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.     

Off-plane grazing-incidence blazed grating with radial grooves as an efficient spectral purity filter for EUV lithography

It was found that the high-blaze-angle reflective diffraction grating operating in the off-plane grazing-incidence configuration allows the separation and focusing of a 2% wavelength band in the vicinity of 13.5 nm. A model of a cooled multiple grating with a fan-groove geometry was used to separate the desired spectral range and to achieve a record efficiency and stigmatic focusing of images at high dispersion of adjacent orders. The highest relative efficiency in the range of 0.96–0.99 and reflectances from 0.71 to 0.96 can be achieved for an off-plane fine-pitch grating irradiated at angles of 70°–85° with a converging unpolarized light beam from a EUV collector. Such efficiency is higher than that of the corresponding in-plane configuration. The absolute efficiency of 0.72 was achieved in the minus-first order of a Mo-coated test Si grating with 5000 grooves/mm in unpolarized light using the PCGrate^®-SX? code and the AFM-measured groove profile.     

13.4nm软X射线干涉光刻透射光栅的优化设计

基于严格的矢量耦合波方法,结合纳米级光栅实际制作工艺,定量分析了在13.4 nm软X射线(TE偏振)正入射条件下,光栅材料、厚度、占空比、梯形浮雕底角大小等因素对光栅一级衍射效率的影响.结果表明,在此波段处,Si3N4、Cr、Au浮雕的相位作用对光栅衍射起重要影响,其中非金属材料Si3N4比金属材料Cr、Au的相位作用更明显.最后优化得到了用Si(或Si3N4)做衬底的si3N4、Cr、Au光栅,分析结果显示,其一级衍射效率优于目前用于13.4 nm软X射线干涉光刻的Cr、Si3N4复合光栅.     

Studies of shrinkage as a result of holographic recording in acrylamide-based photopolymer film

We studied the shrinkage in acrylamide-based photopolymer by measuring the Bragg detuning of transmission diffraction gratings recorded at different slant angles and at different intensities. Transmission diffraction gratings of spatial frequency 1000 lines/mm were recorded in an acrylamide-based photopolymer film having 60±5 μm thickness. We have obtained the grating thickness and the final slant angles from the Bragg curve and hence calculated the shrinkage caused by holographic recording. The shrinkage of the material was evaluated for three different recording intensities 1, 5 and 10 mW/cm², while the total exposure energy was kept constant at 80 mJ/cm². From the experimental results it can be seen that the shrinkage of the material is higher for recording with lower intensities and the corresponding values are 1.9%, 1.3% and 1%.     

光栅周期包含的Bragg层数对Bragg型凹面衍射光栅的影响

单个衍射光栅周期所包含的Bragg周期层数是连续Bragg齿型凹面衍射光栅的主要参数之一,该参数可改变光栅齿结构,对凹面衍射光栅的分辨力.自由光谱范围及衍射效率有重要影响.本文通过理论分析与仿真模拟,对比了4种不同层数的Bragg型凹面衍射光栅的特性参数.研究结果表明:在衍射光栅尺寸不变的情况下,改变单个光栅周期包含的Bragg周期层数不会显著提高器件主衍射级次的分辨力;单个光栅周期包含的Bragg周期层数与光栅可衍射的级次数成正相关.单周期层数的Bragg凹面衍射光栅的主衍射级次效率最高,其可衍射的级次数最少,且其他衍射级次分散的能量最少;增加单个光栅周期所包含的Bragg周期层数会降低主衍射级次的自由光谱范围.该研究对于设计低插损、高分辨率、宽工作波段的波分复用器或光栅光谱仪具有重要的指导意义.     

软X射线位相型金透射光栅的设计与制作

根据衍射光栅的标量理论,计算并讨论了金透射光栅在软X波段衍射效率对光栅厚度和占宽比的依赖关系.结果表明,选择合适的光栅槽深和占宽比,高达 21.9%的衍射效率可能被获得,远高于振幅型光栅的+1级衍射效率10.14%.通过全息光刻与电镀转移技术制作的位相型金透射光栅由300nm的聚酰亚胺薄膜支撑,光栅槽深200nm,占宽比为0.55,周期为1μm,面积为20mm×5mm.在国家同步辐射装置上,测得其+1级透射衍射效率在波长λ=7.425nm时获得最大值,约为16%. 关键词： 透射位相光栅 全息光刻 电镀     

Can one and two-dimensional solid-state NMR fingerprint zeolite framework topology?

