LO-RAY-LIGH@ Diffraction Gratings in UV-VIS Spectroscopy

It has been more than half a century since the release of the first Shimadzu UV-VIS （UV-visible） spectrophotometer QB-50 in 1952, and during this time more than 160,000 UV-VIS spectrometers have been produced and installed in a wide variety of different applications. A lot of technical innovations have been implemented to improve the performance and significantly reduce the stray light levels. The latest innovation during development of sophisticated spectrophotometers is based on a new holographic exposure method and optimized etching process which has made it possible to produce both high-efficient and exceptionally low stray light gratings. These LO-RAY-LIGH~ gratings have guaranteed values of stray light at the intermediate position between zero-order and first-order lights. The values are measured by Shimadzu＇s laser stray-light-measuring system. The latest development in the series of UV-VIS spectrophotometers is the UV-2700 which is a true double beam double monochromator system in a compact design for high-precision spectral analysis of a wide range of samples including organic and inorganic compounds, biological samples, optical materials and photovoltaics. The high performance optical system is designed with ＂LO-RAY-LIGH＂ diffraction gratings, featuring highest efficiency and exceptionally low stray light. The spectrophotometer operates in the wavelength range from 185 nm to 900 nm and allows highly sophisticated applications such as direct measurement of high density samples up to 8 absorbance units without dilution.

Detection of the spatiotemporal field of a single-shot terahertz pulse based on spectral holography

According to electro-optical sampling theory, we propose a new method to detect the spatiotemporal field of a single- shot terahertz pulse by spectral holography for the first time. The single-shot terahertz pulse is coupled into a broadened chirped femtosecond pulse according to electro-optical sampling theory in the detecting system. Then the reference wave and the signal wave are split by Dammann grating and spread into the interference band-pass filter. The filtered sub-waves are at different central-frequencies because of the different incident angles. These sub-waves at different central-frequencies interfere to form sub-holograms, which are recorded in a single frame of a charge coupled device （CCD）. The sub-holograms are numerically processed, and the spatiotemporal field distribution of the original terahertz pulse is reconstructed. The computer simulations verify the feasibility of the proposed method.

Effects of the Change in Average Permittivity and Conductivity of Grating on Diffraction Efficiency

A model describing the propagation of optical waves in a hologram volume grating is studied. Then the effects of the change in the average permittivity and conductivity of a grating on diffraction efficiency are discussed. Finally a comparision of the results of this model with those by Solymar is made. The authors come to a conclusion that the effects of the change can be compensated.

Polarization conversions of diffractive wave plates based on orthogonal circular-polarization holography

A polarization holographic grating, which integrates the functions of a grating and a wave plate and is called a diffractive wave plate, is recorded by two beams （left and right circularly polarized） of a 532 nm laser in an azo polymer with a liquid-crystal structure. The polarization conversion characteristics of the diffractive wave plates are investigated with a detecting light of 650 nm by metering the polarization state of first-order diffracted light. It is confirmed that the diffractive wave plates convert the incident linear polarization into circular polarization for a linearly polarized probe laser and reverse the sense of rotation of the circular polarization when the detecting light is circularly polarized light.

Optical design of the time-resolved ARPES beamline of the new material spectroscopy experimental station for the update of CAEP THz-FEL facility

The Chinese Academy of Engineering Physics Terahertz Free Electron Laser Facility(CAEP THz FEL,CTFEL)is the only high-average power free electron laser terahertz source based on superconducting accelerators in China.The update of the CTFEL is now undergoing and will expand the frequency range from 0.1–4.2 THz to 0.1–125 THz.Two experimental stations for material spectroscopy and biomedicine will be built.A high harmonic generation(HHG)lightsource based beamline at the material spectroscopy experimental station for time-resolved angle-resolved photoemission spectroscopy(ARPES)research will be constructed and the optical design is presented.The HHG lightsource covers the extreme ultraviolet(XUV)photon energy range of 20–50 eV.A Czerny–Turner monochromator with two plane gratings worked in conical diffraction configuration is employed to maintain the transmission efficiency and preserve the pulse time duration.The calculated beamline transmission efficiency is better than 5%in the whole photon energy range.To our knowledge,this is the first time in China to combine THz-infrared FEL with HHG light source,and this experimental station will be a powerful and effective instrument that will give new research opportunities in the future for users doing research on the dynamic evolution of the excited electron band structure of a material’s surface.

