Time-compensated grazing-incidence monochromator for extreme-ultraviolet and soft X-ray high-order harmonics

The use of a grating monochromator for the selection of one or more high-order laser harmonics produced by a femtosecond pulse interacting with a gas jet may alter the duration of the pulse itself. This is due to the differences in the optical paths of the rays caused by ordinary diffraction when a grating is used. The time stretching can be almost eliminated by using two gratings in time-compensated configurations. Unfortunately, the classical diffraction mounting has low efficiency, overall in the extreme-ultraviolet region. High broadband efficiency can be obtained by using the conical diffraction mounting. A time-compensated monochromator with toroidal gratings used in conical diffraction is here presented. It is shown that the time compensation is very effective in a broad spectral region, ranging from VUV to soft X-rays, with much higher efficiency than the classical diffraction mounting. PACS 42.65.Ky; 42.79.Dj; 42.65.Re; 41.85.Si     

全息离子束刻蚀衍射光栅

全息离子束刻蚀衍射光栅集中了机械刻划光栅的高效率和全息光栅的无鬼线、低杂散光、高信噪比的优点．全息离子束刻蚀已作为常规工艺手段应用于真空紫外及软x射线衍射光栅的制作．文章对全息离子束刻蚀衍射光栅的制作方法、主要类型、研究现状和应用进行了综述．     

Angularly separated harmonic generation from intense laser interaction with blazed diffraction gratings

We made numerical simulations of the generation of narrowband beams of extreme ultraviolet radiation from intense laser interaction with a blazed grating surface. Strong fifth harmonic emission into its blazed diffraction order was observed as well as heavy suppression of the fundamental frequency with comparison to a typical harmonic spectrum from a flat target. The results demonstrate a new highly efficient method of generating near-monochromatic harmonics from the fundamental with minimal effect on the pulse duration.     

凹面光栅衍射效率的研究进展

凹面光栅因同时具有聚焦和色散功能而广泛应用于各类紫外、可见和红外波段的光谱分析仪器中,尤其是平场凹面光栅可以结合线阵或面阵探测器来实现即时分析。凹面光栅衍射效率的高低直接影响光谱仪器的信噪比和信号采集,其相关研究也逐渐为人们所关注。介绍了凹面光栅衍射效率的研究进展,比较了由机械刻划法和全息法制作的凹面光栅在掠入射下衍射效率的差别,分析了现有计算衍射效率方法的优缺点,并且对凹面光栅衍射效率的研究趋势做了简要预测,提出了需要同时在凹面光栅的主截面和非主截面内考虑光束对其衍射效率的影响。     

Single order soft X-ray diffraction with quasi-random radius pinhole array spectroscopic photon sieves

A novel single order diffraction grating in the soft X-ray region, called quasi-random radius pinhole array spectro- scopic photon sieves （QRSPS）, is proposed in this paper. This new grating is composed of pinholes on a substrate, whose radii are quasi-random, while their centers are regular. Analysis proves that its transmittance function across the grating bar is similar to that of sinusoidal transmission gratings. Simulation results show that the QRSPS can suppress higher-order diffraction effectively. And the QRSPS would still retain its characteristic of single order diffraction when we take the effect of X-ray penetration into account. These properties indicate that the QRSPS can be used in the soft X-ray spectra measurement.     

High-efficiency multilayer-coated ion-beam-etched blazed grating in the extreme-ultraviolet wavelength region

We describe a simple method to fabricate blazed gratings used in the extreme ultraviolet wavelength region. The method uses an argon and oxygen mixed-gas ion beam to directly etch the grating substrate through a rectangular profile photoresist grating mask. With this method the etched grating groove profile can be well controlled. An Mo/Si multilayer-coated specimen with a blaze angle of 1.9 degrees was fabricated and measured. At an incident angle of 10 degrees and a wavelength of 13.62 nm, the diffraction efficiency of the negative second order reaches 36.2%.     

