铬胶全息干板及其在全息领域中的应用

重铬酸盐明胶(简称铬胶)作为全息记录介质,具有高衍射效率、高分辨率(6000线/毫米)、高信噪比和低噪音等特性。最近十几年来广泛引起人们的注意。铬胶全息干板不仅可以用于氦镉激光(441nm)、氩激光(488nm,514nm),而且经过光谱增感后,还可以用于氦氖激光(633nm)。用铬胶全息干板可以制做光栅、光学透镜、滤波器等多种全息光学元件,而且体小质轻、形状可变,在空间技术、军事领域特别受到重视。本文介绍了铬胶作为全息记录介质在国外的发展情况;铬胶全息干板的全息特性、制做、处理程序以及影响因素,此外还介绍了铬胶全息干板在全息领域中的各种应用。     

近地空间下X/EUV透射光栅的热力学有限元分析

为了实现极紫外透射光栅光谱仪在近地空间的应用,针对其核心色散元件2000线/毫米X/EUV透射光栅,本文采用有限元方法建立了机械模型并对其热学性能和耦合特性进行计算机模拟计算,通过模拟热膨胀系数不同的材料构成的薄膜光栅在近地空间受到太阳辐照后的温度场,得到该光栅表面的热形变分布.结果表明,在高真空热环境下,该透射光栅表面形变量平均可达0.56μm,而影响光栅周期的纵向形变平均值则为71.5 nm.由于热形变会对光栅衍射效率产生重要影响并导致光谱仪精度和性能的下降,利用有限元分析模拟的结果,进一步优化光栅的封装和设计制作,使其栅线处纵向热形变趋近于零,为2000线/毫米X/EUV透射光栅在太阳极紫外辐射探测器上得到应用提供了科学依据和有效支持.     

一种双层光栅分束器的设计

分束器在集成光学等领域具有重要应用价值。随着对分束比、衍射效率及光束光强均匀性的不断提高以及工艺水平的改善,相继提出了各种变异型位相光栅。本文讨论了一种双层结构的光栅分束器的设计方法。双光栅分别蚀刻在介质层的两面。     

新型反射式闪耀光栅楔形平板

提出并设计了一种新型光学元件——反射式闪耀光栅楔形平板。在玻璃楔形平板的倾斜表面上加工锯齿形闪耀光栅,在光栅的表面镀相应的金属反射膜,形成反射式闪耀光栅。当光线垂直楔形平板底面入射时,闪耀级次的衍射光可以沿入射方向返回,使该级次衍射光的能量得到充分利用,可以应用在在需要保持反射光线方向不变的场合。该元件兼具闪耀光栅和楔形平板的特性,通过实验对光线的能量和方向特性进行了验证,实验结果表明, 1级衍射光沿入射光线方向返回,并且能量的89.36%都集中在这一级上。转角测量的实验结果表明,该元件能使转角测量的范围扩大为0~360°以及大于360°的任意角度,转角测量的重复性精度可以达到0.632″。     

衍射频谱法测光栅膜层厚度

根据傅立叶光学理论从光栅的衍射频谱中可以反推光栅本身的多种信息,包括其形貌特征。 利用矩形相位光栅的傅立叶变换,推导出零级和一级衍射光强和矩形相位光栅膜层厚度之间的函数关系,据此可在测得零级和一级次光强后,推算出光栅膜层厚度。以台阶仪作为标准,该方法的测量误差在4%以内。     

层数变化对ZnO/In2 O3多层膜微观结构及光电性能的影响

用直流磁控溅射和热氧化法在玻璃衬底上制备ZnO/In2O3透明导电多层膜,当总厚度一定时,调节溅射沉积的层数与相应各层膜的厚度,研究该多层膜微观结构、光学性能和电学性能的变化.XRD和SEM分析表明:随着溅射沉积层数的增加,In2O3衍射峰的强度不断地减弱,ZnO衍射峰出现了不同的晶面择优取向;多层膜表面的ZnO晶粒粒径变小,光洁度增加.四探针法方块电阻测试表明:低温热氧化时,ZnO/In2O3多层膜的方块电阻随层数的增加而上升;高温氧化时,ZnO/In2O3多层膜的方块电阻随层数的增加而下降.可见光光谱分析表明:随着溅射沉积层数的增加,ZnO/In2O3多薄膜在可见光区的平均透过率增大,透过率的峰值向短波方向偏移.     