In this contribution, we have explored the potential and strength of one-dimensional (1D) ²⁹Si and two-dimensional (2D) ²⁹S–²⁹Si and ²⁹Si–¹⁷O NMR as invariants of non-oriented graph for fingerprinting zeolite frameworks. 1D and 2D ²⁹Si NMR can indeed provide indications on the graph vertices, edges and allow the construction of the adjacency matrix, i.e. the set of connections between the graph vertices. From the structural data, hypothetical 1D ²⁹Si and 2D ²⁹Si–²⁹Si NMR signatures for 193 of the zeolite frameworks reported in the Atlas of Zeolite Structures have been generated. Comparison between all signatures shows that thanks to the 1D ²⁹Si NMR data only, almost 20% of the known zeolite frameworks could be distinguished. Further NMR signatures were generated by taking into account 2D ²⁹Si–²⁹Si and ²⁹Si–¹⁷O correlations. By sorting and comparison of all the NMR data, up to 80% of the listed zeolites could be unambiguously discriminated. This work indicates that (i) solid-state NMR data indeed represent a rather strong graph invariant for zeolite framework, (ii) despite their difficulties and costs (isotopic labeling is often required, the NMR measurements can be long), ²⁹Si and ¹⁷O NMR measurements are worth being investigated in the frame of zeolites structure resolution. This approach could also be generalized to other zeolite-related materials containing NMR-measurable nuclides.     

Spectral resolution enhancement without increasing the number of grooves in grating-based spectrometers

A simple scheme of an optical setup to enhance the spectral resolution of diffraction gratings without increasing the number of grooves is presented. A plane-parallel mirror pair, which consists of a 100% reflectivity mirror and a 50% reflectivity mirror, is placed upon a grating. For certain values of the mirror gap and the angle between the grating and the mirrors, the effective size of the grating doubles, as does the resolution. Using a grating of 830 grooves/mm and a narrow-band diode laser that is tunable around 773 nm, we experimentally demonstrated an enhancement of the resolution by a factor of 2.     

Hydrophobic and antireflective characteristics of thermally oxidized periodic Si surface nanostructures

We reported the antireflective properties of periodic silicon (Si) subwavelength gratings and flat substrates in combination with thermal oxidation for an effective surface passivation. Moreover, theoretical calculations and analysis based on rigorous coupled-wave analysis simulation were performed. For thermally oxidized Si subwavelength grating structures, the reflectance was significantly reduced compared to that of the thermally oxidized flat Si substrates in wide ranges of wavelengths and angles of incidence. As the oxidation time increased, the reflectance became lower with increasing SiO _x thickness on Si subwavelength gratings due to the more graded effective refractive index profile from air to the Si via the thermally oxidized Si subwavelength gratings with increased height. By incorporating a thermal oxidation process into the Si subwavelength gratings, a more hydrophobic surface with good surface passivation was obtained.     

单级衍射量子点阵光栅的聚焦离子束直写法制备及光学性能检测

采用聚焦离子束直写技术,成功制作了面积为200μm×200μm,线密度500 mm 1,圆孔直径800 nm,金吸收体厚度为500 nm的单级衍射量子点阵光栅.研究了该光栅在波长442 nm激光下不同传输距离的衍射特性以及相对衍射效率.实验结果表明,量子点阵光栅不存在高级衍射,只保留了±1级和0级衍射,具有良好的单级衍射特性.1级衍射与0级衍射间距随传输距离的增大而增大,实测值与理论计算值相符.     

一种制作超高频全息光栅的新方法

为了满足测量的高分辨率和灵敏度，基于光栅为关键元件的光学测量方法要求光栅有很高的频率。在已有的高折射率介质制栅方法的基础上提出了一种新的制作超高频全息光栅的方法，该方法制栅准确、简单、方便，其特点是所制光栅的频率与激光波长及介质的折射率无直接关系，而是等于制栅光路所得频率与两倍母栅频率之和。实验表明，利用该方法制得１００００线／ｍｍ的光栅是完全可能的     

Flexible gratings fabricated in polymeric plate using femtosecond laser irradiation

Flexible gratings embedded in poly-dimethlysiloxane (PDMS) were fabricated using femtosecond laser pulses. Photo-induced gratings in a flexible PDMS plate were directly written by a high-intensity femtosecond (130 fs) Ti: Sapphire laser (λ_p=800 nm). Refractive index modifications with 4 μm diameters were photo-induced after irradiation of the femtosecond pulses with peak intensities of more than 1×10¹¹ W/cm². The graded refractive index profile was fabricated to be symmetric around the center of the focal point. The diffraction efficiency of the grating samples is measured by an He-Ne laser. The maximum value of refractive index change (Δn) in the laser-modified regions was estimated to be approximately 3.17×10⁻³.     

Ge quantum dot molecules and crystals: Preparation and properties

Templated self-organization has been used to prepare two-dimensional arrays as well as three-dimensional quantum dot crystals (QDC) containing Ge dots in a Si host crystal. Si(1 0 0) substrates have been patterned with two-dimensional hole gratings using extreme ultra-violet interference lithography (EUV-IL) and reactive ion etching. The EUV-IL was realized by multiple beam diffraction using Cr gratings on SiN_x membranes fabricated by e-beam lithography. Si/Ge overgrowth was performed by molecular beam epitaxy. The impact of the microscopic shape and size of the prepattern using the mask design and the EUV-IL exposure dose as parameters on the Ge dot nucleation has been studied with atomic force microscopy, transmission electron microscopy and photoluminescence measurements. Adjusting the growth parameters in multiple layer deposition the initial two-dimensional configuration was transferred into three-dimensional QDC.     