多层膜闪耀光栅衍射的运动学研究

用 X射线运动学理论对软 X射线多层膜闪耀光栅的衍射特性进行了详细的研究 ,得到了衍射规律的一般表达式 ,讨论了产生衍射极大值的条件、光谱特性 ,不同于光栅和多层膜的色散特性。以及用作软 X射线单色器的一般性问题。发现只要选择合适的光栅参数 ,便可以将衍射光的大部分能量集中到某一个非零衍射级上。     

Applications of VUV extra‐focus mechanism: high‐performance dual‐mode monochromator from VUV to soft X‐ray

A new monochromator scheme is presented in which an extra‐focus constant‐included‐angle varied‐line‐spacing cylindrical‐grating monochromator (extra‐focus CIA‐VCGM) is conveniently combined with a variable‐included‐angle varied‐line‐spacing plane‐grating monochromator (VIA‐VPGM). This dual‐mode solution delivers high performance in the energy range from vacuum ultraviolet (VUV) to soft X‐ray. The resolving power and the efficiency of this dual‐mode grating monochromator are analyzed in detail based on realistic parameters. Comparisons with the commonly used variable‐included‐angle plane‐grating monochromator and normal‐incidence monochromator (VIA‐PGM/NIM) hybrid monochromator are made.     

Massive: The Hunt for the God Particle,by Ian Sample

For almost a hundred years the diffraction grating has been among the most important of scientific tools. The methods of ruling gratings for use in all regions of the spectrum from the soft x-ray region to the infra-red are described. The properties of ideal and imperfect gratings are considered and an account of present-day scientific and industrial uses is given.     

Single-order soft x-ray spectra with spectroscopic photon sieve

A single-order diffraction transmission grating named spectroscopic photon sieve(SPS) for soft x-ray region is proposed and demonstrated in this paper. The SPS consists of many circular pinholes located randomly, and can realize both free-standing diffractions and the suppression of higher-order differations. In this paper, the basic concept, numerical simulations, and calibration results of a 1000-lines/mm SPS for soft x-ray synchrotron radiation are presented. As predicted by theoretical calculations, the calibration results of a 1000-lines/mm SPS verify that the higher-order diffractions can be significantly suppressed along the symmetry axis. With the current nanofabrication technique, the SPS can potentially have a higher line density, and can be widely used in synchrotron radiation, laser-induced plasma diagnostics, and astrophysics.     

Highly resolved EUV beam-foil spectra of silicon

Spectra of foil-excited ions at tandem energies in the EUV region show many unclassified lines. In order to provide a basis for term analysis, high resolution spectra of Si are taken using a ruled 600 l/mm grating in 3^rd diffraction order and two holographic gratings of 1,200 l/mm resp. 3,600 l/mm in first diffraction order. With the latter grating the resolution power of a 2.2 m grazing-incidence monochromator is sufficient to measure fine-structure splittings of inter-shell transitions of O VI–O VIII and Si X–Si XII in the wavelength rangeλ < 20 nm. The performance of the gratings is demonstrated.     

软X射线多层膜光栅的衍射特性

用X射线运动学理论对软X射线多层膜光栅的衍射特性进行了研究。发现其衍射规律与多层膜的布拉格衍射和普通光栅衍射有本质的区别,可将衍射能量集中于某一衍射级上,同时它又保持了多层膜的高反射率和光栅的高分辨本领等优良特性。     

Design, Fabrication and Test of a Soft X-Ray Even-Order Transmission Grating

Most transmission gratings in the x-ray region work with their first orders and dispersion is limited by the line density achievable with current fabrication technology. We present a novel design of a two-dimensional x-ray transmission grating. The grating works with higher dispersion using its second orders, and the influence from first and third orders can be suppressed. A grating according to the novel design is fabricated and its diffraction performance is tested in comparison with a traditional x-ray transmission grating with the same line density. The novel grating could be especially useful when high dispersion is desired while the fabrication of high-density gratings becomes more difficult.     

Diffraction gratings for short-wave radiation: Modern requirements and achievements

Recent achievements in the field of making and certifying gratings for the soft X-ray and extreme ultraviolet regions are described, including those intended for space flights and having new or record characteristics of diffraction efficiency. The diffraction efficiency of gratings is investigated both by computation using the electromagnetic PCGrate® code with realistic data for layers, and by measurements using synchrotron radiation.     