宽光谱监控法镀制高精度增透膜的研究

本文介绍了使用宽光谱监控系统镀制增透膜的基本原理和技术特点.给出了针对不同的膜层特性计算评价函数的方法,分别为能量法和特征点法,能量法适合膜层的光学特性对每一个波长点的权重要求都是一样的,特征点法适合于只对膜层光学特性的某几个特定波长的要求较高,并根据膜料光学参数的特性,分别设置权重因子,其它波长忽略不计.用工艺曲线代替理论设计曲线作为目标曲线,解决实际镀制的光谱特性与理论值存在偏差的问题,使评价函数的极小值趋近于零,达到最佳膜厚.这种简单而准确的方法对于提高宽带增透膜镀制精度和成品率有显著的效果,具有实际的应用价值.     

C/W多层膜的制备及其光学特性

介绍了软X射线波段C/W多层膜的制备和光学性能检测.采用高真空直流磁控溅射方法在超光滑硅基片上制作了C/W多层膜,用X射线衍射(XRD)仪,小角测量方法测试多层膜的光学性能,采用透射电镜(TEM)观测多层膜断层样品的微观结构,并在同步辐射软X射线光束线上,测试了所制备的C/W多层膜样品的反射率,然后对测试结果进行拟合分析.结果表明,所制备的C/W多层膜样品的质量较高,界面清晰,粗糙度小,所有膜层均为无定形态,没有晶相生成,以44.2°入射在5.9 nm处有约6%的反射率.     

ZAO/metal/ZAO多层膜光学性能优化设计

为获得高质量的透明导电薄膜,采用计算机辅助,对ZAO/metal/ZAO多层膜系统进行最优化设计.应用基于薄膜特性矩阵的分析方法,计算包含吸收膜的多层膜系的光学特性,并以整个膜系在可见光区内的光透射系数作为最优化设计的准则.根据优化结果,以磁控溅射方法在玻璃基片上逐次溅射ZAO,metal,ZAO薄膜,最终获得可见光区内最高透光率为86.6%,方电阻为6.5Ω/□左右的多层膜.     

基于交叉式Czerny-Turner结构的光纤光栅解调光路设计及像差校正

为满足光纤光栅传感系统的解调仪器高分辨力、微型化的需求,针对光纤光栅传感1 550 nm波段设计了光谱成像法光纤光栅解调系统的分光光路系统.成像系统形式采用交叉式Czerny-Turner结构,分析了使用超环面镜代替球面镜、在结构中加入额外的柱面透镜或柱面反射镜以及使衍射光栅工作在发散光条件下的3种校正像散方法的特点,最终选用使衍射光栅工作在发散光条件下的校正像散方法,实现在不加入附加光学元件条件下的像散校正,同时采用小角度入射的方法减小系统彗差.通过Zemax对成像系统进行了参数优化与光线追迹分析,优化结果证明了上述像差校正方法适用于光纤光栅解调.在解调光谱范围内,可明显分开波长间隔为1 nm的光斑,满足光纤光栅解调的分辨力需求.     

Efficiencies of master, replica, and multilayer gratings for the soft-x-ray-extreme-ultraviolet range: modeling based on the modified integral method and comparisons with measurements

