HIGH DAMAGE THRESHOLD AL2O3/SIO2 DIELECTRIC COATINGS FOR EXCIMER LASERS

Today there are hardly any products in optical industry which do not employ optical coatings. Mainly in the UV spectral region, laser induced damage thresholds of these coatings are a limiting factor for the development of cost-effective optics. The high power optical components and dielectric coatings have to be developed to cavity optics, beam relay optics, mask imaging optics, and masks. Therefore, we used ultralow loss conventional electron-beam evaporation for Al2O3/SiO2 dielectric multilayers. Based on a fundamental coating technique, both multilayer 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, absorption measurements, and spectroscopy of sputtered neutrals.