Electron Kinetic Theory Approach For Picosecond Laser PUlse Heating

Nonequilibrium heating occurs in a metallic substrate as the heating time approaches the electron-phonon energy relaxation time. In this case, the Fourier heating model fails to predict the correct temperature rise in the surface vicinity of the substrate. Consequently, the heating process needs to be examined at the microscopic level. In thisstudy, laser picosecond pulse heating of gold is considered. The governing transport equation is derived introducing an electron kinetic theory approach. The resulting high-order differential equation describing the energy transport is decomposed into two differential equations similar to those in the two-equation model. The predictions of the electron kinetic theory approach are compared with the two-equation model results for different values of the thermophysical properties of the substrate. It is found that for particular values of mean-free path and the fraction of excess electron energy transfer to lattice site, both predictions are identical. Moreover, the material response to heating pulse is very sensitive as the values of the thermophysical properties of the substrate change.