Reaction ion etching process for improving laser damage resistance of fused silica optical surface

Abstract

Laser induced damage of fused silica optics occurs primarily on optical surface or subsurface resulting from various defects produced during polishing/grinding process. Many new kinds of surface treatment processes are explored to remove or control the defects on fused silica surface. In this study, we report a new application of reaction ion etching (RIE)-based surface treatment process for manufacture of high quality fused silica optics. The influence of RIE processes on laser damage resistance as a function of etching depth and the evolution of typical defects which are associated with laser damage performance were investigated. The results show that the impurity element defects and subsurface damage on the samples surface were efficiently removed and prevented. Pure silica surface with relatively single-stable stoichiometry and low carbon atomic concentration was created during the etching. The laser damage resistance of the etched samples increased dramatically. The increase of roughness and ODC point defect with deeper etching are believed to be the main factors to limit further increase of the damage resistance of fused silica. The study is expected to contribute to the development of fused silica optics with high resistance to laser induced degradation in the future.

Effects of Ion Beam Etching on the Nanoscale Damage Precursor Evolution of Fused Silica

“…Some researchers have developed a practical technology called reactive ion etching (RIE) by combining dynamic HF chemical etching to compensate for the shortage of HF acid chemical etching for fused silica. The LIDT of fused silica surface immensely improves through the treatment of 1 µm RIE and 3 µm HF etching [14,15]. The removal amount is immensely reduced, and high surface precision is ensured when improving laser damage resistance using the two optimized technologies.…”

Traceless mitigation of laser damage precursors on a fused silica surface by combining reactive ion beam etching with dynamic chemical etching

“…Plasma etching is ideal for surface modication of fused silica as they present anisotropic means to remove the physicalstructure defects (e.g., scratches or pits) without any trace and thus smooth the optical surface. 15 Although chemical structure defects such as oxygen-deciency center (ODC) or others might be generated during plasma etching, 16 HF-etching can be used as a next step to remove them. In our previous letter, 17 we evidenced the combined process of reactive ion etching (RIE) and dynamic chemical etching (DCE) is an effective method for signicantly improving the damage resistance of fused silica optics while keeping the surface quality non-degraded.…”

Advances in IBS Coatings for space applications on the topics of curved surfaces and laser damage

“…Stolz et al [2] an exceptionally high LIDT was presented for an EB mirror for 1064nm that was ion etched before coating. Sun et al [3] improved the LIDT of fused silica substrates at 355nm for 3ns of pulse duration, and verified for an optimized etching process very low atomic carbon concentration at the surface, as well as improved surface roughness. In current activities, this promising technology is validated for UV antireflective coatings within the ESA contract 4000119563/17/NL/BJ.…”