Combination of reaction ion etching and dynamic chemical etching for improving laser damage resistance of fused silica optical surfaces.

In this Letter, an effective combined process of reaction ion etching (RIE) and dynamic chemical etching (DCE) is applied for significantly improving the damage resistance of fused silica optics, while minimizing the removal amount. By optimizing the combination process and removal depth, a near-perfect optical surface of fused silica with relatively low roughness (<0.7  nm) is created with 1 μm RIE pretreatment and 3 μm DCE retreatment. In this case, the sample has a 2.4 times enhanced 0% probability damage threshold compared to the original sample. We show that the optimized combining process with a low removal amount is superior to a conventional HF-based etching process with a high removal amount in enhancing damage resistance and controlling the surface shape and roughness of fused silica. The results advance our understanding of a key factor influencing the RIE-DCE matching relationship and can lead to further optimization of associated applications, ranging from material processing to high-power laser systems.