基于可调剪切干涉曝光方法的大口径液晶偏振光栅制备

为了解决传统偏振全息干涉方法受限于过长的光路难以制备长周期的大口径液晶偏振光栅的问题,提出了基于液晶偏振光栅模板的可调剪切干涉曝光方法,并通过理论分析了制备偏振光栅的周期随模板方位角及沿光轴轴向位置的变化。利用小口径高效液晶偏振光栅作为模板搭建可调剪切干涉曝光光路,并基于此制备了数十微米周期的200 mm口径液晶偏振光栅,平均衍射效率达到99%以上,平均周期约为59.86μm,周期分布不均匀性约为0.07%。实验结果表明,调剪切干涉曝光方法能够制备大口径的长周期偏振光栅,周期和效率分布均匀,还具备周期易于调节、结构紧凑和抗振动干扰强等优势。

基于偏振全息术制备Pancharatnam-Berry相位光栅

PB相位光栅既具有对入射光偏振方向敏感的独特性质,同时又具有较宽的响应带宽和较高的单级衍射效率.采用基于偏振全息记录的液晶技术,将光敏偶氮染料SD-1旋涂在单面导电的ITO玻璃基板上,曝光后可得到具有偏振周期性旋转图案的取向层.结合FDTD模拟仿真,设计了PB相位光栅制备方案并搭建了实验装置.设计PB相位光栅衍射效率的检测光路,验证其高效的单级衍射.搭建圆偏振光旋向检测光路,验证了PB相位光栅改变入射圆偏振光旋向的特性.

Higher order harmonics suppression in extreme ultraviolet and soft x-ray

The extreme ultraviolet and soft x-ray sources are widely used in various domains. Suppressing higher order harmonics and improving spectral purity are significant. This paper describes a novel method of higher order harmonics suppression with single order diffraction gratings in extreme ultraviolet and soft x-ray. The principle of harmonic suppression with single order diffraction grating is described, and an extreme ultraviolet and soft x-ray non-harmonics grating monochromator is designed based on the single order diffraction grating. The performance is simulated by an optical design software. The emergent beams of a monochromator with different gratings are measured by a transmission grating spectrometer. The results show that the single order diffraction grating can suppress higher order harmonics effectively, and it is expected to be widely used in synchrotron radiation, diagnostics of laser induced plasma, and astrophysics.

变间距光栅刻线密度的测试精度分析

介绍了衍射法测量变间距光栅线密度的测量系统。该测量系统由激光器、准直镜、光栅转动台（含角度测量仪）、直线工作台、光栅调节架、探测器和待测光栅组成。分析了系统中各种误差对测量精度的影响，以及变间距光栅参数的变化对光学系统的影响和补偿办法。计算表明，该系统的测试精度满足光束线对光学系统的性能要求。

凸面光栅成像光谱仪的研制与应用

考虑传统光栅成像光谱仪受光学畸变的限制难以同时实现大光学孔径和小型化要求,利用全息法设计并制作了凸面光栅,并以该凸面光栅作为核心元件研制了便携式成像光谱仪。该光谱仪以推扫方式进行目标扫描,获取成像光谱数据立方。仪器的光谱分辨率为2.4nm,光谱谱线弯曲为0.1%,色畸变为0.6%,体积为209mm×199mm×110mm。介绍了仪器的工作原理和结构设计,并进行了实验室检测和室外花卉实际光谱测量。测试结果表明:凸面光栅成像光谱仪的光谱分辨率为2.1nm,光谱谱线弯曲为0.09%,色畸变为0.6%,均满足设计要求,实际花卉光谱测试亦取得了较为理想的结果。

