Optical filter of the window on 0∼25 degree incidence angle 980nm semiconductor detector

In this paper a window with band-pass filter is used on 980nm semiconductor detector. The window is designed with substrate HW800, materials whose index are N h =2.4, N l =1.7, and center wavelength 990nm. Ion Beam Associated Deposition (IBAD) is introduced to film-growing process for improving the film structure and developing the gas' ability of reaction. And all processes are monitored by both optical and crystal controller. Finally we obtained the experimental results, with good average transmissivity T avg >90% not only on waveband 960–1030nm at 0 incidence angle, but also on waveband 940–1000nm at 25 incidence angle. This window blocks off other waveband(400–760nm, 1100–1200nm) as noise, and obtains good signal intensity from 0°–25° incidence angle at the same time. At the same time, this design overcomes the shortcomings such as high cost and difficulty in control, in the case when double-side film-growing is necessary in traditional processes.