Heat Transfer Mechanisms During Short-Pulse Laser Heating of Metals

TLDR

The heating process involves radiation energy deposition on electrons, subsequent electron transport, and lattice heating through electron–lattice interactions. The study investigates microscopic heat transfer mechanisms during ultrafast laser heating of metals. The authors model electron transport and electron–lattice interactions using the Boltzmann transport equation, with the scattering term derived from quantum mechanics to capture elastic and inelastic contributions. Solving the Boltzmann equation yields a hyperbolic two‑step radiation heating model that captures the hyperbolic energy flux and electron–lattice nonequilibrium, with predictions matching experimental data for subpicosecond laser heating.

Abstract

This work studies heat transfer mechanisms during ultrafast laser heating of metals from a microscopic point of view. The heating process is composed of three processes: the deposition of radiation energy on electrons, 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 electron-lattice interactions. The scattering term of the Boltzmann equation is evaluated from quantum mechanical considerations, which shows the different contributions of the elastic and inelastic electron-lattice 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 by electrons and the nonequilibrium between electrons and the lattice during fast heating processes. Predictions from the current model agree with available experimental data during subpicosecond laser heating.