SHORT-PULSE LASER-HEATING ON METALS

This work analyzes microscopic radiation metal interactions in short-pulse laser heating processes and their effects on the material thermal response. The radiation metal interactions are treated as a coupled two-step process: (1) the absorption of photon energy by electrons and (2) the subsequent heating of the metal lattice through electron-phonon collisions. Key parameters, pulse duration to relaxation, relaxation to diffusion, and heating intensity, are introduced to classify this two-step heating regime and the conventional one-step heating regime. In the two-step heating regime. the microscopic energy transfer among photons, electrons and phonons enlarges the size of the heat-affected region and lowers the peak metal lattice temperature rise significantly. The predicted transient reflectivity changes agree with sub-picosecond laser heating experiments.