全息法制备二维电调谐聚合物/液晶光栅

介绍了利用激光干涉形成的亮条纹引发预聚物/液晶的混合物相分离,制备了二维电调谐光栅。在对样品进行一次曝光之后,将样品绕着基板中心的法线方向转动一定的角度(如90°),再进行一次曝光,获得格子结构的聚合物/液晶二维光栅。实验结果表明,光栅中的聚合物和液晶在二维空间上呈周期性分布,其衍射图样为空间点阵且衍射效率可以利用电场进行调节。

多条转动拉曼谱线雷达测量对流层大气温度

由于对流层大气中气溶胶的存在,传统的利用大气中瑞利散射和振动拉曼散射测量大气温度的方法具有一定的局限性,然而利用大气N2和O2分子的的转动拉曼信号获得大气温度信息的方法不受对流层大气中气溶胶的影响。因此利用N2和O2分子纯转动拉曼散射激光雷达开展了测量对流层下部温度分布的实验研究。现有的转动拉曼雷达系统基本上是通过获取单一的转动拉曼谱线来反演大气温度,这就导致了系统的信噪比低,不能很好的反演温度。作者在双光栅单色仪的基础上提出了一种新的雷达信号分光系统。这种新的分光系统的每条通道所获得的信号并不是单独的转动拉曼谱线,而是多条转动拉曼谱线之和,这样就能提高整个系统的信噪比。在较小的激光能量和小口径望远镜的情况下,利用这种方法,雷达系统可以在几公里内获得较好的信噪比。最后实验得到了对流层0.3～5km高度内的大气温度分布,它与球载无线电探空仪比较,二者一致性较好。

探测低空大气温度分布的转动拉曼激光雷达

提出了一种新的探测对流层低层大气温度的转动拉曼激光雷达方法,通过测量N2和O2的后向散射的纯转动拉曼谱的强度,计算它们的比值来确定大气温度的垂直分布,并对其性能进行了数值模拟。转动拉曼激光雷达的光源是一个调Q的Nd:YAG激光器,经扩束器后输出能量200mJ;采用双光栅单色仪提取所需要的氮气和氧气的转动拉曼谱;接收机采用光电倍增管和双通道光子计数器,量子效率是10%(48000个脉冲累加)。夜晚它对近地面10.2km高度内的探测信噪比在10:1以上,白天它对近地面3.6km高度内的探测信噪比在10:1以上,计算的温度与模拟用的温度真值阔线相差约0.3K。

用于1m Seya-Namioka单色仪的1200lp/mm Laminar光栅

针对国家同步辐射实验室燃烧与火焰实验站中1mSeya-Namioka单色仪对光栅的需求,采用全息离子束刻蚀工艺制作了1 200lp/mm Laminar光栅。首先,通过光刻胶灰化技术调节光刻胶光栅掩模占空比,在理论设计的误差允许范围内,对此光栅掩模进行扫描离子束刻蚀;然后,将光栅图形转移到光栅基底中去除残余光刻胶;最后,采用离子束溅射法镀制厚约40nm的金反射膜,采用热蒸发法镀制厚约60nm的铝反射膜。用原子力显微镜分析光栅微结构,结果显示光栅槽深为40nm,占空比为0.45。同步辐射在线波长扫描测试结果表明,镀铝光栅效率明显高于镀金光栅,获得的实验结果与理论计算结果基本符合。镀金光栅已替代进口光栅在线使用3年,其寿命大大超过复制光栅,基本满足了燃烧实验站的实验研究需求。

平面光栅双单色仪的光学系统设计

平面光栅双单色仪是构成光栅衍射效率测试仪的重要组成部分,为了完成光栅衍射效率测试仪的研制,需要对平面光栅双单色仪的光学系统进行设计和模拟。仪器主要由光源、前置单色仪、测量单色仪和探测器组成;结合仪器的实际使用需要,确定了光源、探测器和光路结构,根据仪器的设计要求,分别对前置单色仪和测量单色仪的光学系统进行设计和模拟,给出了各自光学系统的像面点列图和实际光线追迹数据。设计结果保证了仪器光学系统的测量准确性。

