UV laser conditioning of the sol-gel SiO2 film coated fused silica optics

Surfaces of transmitting optical components for high power lasers require film coatings or other treatment to reduce their reflectivity and the attendant loss. However, laser induced damage of the antireflective (AR) coating usually limits the laser's maximum power. Experimental studies of ultra-violet (UV) laser conditioning of sol-gel coated fused silica optics was carried out to increase the laser-induced damage threshold (LIDT). The results indicate that: LIDT of coated fused silica optics is increased by nearly 50% at 351nm@5nsafterUVIaserconditioning(*); the gray haze was observed on the surface of the coated fused silica optics after UV laser conditioning with high laser fluence, and the gray haze would change to damage sites under irradiation of even higher laser fluence; the gray haze intensively reduces the transmittance of the coated fused silica optics, which means the UV laser conditioning of the coated fused silica optics should be performed with laser fluence lower than the LIDT of gray haze. (C) 2017 Elsevier GmbH. All rights reserved.