INVESTIGATION OF THE ABSORPTION INDUCED DAMAGE IN ULTRAVIOLET DIELECTRIC THIN-FILMS

The interaction of UV laser radiation with optical coatings is investi gated by a pulsed two-probe-beam photothermal technique. UV laser dama ge resistance studies on LaF3/MgF2, Al2O3/SiO2, HfO2/SiO2 multilayer s tacks are performed at lambda=248 nm and tau=20 ns, By investigating t he relationship of the number of high-low (HL) pairs and the substrate material, optical and thermal coating properties are shown to be resp onsible for UV single-shot laser damage. The damage threshold of selec ted samples is influenced by the deposition technique, The influence o f the bandgap energy of typical UV thin film oxide materials on the da mage is investigated. Furthermore, multishot damage measurements on La F3/MgF2 high-reflection multilayer coatings reveal the accumulation of laser energy in the predamage range and lead to an increase in absorp tion. (C) 1997 Society oi Photo-Optical Instrumentation Engineers.