ArF radiation resistance of optical coatings on CaF2 in relation to the surface finish of the substrate
CaF2 has received increasing attention as a promising substrate for coatings in the VUV range. Optimization of the optical properties of these optical components requires the study of basic characteristics of the coated and uncoated CaF2 substrates such as surface roughness, optical performance, absorption and scatter losses, and laser induced damage threshold. The investigations have revealed the influence of different substrate polishing grades on the quality of AR-193nm -and HR-193nm/0 degrees coated samples. LIDT values at the ArF-excimer laser wavelength were measured as high as 5.6 J/cm2 and 4.6 J/cm2 for the best AR- and HR-coated samples, respectively.