Performance and stability evaluation of LaF₃ thin film waveplates for highpower 266 nm laser applications

Abstract

Glancing angle deposition (GLAD) enables the fabrication of thin film waveplates suitable for compact ultraviolet (UV) laser systems. SiO2 material is commonly employed due to its high laser resistance. However, all-silica waveplates exhibit instability under varying humidity because of water adsorption in the porous structure. Here, we demonstrate anisotropic LaF3 coatings deposited using both electron beam and thermal evaporation technologies. LaF3-based waveplates were fabricated and characterized under changing humidity conditions. LaF3 waveplates exhibited markedly improved environmental stability, with retardance decreasing only by 0,8% in a dry environment, compared with 5% decrease for SiO2 waveplates. These findings position LaF₃ material as a strong candidate for environmentally stable, low-loss UV polarizing optical coatings, particularly for components operating at 266 nm.