Effect of Pulse Width and Fluence of Femtosecond Laser on Electron--Phonon Relaxation Time

The electron--phonon relaxation time as functions of pulse width and fluence of femtosecond laser is studied based on the two-temperature model. The two-temperature model is solved using a finite difference method for copper target. The temperature distribution of the electron and the lattice along withspace and time for a certain laser fluence is presented. The time-dependence of lattice and electron temperature of the surface for different pulse width and different laser fluence are also performed, respectively. Moreover, the variation of heat-affected zone per pulse with laser fluence is obtained. The satisfactory agreement between our numerical results and experimental dataindicates that the electron--phonon relaxation time is reasonably accurate with the influences of pulse width and fluence of femtosecond laser.