HF酸刻蚀提升熔石英亚表面划痕抗损伤性能的机理

用HF酸刻蚀熔石英元件,研究刻蚀对元件后表面划痕的形貌结构及损伤性能的影响,探索损伤阈值提升的原因.时域有限差分算法理论计算结果表明:对于含有50 nm直径氧化锆颗粒的划痕,对入射光调制引发场增强的最大值是入射光强的6.1倍,且最强点位于划痕内部氧化锆颗粒附近,而结构相同但不含杂质的划痕引发的最大场增强为入射光强的3.6倍,最强区位于划痕外围;HF酸刻蚀能够有效去除划痕中的杂质,改变划痕结构,增加其宽深比值,经刻蚀的划痕对入射光调制引发场增强降低到入射光强的2.2倍.实验结果表明,经过深度刻蚀的划痕初始损伤阈值较刻蚀之前提高一倍多;光热弱吸收测试仪测试刻蚀后划痕对1 064 nm激光的吸收最大值仅为230 ppm.HF酸刻蚀同时可以提升元件整体损伤阈值,由于元件上无缺陷区域损伤阈值随刻蚀的深入先增加后降低,因此HF酸刻蚀应进行到元件损伤阈值提升到最大值为止.

Mechanisms of HF Solution Improving Damage Properties of Fused Silica Subsurface Cracks

Fused silica optic was etched by HF solution, the morphology and damage properties of micro subsurface cracks were studied, and factors increased crack damage properties were explored. Finite difference time domain algorithm was used to calculate light intensification in the vicinity of cracks. Calculation results show that light intensification caused by crack contained with ZrO₂ particle (diameter 50 nm) is 6.1 times of the incident light, and the maximum intensity lies inside the crack and close to the particle. However the light intensification caused by crack with the same structure and without particles inside is 3.6 times of the incident light, and the maximum intensity lies outside the crack. By HF etching, contaminations in crack are eliminated, breath depth ratio of the crack is increased, and light intensification caused by the etched crack is only 2.2 times the incident light. Experimental results also indicate that damage threshold of deeply etched crack is increased by one time, and 1 064 nm absorption of it is only 230 ppm. Damage performance of crack free area is also improved by HF ethcing, but damage threshold of the crack free area does not increase as along as etching proess goes on. It begins to decrease after reaching a maximum value, thus etching process will terminate till damage threshold of the crack free area reaches its maximum value.