Preparation of ultra-broadband antireflective coatings for amplifier blast shields by a sol–gel method

摘要： A type of λ/4–λ/4 ultra-broadband antire?ective coating has been developed using modi?ed low refractive silica and high refractive silica layers by a sol–gel dip coating method for ampli?er blast shields of the Shen Guang II high power laser facility (SG-II facility). Deposition of the ?rst layer (high refractive index silica) involves baking at 200 ?C in the post-treatment step. The second layer (low refractive index, n = 1.20) uses low refractive index silica sol modi?ed by acid catalysis. Thermal baking at temperatures no less than 500 ?C for 60 min offers chemical stability, ethanol scratch resistance, and resistance to washing with water. The average residual re?ection of dual-side-coated fused silica glass was less than 1% in the spectral range from 450 to 950 nm. Transmission gain has been evaluated by taking into account angular light, and the results show that the transmission gain increases with increasing light incidence. Even at 60?, the transmission spectrum of the broadband antire?ective coating effectively covered the main absorption peak of Nd:glass.