New microelectromechanical cavities for gigahertz frequencies

A possibility of creating micrometer-sized microelectromechanical cavities operating at gigahertz frequencies is considered. A thin film of a dielectric (ferroelectric) with a high dielectric permeability and electric strength is included into the cavity structure. Specific features of device operation and its structure are described by a mathematical model that allows one to find exact relations between the parameters characterizing natural oscillations of the moving element and the triggering voltage.     

Characterization of the diffraction properties of quantum-dot-array diffraction grating

A new dispersive element named as quantum-dot-array diffraction grating [L. F. Cao, China patent No. 200410081499 (August 10, 2004)] for visible light has been developed and characterized experimentally. A large number of quantum dots distributed on a substrate as sinusoidal function can be used to diffract x rays without higher-order diffraction. The experimental patterns show that the higher-order diffractions which inevitably exist in the spectrum recorded using traditional diffraction gratings can be eliminated effectively by this newly designed element. It indicates that quantum-dot-array diffraction grating could be an attractive alternative of presently used diffraction grating in soft x-ray spectroscopy application to get rid of the higher-order diffraction distortions.     

Near fields of periodic gratings calculated using rigorous electromagnetic theory

Rigorous electromagnetic theory (REMT) can be used to calculate the fields above dielectric and metallic gratings. In this paper, by including evanescent orders, the near fields are presented. The Legendre method is used to carry out these calculations. In this method the fields in each of the homogeneous sections along a grating period are approximated by Legendre polynomials. This method is an exact eigenfunction method in which the eigenvalues are found using simple matrix eigenvalue/eigenvector algorithms. By carefully dealing with the boundary conditions, extremely deep and highly conducting gratings can be examined. The convergence of the diffraction orders and nonimplicit power conservation are used to test the results. Contour plots showing the absolute value of the E-field near gratings for a large range of periods, depths, duty cycles, angles of incidence, and surface profiles are presented.     

Near fields of periodic gratings calculated using rigorous electromagnetic theory

Rigorous electromagnetic theory (REMT) can be used to calculate the fields above dielectric and metallic gratings. In this paper, by including evanescent orders, the near fields are presented. The Legendre method is used to carry out these calculations. In this method the fields in each of the homogeneous sections along a grating period are approximated by Legendre polynomials. This method is an exact eigenfunction method in which the eigenvalues are found using simple matrix eigenvalue/eigenvector algorithms. By carefully dealing with the boundary conditions, extremely deep and highly conducting gratings can be examined. The convergence of the diffraction orders and nonimplicit power conservation are used to test the results. Contour plots showing the absolute value of the E-field near gratings for a large range of periods, depths, duty cycles, angles of incidence, and surface profiles are presented.     

宽波段金属光栅设计中闪耀波长对光栅异常的补偿效应

给出适用性强、工艺上易于实现的单闪耀面宽波段金属光栅设计新方法。基于Rayleigh异常和共振异常两种不同的光栅异常机理,分别讨论了它们出现的条件,在光栅电磁场理论的基础上,数值分析了TE波、TM波闪耀波长的分布规律,发现了闪耀波长与光栅异常、光栅光谱范围的关系,提出了用TM波第一闪耀波长补偿Rayleigh异常或共振异常实现制作宽波段金属光栅的设计思想。同时,指出了TM波第一闪耀波长对Rayleigh异常的补偿效应,只是它对共振异常的补偿效应的极限情况。给出了将补偿效应应用于紫外可见分光光度计、近红外分光光度计和红外分光光度计用不同刻线密度宽波段金属光栅的设计实例。补偿效应法无论在理论设计上还是在工艺实现上都要优于传统的宽波段金属光栅设计方法,它可以使得用于各个波段上的宽波段金属光栅衍射效率都在40%以上。     

