低亚表面损伤石英光学基底的加工和检测技术

制备低亚表面损伤的超光滑光学基底,是获得高损伤阈值薄膜的前提条件。针对石英材料在不同加工工序中引入亚表面损伤层的差异,首先利用共焦显微成像结合光散射的层析扫描技术,对W10和W5牌号SiC磨料研磨后的亚表面缺陷进行了检测,讨论了缺陷尺寸与散射信号强度、磨料粒径与损伤层深度间的对应关系;同时,采用化学腐蚀处理技术对抛光后样品的亚表面形貌进行了刻蚀研究,分析了化学反应生成物和亚表面缺陷对刻蚀速率的影响、不同深度下亚表面缺陷的分布特征,以及均方根粗糙度与刻蚀深度间的联系。根据各道加工工艺的不同采用了相应的亚表面检测技术,由此来确定下一道加工工序,合理的去除深度,最终获得了极低亚表面损伤的超光滑光学基底。

Fabrication and detection technique of fused silica substrate with extremely low subsurface damage

The supersmooth optical substrate with extremely low subsurface damage is essential to obtain high laser damage threshold films. In view of the difference in subsurface morphology, the laser confocal microscope technique combined with light scattering method is firstly used to detect the subsurface defects of fused silica substrates ground by brand W10 and W5 SiC abrasive particles, and the relation between the defects size and the scattering intensity are discussed. Then chemical etching method is introduced to expose the inner features at arbitrary depth for the polished sample, the influences of chemical resultant and redeposition layer on etching rate are analyzed, and the distribution and depth of damage layer are estimated. Furthermore, the relation between RMS roughness and etching