不锈钢膜对激光诱导熔石英表面损伤的影响

Stainless steel film′s contamination effects on laser-induced damage to fused silica surface

在高功率激光系统中,对于光学元件的激光损伤阈值和损伤增长的研究意义重大。采用磁控溅射方法在熔石英基片上镀12 nm厚的不锈钢膜,使用椭偏仪和紫外-可见光分光光度计测量其厚度和透过率,分别使用S-on-1和R-on-1方法测量样品损伤阈值,比较后证明S-on-1测量方法较为科学。使用S-on-1方法进行激光损伤增长实验,发现损伤点横向尺寸和纵向深度随辐照次数均以e指数形式变化,且相比洁净熔石英基片,样品损伤点横向尺寸损伤增长因子高出41%,样品损伤点纵向深度损伤增长因子高出39%。在激光辐照一定发次后,损伤点纵向深度继续增长,损伤点横向尺寸增长速度不断减缓,最终停止增长,此时样品损伤点横向尺寸与纵向深度比逐渐下降。

Laser-induced optical damage often determines the service lifetime of an optic components in a high power laser system.A set of fused silica windows were artificially contaminated by sputtering the thin film material（Stainless steel）onto the surface to simulate target chamber contamination of optical components.The samples were tested by R/1 and S/1 at 355 nm with a SAGA-S laser to measure the damage threshold.The value of the damage threshold tested by S/1 is relatively accurate by comparing the S/1 and R/1 tests.The growth in lateral diameter and depth has an exponential relationship with the shot number of times.And experimental results show that the exponential growth coefficient of lateral diameter of sample is larger by 41% than that of the clear fused silica.The exponential growth coefficient of depth is larger by 39% than that of the clear fused silica.The speed of the lateral diameter damage growth slowed down and stopped after 20 shots.