Modeling of non-equilibrium laser-induced plasmas

The interaction of an intense laser beam with a medium which is normally transparent to optical or infrared radiation may lead to the formation of a plasma. This phenomenon, often referred to as laser induced breakdown, was observed for the first time in the 1960s, and has since then been investigated. Despite the achievements in understanding the physics of the problem, there still remain some points to be clarified regarding the plasma formation mechanism such as the interplay between multi-photon and cascade ionization, and the role of plasma expansion and beam refraction. Motivated by this scenario, a computational laser-plasma interaction model accounting for beam refraction and attenuation, and cascade and multi-photon ionization is developed. The plasma is treated as a non-equilibrium multi-component fluid based on the Navier-Stokes equations. The propagation of the laser beam is modeled based on an envelope equation. Numerical solutions are obtained based on an implicit finite volume method. Applications consider the laser discharge in quiescent molecular oxygen.