HIGH DAMAGE THRESHOLD AL2O3 SIO2 DIELECTRIC COATINGS FOR EXCIMER LASERS/

Today there are hardly any products in optical industry which do not e mploy optical coatings. Mainly in the UV spectral region, laser induce d damage thresholds of these coatings are a limiting factor for the de velopment of cost-effective optics. The high power optical components and dielectric coatings have to be developed to cavity optics, beam re lay optics, mask imaging optics, and masks. Therefore, we used ultralo w loss conventional electron-beam evaporation for Al2O3/SiO2 dielectri c multilayers. Based on a fundamental coating technique, both multilay er mean background absorption and absorption at localized spikes have been reduced drastically. The resulting KrF laser damage threshold of HR coatings is 16 J cm(-2) (1-on-1, 30 ns MSG). Multilayers have been characterized by atomic force microscopy, photothermal microscopy, abs orption measurements, and spectroscopy of sputtered neutrals.