多层介质膜脉冲压缩光栅近场光学特性分析

利用傅里叶模式理论分析了TE波自准直角入射的使用条件下，多层介质膜光栅的光栅区和多层膜区电场分布的特点.分别讨论了HfO₂和SiO₂为顶层光栅材料时，光栅结构参数对光栅脊峰值电场的影响，结果表明，对于不同膜厚的顶层材料，存在一个最佳膜厚度，使光栅脊峰值电场最小，并且当膜厚增大时，设计大高宽比的光栅可以降低该电场峰值.最后，在大角度条件下使用多层膜光栅也可以降低光栅脊处的峰值电场. 关键词： 衍射光学 多层介质膜光栅 模式理论 损伤阈值

Near-field optical property of multi-layer dielectric gratings for pulse compressor

Multi-layer dielectric gratings for pulse compressor in high-energy laser system must provide high diffraction efficiency. In addition, its laser induced damage property is critical for the system. Nonuniform optical near-field distribution of multi-layer dielectric gratings is one of the important factors to limit its laser induced damage threshold. Electric field distributions in the grating region and multi-layer film region are analyzed by using Fourier modal method. Effects of grating structure on peak magnitude of electric field in grating ridge are analyzed when the top layer material is HfO₂ and SiO₂, respectively. The results show that there exists an optimum top layer thickness, at which the peak magnitude of electric field within grating ridge is a minimum. And the peak electric field in the grating ridge can be reduced by designing top gratings with high aspect ratio structure when top layer thickness is increasing. Finally, the peak electric field in the grating ridge can also be reduced when the multi-layer dielectric grating is used at big incident angle.