Scaling laws in laser-induced potassium dihydrogen phosphate crystal damage by nanosecond pulses at 3ω

A model for the description of laser-induced damage in bulk potassium dihydrogen phosphate (KDP) by nanosecond laser pulses is addressed. It is based on the heating of nanometric plasma balls whose absorption efficiency is described through the Mie theory. The plasma optical indices are then evaluated within the Drude model framework. This modeling provides an evaluation of the scaling law exponent x linking the damage threshold laser pulse energy density F-c to the pulse duration tau as F-c=alpha tau(x), where alpha is a constant. The inverse problem for which the knowledge of experimental data allows one to determine physical parameters of the model is considered. The results suggest that the critical plasma density is reached in a time much shorter than the pulse duration. Information about the nature of defects responsible for the damage initiation is also provided. (C) 2008 Optical Society of America.