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.