

凹面衍射光栅兼具色散分光与光束聚焦功能,同时具有像差校正、低杂散光、无鬼线和高信噪比等优势而受到光谱仪器领域的广泛关注。衍射效率作为凹面光栅最重要的技术指标之一,其测量技术水平逐渐成为光谱仪器行业最为关注的课题之一。传统方法一般采用双单色仪结构实现凹面光栅衍射效率的测量,该方法主要存在两方面问题,一是测量标准反射镜和待测光栅的出射光谱带宽不同,二是光栅叠级、杂散光的影响;上述问题的存在降低了高性能凹面光栅衍射效率测量的准确性。本文提出了一种基于傅里叶光学原理测量凹面光栅衍射效率的新方法;针对该方法建立了凹面光栅衍射效率测量的数学模型,并采用光学追迹和傅里叶光学方法相结合对其进行了仿真分析,从而验证了该方法的正确性;针对动镜横移误差、倾斜误差、光源稳定性、动镜运动距离误差等因素影响凹面光栅衍射效率测量精度的问题,提出引入辅助探测器的方法来进一步提高衍射效率测量精度,并对有无辅助探测器情况下的上述误差对衍射效率的影响进行了数学推导和仿真分析,分析结果表明引入辅助探测器可以有效抑制了上述误差对凹面光栅衍射效率测量的影响。对比传统双单色仪测量方法而言,该方法不仅能够解决传统测量方法存在的问题,同时还具有多波长同时测量、高光通量、高分辨率、高波数精度等优势,可以有效提高凹面光栅衍射效率的测量精度和测量效率。     

Polarization modulation of a submillimetre laser

A concept is described whereby simultaneous independent oscillation may be obtained at slightly different frequencies on two orthogonally linearly polarized modes of the same laser cavity. It involves simply replacing one of the end mirrors with a suitable diffraction grating, reflecting in zeroth order. Experiments on an HCN laser (λ = 337 μm) show that the technique works successfully, though only on certain of the transverse modes; mode structure analysis has been performed to show which modes are involved. Polarization modulation at the difference frequency of 0.9 MHz, determined by the choice of grating, has been observed; its frequency stability is fully adequate for heterodyne interferometry or similar purposes. The technique should be applicable to other lasers.     

真空紫外波段光栅二级衍射效率测量装置

利用光栅二级衍射会影响反射样品光谱反射率结果的原理,通过计算不同光谱反射率获得了光栅二级衍射效率。介绍了测量二级衍射效率的实验装置,该装置采用双光路单色仪结构,使用已知光谱辐亮度氘灯作为光源,探测器为光电倍增管,通过水杨酸钠膜将紫外光转为可见光。以波长161nm为例,测量了5块反射镜样片,计算得到光栅二级衍射效率为0.00611×(1±0.0777)。分析表明,该方法采用的测试装置简单,系统不确定度为14.08%,可以实现真空紫外波段光栅二级光谱衍射效率的连续测量。     

Observation of electron diffraction due to a reflection grating in an electron wave transistor

We investigate quantum transport in the presence of an electron reflection grating fabricated in an electron wave transistor structure. The grating is made up of a periodically corrugated potential wall by which the electron waves are coherently scattered. We observe a number of peaks with respect to the gate voltage in the low-temperature conductance measurements. The conductance oscillations are attributed to the electron diffraction effect, and the peak positions agree well with those predicted by the Fraunhofer diffraction condition.     

Shape resonances in nested diffraction gratings

The diffraction problem of a plane wave impinging on a grating formed by nested cavities is solved by means of the modal method, for s and p polarization modes. The cavities are formed by perfectly conducting sheets that describe rectangular profiles. The electromagnetic response of the grating is analyzed, paying particular attention to the generation of resonances within the structure. The dependence of the resonances on the geometrical parameters of the grating is studied, and results of far and near field are shown. The results are checked and compared with those available in the literature for certain limit cases.