Optical Properties of Durable Oxide Coatings for Infrared Applications

摘要

There is a continuing need for durable and protective coatings for long wavelength infrared (LWIR) windows and domes as a result of the environmental and mechanical vulnerability of most LWIR transparent materials. Diamond coatings would be ideal except for the fact that relatively high deposition temperatures are required to deposit films having low optical absorption. Diamond-like carbon films deposited at low temperatures are typically too absorbing or highly stressed. Certain transition metal oxide films can be used successfully for many applications, are very durable and can be deposited by traditional thin film deposition methods. In this study, Y_2O_3, ZrO_2 and HfO_2 films are deposited and characterized, in particular their absorption coefficients as a function of wavelength are derived at wavelengths in the LWIR. Durable oxide coatings are deposited over full-size LWIR windows.