RGB三通道衍射望远镜光学成像系统设计

基于目前研究较热的大口径衍射望远镜技术，提出一种在可见光范围内进行成像的衍射望远镜光学系统方案。该方案解决了目前衍射望远镜存在的成像频谱范围较窄的问题，可以在可见光范围内获取彩色图像，设计方法是将衍射元件沿径向分为3个通道，分别对R、G、B三个颜色通道进行成像，每个通道的成像带宽为40 nm，通过控制系统参数使3个通道的像在像面处重合，获取彩色图像。设计了基于25 m口径衍射主镜的三通道望远镜光学系统，并对该系统进行建模仿真，仿真结果与设计理论相符。该方案可以增加成像的频谱范围，其像面光斑具有与单通道系统像面光斑近乎相同的主瓣宽度。     

衍射极限尺度下的亚波长电磁学

作为波的本性之一,衍射是现代物理学的重要研究内容.衍射导致自由空间中波的能量不能被无限小地聚集,从而为成像、光刻、光存储、光波导等技术设定了一个原理性的障碍——衍射极限.对于电磁波和光波而言,尽管通过提高介质的折射率可以压缩衍射效应,但由于自然界中材料的折射率有限,该方法存在很大限制.近年来,随着表面等离子体光学的兴起,表面等离子体在超越传统衍射极限方面的能力和应用前景受到了学术界的关注.本文从亚波长电磁学的角度出发,介绍衍射极限研究的历史,综述了突破衍射极限的理论方法.首先,利用金属介质表面等离子体激元的短波长特性,可将等效波长压缩一个数量级以上,在纳米尺度实现光波的聚焦或定向传输;更进一步,通过人为设计超构材料和超构表面,利用结构化金属和介质中的局域谐振、耦合等特殊电磁响应,可实现亚波长局域相位调制、超宽带色散调控、近完美吸收、光子自旋轨道耦合等,从而突破传统理论的诸多局限,为下一代电磁学和光学功能器件奠定重要基础.     

Laterally deformable nanomechanical zeroth-order gratings: anomalous diffraction studied by rigorous coupled-wave analysis

We describe a novel optomechanical device that produces strong reflectance and polarization modulation of incident light. The structure is based on a suspended nanomechanical grating with lateral deformability, and rigorous coupled-wave analysis has been used to fully model the optical properties of the device. The grating consists of two interdigitated gratings that may be moved with respect to each other with an applied force. The structures proposed here are designed to be readily manufacturable with device processing developed for surface-micromachined microelectromechanical systems and with known microelectromechanical systems materials, such as silicon, silicon nitride, and amorphous diamond. As the spacing of the grating is changed, an anomalous diffraction effect is observed, a Wood's type anomaly in which there exists a resonance in propagating leaky modes within the grating, resulting in a dramatic change in the reflectance characteristics for slight changes in the grating. One of the unique features of this structure is that a reflected optical signal can be used to detect subangstrom in-plane motion of structures greater than 10 nm.     

Binary diffractive beam splitters with arbitrary diffraction angles

Diffractive optical beam splitters designed with iterative Fourier transform type algorithms can produce only certain diffraction angles given by the spatial frequencies used for the computations, which are multiples of a certain base spatial frequency. We have developed a design algorithm that overcomes this limitation and can be used to compute binary diffractive elements with arbitrary diffraction angles. The simulated and experimentally measured properties of optical elements producing beam arrays in circular arrangements are presented and discussed.     

半导体微结构物理效应及其应用讲座第1讲布拉格衍射效应在半导体光电子器件中的应用与发展

文章对布拉格衍射效应在半导体光电子材料和光电子器件，特别是在光纤通信中的光电子器件的应用和发展进行了详细的介绍．文中以布拉格光栅衍射效应的光反馈和选模功能为主线，逐一介绍了X射线双晶布拉格衍射技术在半导体材料、特别是在量子阱和应变量子阱超薄层晶体生长和质量控制方面的作用，介绍了内建布拉格光栅对光通信用光信号源的发展所起的重要作用，波导光栅在复用和解复用过程中的作用，以及光纤布拉格光栅在全光纤通信系统中的应用及发展等．     

Coupled-mode theory of Bragg diffraction in the presence of multiple internal reflections

In acoustooptic and some crystalline holographic recording materials, the Bragg diffraction efficiency can be strongly affected by multiple internal optical reflections. The coupled-wave theory of this effect is given in this paper.     

