二维光栅频谱分析及在精密测量中的应用

根据傅里叶光学的相关理论对二维衍射光栅的频谱特性进行了分析,并对分析结果进行了模拟和实验验证；基于衍射光栅应用于微位移的理论,提出利用二维衍射光栅作为测量的基准元件,组成单个光源和单二维衍射光栅的二维平面微位移精密测量系统,并根据实验测量结果验证了这是一种具有纳米准确度的可行测量方法.     

五维自由度衍射光栅精密测量系统（英文）

为了在保证结构简单的前提下,实现衍射光栅精密测量系统的大量程、高精度、多维度测量,设计了能够同时测量位移和角度的五维自由度衍射光栅精密测量系统。基于利特罗对称式光路结构,采用高刻线密度的一维衍射光栅以及外差干涉原理实现了沿光栅矢量方向和光栅法线方向的二维位移测量;通过引入高精度的位置灵敏探测器,结合±1级衍射光与光栅之间的角度变化关系实现了对光栅俯仰、偏摆和滚转三个维度的角度误差测量。实验结果表明:该衍射光栅精密测量系统能够实现分辨力优于4 nm的二维位移测量以及分辨力优于1″的三维角度测量,其位移测量范围只受限于光栅的尺寸,量程大大增加。该衍射光栅精密测量系统在精密测量领域有重要意义。     

二维消像差平面场型凹面光栅的设计与成像分析

给出了二维消像差平面场型凹面光栅的一般设计方法，推导了三点消像差光栅的成像条件，分析了平面场型光栅的成像质量与色散、分辨率及光栅宽度的关系。     

剪切光束成像技术对纵深目标的成像

剪切光束成像技术是一种能透过大气湍流对远距离目标实现高分辨率成像的主动成像技术.现有相关研究中所采用的目标均为二维平面目标,然而现实中的目标一般都具有三维形貌,目标纵深对回波信号产生的延迟或对成像质量产生不利影响.从剪切光束成像理论出发,在二维目标成像模型的基础上建立了三维纵深目标成像模型,并利用该模型研究了两剪切光与参考光间的频差及目标纵深对成像的影响.仿真结果表明,随着拍频的增大,重构图像质量逐渐下降.剪切光束成像技术可通过减小拍频来提高真实目标成像质量.     

基于径向剪切干涉仪的三维位移测量技术

本文提出一种基于双圆光栅径向剪切干涉仪的三维位移测量方法,其测量原理是径向剪切干涉仪所形成的莫尔条纹不仅由二维平面内位移决定,轴向位移会在+1和–1级莫尔条纹之间产生一个特定的相移.首先,基于标量衍射理论对双圆光栅径向剪切干涉仪的+1和–1级莫尔条纹强度分布进行推导,建立了三维位移量与莫尔条纹强度分布的精确解析关系;其次,在频谱分析的基础上,利用半圆环滤波器进行空间滤波,实现+1和–1级莫尔条纹的同时成像;然后,提出了从莫尔条纹图中定量提取三维位移的算法,并通过数值模拟进行验证;最后,实验结果验证了该方法测量平面内位移的最大绝对误差为4.8×10^–3 mm,平均误差为2.0×10^–4 mm,轴向位移的最大绝对误差为0.25 mm,平均误差为8.6×10^–3 mm.该方法具有装置简单、测量精度高、非接触、瞬时测量等特点,可实现三维位移的同时测量.     

聚束非相干合成孔径激光成像雷达研究

反射层析激光成像雷达只能获得目标的二维轮廓像,不能对平面目标进行成像。报道了聚束模式下的非相干合成孔径激光成像雷达实验,在这种成像模式下,可以对二维平面目标进行图像重构。采用侧视观察的模式获取目标的角度-距离-强度信息,然后通过滤波反投影实现平面目标的图像重建,并进行了计算机仿真,证明了实验结果的正确性。该系统作为非相干合成孔径激光雷达的一种,实现了区别于目标轮廓的二维成像,具有一定的实际意义和使用价值。     

体全息成像系统中非周期体光栅的深度选择性研究

由一束球面波和一束平面波或者两束球面波干涉所形成的体全息光栅,由于其光栅矢量在全息图体积内是随位置的变化而变化的,所以被称为非周期型的体光栅。主要研究了用于体全息三维成像系统的非周期体光栅的深度选择特性。根据叠加的原理,将非周期体光栅看作多个固定周期的基元体光栅的叠加,结合耦合波理论分析非周期体光栅的衍射特性。采用这一方法,利用Matlab软件模拟,研究了两束记录光夹角对所记录的非周期体光栅深度选择性的影响和在两束记录光夹角相同时,球面参考光体全息成像系统及平面参考光体全息成像系统深度选择性的差别,最后在光折变晶体材料中进行非周期型和周期型体光栅的记录和再现,对模拟结果进行了实验验证。     