Electric field controlled higher-order diffraction images of paraelectric potassium lithium tantalate niobate

We report some electric field controlled photorefractive higher-order diffraction phenomena of a paraelectric phase potassium lithium tantalate niobate crystal doped with iron. In experiments, a p-polarized semiconductor laser (532 nm) was used to record grating at a small incident angle. Higher-order diffraction images were observed when the signal beam was focused behind and in front of the crystal. Then the higher-order diffraction images were reconstructed by a p-polarized He–Ne laser (632.8 nm) in the direction perpendicular to the surface. The higher-order diffraction images could be controlled by the external electric field. A theory about the higher-order diffraction images of the K and 2K grating is developed. The results show that the even order diffraction images of the K grating and the odd order diffraction of the 2K grating overlap each other. The odd order diffraction images of the K grating are diffracted in unattached direction. The electric field controlled higher-order diffraction image provides a useful method for optical information processing.     

SiC/W/Ir multilayer-coated grating for enhanced efficiency in 50-100 nm wavelength range in Seya-Namioka mount

A broadband [SiC/W/Ir](2) multilayer coating was deposited onto a diffraction grating to enhance the grating efficiency in the 50-100 nm wavelength range in a Seya-Namioka mount. The holographic ion-beam etched grating had a laminar profile with 1200 lines/mm. The coating was designed by using the subquarterwave multilayer theory. The measurement results show that the efficiency in the -1st diffraction order is greater than 9.3% throughout the wavelength range of 50-100 nm, which is obviously higher than that of single-layer gratings with SiC, Ir, or Au coatings.     

White-beam X-ray diffraction and radiography studies on high-boron-containing borosilicate glass at high pressures

ABSTRACT

Multi-angle energy-dispersive X-ray diffraction studies and white-beam X-ray radiography were conducted with a cylindrically shaped (1?mm diameter and 0.7?mm high) high-boron-content borosilicate glass sample (17.6% B₂O₃) to a pressure of 13.7?GPa using a Paris-Edinburgh (PE) press at Beamline 16-BM-B, HPCAT of the Advanced Photon Source. The measured structure factor S(q) to large q?=?19 Å^?1 is used to determine information about the internuclear bond distances between various species of atoms within the glass sample. Sample pressure was determined with gold as a pressure standard. The sample height as measured by radiography showed an overall uniaxial compression of 22.5% at 13.7?GPa with 10.6% permanent compaction after decompression to ambient conditions. The reduced pair distribution function G(r) was extracted and Si–O, O–O and Si–Si bond distances were measured as a function of pressure. Raman spectroscopy of the pressure recovered sample as compared to starting material showed blue-shift and changes in intensity and widths of Raman bands associated with silicate and four-coordinated boron.     

Evaluation of the curvature of an object by Talbot interferometry

In this study a modified method of Talbot interferometry is developed to evaluate the curvature of an object. The tilt angle of moiré fringe formed by two gratings is related to the wavelength, the grating periods, the angle between these two gratings, and the object curvature. Therefore, substituting the known experimental parameters into a special derived equation the object curvature can be evaluated. In order to show the validity of this method, stainless steel balls with curvatures of 1.326 and 1.261 mm⁻¹ were measured. The measurement resolution of curvature was about 3.729 × 10⁻³ mm⁻¹. It is shown that this method is suitable for both transmission and opaque objects with high accuracy.     

折射率介质在制栅和云纹干涉法中的应用

利用光在折射率介质中传播可以减小光波波长的性质，提出用折射率介质法制作高频全息光栅技术，使光栅频率突破理论极限２／λ；并将折射率介质应用于云纹干涉法中，当试件栅频率为６００１／ｍｍ时，虚栅频率可达到６０００１／ｍｍ，利用其±５级衍射光进行干涉，测量灵敏度由０．８３μｍ提高到０．１６μｍ。     

Dynamics of pulsed recording of holographic diffraction gratings in photopolymer materials

The dynamics of recording holographic diffraction gratings in photopolymer material using 10-ns pulses of Nd:YAG laser radiation (532 nm) was investigated. The formation of permanent and intermediate gratings was observed. Optimization of the photopolymer composition for pulsed recording was performed. The kinetic photopolymerization models taking into account the mechanisms of radical destruction due to recombination and by impurities are verified. Measurement of the recording kinetics at different recording angles showed that diffusion does not affect the hologram formation for times of the same order of magnitude as the recording duration (0.1 s) at a length of the grating half-period. Samples of the photopolymer composition in triethanolamine were investigated and diffusion of oligomeric acrylamide molecules was revealed. The diffusivity was found to be 1.1 × 10^?9 cm²/s.     

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.