The near-normal-incidence efficiencies of a 2400-groove/mm holographic master grating, a replica grating, and a multilayer grating are modeled in the soft-x-ray-extreme-ultraviolet (EUV) regions and are compared with efficiencies that are measured with synchrotron radiation. The efficiencies are calculated by the computer program PCGrate, which is based on a rigorous modified integral method. The theory of our integral method is described both for monolayer and multilayer gratings designated for the soft-x-ray-EUV-wavelength range. The calculations account for the groove profile as determined from atomic force microscopy with a depth scaling in the case of the multilayer grating and an average random microroughness (0.7 nm) for the short wavelengths. The refractive indices of the grating substrate and coatings have been taken from different sources because of the wide range of the wavelengths (4.5-50 nm). The measured peak absolute efficiency of 10.4% in the second diffraction order at a wavelength of 11.4 nm is achieved for the multilayer grating and is in good agreement with a computed value of approximately 11.5%. Rigorous modeling of the efficiencies of three similar gratings is in good overall agreement with the measured efficiency over a wide wavelength region. Additional calculations have indicated that relatively high normal incidence efficiency (of at least several percent) and large angular dispersion in the higher orders can be achieved in the 4.5-10.5-nm range by application of various multilayer coatings.     

Design of multilayer extreme-ultraviolet mirrors for enhanced reflectivity

We show numerically that the reflectivity of multilayer extreme-UV (EUV) mirrors tuned for the 11-14-nm spectral region, for which the two-component, Mo/Be and Mo/Si multilayer systems with constant layer thickness are commonly used, can be enhanced significantly when we incorporate additional materials within the stack. The reflectivity performance of the quarter-wavelength multilayers can be enhanced further by global optimization procedures with which the layer thicknesses are varied for optimum performance. By incorporating additional materials of differing complex refractive indices-e.g., Rh, Ru, Sr, Pd, and RbCl-in various regions of the stack, we observed peak reflectivity enhancements of as much as ~5% for a single reflector compared with standard unoptimized stacks. We show that, in an EUV optical system with nine near-normal-incidence mirror surfaces, the optical throughput may be increased by a factor as great as 2. We also show that protective capping layers, in addition to protecting the mirrors from environmental attack, may serve to improve the reflectivity characteristics.     

Polarization and efficiency of a concave multilayer grating in the 135-250-Å region and in normal-incidence and SeyaNamioka mounts

A molybdenum/silicon multilayer coating was applied to a holographic ion-etched blazed grating substrate that had 2400 grooves/mm and a radius of curvature of 2.2 m. Scanning probe microscopy yielded the same surface microroughness (5 ? rms) before and after deposition of the multilayer. The efficiency and polarization performance of the grating was measured by synchrotron radiation in the 135-250-? wavelength region. In the second grating order and the second Bragg order of the multilayer coating, the peak normal-incidence efficiency was 7.5% at a wavelength of 147 ?, representing a groove efficiency of 27%. At an angle of incidence of 35°, the polarization performance of the grating was 95%-100% in the 210-250-? wavelength region. In a Seya-Namioka spectrometer mount at an angle of incidence of 30°-40°, the grating is a nearly perfect polarizing optical element in the wavelength bands between 125 and 300 ?, which are covered by the multilayer coating.     

High-efficiency x-ray gratings with asymmetric-cut multilayers

We present the fabrication and analysis of efficient and highly dispersive gratings for the x-ray and extreme ultraviolet (EUV) regime. We show that an asymmetric-cut multilayer structure can act as a near-perfect blazed grating. The precision and high line density are achieved by layer deposition of materials, which can be controlled to the angstrom level. We demonstrate this in the EUV regime with two structures made by cutting and polishing magnetron-sputtered multilayer mirrors of over 2000 bilayers thick, each with a period of 6.88 nm. These were cut at angles of 2.9° and 7.8° to the surface. Within the 3% bandwidth rocking curve of the multilayer, the angular dispersion of the diffracted wave was in agreement with the grating equation for elements with 7250 and 19,700 line pairs/mm, respectively. The dependence of the measured efficiency was in excellent agreement with a formulation of dynamical diffraction theory for multilayered structures. At a wavelength of 13.2 nm, the efficiency of the first-order diffraction was over 95% of the reflectivity of the uncut multilayer. We predict that such structures should also be effective at shorter x-ray wavelengths. Both the Laue (transmitting) and Bragg (reflecting) geometries are incorporated in our formalism, which is applied to the analysis of multilayer Laue lenses and focusing and dispersing Bragg optics.     

