Relaxation processes in laser-excited dielectrics

Ultrashort laser pulses generate free electrons in dielectrics and thus enable the absorption of laser energy. The electron density is a crucial parameter here, but also the energy distribution of the excited electrons plays a remarkable role. We calculate it in detail with help of full Boltzmann collision integrals. Here, we show a standard example of the evolution of the distribution function of electrons in valence-as well as in conduction band, and analyze the influence of different collision processes. The energy distribution can deviate from a Fermi distribution for several hundreds of femtoseconds, driven by an interplay of secondary ionization processes and the cooling by the lattice. We study in detail these relaxation processes and discuss their mutual influence.