阵列光栅压缩器的空域特性

 引入角度偏差、位移偏差作为拼接光栅系统的物理参数，定义了拼接光栅的孔径函数，利用傅里叶角谱理论研究了高斯脉冲入射拼接光栅压缩器后的远场分布特性。研究表明：出射脉冲仍然是高斯型脉冲，但包络中心发生偏移，偏移量由角度偏差量和光束口径决定;位移偏差引入的相位随着拼接光栅压缩器传递，其对远场焦斑的影响，取决于每片子光栅的非整数倍光栅常数的横向位移偏差和纵向位移偏差的综合作用。通过数值计算得到了各维偏差对阵列光栅压缩器空域特性的影响,计算表明:光栅面外角度偏差(俯仰左右)和条纹平行度偏差都必须控制在1 mrad以内，在此范围内，应将位移偏差控制在52 nm以内。     

新型双通道差分偏振干涉成像系统

针对Wollaston棱镜和Savart偏光镜(SP)组合的差分成像光谱系统存在光线溢出和无法改变系统光程等问题,设计了一种新型双通道差分偏振干涉成像系统.此系统不仅可获取正交偏振图像,还可以通过调整Savart偏光镜的厚度来改变系统光程.介绍了该系统的结构、理论原理,并利用琼斯矩阵推导出四束偏振光线的复振幅及其相干光干涉强度表达式.分析了宽视场Savart偏光镜(WSP)和可调光程的Savart偏光镜(MSP)的分束特性,得出WSP相较于SP具有更好的剪切能力和WSP可优化系统光路的结论.获得了不同楔形结构角下MSP的光程差、横向剪切量随楔形移动量的变化曲线.通过实验验证,获取了不同剪切量下的干涉图像和复色光下平行、垂直分量的空间图像,进而获得了总的强度图像和差分强度图像.得出差分强度图像相较于偏振强度图像具有较高对比度的结论.研究结果对双通道成像光谱系统的性能优化具有一定的参考意义.     

合成孔径激光成像雷达(Ⅳ):统一工作模式和二维数据收集方程

提出了合成孔径激光成像雷达(SAIL)的一种统一的工作模式,即激光雷达运动的同时进行光束扫描.同时推导了点目标激光雷达方程,据此还定义了SAIL二维数据收集方程,二维数据收集方程组是合成孔径激光雷达的数据产生和收集过程中的完整数学表达,并给出了统一模式的二维数据收集方程.从统一工作模式可以分解出条带扫描模式、聚束模式、滑动聚束模式和光束扫描模式,及其相应的简化二维数据收集方程.上述的光束扫描模式是一种激光雷达和被观察面之间相对静止而只采用光束扫描实现孔径合成成像的新方法,具有特殊的应用范围.     

Phase diffraction gratings based on a Si(400) crystal

The X-ray optical properties of diffraction gratings fabricated on the basis of a Si(400) crystal with a period of D = 1 μm are studied by triple-crystal X-ray diffractometry. The diffraction gratings are manufactured both by silicon profiling during the process of plasma chemical etching and by forming a phase-shift grating on the surface of a Si crystal. The principal difference in the diffraction properties of these gratings is demonstrated. The presence of an Au phase-shift grating is shown to lead to the formation of a two-dimensional diffraction pattern, whereas Si profiling leads to the formation of only a one-dimensional diffraction pattern.     

Diffraction from angular multiplexing slanted volume hologram gratings

The diffraction characteristics of the volume holographic gratings made by multiexposures with angular multiplexing during its construction is investigated. Because of the reflection by the interface between the emulsion and the substrate or the air there is an extra unslanted periodic structure inside a slanted grating, it will affect properties of the slanted volume holographic gratings. When the angle between the surface of the substrate and the grating plane of the slanted grating is less than a certain value, an extra peak accompanying the main peak will appear in the diffraction spectrum. But, when the angle is larger than the certain value, one designed and expected main peak will disappeared while the extra peak is kept and observed. This phenomenon limits the capacity of the volume hologram for the application in wavelength-division multiplexing (WDM).     

