A Simulation Study Of The Electron Relaxation Effect In The Femtosecond Laser Interaction With Gold Nanofilm

The femtosecond laser interaction with gold nanofilm is extremely complex. The two-step heat conduction in the interaction has been largely modeled by the parabolic two-temperature model. Recently, it was shown that the parabolic two-temperature model is inappropriate for the ultrafast laser-metal interaction for the lasers with a pulse duration less than or comparable to the electron relaxation time, and that the hyperbolic two-temperature model should be adopted. In this work, the irradiation of gold nanofilm by the laser pulses with the durations of10,50and100fs is simulated by the combined these two two-temperature models and molecular dynamics method. The distributions of the electron and lattice temperatures and stresses in the nanofilm are obtained to examine the applicability of the two-temperature models for simulating sub-100fs laser pulses interaction with metals. Numerical results show that the effect of electron relaxation time on temperatures and stresses is significant without considering the ballistic motion of excited electrons. Instead, this effect is found trivial with including the ballistic heat transport. Since the energy transport due to the electron ballistic motion has been experimentally confirmed for gold, we can conclude that the electron relaxation effect could be overestimated in the previous study because of the neglect of the heat transport by the electron ballistic motion, and that the parabolic two-temperature model is still valid to simulate the sub-100fs laser pulses with gold.