Extended lifetime of fluoride optics

Abstract

Surface and coating technology plays an important role for extending lifetime of fluoride optics for ArF excimer laser applications. Optically finished CaF2 optics is characterized as top surface and subsurface by means of non-distractive quasi-Brewster angle technique. The subsurface is revealed by removing the top surface via distractive methods. Color centers on plasma ion and laser irradiated CaF2 optics are discussed. The results suggest that fluorine depletion is associated with laser damage, dense smooth coatings enable one to extend the lifetime of CaF2 optics.