Ionization-induced dynamics of laser-matter interaction in a focused laser pulse: A comparative analysis

We study the laser-matter interaction via optical-field ionization of a medium in a focused ultrashort laser pulse by means of the finite-difference-time-domain modeling of Maxwell's equations. General aspects of the ionization-induced dynamics with TE- and TM-polarized laser pulses are analyzed. It is shown that there are two qualitatively different regimes of the interaction depending on the angle of the laser beam focusing. At comparatively low angles plasma distributions are smooth; however, due to departure from the quasioptical behavior of light rays in self-generated plasma, lateral large-scaled plasma structures can also be produced, leading to additional beam focusing and correspondingly to higher electron densities. At tight focusing, small-scaled plasma structures are generated that strongly influence field distribution, energy deposition, and scattering characteristics. The influence of electron collisions and the Kerr effect are also analyzed.