VUV light scattering measurements of substrates and thin film coatings

We have developed a system that measures total and angle resolved light scattering, reflectance and transmittance at 193 nm and 157 nm. This system allows the investigation of substrates and coatings for vacuum-ultraviolet (VUV) components with high sensitivity, down to scattering levels of 1 ppm for total scatter measurement. The dynamic range of the angle resolved scatter measurement set-up exceeds 9 orders of magnitude. Methods for evaluating the quality of CaF2 substrates for low loss optical components for 157 nm are presented. By using roughness data from Atomic Force Microscopy (AFM) measurements combined with scattering measurements surface roughness as well as inhomogeneities in the bulk of the material can be studied. Results are also presented of anti-reflective (AR) and highly reflective (HR) multiplayer coatings on CaF2.