Design And Preparation Of Antireflection Films On Infrared Glass Substrate

With the development of infrared technology,chalcogenide glass with excellent performance has been used as an infrared optical component,but the transmittance of chalcogenide glass in the 3-5μm band can not meet the requirements of use,and infrared thin film used in infrared detectors is also easy to be damaged by strong laser blows.In this project,an infrared film with good transmittance in the 3-5μm band and laser resistance at 1064 nm was designed and prepared for the problems of easy shedding,low transmittance,and poor laser resistance of chalcogenide glass(As₄₀Se₆₀)substrate.Ge,Zn Se,Zn S and Yb F₃monolayer films were deposited by ion beam assisted thermal evaporation technique.Ge material and Zn Se material were used as the transition layer between film and substrate,and Zn S and Yb F₃materials were combined to design the film system.The structure of the film system 1 designed with Ge material as the transition layer material is S/0.16H0.15M0.11L0.15M0.24H0.78L0.19M/A,（H-Ge,M-Zn S,L-Yb F₃）.The theoretical design spectral performance of the film is:the average transmittance of the double-sided coating sample designed in the range of 3-5μm is 98.09%,the peak transmittance is 99.9%,and the average transmittance of the single-sided coating sample in the range of 1064±40 nm is8.77%.The structure of the film system 2 designed by using Zn Se material as the transition layer is S/0.61H0.21L0.32M0.26L0.2M0.2M0.32L0.28M0.17L0.35M0.28L0.13M0.61L/A,（H-Zn Se,M-Zn S,L-Yb F₃）,the theoretical design spectral performance of the film is:in the range of 3-5μm,the average transmittance of the double-sided coating sample is 95.67%,the peak transmittance is 99.11%,and the average transmittance of the single-sided coating sample in the range of 1064±40 nm is 7.62%.The thin films were prepared by ion beam assisted thermal evaporation technology,and their spectral properties were tested.The test results show that the average transmittance of the two groups of double-sided coating samples in the 3-5μm band is 96.12%and 95.38%,respectively.The peak transmittance is 99.8%and 99.07%,respectively,and the average transmittance of the single-sided coating samples in the range of1064±40 nm is 5.34%and 4.46%,respectively.Starting from the residual stress of the film caused by the difference in the thermal expansion coefficient between the chalcogenide glass and the film material,the residual stress of the film is reduced by optimizing the baking temperature and ion energy in the preparation process,thereby improving the adhesion of the film on the chalcogenide glass substrate.In the optimization of the process parameters of the two groups of films,the best parameters for the two groups of films to meet the requirements of the adhesion test were obtained.The baking temperature was 70°C,the ion energy was 100 e V,and the ion beam current was 20 m A.Under this parameter,the residual stresses of the two groups of multilayer films were-2.5 MPa and-30.0 MPa,respectively.The laser damage threshold test of the thin film showed that the laser damage threshold of the Zn S and Yb F₃monolayer films prepared without ion beam assistance was 3.3 J/cm²and8.6 J/cm²,respectively,and the laser damage thresholds of the prepared thin film after using ion beam assisted were 5.2 J/cm²and 12.4 J/cm²,respectively.According to the best process parameters,the single-layer film and two groups of multilayer films were prepared and the laser damage threshold was measured,the laser damage threshold of film 1 was low,and the influencing factor was that Ge material with large absorption and extremely low laser damage threshold was added to film 1,and the laser damage threshold of film 2 was 7.6 J/cm².