The Study Of Three Wave Bands Filters Used In Free Space Communication System

The filter is often used to interfere the spectral spectrum into different bands in free space laser communication. This article mainly introduces the research and preparation of three bands of near infrared optical filter. According to the design theory,TiO2was selected as the material of high refractive index and SiO2as the low one to realize the high transmittance in double bands of770～860nm and1530～1575nm spectral range while high reflection in1615～1700nm, which film stack is designed by film design software, and electron gun and ion-assisted deposition system were used for preparation. The process flow has been optimized through the adjustment of process parameters to get a good thickness uniformity of less than3%by adjusting the compensation bezel. Although the film is thick, it meets the use requirement by the test of optical properties, mechanical properties and resistance to the environment well. In an addition to these, the quality of the coating surface successfully passed the test of the surface profile instrument, meanwhile, profile p-v value is changed to achieve the desired requirements.