熔石英表面划痕附近电磁场分布模拟分析

 亚表面缺陷是造成固体激光器光学器件损伤阈值过低的重要原因，而表面划痕是缺陷中重要的一种。使用时域有限差分方法（FDTD）模拟了熔石英表面圆柱形、三角形划痕对激光电磁场的调制作用，绘出了2维电磁场强度分布图，计算出划痕尺寸不同时电磁场的最大强度。数值计算结果表明，尺寸为二倍波长的划痕可以获得最大的电磁场强度，此时容易导致自聚焦；亚波长级和足够大尺寸的划痕作用基本可以忽略。一定尺寸的划痕，深度越大，最大场强也越大，但当划痕过深时最大场强反而会降低。

Simulation and analysis of electromagnetic field distributing around fused silica scratch

Subsurface damage has been the main cause to lower the laser-induced damage threshold of optics components in high power solid laser system, and one important kind of these is scratch. Finite difference time domain (FDTD) method was used to simulate the electromagnetic distribution around column form or triangular scratch in fused silica. 2D electric field amplitude distribution was illustrated, and maximal values of electric field amplitude vs scratch sizes were calculated. The conclusion displays that the electric field amplitude is maximal when the scratch size is 2λ wide, which is easy to cause self-focusing, the effect can be neglected when scratchsize is sub-wavelength level or large enough. The larger the depth is,the larger the maximal value is when the size is the same, but it becomes smaller when scratch is too deep.