THERMOELASTIC AND ABLATION MECHANISMS OF LASER DAMAGE TO THE SURFACESOF TRANSPARENT SOLIDS

An investigation is reported of the relationships governing laser dama ge to the surfaces of transparent dielectrics, initiated by absorbing inclusions, under repeated irradiation conditions. It is shown that ul trashort pulses produce damage by the ablation mechanism, whereas 'lon g' laser pulses cause damage by the thermoelastic mechanism. The relat ionships established for the change in the damage mechanism with chang e in the pulse duration apply also to intrinsic (collisional and multi photon ionisation) damage mechanisms.