神光Ⅲ的光学系统具有高功率密度运行的特点,对光学元件的抗激光损伤能力等提出了很严格的要求.光学元件内部的微缺陷会引起局域场强增强,采用时域有限差分方法对亚波长量级的缺陷进行了电磁场的数值模拟,并对数值计算的参数选取给出了定量的判断.

Optical system of Shenguang-Ⅲ works under high power condition and demands that optical elements are highly resistant to laser damage. Micro-defects in optical element may cause enhancement of electric field in small area which will lead to lower laser damage threshold. In this paper, Time-domain finite difference method(FDTD) is used to simulate distribution of electromagnetic field. Quantitative judgement of selection of computation parameters is given. The results show that if micro-defects(such as pore, impurity, etc) exist in the optical material, the intensity of electric field is enhanced by several times.