Higher-order diffraction images in photorefractive materials

We report some photorefractive higher-order diffraction phenomena of a liquid crystal polymer composite. The photorefractive composite consists of the polymer poly[N-vinylcarbazole] (PVK) doped with the chromophore 4,4′-n-entylcyanobiphenyl (5CB) and the sensitizer C₆₀. In two-wave coupling experiments, the signal beam was interfered by a mutually coherent reference beam within composite materials at a small incident angle. Results are given when the composite was placed behind the focal plane, in front of the focal plane, and in the focal plane. Higher-order diffraction images were obtained by amplification and reduction. A theory of the properties of higher-order diffraction images in a photorefractive liquid crystal polymer composite is developed. The theory is in good agreement with the results of experimental work. The experiments demonstrate the feasibility of optical image processing.     

光盘光学系统的矢量衍射理论分析

本文以完整的矢量衍射理论分析了光盘光学系统。首先将入射的聚焦光束分解为平面波谱 ,得到每个平面波的振幅矢量 ;然后计算光盘对每个平面波的衍射 ,得到衍射波的振幅矢量 ,从而得到了整个衍射波场的空间频谱 ;最后计算物镜光瞳上的能通量 ,得到光盘系统的读出信号。在衍射计算中 ,光盘被定义为二维金属光栅 ,根据信息符的不同模型 ,选用坐标变换方法、耦合波方法或模态方法。对于典型的 DVD光学系统来说 ,矢量理论的结论与标量理论相差甚远 ,要得到正确的结果就必须采用矢量衍射理论     

Double-sided laser heating system at HPCAT for in situ x-ray diffraction at high pressures and high temperatures

An overview of a YLF:Nd laser heating system at the undulator x-ray diffraction station (16ID-B) of the high-pressure collaborative access team (HPCAT) of the Advanced Photon Source is presented. Based on the double-sided laser heating technique, the system is designed with considerable effort on the mechanical and optical stabilities, features for user-friendly operation, and the capability of accommodating diamond anvil cells of various heights up to 68?mm. This system has been used for x-ray diffraction studies of a wide range of materials to over 150?GPa and above 3000?K. Applying the laser heating technique to radial x-ray diffraction studies at simultaneous high-pressure and high-temperature (PT) conditions requires heating to be conducted at variable angles relative to the x-ray direction. A rotation laser heating design is discussed.     

Fibonacci光栅衍射频谱的自相似结构

本文设计并制作了一种按Ｆｉｂｏｎａｃｃｉ数列规则排列的准周期衍射光栅，从理论和实验两方面计算与显示了该光栅的自相似衍射频谱，这对准晶体光学中非周期的频率分析研究有一定的理论和实用价值。     

Echelle diffraction grating demultiplexers with a single diffraction passband

Planar multiplexers based on echelle gratings are very popular devices for optical communication applications. However, the available channel number is restricted by the concept of free spectral range (FSR) due to their high operating diffraction order. Now, we can break the restriction of the FSR concept, and most of wavelengths in the operating passband of echelle grating multiplexers can be used based on a variable diffraction order design. We present the design, fabrication, and characterization of the echelle grating multiplexer with a single diffraction passband based on silica platform.     

Laser beam characteristic for laser resonators with diffraction optical elements

The matrix eigenvalue method is used to analyze a laser resonator composed of diffraction optical elements. The results show that this type of resonator can separate fundamental mode and high order modes effectively. The output beams can be designed for different requests.     

Polarization holographic gratings with high diffraction efficiency recorded in azopolymer PAZO

Azopolymers are one of the most efficient materials able to record the polarization state of light. They have numerous applications, such as data storage and diffractive optical elements with unique polarization properties. An essential parameter for each diffractive element is its diffraction efficiency η. In order to optimize the recording conditions and obtain high-efficient polarization holographic gratings, in the present work we study the dependence of the diffraction efficiency on the recording angle and thickness of a series of azopolymer layers. Three recording angles are used ??10°, 20° and 30° and three series of thin films with thicknesses 470, 850 and 2400 nm from the water-soluble azopolymer PAZO. The gratings are inscribed by two plain waves with left and right circular polarization from a He-Cd gas laser (442 nm). The diffraction efficiency of the gratings is probed with a right hand circularly polarized beam from a probe laser with wavelength 635 nm. The kinetics of diffraction efficiency η(t) in the +?1 diffraction order are presented and compared. Our experimental results indicate that highest diffraction efficiency (more than 40%) is obtained for the sample with thickness 2400 nm and for recording angle 10°. As the holographic recording in azopolymers is usually accompanied by formation of surface relief gratings, the surface topography of the recorded samples is also investigated by atomic force microscopy.     

