Properties of SiO 2 and Al 2 O 3 films for use in UV optical coatings

Properties of single-layer and multilayer Al₂O₃/SiO₂ coatings deposited by Plasma Ion Assisted Deposition (PIAD) and Low Loss Reactive Evaporation (LL-RE) have been studied with emphasis on their use in the UV and VUV spectral region. The influence of significant deposition parameters, mainly the bias voltage in the case of PIAD and the substrate temperature in the case of LL-RE, on the optical and structural properties as well as on the film stress is investigated by spectrophotometry, IR- spectroscopy, light scattering, atomic force microscopy, and laser beam deflection stress measurements. Laser photon interaction with single-layer films and multilayer coatings was studied for the different wavelengths of excimer lasers (ArF (193 nm), KrF (248 nm), XeCl (308 nm) and the 3rd harmonic (355 nm) of the Nd:YAG solid state laser. High laser damage resistance and environmentally stable optical characteristics have been accomplished for multilayer coatings, especially for KrF (248 nm) excimer laser. The influence of the surface roughness of the substrates on the surface topography and the related scatter losses of the coatings has been investigated by integrated light scattering and atomic force microscopy measurements.