Preparation of Transmissive Optics Coated by Sol-gel Method With High Laser-induced Damage Threshold

Transmissive optics with high laser-induced damage threshold (LIDT) were prepared, with K9 and silica glass as substrates that were coated with sol-gel porous silica coatings, for 1 064 nm and 355 nm laser irradiation. The factors that effect LIDT were systematically analyzed considering both the coating and substrate qualities. The LIDTs of the optics substantially increase by combining the substrate treating and film modification. The film modification was realized by two steps, that is, modifying the silica sol with polyethylene glycol and coating with ammonia treatment. The film eventually features less structural defects and better uniformity, and presents stronger ability of resisting laser damage than the substrate without any treatment. As for the substrate treatment, chemical etching and super-polishing were employed to obtain super smooth surface and less-defects subsurface, which resulted in an increase in the LIDT of K9 glass (at 1 064 nm) by 1.3 times and that of silica glass (at 355 nm) by 4.1 times. The LIDTs of this optics don’t decrease after the treated glass were coated with the modified films, meaning that the LIDTs of the modified films are high enough to match the treated substrates.