熔石英亚表面杂质颗粒附近光场调制的三维模拟

熔石英亚表面缺陷是光学材料低损伤阈值的主要因素之一.本文建立了熔石英亚表面三维球形杂质颗粒模型,采用三维时域有限差分方法对杂质附近的光场进行了数值模拟,分析了杂质的介电常数与尺寸对光强增强因子的影响,结果显示:介电常数小于熔石英的杂质,其光强增强因子不随尺寸、介电常数的改变而改变,均保持为4左右;当介电常数为6.0时,半径为1.5λ,2λ及2.5λ的杂质,相应的光强增强因子分别为50.1588,73.3904及102.9953,即增强因子随杂质尺寸的增大而增大;恰 关键词： 杂质颗粒 三维时域有限差分 数值计算 光强增强因子

Three-dimensional numerical simulation of light field modulation in the vicinity of inclusions in silica subsurface

One of the important factors of the low laser induced damage threshold is the defects in the subsurface of fused silica. The three-dimensional model of a spherical inclusion in the subsurface is established in this study. Three-dimensional finite-difference time-domain method is used to calculate and simulate the light field distribution in the vicinity of inclusions. The effects of dielectric constant and inclusion size are analyzed, separately. The results show that the light intensity enhancement factor (LIEF) does not change with the size and the dielectric constant of the inclusions when the dielectric constant is smaller than that of fused silica, where the LIEF is kept at about 4. When the dielectric constant is 6.0, the LIEFs are 50.1588, 73.3904 and 102.9953 for the inclusions with sizes of 1.5λ, 2λ and 2.5λ respectively. When the inclusion size is constant, the LIEF will increase with the increase of dielectric constant. The light enhancement for the round inclusions is much higher than that for the ellipsoidal inclusions. Therefore, the round inclusions with large size and dielectric constant significantly enhance the electric field.