Analysis of the Nonequilibrium Heat Transport Time of Electrons in Cu Films Irradiated by a Femtosecond Laser Beam
X.F. Xu, X.L. Li, Q.W. Wang, F.F. Yang and Y.F. Gao
The finite element method (FEM) is used to simulate the changes of electron temperature and lattice temperature in Cu films during the femtosecond laser pulses heating. The simulation results show that during the electron nonequilibrium relaxation time, the full width at half maximum (FWHM) time of the electron temperature will rise with the increase of the pulse number, the width and pulses interval; however, the electron nonequilibrium relaxation time is independent of both the pulses interval and pulse width, but increased with the number of excitation pulses. By the laser heating with the four pulses of 300 fs, and the pulses interval of 520 fs, the FWHM time of electron temperature is 5.6 ps, and the electron nonequilibrium relaxation time is 15 ps. Compared with the single pulse heating that the FWHM time of electron temperature is 1 ps, and the electron nonequilibrium relaxation time is 8 ps, they have been significantly improved.
Keywords: Femtosecond laser, copper, Cu, films, electron temperature, lattice temperature, electron nonequilibrium relaxation