Different regimes of heat propagation in metals irradiated by subpicosecond laser pulses are studied on the basis of a two-temperature diffusion model. Analytical solutions for the heat conduction equation, corresponding to the different temperature dependences of the electron thermal conductivity, are obtained. It is shown that in case of a strong electron-lattice nonequilibrium, the heat penetration depth grows linearly with time, and the heat propagation velocity decreases with increasing laser fluence. Investigations of this “counterintuitive” regime of heat propagation are performed.

• Received 14 July 1997

DOI:https://doi.org/10.1103/PhysRevB.57.14698