Reflectivity Enhancement of Silver-based Mirror in the wavelength range 400nm-450nm

摘要

With the development of remote sensing technology, the short working wavelength has been extended to 400nm in manycurrent international spatial optical remote sensors. However, the reflectance in the wavelength range from 400nm to450nm cannot meet the requirement for silver-based mirror. In order to solve this issue, SiO_2 and Ta_2O_5 used asreflectivity enhancement layers are deposited on the silver layer. Simultaneously, the two dielectric films also protect themetallic silver film to from corroding in complicated environment. During the deposition process of Ta2O5 dielectriccoating material, oxygen partial pressure, anode voltage and current of the ion source are optimized to get higherrefractive index. The values of stress of the SiO_2 layer and the Ta_2O_5 layer are analyzed to get the adhesive coatings bythe Stony formula and the process parameters of SiO2 dielectric coating material are obtained. The optical constants ofthese two dielectric films are established by using the Cauchy dispersion formula and the incoherent reflective theory,and then the thicknesses of them are optimized by simplex algorithm. SiO_2 layer and Ta_2O_5 layer are sequentiallydeposited on the silver layer. The measurement results show that the average reflectivity of the wavelength ranges400nm-450nm and 400nm-900nm reaches over 95% and 98%, respectively. The reflectivity enhanced silver-basedmirror also passes the adhesion test according to relevant technique requirements.