熔石英元件抛光加工亚表面缺陷的检测

摘要

Accurate detection of subsurface defects is the premise and foundation for research of subsurface damage of fused silica optics,which is crucial to ensure machining quality. The subsurface defects that generated in polishing process, such as hydrolysis layer, defect layer depth and subsurface damage morphology of fused silica components were quantitatively detected by HF acid etching method in this paper. Type and element content of impurities along the depth distribution were studied by X⁃ray fluorescence spectrometry technology, and the method for determining the depth of subsurface damage was presented. Because there existed hydrolysis layer and sub⁃surface defects layer, with the increase of etching time, the etch rate showed a decreasing trend and etching rate decreased significantly in the initial stage. When the etching depth exceeded a certain value, the defect layer would be completely removed by etching method, then etch rate remained unchanged. In addition, there were a variety of surface and sub⁃surface defects in polishing surface, so there were also some differences in subsurface damage morphology, width and depth of the scratches at different etching depths.%亚表面缺陷的准确检测是进行亚表面损伤研究的前提和基础，对保证光学元件加工质量至关重要。基于HF酸化学蚀刻法对熔石英元件抛光加工产生的亚表面水解层、缺陷层深度和亚表面损伤形貌进行了定量检测，并利用X射线荧光光谱法研究了熔石英抛光试件杂质元素的种类和元素含量沿深度分布规律，提出了熔石英元件抛光加工亚表面损伤深度的判定方法。研究表明：由于水解层和亚表面缺陷层的存在，熔石英抛光试件的蚀刻速率随着时间的增加呈现递减的趋势，且在蚀刻的初始阶段蚀刻速率下降尤为明显；当蚀刻深度超过某一特定值后，全部或部分覆盖在水解层以下的缺陷层将会被完全蚀刻去除，蚀刻速率基本保持不变；另外，熔石英抛光试件存在多种形式的表面及亚表面缺陷，在不同蚀刻深度，亚表面损伤形貌、划痕的宽度和深度也存在一定的差异。