: Kaiser, N.; Welsch, E.; Ettrich, K.; Blaschke, H.; Schäfer, D.; Thomsen-Schmidt, P.

Abstract
The interaction of UV laser radiation with optical coatings is shown to be properly investigated by a pulsed two probe-beam photothermal technique. UV laser damage resistivity studies on LaF3/MgF2, Al2O3/SiO2, HfO2/SiO2 multilayer stacks have been performed at lambda = 248 nm, tau = 20 ns. Investigating these by changing the number of (HL) pairs and the substrate material, optical and thermal coating properties were shown to be responsible for UV single-shot laser damage. Similarly, the damage threshold of selected samples is to be influenced by the deposition technique. The influence of the bandgap energy of typical UV thin-film oxide materials on the damage has been investigated. Furthermore, multishot damage measurements on LaF3/MgF2, high-reflecting multilayer coatings reveal the accumulation of laser energy in the predamage range.