Investigation of the absorption induced damage in ultraviolet dielectric thin films

The interaction of UV laser radiation with optical coatings is investigated by a pulsed two-probe-beam photothermal technique. UV laser damage resistance studies on LaF3/MgF2, Al2O3/SiO2, HfO2/SiO2 multilayer stacks are performed at lambda = 248 nm and tau = 20 ns. By investigating the relationship of the number, of high-low (HL) pairs and the substrate material, optical and thermal coating properties are shown to be responsible for UV single-shot laser damage. The damage threshold of selected samples is influenced by the deposition technique. The influence of the bandgap energy of typical UV thin film oxide materials on the damage is investigated. Furthermore, multishot damage measurements on LaF3/MgF2, high-reflection multilayer coatings reveal the accumulation of laser energy in the predamage range and lead to an increase in absorption.