Design and preparation of laser film on sapphire substrate

Sapphire crystal as a kind of good material has a good transmittance in the ultraviolet, visible, infrared, which was widely used in the high-intensity laser system as the window material. Anti-reflection thin films on sapphire substrate were commonly used in high-energy laser system in the middle infrared bands 3~5μm and these thin films are very easily damaged for high energy laser system. In this paper, we adopt thermal evaporation technique on the sapphire substrate was prepared by design of single layer and multilayer anti-reflection coatings system so that the infrared transmittance satisfy the design requirements. The results of transmittance and laser damage performance tests show that the anti-reflection coating of 3~5μm transmittance is more than 97% on average, Laser-induced damage threshold (LIDT) is more than 5J/cm2 (1064nm), which means that this method could obtain a high-quality laser film.