Analysis on effects of thermal treatment on refractive index and absorption properties of SiO₂ film

SiO2 films were deposited on fused silica substrates by ion beam sputtering technology and the effects of thermal treatment on optical properties were studied by ellipsometry technology and surface thermal lens technology. The effects of thermal treatment temperature on refractive index of IBS-SiO2 films were very large, as the increase of thermal treatment temperature, refractive index of SiO2 films first decrease and then increased, when the thermal treatment temperature was 550 ℃, the refractive index was the minimum. After thermal treatment, the weak absorption of SiO2 films were all reduced, the value of weak absorption was about 2 ppm. When the thermal treatment temperature was 550 ℃, the least weak absorption of 1.1 ppm was obtained. The results show that refractive index and absorption properties of IBS-SiO2 films can be largest improved by the proper thermal treatment temperature.