Self-talk of Reflection Hologram During its construction

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量子阱红外探测器的光耦合

本文从有效质量近似理论出发,在量子阱导带内子带间光吸收分析的基础上,评述了ｎ型量子阱红外探测器的光耦合。着重研究适宜于量子阱红外探测器的不同种类的光栅,并从理论上优化出高耦合效率的各种光栅参数     

两种亚波长金属波片的透射特性对比

综合等效介质理论和表面等离子激元(SPP)Bloch模型,对比分析了两种新的亚波长光栅结构:二维矩形金属光栅和二维椭圆柱金属光栅。利用时域有限差分(FDTD)算法,对比分析了两种结构的透射率及其相位延迟与入射光波长及偏振角变化的关系,尤其两种结构实现λ/4波片功能所对应的透射特性。仿真结果表明,当入射光偏振角为75°时,两种结构均可实现λ/4波片功能,此时二维矩形和椭圆柱金属光栅的透射率分别为0.77和0.67,表明二维矩形金属光栅比椭圆柱光栅具有更好的透射效果。对应550～800nm的入射波长,两种光栅在各自允许的入射偏振角范围内均表现了较为平坦的宽带透射特性。     

基于啁啾相移光纤光栅的滤波器设计及应用

相移光纤光栅作为透射型带通滤波器件降低了使用成本和插入损耗.在光通信和传感领域有着较高的应用价值.啁啾相移光纤光栅的透射峰波长和数量由相移点的位置和数量来确定,透射峰特性受相移量的影响.采用分段切趾的方法获得满足光通信要求的滤波特性,利用传输矩阵法分析了切趾前后透射峰特性的变化,结果表明:切趾改善了滤波器的幅度和相位响应,依据滤波器的设计要求选取不同的切趾函数以及切趾比例;切趾还大大减弱了透射峰波长和深度对相移量的敏感度,适当切趾后相移量的影响可以忽略.并提出一种应用双通道啁啾相移光纤光栅滤波器产生脉冲毫米波副载波信号的方案.     

Instantaneous phase shifting arrangement for microsurface profiling of flat surfaces

Phase shifting interferometry is a well-established technique for non-contact surface profile measurement. Though phase shifting technique has many advantages, it is marred by a few inaccuracies due to the vibration and mechanical movement of the phase shifter itself. Significant amount of work is reported to theoretically compensate these error sources. But for a few works, prominent achievements have not been reported in eliminating these error sources in phase shifting interferometry. In this paper, a novel optical layout, in combination with instantaneous phase shifting interferometry is described. Experiments were carried out with this setup on a super mirror with a λ/20 surface roughness, to demonstrate the validity of the principle.     

Diffraction gratings: aberrations and applications

Diffraction grating is an optical instrument, which is advantageously used for scientific research in spectroscopy and spatial filtering. It has many other applications in science and technology such as wavelength selectors for tuneable lasers, selective surfaces for solar energy, masks for photolithography, beam sampling mirrors for high power lasers, spectrometers in extreme UV and X-ray regions for space optics, metrology, phase measuring interferometry and pattern recognition, etc. Although the holographic gratings have many advantages over the ruled gratings but they have not yet eliminated completely the classical ruled gratings as the ruled gratings have their own importance in many applications. Therefore, in this article, both the ruled and holographic gratings will be discussed, in particular, their focusing properties, aberrations, and their applications.     

基于亚波长二维光栅的入射角不敏感颜色滤光片研究

提出了一种基于二维亚波长光栅的具有非偏振光入射下入射角不敏感特性的反射式颜色滤光片. 采用严格耦合波分析方法详细分析了光栅周期、光栅层厚度以及固定光栅占空比下光栅的结构尺寸对反射率峰值、反射带位置及带宽的影响. 结合入射角不敏感特性, 经过优化设计得到了光栅的最终结构参数, 获得了中心波长424 nm, 峰值反射率56%, 带宽45 nm的反射滤光片.模拟结果表明, 在非偏振光入射下, 此滤光片的反射光谱表现出显著的入射角不敏感特性. 当入射角高达60°时反射带的中心波长偏移6 nm 反射率下降6%带宽增加8 nm 其参数没有较大变化通过调整光栅的结构参数可在400–520 nm范围内调节滤光片的中心波长以获得不同颜色的入射角不敏感滤光片. 关键词： 反射式滤光片 二维亚波长光栅 入射角不敏感 严格耦合波分析     

High-power laser beam shaping by inseparable two-dimensional binary-phase gratings for surface modification of stamping dies

For surface modification of stamping dies, an inseparable two-dimensional binary-phase gratings is introduced to implement the wavefront transformation of high-power laser beams. The design and fabrication of the gratings are described in detail. Two-dimensional even sampling encoding scheme is adopted to overcome the limitations of conventional Dammann grating in the design of two-dimensional output patterns. High diffractive efficiency (>70%) can be achieved through the transformation of the Gaussian laser beam into several kinds of two-dimensional arrays in focal plan. The application of the binary-phase gratings in the laser surface modification of ductile iron is investigated, and the results show that the hardness and the wear resistance of the sample surface were improved significantly by using the binary-phase gratings.