Absorption of laser light by ions as a mechanism of optical damage in solids

Abstract

A model is suggested for damage of pure transparent dielectrics by ultrashort laser pulses. This model is based on the following concepts. The crystal atoms can absorb light performing, simultaneously, diffusion jumps. After such a jump a defect is generated in the lattice. Accumulation of defects leads to amorphization of the sample. It is believed that amorphization of the focal region of the crystal is the initial stage of the damage. Dissipation of this energy spools the further stages of damage, up to the crack formation. Absorption of light and diffusion jump is a single quantum-mechanical transition. It is inertial-free, and therefore it can be caused by pulses of any duration.It is only important that there should be a sufficient number of diffusion jumps during the pulse for the focal region to get amorphized. This defines a threshold condition for the damage. In the present paper the quantum mechanical probability of photo induced diffusion jumps is found, as well as the critical parameters of the laser field. Estimates for these parameters resulted in realistic values, thus the suggested scenario can play an essential role in optical damage.