Understanding the effect of HF-based wet shallow etching on optical performance of reactive-ion-etched fused silica optics

Laixi Sun; Ting Shao; Xinda Zhou; Weihua Li; Fenfei Li; Xin Ye; Jin Huang; Shufan Chen; Bo Li; Liming Yang; Wanguo Zheng

doi:10.1039/d1ra04174f

Understanding the effect of HF-based wet shallow etching on optical performance of reactive-ion-etched fused silica optics

RSC Adv. 2021 Sep 1;11(47):29323-29332. doi: 10.1039/d1ra04174f.

Authors

Laixi Sun¹, Ting Shao¹, Xinda Zhou¹, Weihua Li¹, Fenfei Li^{1

2}, Xin Ye¹, Jin Huang¹, Shufan Chen¹, Bo Li¹, Liming Yang¹, Wanguo Zheng^{1

3}

Affiliations

¹ Research Center of Laser Fusion, China Academy of Engineering Physics Mianyang 621900 P. R. China yexin@caep.cn.
² School of Materials Science and Engineering, Southwest University of Science and Technology Mianyang 621010 P. R. China.
³ IFSA Collaborative Innovation Center, Shanghai Jiao Tong University Shanghai 200240 P. R. China.

Abstract

The optical performance of fused silica optics used in high-power lasers is known to depend not only on their surface damage resistance, but also on their surface quality. Previous studies have shown that good fused silica damage performance and surface quality can be achieved by the use of reactive ion etching (RIE), followed by HF-based wet shallow etching (3 μm). In this study, two kinds of HF-based etchants (aqueous HF and HF/NH₄F solutions) were employed to investigate the effect of HF-based etching on the optical performance of reactive-ion-etched fused silica surfaces at various HF-based shallow etching depths. The results showed that the addition of NH₄F to HF solution makes it possible to produce a high-quality optical surface with a high laser-induced damage threshold, which is strongly associated with the surface roughness and fluorescence defect density. Additionally, changing the HF-based etching depth over the range from 1 μm to 3 μm can affect the surface damage resistance and absorption performance of RIE-treated fused silica. The light-scattering results indicate that the point defect density plays an important role in the determination of the HF-based etching depth. Understanding these trends can enable the advantages of the combined technique of RIE and HF-based etching during the fabrication of high-quality fused silica optics.