Absorption in and laser damage to KDP and DKDP crystals

A description is given of an optoacoustic method for determination of weak optical absorption utilizing acoustic resonance properties of the investigated samples. Application of this method to KDP and DKDP crystals demonstrated its extensive potentialities and made it possible to determine separately the bulk and surface absorption of the first and second harmonics of a neodymium laser. The energy absorbed in a damage region and the pressure in this region were determined at radiation intensities corresponding to the damage threshold. The process of damage by 40-ns laser pulses occurred at the same pressure in samples with damage thresholds (optical strengths) differing by tens of times. A breakdown mechanism, characteristics of the damage region, and some properties of the damage-initiating absorbing centers were determined.