Collision frequencies and absorption calculations for ultra-short laser interactions with dielectric materials
Résumé
Laser-induced electronic excitation, absorption and relaxation are the key issues in ultra-short laser interactions with dielectric materials. To numerically analyze these processes, a detailed non-equilibrium model is developed based on the kinetic Boltzmann equations without any appeal to the classical Drude model. The calculations are performed including all possible collisional processes. As a result, electron energy distributions are obtained allowing a better analysis of ultra-short laser interactions. A remarkable effect of the laser-field on collision frequencies is demonstrated leading to smaller free-carriers absorption than the one predicted by Drude model with a non-field dependent collision frequency. Both electron-electron and electron-phonon relaxation are then examined, and the mean energy density of the electron sub-system is investigated as a function of laser fluence and pulse duration. The developed model is useful for many laser applications including high precision in laser treatment, laser-assisted atomic probe tomography, and for the development of new powerful laser systems. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.