Influence of temperature variation on polarization characteristics of silver thin film mirror

Optical payloads in space remote sensing applications impose increasingly high requirements on system polarization control. As a wide spectral reflector, the polarization characteristics of silver thin film mirror usually changes with the ambient temperature. In this paper, silver thin film mirrors with low polarization sensitivity are designed and fabricated. The changes of polarization characteristics and reflection spectrum of the mirrors with room temperature from 25℃ to 150℃ are investigated at 45° and 60° incident angles. The refractive index of silver thin film increases in spectral range of 350 nm to 1 200 nm with the increase of temperature. The phase difference Δ between the s and p light in the reflected light of the silver film mirror is reduced in the wavelength range of 350 to 600 nm, keep stable in 600-650 nm, and increases in the wavelength range of 650 to 1 200 nm. The surface morphology of the silver film and mirror changes, and the surface scattering and absorption increases when temperature reaches 125℃, resulting in a decrease in reflectivity in the 350-900 nm band and even a decrease of about 25% in the wavelength of 350 nm.