高效平面全息衍射光栅的获取方法

从全息衍射光栅的制作原理出发,介绍了全息光栅的主要制作方法,并与刻划光栅对比分析了全息衍射光栅的诸多优点。通过利用光栅设计的耦合波理论对全息衍射光栅槽型、槽深及槽间距等进行了优化设计,同时利用离子束刻蚀技术获得了高效率全息光栅。文中全面分析了制作高效率平面全息光栅的各项关键技术。     

非异常区TM偏振波宽波段特性在激光器调谐光栅设计中的应用

通过刻划工艺控制光栅槽形零级面宽度,使-1级和0级衍射效率同时达到期望值是激光器调谐光栅研制中的技术难题。基于光栅电磁场理论,利用光栅非异常区入射波长与光栅周期之比λ/d≈1.414附近较宽波段范围内TM偏振波的衍射效率变化梯度小,而且同一波长的衍射效率随闪耀角增大呈单调递增或随槽顶角增大呈单调递减趋势的特性,给出了-1级振荡0级输出激光器调谐光栅的全三角槽形模型及设计方法。该方法用常规三角槽形光栅即可实现任意比值的-1级与0级衍射能量分布,避免了以往通过控制类梯形槽形零级面宽度来制作此类光栅的工艺不确定性,降低了制作难度。应用该模型设计并制作了-1级衍射效率为65%的0级输出激光器调谐光栅,其在10.6μm处的衍射效率误差为0.6%。该方法还适用于-1级振荡-1级输出激光器调谐光栅的设计,实现了两类激光器谐振光栅在设计方法以及制作工艺上的统一。     

Alignment measurement of two-dimensional zero-reference marks

Alignment with submicron or even nanometer scale resolution is of vital importance in precision engineering. By superimposing a pair of specially coded two-dimensional gratings, the correct alignment position of the two gratings can be obtained by detecting the maximum output of the sharp intensity peak. In this paper, design and fabrication of such two-dimensional zero-reference gratings are introduced. The arrangement of the experiment system is presented in detail. The alignment measurement of the reference marks is tested, and the results are compared with those obtained by autocorrelation method and diffraction analysis. It is found that experimental results are in good agreement with theoretical analysis.     

衍射光栅分度误差的检测

提出了光栅分度误差的检测方法,指出了它在光栅检验中的应用.     

双矩形光栅衍射特性分析

双光栅系统的衍射一干涉效应非常重要,现从置于透镜前方的任意两个衍射屏出发,推出透镜后焦平面的光强分布可以用两个衍射屏的振幅透射率函数的相关来表示,然后把该结论用于两个完全一样的矩形光栅,得出了双矩形光栅在一些特殊间距时透镜后焦面上的光强分布可以表示为周期不同的三角形光栅透过率。     

用拼接法获取大面积衍射光栅

近年来大面积衍射光栅已成为许多大型高技术工程项目的关键元件,它的获取方法也一直是光栅界探求的目标,本文简要回顾衍射光栅研制技术的发展历史,介绍了衍射光栅的发展趋势以及国内外研制大面积衍射光栅的技术现状,说明了拼接光栅的原理、方法以及利用这种方法来获取大面积衍射光栅的诸多优点.目前拼接光栅中各小光栅的衍射波阵面的位相还没有做到完全一致,要做到一致还需做很多工作,但用拼接手段来获取大面积光栅已是一种非常有效的方法.     

表面等离子体激元透镜设计及其数值计算

提出了一种新的表面等离子体激元透镜的设计方案,该方案通过在两个亚波长小孔的外表面放置电介质光栅实现对入射光束的有效会聚。利用遗传算法研究了波导中表面等离子体激元的色散关系,结果表明,通过调节亚波长小孔的宽度和介电常数可以有效地调控有效折射率,从而实现对亚波长金属平板波导结构中表面等离子体激元传播特性的调控。利用时域有限差分方法(FDTD)结合完美匹配层(PML)边界条件数值模拟了此结构中的光场分布,讨论了光栅周期数对成像特性的影响,从而深入理解了纳米聚焦效应的物理机制。结果显示,随着表面光栅数的增多,焦距和焦斑大小都在增加。光栅数从5增加至11时,焦距由1.715μm增大至2.325μm,焦斑大小由0.615μm增大至1.715μm,这一结构有可能被用作未来集成光路中的纳米聚焦器件。     