Upgrade of beamline BL08B at Taiwan Light Source from a photon‐BPM to a double‐grating SGM beamline

During the last 20 years, beamline BL08B has been upgraded step by step from a photon beam‐position monitor (BPM) to a testing beamline and a single‐grating beamline that enables experiments to record X‐ray photo‐emission spectra (XPS) and X‐ray absorption spectra (XAS) for research in solar physics, organic semiconductor materials and spinel oxides, with soft X‐ray photon energies in the range 300–1000 eV. Demands for photon energy to extend to the extreme ultraviolet region for applications in nano‐fabrication and topological thin films are increasing. The basic spherical‐grating monochromator beamline was again upgraded by adding a second grating that delivers photons of energy from 80 to 420 eV. Four end‐stations were designed for experiments with XPS, XAS, interstellar photoprocess systems (IPS) and extreme‐ultraviolet lithography (EUVL) in the scheduled beam time. The data from these experiments show a large count rate in core levels probed and excellent statistics on background normalization in the L‐edge adsorption spectrum.     

Calibration of a compact XUV soft X‐ray monochromator with a digital autocollimator in situ

A digital autocollimator of resolution 0.1 µrad (0.02 arcsec) serves as a handy correction tool for calibrating the angular uncertainty during angular and lateral movements of gratings inside a monochromator chamber under ultra‐high vacuum. The photon energy dispersed from the extreme ultraviolet (XUV) to the soft X‐ray region of the synchrotron beamline at the Taiwan Light Source was monitored using molecular ionization spectra at high resolution as energy references that correlate with the fine angular steps during grating rotation. The angular resolution of the scanning mechanism was <0.3 µrad, which results in an energy shift of 80 meV at 867 eV. The angular uncertainties caused by the lateral movement during a grating exchange were decreased from 2.2 µrad to 0.1 µrad after correction. The proposed method provides a simple solution for on‐site beamline diagnostics of highly precise multi‐axis optical manipulating instruments at synchrotron facilities and in‐house laboratories.     

多层介质膜脉宽压缩光栅的严格矢量分析

用于展宽和压缩激光脉冲的多层膜脉宽压缩光栅是由多层介质高反膜和位于其顶层的浮雕光栅构成。以设计的高反射多层膜为基础,利用傅里叶模式理论分析了其衍射场分布,给出了TE波自准直角入射的使用条件下,多层介质膜脉宽压缩光栅衍射效率的表达式。以-1级衍射效率为评价函数,分别讨论了HfO2和SiO2为顶层材料时,多层膜脉宽压缩光栅-1级衍射效率高于0.95的光栅结构参量范围。结果表明,在该条件下,选择HfO2为顶层材料时,光栅结构参量有较大的取值范围。给出了优化的光栅结构参量,并分析了光栅制作误差及其使用条件的宽容度,对光栅制作工艺和使用具有一定的指导意义。     

High-order diffraction suppression using modulated groove position gratings

Conventional diffraction gratings composed of a series of equally spaced slits suffer from wavelength overlapping caused by high-order diffraction. Here modulated groove position gratings (MGPGs) are proposed to significantly suppress the high diffraction orders. Both numerical solution and experimental results demonstrate the effectiveness of MGPGs. The suppression ratio is determined by the number of grating grooves used. By using an MGPG with 10,000 grooves, a suppression ratio as high as 18,000 can be obtained. In addition, the minimum linewidth is kept to 1/4 of the grating period, which enables grating realization with high line density employing today's nanofabrication technology. Our results should be of great interest in both diffraction grating theory and applications, particularly due to MGPGs' applicability in a wide wavelength range and realizability with high line density.     

All-reflective femtosecond optical pump-probe setup for transient grating spectroscopy

We developed a pump-probe setup that can be used for free electron lasers based four-wave mixing experiments in the extreme ultraviolet/soft x-ray spectral range. The main feature of the proposed optical layout is the absence of transmission optics. Test measurements on liquid and solid samples carried out using the transient grating technique in both transmission and reflection geometry demonstrate the reliability of the setup.     

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.