Graded Refractive-Index SiO_x Infrared Rugate Filter Prepared by Reactive Magnetron Sputtring

Rugate filter is a special inhomogeneous optical coating. The graded refractive-index profile makes it have better optical and mechanical properties than conventional homogeneous optical coating. The graded refractive index SiO_x (0≤x≤2) coating materials with precisely controlled refractive index ranging from 2.74 to 1.59 (λ=1550 nm) are deposited by tuning its oxidation degree in reactive magnetron sputtering. Then high quality SiO_x infrared rugate filters are successfully designed and fabricated by choosing proper refractive index amplitude apodization function and introducing refractive index matching layer on the interface, which provides a practical and economical technique for industrial fabrication of rugate filters.