A simulation study of the electron relaxation effect in the femtosecond laser interaction with gold nanofilm

• 1、Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027

Abstract：The two-step heat conduction in the femtosecond laser interaction with gold nanofilm has been largely described by the parabolic two-temperature model. Recently, it was shown that the parabolic two-temperature model is inappropriate for the ultrafast laser-metal interaction when the pulses duration is 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 a gold nanofilm by the laser pulses with the durations of 10 and 100 fs is simulated by the methods combining the parabolic and hyperbolic two-temperature models with the framework of molecular dynamics. The distributions of the electron and lattice temperatures and stresses in the nanofilm are obtained. Numerical results show that the effect of electron relaxation on the material responses is significant when the energy transport due to the ballistic motion of excited electrons is not considered. Instead, this effect is found trivial with including the ballistic heat transport. Since the energy transport by the electron ballistic motion has been experimentally confirmed for gold, it is concluded that for the sub-100-fs laser interaction with gold the electron relaxation effect could be neglected and the parabolic two-temperature model is still valid.

Keywords： Computational solid mechanics Femtosecond laser Molecular dynamics Ballistic motion Electron relaxation time Gold thin film