多孔SiO2膜层经热处理后,具有很高的激光破坏阈值,但是结构中有许多Si-OH亲水基团,导致光学透过率受环境相对湿度的影响很大。实验目的是改善膜层内部结构,使膜层结构中的亲水基团转变为疏水基团,提高膜层的疏水性,增强膜层的透过率稳定性。系统地研究了膜层透过率随时间变化的规律,在氨气和六甲基二硅氮烷(HMDS)混合气氛下热处理膜层,处理后生成Si-O-Si(CH3)3非极性疏水基团,使膜层的疏水性大大提高,因而膜层的透过率稳定性有大幅度提高。稳定性的提高延长了膜层的寿命。处理后膜层的表面粗糙度良好,均方根表面粗糙度(RMS)为3.575,平均粗糙度(RA)为2.850,能够满足大型激光器精密化发展的要求。

Although the porous silica antireflective (AR) coating has high laser damage threshold after heat treatment, its transmission is correlated with environment relative humidity due to many Si-OH hydrophilic groups on the coating surface. The aim of the experiment is to modify internal component, enhance the hydrophobic performance and improve the transmission stability of the films. In this paper, Si-O-Si(CH3)3 non-polar hydrophobic groups appear on the coating surface through atmosphere treatment of ammonia and HMDS (hexamethyl-disilazane), causing hydrophobic performance, thus the stability and life of AR coating are improved greatly. This is very important for coating to use in laser device. The results also show that the coating surface is smooth after above treatment, and its roughness is estimated to be 3.575 for root-mean-square value and 2.850 for average value which meets the precision requirement of large scale laser.