基底亚表面裂纹对减反射膜激光损伤阈值的影响

Influence of Subsurface Cracks on the Laser Damage Resistance of Anti-Reflection Coated Fused Silica

利用化学沥滤技术,分析了亚表面裂纹对基底表面和减反射膜激光损伤阈值(LIDT)的影响。通过去除或保留研磨裂纹,获得了亚表面裂纹数密度有明显区别的两类基底。为了凸出亚表面裂纹层的作用,基底采用化学沥滤去除另外一种可能的影响因素,即再沉积层中的抛光杂质。然后采用电子束蒸发镀制HfO2/SiO2减反射膜。355nm激光损伤阈值测试结果和损伤形貌分析证实了基底亚表面裂纹对减反射膜抗激光损伤能力的负面影响。根据熔石英基底抛光表面的烘烤现象,提出了亚表面缺陷影响膜层激光损伤的耦合模型。

The impact of subsurface cracks on the laser damage resistance of bare and anti-reflection （AR） coated fused silica are experimentally investigated using chemical leaching. Two kinds of substrates with the subsurface cracks number density of obviously different are obtained by retaining or removing the grinding cracks. To highlight the effect of the subsurface cracks, the photoactive impurities in the polishing layer, as a competing damage mechanism, are minimized by chemical leaching. Then the HfO2/SiO2 anti-reflection coatings are deposited by electron beam evaporation. 355 nm laser-induced damage threshold （LIDT） test results and damage morphology analysis verifie the negative effect of subsurface cracks on the LIDT of AR coated surfaces. According to the heating morphology of polished fused silica surface, a coupling model between the subsurface defects of substrate and the laser damage of coatings is proposed.