小型高光谱分辨率光栅单色仪的研制

单色仪是成像光谱仪进行光谱连续定标的必备设备,为了对高光谱成像光谱仪进行连续光谱定标,设计了一种轻小型高光谱分辨率的光栅单色仪。采用水平式Czerny-Turner光路结构,以高光谱分辨率为出发点,通过推导计算,从光栅选型、焦距计算、狭缝尺寸的确定等方面详细论述了光栅单色仪的设计思路,给出仪器的重要必要结构参数,并论述了这些结构参数对仪器光谱分辨率和体积的影响。根据光栅单色仪的光路特点,对入射狭缝组件、准直物镜组件和成像物镜组件、扫描结构、机身等进行轻小型机械结构设计,并给出正弦杆扫描机构的结构参数与仪器输出波长和波长扫描精度的数学关系,完成了仪器的整体结构设计和装调。应用汞灯可见光光谱进行波长定标,采用最小二乘法得到定标曲线,并提出步进数极限误差与定标曲线相结合的方法,求得仪器的波长重复性和波长准确度;仪器在400~800nm波长范围内,光谱分辨率优于0.1nm,波长重复性达±0.096 6nm,波长准确度达±0.096 9nm。

一种单光束紫外-真空紫外分光光度计的设计

设计了一种单光束紫外-真空紫外分光光度计，主要由150W氘灯辐射源、前置超环面聚光镜、Seya-Namioka全息凹面光栅单色仪、后置反射光学系统、光学调制器、样品/探测器转台、光电倍增管探测器及计算机控制系统组成。利用ZEMAX光学设计软件，对该单光束紫外-真空紫外分光光度计光学系统进行了优化设计，并设计了正弦波长扫描机构。对设计结果进行了分析，从设计结果的分析表明，所设计的单光束紫外-真空紫外分光光度计满足设计指标要求，扫描光谱范围115-400nm，光谱分辨力小于0．5nm，波长精度小于0.1nm。

I型全息凹面光栅制作误差对光谱像的影响分析

通过对I型全息凹面光栅制作参量误差对光谱像的影响进行数值计算发现:1)两记录臂长的相对误差而不是绝对误差决定光谱像的展宽程度,即使绝对误差较大,只要两记录臂长的误差值相同,像宽也没有明显改变;2)由于I型光栅的记录臂一般较长,记录角度误差对像宽的影响不大,但会影响光栅的刻线密度,导致光谱成像位置的偏移;3)曲率半径误差对像宽的影响较大.通过数值模拟明确了I型全息凹面光栅制作的误差容许范围,找到了对光谱像宽度影响较大的误差来源,从而为此类光栅的制作提供理论指导,有助于制作出高质量光栅,降低罗兰圆光谱仪的调节难度.

智能化多光栅单色仪的研制

针对传统光栅单色仪的工作缺陷,采用一个高精度细分步进马达,实现了３个不同光谱区之问光栅的自动转换、波长扫描和滤色片置换等功能．新设计研制的单色仪具有结构简单、工作可靠、光谱范围宽等优点,其原理和方法可在光电子领域获得重要应用．

一步法设计单色仪凹面全息光栅

凹面全息光栅是光谱分析仪器的核心器件之一,其成像质量直接决定了光谱分析仪器的分辨本领。利用光程函数理论设计凹面全息光栅是一个繁琐的求解非线性方程组的过程,该过程分两步进行,每步需要求解四个非线性方程。分两步求解不但过程麻烦,还不可避免地引入了取舍误差,降低了最优参数的精度。为了解决该问题,本文提出了一种设计单色仪凹面全息光栅的新方法——一步法,该方法不但可以简化求解过程、降低最优参数的误差,还可以方便地控制整体像差的变化趋势。采用有较强全局搜索能力的遗传算法求解该方法中非线性方程的极值问题,并与传统的方法对比验证了该方法的可行性和正确性,结果表明,一步法不但在方法上比两步法简便,其设计结果还优于两步法。