摘要
不同于国际上其他空间项目采用光栅切换的光谱获取方式,中国空间巡天望远镜采用近焦面拼接光栅的方式获取大视场、宽波段无缝光谱,波长覆盖范围为250~1000nm,光谱分辨率R≥200。国内紫外透射衍射光栅的天文应用尚在起步阶段,制作难度高,且不能从国外获得。经过多年努力,光栅性能在近期获得了较大提升。本文针对紫外光栅的科学应用性能和使用条件,分析了衍射光栅制作参数的优化,给出了衍射效率随入射角、入射光偏振态以及光栅槽形结构参数的变化规律。相关数据对在轨流量定标具有借鉴价值。通过选用不同的光栅结构参数对衍射效率特性进行分析,发现了紫外光栅峰值波长与顶角投影在每个周期上的比值之间的近似线性表达关系。本文讨论了满足科学需求的参数许可域,并将其用于控制光栅制作参数。多次试验后,光栅槽形结构参数和形状得到了精确控制,获得了性能优异的衍射光栅。制作的光栅线密度为333line/mm,闪耀角为12.51°,峰值效率波长控制在315nm,紫外波段实测峰值衍射效率为72.3%,平均效率为65.1%。该光栅的槽形、波前质量等均控制在较高水平,衍射波前质量均方根(RMS)达到0.06λ,峰谷值(PV值)达到了0.33λ。采用该光栅可获得良好的成像质量。
Objective Chinese Space Survey Telescope obtains large field of view,wideband slitless spectrum by adopting near focal plane mosaic gratings instead of by switching gratings which are used by other space projects.The spectral resolution is greater than 200,with spectral coverage ranging from 250 to 1000nm.Gratings with high diffraction efficiency and good spectrum imaging performance are critical for scientific performance.Domestic ultraviolet transmission diffraction gratings are rarely used in astronomy.To meet the scientific requirements in the U-band,holographic ion beam etching is used to create ultraviolet gratings with wavelengths ranging from 250 to 425nm.The gratings’ various performances are evaluated.Methods Grating groove parameters are designed by taking into account both first-order diffraction efficiency,suitable zeroth-order diffraction efficiency,and peak efficiency wavelength.Grating fabrication parameters and groove profile are optimised using numerical simulation programmes while scientific performance is taken into account.Diffraction efficiency uniformity is achieved across a wide range of incident angles caused by non-telecentric optics and polarised light from various scientific objects.Sensitivity parameters are integrated into acceptable parameter domains to guide the fabrication of ultraviolet gratings.The groove parameters can be well controlled after a few iterations,and ultraviolet gratings are successfully developed.Two metrics are compared based on two groups of grating groove characteristic parameters,groove depth and the ratio of top angle projection,and the left and right bottom angles.The first metric is found to be suitable for describing peak diffraction efficiency and peak wavelength position,while the second metric is found to be suitable for describing average diffraction efficiency.Diffraction efficiency has a peak wavelength position that is roughly linear to the first metric.Results and Discussions The grating performance of ultraviolet wavelength has been greatly improved after years of effort.After several experiments,the grating groove parameters and shape are precisely controlled,yielding a diffraction grating with a groove density of 333 line/mm,blaze angle of 12.51°,and peak efficiency wavelength of 315 nm.The grating performs admirably.Peak diffraction efficiency is 72.3%,with an average efficiency of 65.1%.Peak wavelength position can also be controlled.The groove shape and diffraction wavefront of the grating are controlled at a high level,and the diffraction wavefront RMS reaches 0.06λ and PV value reaches 0.33λ.The application of the grating can obtain good spectrum imaging performance.Conclusions The performance of astronomical ultraviolet gratings is optimised in groove parameters to achieve the best average efficiency under a variable incident angle and controlled polarisation sensitivity operating conditions.After a few turns of fabrication and evaluation,good grating performance is achieved.This will be a contribution to the application of sky spectrum surveys.
作者
陈力斯
胡中文
邱克强
姜海娇
Chen Lisi;Hu Zhongwen;Qiu Keqiang;Jiang Haijiao(National Astronomical Observatories/Nanjing Institute of Astronomical Optics&Technology f Chinese Academy of Sciences,Nanjing,Jiangsu 2100^2,China;Key Laboratory of Astronomical Optics&Techyiology,Chinese Academ y of Sciences,Nanjing Institute of Astronomical Optics&Technology,Nanjing,Jiangsu 210042,C/ima;University of Chinese Academy of Sciences,Beijing 100049,China;University of Science and Technology of China,Hefei,Anhui 230027,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2022年第6期147-158,共12页
Chinese Journal of Lasers
基金
国家自然科学基金(11927804,11873013)。
关键词
光栅
光谱巡天
衍射效率
衍射波前
像质
grating
spectrum survey
diffraction efficiency
diffraction wavefront
image quality
