Femtosecond laser-induced heating of electron gas in aluminium

The distribution function of free electrons in metal is calculated for irradiation of aluminium with an ultrashort laser pulse of moderate intensity. We consider inverse Bremsstrahlung absorption, electron-electron and electron-phonon interaction. Our theoretical model is based on Boltzmann equations and describes each considered process by a corresponding collision integral. The results show the excitation and relaxation of the free electron gas. Energy transfer to the phonon gas is calculated. Our model predicts linear absorption for intensities up to damage threshold. The calculated absorbed energy compares very well with known absorption characteristics.