Influence of ion beam figuring (IBF) on reflectivity of monocrystalline silicon

The rapid development of high-power optical system and free electron laser put higher request forward the reflectivity performance of monocrystalline silicon optical materials. In this paper, the surface characteristics of monocrystalline silicon elements before and after ion beam figuring are tested. Firstly, the photothermal absorption was measured at the infrared band of 1064 nm, which shows that the absorption amplitude of the processed region is higher than the other. Then, the power spectral density function(PSD) was used to compare the surface roughness in different frequency bands. And surface reflectivity of the processed infrared band is improved by 5% measured by spectrophotometer. The experimental results show that after ion beam figuring, the hydrolyzed layer of monocrystalline silicon optical element is exposed, and the absolute reflectivity and photothermal absorption performance are improved, which can improve the performance of optical element in high power laser system.