HEAT-TRANSFER MECHANISMS DURING SHORT-PULSE LASER-HEATING OF METALS

This work studies heat transfer mechanisms during ultrafast laser heat ing of metals from a microscopic point of view. The heating process is composed of three processes: the deposition of radiation energy on el ectrons, the transport of energy by electrons, and the heating of the material lattice through electron-lattice interactions. The Boltzmann transport equation is used to model the transport of electrons and ele ctron-lattice interactions. The scattering term of the Boltzmann equat ion is evaluated from quantum mechanical considerations, which shows t he different contributions of the elastic and inelastic electron-latti ce scattering processes on energy transport. By solving the Boltzmann equation, a hyperbolic two-step radiation heating model is rigorously established. It reveals the hyperbolic nature of energy flux carried b y electrons and the nonequilibrium between electrons and the lattice d uring fast heating processes. Predictions from the current model agree with available experimental data during subpicosecond laser heating.