Global optimization of two-multilayer mirror objective for focusing soft X-ray high harmonics
Global optimization of two-multilayer mirror objective for focusing soft X-ray high harmonics
复制标题
用于聚焦软X射线高次谐波的两层多层镜物镜的全局优化
DOI：
10.1117/12.2520543
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Chen Jun
中科院分区：
文献类型：
--
作者：
Toyoda Mitsunori;Yamashita Shota;Chen Jun
为了使软X射线聚焦物镜的光学设计具有全局优化能力，本文提出了一种基于几何光学的解析和数值相结合的设计方法。我们假设两个球面镜物镜的玻璃入射配置。首先，系统布局参数之间的关系，即，曲率半径、镜间距和焦距的近似计算公式，以描述所有可能的定焦距镜布局。然后，应用数值光线追迹法计算了反射镜物镜的聚焦特性，以寻求实用的低像差光学设计。作为设计实例，所提出的方法被应用到一个双球面镜物镜一维聚焦软X射线高次谐波。我们成功地找到了三种实用的低像差设计。计算结果表明，当物镜焦距f = 100 mm，数值孔径NA = 0.02时，焦平面上的光斑尺寸可以达到100 nm左右。这些结果表明，所提出的方法是能够与玻璃入射配置的反射镜物镜的全局优化。
To bring global optimization capability on optical design of a focusing objective in soft X-ray region, we describe novel design approach by combining analytical and numerical methods based on geometric optics. We assume two-spherical mirror objective of glazing-incidence configuration. First, relationship between system layout parameters, i.e., radii of curvatures and mirror separations, and focus length is derived with paraxial approximation, to describe all feasible mirror layouts with constant focal length. Then, focusing property of the mirror objectives are computed by applying numerical raytracing method, to seek practical optical designs with low aberrations. As design examples, the proposed method is applied to a two-spherical-mirror objective for one-dimensional focusing of soft X-ray high harmonics. We successfully find three kinds of practical designs with low aberration. The calculation results show that we can expect small spot size close to 100 nm on the focal plane, for the case that the objective has moderate focal length (f = 100 mm) and numerical aperture (NA = 0.02). These results indicate that the proposed approach is capable of global optimization of the mirror objective with glazing-incidence configuration.