Heating of solid targets with laser pulses

TLDR

Analytical and numerical solutions of the heat‑conduction equation for absorbing media under pulsed laser irradiation are presented. Temperature distributions are calculated using multiple laser‑irradiance models, comparing surface and volume heat‑generation mechanisms. When the thermal diffusion depth exceeds the optical attenuation depth, surface and volume heating models agree, but when the diffusion depth is comparable to or smaller, the surface model predicts markedly different temperatures; numerical examples for tungsten illustrate these effects for picosecond pulses.

Abstract

Analytical and numerical solutions to the heat−conduction equation are obtained appropriate to the heating of absorbing media with pulsed lasers. The spatial and temporal form of the temperature is determined using several different models of the laser irradiance. Both surface and volume generation of heat are discussed and the results obtained using each model are compared with each other and with previously known results. It is found that if the depth of thermal diffusion for the laser pulse duration is large compared to the optical attenuation depth, the surface and volume generation models give nearly identical results. However, if the thermal diffusion depth for the laser pulse duration is comparable to or less than the optical attenuation depth, the surface generation model can give significantly different results compared to the volume generation model. Specific numerical results are given for a tungsten target irradiated by pulses of different temporal durations and the implications of the results are discussed with respect to the heating of metals by picosecond laser pulses.