Non-equilibrium heat transport of electron in Cu films irradiated by three femtosecond laser beams

To observe the changes of electron non-equilibrium heat transport time with the femtosecond laser beam parameters in the Cu films, the electron and the lattice temperature curves were studied based on the finite element method and the experimental testing. The simulation results show that the time of electron non-equilibrium heat transport in Cu films will rise with the increasing of both the pump beams number and the energy density of the pulses. The time of electron non-equilibrium heat transport by three pump beams heating was three times higher than that by the single pump beam heating. These results were verified by three femtosecond laser beams pump-probe experimental system. The experimental results show that the transient reflectivity of the Cu films appear three peaks when the Cu films are irradiated by three pump beams with a certain delay, and the time of electron non-equilibrium heat transport has been prolonged greatly. Consequently, the thermal barrier of the device processing is eliminated and the quality, accuracy and efficiency of the femtosecond laser processing are improved.