Laser damage studies on MgF2 thin films

The results of laser damage studies performed at 248 nm (KrF excimer laser) on MgF2 thin films deposited by different techniques (electron-beam evapor ation, thermal boat evaporation, and ion-beam sputtering) on fused silica a nd CaF2 substrates are presented. We find that the films deposited on CaF2 substrates by the electron-beam evaporation technique present the highest d amage threshold fluence (9 J/cm(2)). The photoacoustic (PA) beam deflection technique was employed, in addition to microscopical inspection, to determ ine laser damage fluences. We confirm, by scanning electron microscopy anal ysis of the damaged spots, the capability of the PA technique to provide in formation on the mechanisms leading to damage. The dependence of both laser damage fluence and damage morphology on the film deposition technique, as well as on the film substrate, is discussed. (C) 2001 American Vacuum Socie ty.