Non-equilibrium heat transport of copper-silver alloy films by femtosecond laser with double pump beams

Femtosecond laser pump-probe method is a useful tool to study the transient reflection phenomenon on metal films. Using double pump beams in femtosecond laser pump-probe system can both increase the electron non-equilibrium heat transport time and degrade the noise by adjust the experimental optical path. In this paper, the transient non-equilibrium heat transport processes of the copper-silver alloy films were studied by using femtosecond laser pump-probe method of double pump beams. The electron-lattice interactions were analysed and the electron non-equilibrium heat transport time was measured. The transient reflection phenomenons on copper-silver alloy films with the diverse film thickness were different, and the non-equilibrium heat transport time was inversely proportional to the film thickness. Two sudden changes which ascend abruptly appeared in the transient reflection signals, that is, twice electron non-equilibrium heat transport occurred in the copper-silver alloy films. With this method, the non-equilibrium heat transport time can be extend more than two times, which is expected to reduce the influence of thermal barrier and improve production efficiency.