Development and calibration of mirrors and gratings for the soft x-ray materials science beamline at the Linac Coherent Light Source free-electron laser

This work discusses the development and calibration of the x-ray reflective and diffractive elements for the Soft X-ray Materials Science (SXR) beamline of the Linac Coherent Light Source (LCLS) free-electron laser (FEL), designed for operation in the 500 to 2000 eV region. The surface topography of three Si mirror substrates and two Si diffraction grating substrates was examined by atomic force microscopy (AFM) and optical profilometry. The figure of the mirror substrates was also verified via surface slope measurements with a long trace profiler. A boron carbide (B4C) coating especially optimized for the LCLS FEL conditions was deposited on all SXR mirrors and gratings. Coating thickness uniformity of 0.14 nm root mean square (rms) across clear apertures extending to 205 mm length was demonstrated for all elements, as required to preserve the coherent wavefront of the LCLS source. The reflective performance of the mirrors and the diffraction efficiency of the gratings were calibrated at beamline 6.3.2 at the Advanced Light Source synchrotron. To verify the integrity of the nanometer-scale grating structure, the grating topography was examined by AFM before and after coating. This is to our knowledge the first time B4C-coated diffraction gratings are demonstrated for operation in the soft x-ray region.     

Double slit interferometry to measure the EUV refractive indices of solids using high harmonics

Accurate values of the extreme ultraviolet (EUV) optical properties of materials are required to make EUV optics such as filters and multilayer mirrors. The optical properties of aluminum studied in this report are required, in particular, as aluminum is used as an EUV filter material. The complex refractive index of solid aluminum and the imaginary part of the refractive index of solid iron between 17 eV and 39 eV have been measured using EUV harmonics produced from an 800 nm laser focused to 10(14) Wcm(2) in an argon gas jet impinging on a double slit interferometer.     

Optical design of a spectrometer-monochromator for the extreme-ultraviolet and soft-x-ray emission of high-order harmonics

A grazing-incidence spectrometer-monochromator for diagnostics and application of the extreme-ultraviolet (EUV) and soft-x-ray high-order harmonics generated by the interaction between a few-optical-cycle laser pulse and a gas jet has been fabricated. We address the necessity of high-resolution spectral and spatial analyses of the high-order harmonics as well as their use as short EUV backlighters in pump-probe experiments. The spectrometer that we present uses a variable-line-spaced flat grating illuminated in the converging light coming from a toroidal mirror. The spectrum is stigmatic, and the focal surface is almost flat in a wide spectral region. The detector is a microchannel plate intensifier with a phosphor screen optically coupled to a CCD camera; it can be moved by means of a linear drive to acquire different portions of the spectrum in the 5-75-nm region. The resolution is almost limited by the pixel size of the detector. We apply the same optical scheme to achieve a constant-deviation-angle monochromator by substituting an exit slit for the detector block: The rotation of the grating gives the spectral scanning. A monochromator for the 5-50 nm spectral region is achieved.     

Characterization of a grating-coupled liquid crystal cell using a rigorous theoretical model

Abstract

We use a rigorous differential formalism to model the optical response of a multilayer structure having both a surface-relief grating and containing uniaxial materials. The uniaxial material is, in this case, a layer of liquid crystal that has its uniaxial axis defined by its director. By fitting experimental angle dependent reflectivity data to a multilayer grating model we are able to determine the spatial profile of the liquid crystal director, and show how accurately the optical response of such a system may be modelled.     

Extreme-ultraviolet lensless Fourier-transform holography

We demonstrate 100-nm-resolution holographic aerial image monitoring based on lensless Fourier-transform holography at extreme-UV (EUV) wavelengths, using synchrotron-based illumination. This method can be used to monitor the coherent imaging performance of EUV lithographic optical systems. The system has been implemented in the EUV phase-shifting point-diffraction interferometer recently developed at Lawrence Berkeley National Laboratory. Here we introduce the idea of the holographic aerial image-recording technique and present imaging performance characterization results for a 10x Schwarzschild objective, a prototype EUV lithographic optic. The results are compared with simulations, and good agreement is obtained. Various object patterns, including phase-shift-enhanced patterns, have been studied. Finally, the application of the holographic aerial image-recording technique to EUV multilayer mask-blank defect characterization is discussed.