Surface laser damage thresholds determined by photoacoustic deflection

The technique of intensity dependent photoacoustic probe beam deflection has been applied to the determination of surface damage thresholds. We take advantage of an unambiguous correlation between the degree of laser damage and the energy in the generated acoustic pulse. The high sensitivity of this method, cross checked by measuring scatter losses in reflection, is independent of any surface optical properties. As an example for optical materials, damage thresholds for MgF2 and CaF2 have been determined to be about 1.4 GW/cm2 , and for LiF to be about 0.2 GW/cm2 .