Impact of the electron-phonon coupling factor and electron heat capacity on the thermal response of targets irradiated by femtosecond laser

Abstract

This work investigates the impact of the electron temperature-dependent electron-phonon coupling factor and the electron heat capacity on the thermal evolution of a copper target irradiated by femtosecond laser pulses. These effects were studied using their recently developed two-dimensional two-temperature model. Two models were implemented to account for the electron-phonon coupling calculation. The first were the calculations of the electronic structure of the density of state have been done at high electron temperature. The excitation of the d-band electrons and their contribution to the coupling of the heat between electrons and phonons were considered. The second were the electron-electron collisions and electron-lattice collision rates calculations were performed. The effect of fluence on the thermalization time and on the ablated depth of the copper irradiated by femtosecond laser pulses was studied using these two models and compared with the results assuming constant value for the electron-phonon coupling factor. A comparison between the model of the electron heat capacity based on the density of state calculation and the well-known linear relationship between the electron heat capacity and the electron temperature was also studied.