Diamond-anvil cell for radial x-ray diffraction

We have designed a new diamond-anvil cell capable of radial x-ray diffraction to pressures of a few hundred GPa. The diffraction geometry allows access to multiple angles of Ψ, which is the angle between each reciprocal lattice vector g(hkl) and the compression axis of the cell. At the 'magic angle', Ψ≈54.7°, the effects of deviatoric stresses on the interplanar spacings, d(hkl), are significantly reduced. Because the systematic errors, which are different for each d(hkl), are significantly reduced, the crystal structures and the derived equations of state can be determined reliably. At other values of Ψ, the effects of deviatoric stresses on the diffraction pattern could eventually be used to determine elastic constants.     

反射式单级衍射光栅

介绍了单级衍射光栅的发展趋势, 从理论上论证了单级衍射光栅的可行性, 引入了一种新型衍射光学元件—-准正弦反射式单级衍射光栅(QSRG). 它能有效抑制高级衍射, 可用于提高光谱系统的信噪比和精度. 而通过QSRG的实验结果也验证了此新型色散元件确实具有良好的单级衍射特性, 二级及以上的高级衍射被有效地抑制, 与理论预测几乎一致. 本文的结果可望在反射式光谱测量系统中得到广泛应用.     

晶体X射线劳厄衍射分束特性研究

本文基于X射线衍射动力学分析了劳厄晶体的分束特性,模拟了晶体吸收和入射光角发散对于透射光和衍射光摇摆曲线的影响,定量给出晶体衍射面内角调节范围和晶体加工厚度对于劳厄衍射分束比的调制.在实验中,采用分析晶体和分束晶体的消色散配置限制入射光角发散的影响,实现300μm厚Si(220)晶体面内角调节劳厄衍射分束的精确测量,并得到300μm, 400μm和500μm厚度Si晶体分束比的调节范围,实现了透射光和衍射光强度的定量调制.     

利用衍射光栅探测涡旋光束轨道角动量态的研究进展

涡旋光束是一种携带有轨道角动量的光束,在光学扳手、光通信、旋转探测等领域具有重要的应用价值.由于轨道角动量态是涡旋光束的特征值,因此如何探测光束的轨道角动量态分布至关重要.国内外学者已经提出了多种探测涡旋光束的技术,如干涉法、衍射光栅法、多普勒分析法、超材料表面法等.这些技术中,衍射光栅测量法较为简单易行,应用较广.本综述主要介绍了几种当前利用衍射光栅测量涡旋光束轨道角动量态的主流方法,同时也介绍了如何利用衍射光栅来测量光束的轨道角动量谱.     

红外混合光学系统衍射效率的测量方法及其实现

简要介绍了二元光学器件衍射效率的理论计算方法,给出了一些衍射效率的测量方法,在此基础上设计了一套实用的衍射效率测试系统,并针对一个应用在3~5μm波段的具体红外混合光学系统进行了测试,给出了测试结果,此测试系统对红外混合光学系统的设计加工具有实际意义。     

X-ray diffraction and heterogeneous materials: An adaptive crystallography approach

Cultural heritage materials are often complex and heterogeneous, with a multi-scale architecture. Phases from a variety of crystalline forms co-exist in a wide grain size distribution, with each of these phases keeping in their structural arrangement a memory of the transformations that occurred to the material. Over the last two decades, X-ray diffraction has been applied successfully to the study of cultural heritage materials, with the use of synchrotron facilities offering new possibilities to describe the structural features of such complex materials. The long-range and/or short-range organization of the different crystallographic phases as well as their global position/dispersion in the material are closely related to the properties of the material (optical, mechanical…), its manufacturing process, functionality, or long-term conservation. In this paper, possible diffraction setups and data collection strategies are discussed in order to retrieve adequate data from crystalline and amorphous phases and to take into account single-crystal contributions.     

Comparison of the Gaussian-decomposition and the Fresnel-Kirchhoff diffraction methods in circular and elliptic Gaussian beams

In this investigation, the Gaussian decomposition and the Fresnel-Kirchhoff diffraction methods are compared from different view points. The virtues and faults of each method and also the reliable region of each one are discussed. This work is based on a numerical method for both the circular and elliptic Gaussian beams and results are compared with experimental data. This study is useful for materials exhibit optical Kerr effect such as two photon absorption and thermo-optical nonlinearities.