Laser damage and evolution law of scratches on fused silica in etching

摘要

Fused silica optical elements have been widely used in high power laser systems because of their good optical and mechanical properties. However, defects such as scratches on the surface/sub-surface will inevitably occur in the process of optical components. It will affect the laser damage threshold. To simulate the effect of the defect on performance of laser radiation, evolution law of the scratches in chemical etching must be predefined. In order to determine the influence of scratch, a surface scratcher used to produce a specific scratches on the surface of the elements, and its morphology was characterized and the damage test was performed. By analyzing the morphology and characteristics of the scratches during chemical processing, and recording their fluorescence effects, it is clear that the width of the scratches increases with the depth of the etching, and the laser damage resistance is gradually improved. At the same time, the initial defects of different characteristics were clarified, the evolution rate in chemical etching was not consistent, and the impact on the ability to resist laser damage was different. In general, scratch defects have severely impaired the resistance of the device to laser damage. When the damage threshold of the component without scratches is about 23J/cm2, the damage threshold of the defect location is only less than 5J/cm~2. Through targeted chemical treatment processes, you can increase the threshold of most scratch damage to the level of no scratches.