Electronic excitation and relaxation processes in wide band gap dielectric materials in the transition region of the Keldysh parameter

Numerical modeling of electronic excitation processes induced by ultra-short laser pulses in dielectric materials is performed. The developed model is based on a detailed kinetic description and accounts for the absence of equilibrium in the electronic subsystem. The photoionization process is first analyzed for different laser intensities. It is shown that the probability of this process depends strongly on the Keldysh parameter and effective ionization potential, which are calculated as a function of the laser field. Electron energy distributions are calculated and the average energy is analyzed as a function of laser parameters. For laser intensities corresponding to the maximum of this dependency, only around 1% of electrons are shown to achieve the energy required for the impact ionization.