Investigation of laser-induced damage at 248 nm in oxide thin films with a pulsed photoacoustic mirage technique

Laser damage thresholds at 248nm of TiO,, ZrO, and HfO, thin films of h optical thickness on SQ1 quartz glass substrates are determined by the photoacoustic mirage technique. Damage thresholds correlate with the band gap energy of these materials, as determined by optical spectroscopy. It is demonstrated that the damage resistance can be raised by an additional h/2 SiO, overlayer. Damage thresholds are identical for polycrystalline and amorphous film structure and not influenced by a change of substrate material from quartz to BK7 glass.