光谱学与光谱分析, 2009, 29 (8): 2281, 网络出版: 2010-05-26
光谱仪用平场凹面光栅的凸面母光栅的消像差设计思路
Design Method of Convex Master Gratings for Replicating Flat-Field Concave Gratings
摘要
平场全息凹面光栅是光谱仪中的核心元件之一, 其成像质量和衍射效率直接影响了光谱仪的分辨率和光能利用率。 利用凸面母光栅复制制作凹面光栅, 便于在凸面基底上进行离子束刻蚀以获得高的衍射效率。 为了保证复制的凹面光栅具有高的成像质量, 文章提出一种全息凸面光刻胶光栅的消像差设计方法, 优化中考虑了凸面基底对记录光束的折射效应以及由基底折射率所引入的附加光程。 通过将“光程函数级数展开法”和ZEMAX光学设计软件相结合, 采用粗精两步优化的方法, 显著提高了优化的效率和成功率。 ZEMAX对比仿真结果显示, 复制得到的凹面光栅与传统直接采用全息法制作的凹面光栅的成像质量是相当的。
Abstract
Flat-field concave diffraction grating is the key device of a portable grating spectrometer with the advantage of integrating dispersion, focusing and flat-field in a single device. It directly determines the quality of a spectrometer. The most important two performances determining the quality of the spectrometer are spectral image quality and diffraction efficiency. The diffraction efficiency of a grating depends mainly on its groove shape. But it has long been a problem to get a uniform predetermined groove shape across the whole concave grating area, because the incident angle of the ion beam is restricted by the curvature of the concave substrate, and this severely limits the diffraction efficiency and restricts the application of concave gratings. the authors present a two-step method for designing convex gratings, which are made holographically with two exposure point sources placed behind a plano-convex transparent glass substrate, to solve this problem. The convex gratings are intended to be used as the master gratings for making aberration-corrected flat-field concave gratings. To achieve high spectral image quality for the replicated concave gratings, the refraction effect at the planar back surface and the extra optical path lengths through the substrate thickness experienced by the two divergent recording beams are considered during optimization. This two-step method combines the optical-path-length function method and the ZEMAX software to complete the optimization with a high success rate and high efficiency. In the first step, the optical-path-length function method is used without considering the refraction effect to get an approximate optimization result. In the second step, the approximate result of the first step is used as the initial value for ZEMAX to complete the optimization including the refraction effect. An example of design problem was considered. The simulation results of ZEMAX proved that the spectral image quality of a replicated concave grating is comparable with that of a directly recorded concave grating.
周倩, 李立峰. 光谱仪用平场凹面光栅的凸面母光栅的消像差设计思路[J]. 光谱学与光谱分析, 2009, 29(8): 2281. ZHOU Qian, LI Li-feng. Design Method of Convex Master Gratings for Replicating Flat-Field Concave Gratings[J]. Spectroscopy and Spectral Analysis, 2009, 29(8): 2281.