5. Continuum Models of Ultrashort Laser–Matter Interaction in Application to Wide-Bandgap Dielectrics

This chapter is aimed to provide a basic introduction into the principles of modeling approaches which have been developed for getting insight into various interconnected processes initiated inside transparent materials under the action of ultrashort laser pulses with consequences in volumetric modification of material structure. In view of extreme complexity of the problem, modification mechanisms and their driving processes are still far from complete understanding and require further considerable research efforts. Here we focus our consideration on established approaches that treat matter as a continuum medium. They include models describing laser beam propagation through a non-linear transparent glass or crystal with kinetics of electron plasma generation upon beam focusing and attempts to consider further material evolution with insights into thermodynamic state, stress dynamics, and plastic deformations. We underline that the quality of the final structures is determined by the synergetic action of laser excitation/relaxation kinetics, thermodynamics, and mechanics. The chapter does not pretend to completeness and aims to outline main ideas, achievements, and most intriguing findings which are still waiting for explanations and theoretical treatments.