Parametric aspects of electron–phonon temperature model for short pulse laser interactions with thin metallic films

Abstract

This work studies one-dimensional and two-dimensional heat transfer for short pulse lasers (<1 ps in duration) applied on metals using a two-subsystem (i.e., electrons and phonons) temperature model. In this model laser energy is first deposited on the electrons, which then exchange energy with the lattice. Conduction of energy is by electron motion only and the lattice contributes to the scattering of electrons. The objectives of this study are (a) to analyze the effects of different parameters such as electron specific heat, lattice specific heat, electron–phonon coupling factor, and thermal relaxation time for the one-dimensional electron and lattice temperature distributions using both hyperbolic and Fourier heat conduction formulations; (b) to examine two-dimensional effects including the effects of laser beam radial variance, laser fluence, and laser power in addition to the above parameters; and (c) to solve the transient equation of radiative transfer to incorporate the wave nature of the radiative source for the one-dimensional case.

Heating of opaque surfaces by picosecond laser pulses

“…is a reasonable choice for picosecond laser pulses. The absorbed light energy at first excites electrons into higher energy states that relax exponentially in time dissipating their excitation energy into heat [6,7]. Thus the effective time constant τ in (1b) will be larger than the proper time constant τ L of the laser pulse, if the energy relaxation time τ e is comparable or even longer than τ L (τ e ≈ 0.5 ps [7]).…”

Investigation of the Amorphization of iron and austenitic stainless steel films by supersaturation with Boron, Carbon, Nitrogen and Oxygen

“…By increasing the laser intensity above the plasma ignition threshold, a fully ionized vapor plasma can be identified. Laser heating of metals can be modeled by three basic processes: 1) the deposition of radiation energy on free electrons, 2) the energy exchange between electrons and lattice, and 3) the propagation of energy through media by free electron motion [45,46]. In the course of high power laser heating, where the metal is looked upon as a two-temperature system, the free electrons are heated to an effective temperature much higher than that of the lattice.…”