Design And Preparation Of Laser Film On Sapphire Substrate

The middle infrared band 3～5μm is a window of the commonly used in the detection process, which is often suffer from damage by high energy laser radiation. Therefore many researchers pay more attention to the development of the IR antireflective thin film which has a protective effect against the laser on the lens of the infrared detector. Si, Ge, Sapphire, etc. are commonly used in the mid-infrared materials, but Si and Ge have softer texture and poorer mechanical strength. However, the sapphire has good transmittance in wide band including ultraviolet, visible and infrared light, the sapphire is often used as a high energy laser window material. Therefore the study of design and preparation of laser film on sapphire substrate has important practical significance.Basing on the previous research and fully analyze, we choose SiO2 as low refractive index material and HfO2 as high refractive index material in this paper. Under the principle of the electric field intensity optimization, we got the membrane system G 0.571H 0.143LHL A by using TFCALC software. After repeated experiments and process optimization, we finally adopted thermal evaporation technique and successfully prepared 3～5μm anti-reflection coating on the sapphire substrate.Testing results show that the peak transmittance attained 92.3%, the average transmittance attained 90.3% and laser-induced damage threshold (LIDT) of the thin film reach to 5.3J/cm2 (1064nm,10ns). The prepared films were irradiated by high-energy laser beam, laser damage threshold of AR coating finally increased from 5.3J/cm2 up to 5.9J/cm2, which meet the requirements of the demand.