Increased Laser-Damage Resistance of Sol-Gel Silica Coating by Structure Modification

Sol-gel silica coatings prepared for high-power laser applications were optimized by a two-step structure modification through treatment of the sol with poly(ethylene glycol) (PEG), followed by treatment of the coating with ammonia. The effect of each treatment on the laser-induced damage threshold (LIDT) at 1064 nm wavelength was studied, mainly in terms of the change in the coating's structure. Both of these treatments increased the LIDT, and the greatest LIDT was achieved by combining the two treatments. The LIDT increase can be attributed to the decrease in structural defects such as nodular defect and the variety of pore-distribution, resulting from PEG and ammonia treatments, respectively. The procedure of producing coated glass with high LIDT for 1064 nm laser irradiation was suggested, involving substrate etching, sol modification, and coating treatment.