紫外全息闪耀光栅的制作

通过理论计算研究了影响闪耀光栅衍射效率的因素,并利用离子束刻蚀模拟程序模拟刻蚀闪耀光栅来确定闪耀光栅的制作参数。以理论计算的闪耀光栅参数为依据,以刻蚀模拟程序为指导,基于全息-离子束刻蚀工艺制作了闪耀波长分别为250nm和330nm,光栅尺寸分别为85mm×85mm,60mm×60mm,线密度均为1200lp/mm的闪耀光栅。第一种光栅闪耀角为8.54°,非闪耀角为72°,其250nm波长自准直入射时的-1级衍射光衍射效率约为81%;第二种光栅闪耀角为11.68°,非闪耀角为74°,330nm波长自准直入射时的-1级衍射光衍射效率约为80%。实验结果表明,提出的方法可以在制作闪耀光栅的过程中实现对闪耀角的精确控制,获得的实验结果与理论计算结果符合较好。利用该方法能够在大尺寸基底上获得衍射效率75%的紫外闪耀光栅。     

Effect of temperature on properties of polarization holographic gratings formed in liquid crystal composites

The dependence of the diffraction efficiency of polarization holographic gratings on the temperature of their formation is presented. The temperature range corresponding to the maximum diffraction efficiency of such gratings is determined. The possibility of thermo-optical switching of recorded gratings is demonstrated.     

介质反射光栅中多层膜计算的研究

介绍了采用增强透射矩阵进行计算的严格耦合波方法,将这种方法应用到介质反射光栅的多层膜计算中。通过与商用软件计算结果的对比,证明这种计算方法的计算结果是准确可信的。与已有的计算方法比较,该方法简化了介质反射光栅的计算工作。     

光栅衍射效率的理论计算及实验验证

本文给出了一组可用于计算任意光栅绝对衍射效率的积分方程。通过解这些方程给出了三类光栅的效率曲线:红外光栅、可见光栅和掠入射光栅。本文还分析了光栅槽形顶角对光栅衍射效率的影响,并研究了掠入射光栅槽形衍射面角的选值问题,最后,给出了一些计算效率值的实验结果。     

任意槽形光栅衍射特性的矢量理论分析与计算

根据麦克斯韦基本方程组,推导了描述任意槽形光栅衍射特性的矢量理论分析方法——严格的耦合波方法,该方法可用来分析具有任意面型函数光栅在TE,TM两种偏振模式的平面波入射下的光栅衍射特性.文中讨论了偏振状态及光栅结构参数对几种典型槽形光栅衍射场的影响.     

凹面光栅成像的谱线线形以及杂散光的计算

提出了一种计算凹面光栅成像的谱线强度分布和计算凹面光栅三种随机误差造成的杂散光强度分布的方法。这种方法在采用光线追迹方法的同时,也考虑到了凹面光栅的衍射效率及光栅误差造成的衍射及散射作用。并以—Seya-Namioka型光谱仪为例说明结果。     

非规则几何槽形光栅衍射效率自动计算方法

为了快速地自动计算非规则几何槽形光栅的衍射效率,使用MatLab软件模拟各种槽形,自动获取槽形参数,并根据这些槽形参数运用严格耦合波分析方法,计算光栅的衍射效率。结果表明所设计的计算程序能够快速自动分析非规则几何槽形并计算其衍射效率。该方法可用于循环计算槽形逐渐变化过程中的衍射效率。     

Near-field imaging of surface-enhanced second harmonic generation

Surface-enhanced second harmonic generation from individual topographical defects of an otherwise flat gold film and from metal-coated diffraction gratings was measured using a near-field optical microscope. Experimentally measured second harmonic field distributions were compared with theoretical calculations.