Study Of The Laser Filters Using At The Wave Band Of 1.2-3?m

In optical systems,almost optical components are coated with a variety of films to achieve specific optical properties.For infrared window films used in laser systems,it is demand that they should have the properties of not only improving the transmission performance and image quality of the system,but also being a high laser induced damage threshold.Aiming at the actual requirements of the project,based on the fundamental theory of thin film optics and the characteristics of electric field intensity,the long-pass filter and anti-reflection film structure of the window surface were designed and prepared by using the ion beam-assisted thermal evaporation deposition technique.After processing optimization and post-treatment,the required film samples are obtained.The ZnS and MgF₂ monolayer films,as high and low refractive index materials respectively,were chosen and deposited on a single-side polished Si substrate by using the ion beam-assisted thermal evaporation deposition technique,and the film preparation process parameters and optical constants?n and k?were determined in this paper.Considering the spectral properties and intensity distribution of electric field,the 1.064?m high reflection,1.2-3?m anti-reflection long wave pass filter and 1.2-3?m anti-reflection film were designed by a TFCale software.The film structure:the long-pass film system and the anti-reflection film are G|4H2L1.5H2L2H1.5L2H4L|A and G|3.5H3.5L|A.Long wave pass filter and anti-reflection film were coated on double-side polished Si substrate,and the spectral characteristics and laser damage threshold of the thin-film device were tested.In the 1.2-3?m,the peak transmissivity can approach 98.48%,the average transmissivity is 92.35%and the transmittance is 5.09%at the wavelength of 1.064?m.The laser induced damage threshold?LIDT?of the film sample is 4.3J/cm².?laser wavelength1064nm,pulse width 10ns?Anti-reflection films were prepared on two sides of the double-side polished Si substrate,and the spectral characteristics of the thin-film devices were tested.In the 1.2-3?m band,the peak transmissivity can approach 99.57%and the average transmissivity is 96.21%.At last,The long wave pass films were treated by ion beam and annealing treatment.It was found that the appropriate processing parameters contributed to the improvement of the laser induced damage threshold.When the ion beam energy E=600eV,the LIDT is 5.8J/cm².At annealing temperature t=250°C,the LIDT is 6.3J/cm².