Investigation of Sc2O3 for high laser durability ultraviolet coating applications

Abstract

The potential application of high-power UV lasers as an illumination source has stimulated the study and the development of new materials with high refractive index as constituents for optical devices. As a wide band gap and high refractive index material, Sc2O3 has been explored for UV optical coating applications. The physical and optical properties of Sc2O3 films are strongly dependent upon the deposition method, growth conditions and some postdeposition treatment. Plasma ion assisted deposition (PIAD) is a well-known advanced deposition technique to deposit dense dielectric films with superior optical properties such as smoothness, low scatter, and environmental stability. This research work is to apply PIAD process to obtain homogenous and UV transparent Sc2O3 layers to be paired with SiO2 to prepare UV 266nm antireflection coatings. Higher bandgap materials require higher photon energies when absorbed by a material and converted to electron excitation which promotes a valence electron to the conduction band. This would result in higher laser damage threshold. The coating performance and UV laser induced damage threshold of these AR coatings made with Sc2O3 layered with SiO2 are compared with the coatings made with HfO2-SiO2 paired AR coatings. The Sc2O3-SiO2 paired coatings demonstrate a comparable low reflectivity to AR coatings using HfO2 as high index materials. Furthermore, it shows a higher UV laser damage threshold than HfO2-SiO2 paired AR coatings. Sc2O3 demonstrates its potential application through this research work as optical interference coatings for high power UV laser devices.