熔石英亚表面球形杂质对入射光场的调制作用

Light Field Modulation Induced by Spherical Inclusion in Fused Silica Subsurface

建立激光辐照下熔石英体内球形杂质引起元件损伤的模型。基于Mie理论计算杂质的散射系数,研究杂质颗粒附近的调制光场分布,分析光强增强因子(LIEF)与杂质折射率及半径的关系。结果显示,杂质颗粒半径小于40 nm时,所有类型杂质对光场的调制作用可以忽略;颗粒半径大于40 nm时,对于折射率小于熔石英的非耗散杂质,LIEF随颗粒半径的增大和折射率的减小而增大,且后向散射远强于前向散射;对于折射率大于熔石英的非耗散杂质,随着折射率和半径的增大,LIEF整体趋势增大,局部达到102量级。对于耗散杂质,前向散射强度随颗粒半径的增大先增大后减小,当颗粒半径大于170 nm时,后向散射强于前向散射。

A model of optics component damage induced by a spherical inclusion in fused silica illuminated by a laser beam is developed. Based on Mie scattering theory, scattering coefficients of several common kinds of inclusions are calculated, the light field distributions in the vicinity of inclusions are simulated. Light intensity enhancement factor（LIEF） as functions of refractive index and radius are analyzed. The results show that modulation effect of all kinds of inclusions can be ignored when the radius is smaller than 40 nm; when the radius of the particle is larger than 40 nm, for a non-dissipative particle with refractive index less than that of fused silica,LIEF increases with increasing radius and decreases with increasing refractive index, and the backscattering is much stronger than the forward scattering; when the refractive index is greater than that of fused silica, LIEF increase with the increasing radius and refractive index, and LIEF can reach to the order of 10^2 in some situations. For a dissipative particle, with the increase of radius, forward scattering intensity increases at first and then decreases.When the radius is larger than 170 nm,backscattering intensity is greater than forward scattering intensity.