Laser shortpulse heating-variable properties case

Nonequilibrium energy transport in the surface region of the solid substrate irradiated by a shortpulse laser beam results in high electron and low lattice site temperatures. The rise of electron temperature in the region irradiated by a laser beam depends on the thermophysical properties of the substrate material. The assumption of constant thermophysical properties results in excessive rise of electron temperature in the surface vicinity of the substrate material. Consequently, when modeling the laser shortpulse heating process, variable properties should be employed in the analysis. In the present study, laser shortpulse heating of copper is considered. Electron kinetic theory approach is introduced to model the nonequilibrium energy transport taking place in the surface region of the substrate material. The resulting equation of energy transport is decoupled into two equations as similar to those in the two-equation model. The constant as well as variable properties of the substrate material are introduced in the simulations. It is found that the variable properties have significant effect on electron temperature distribution in the surface vicinity of the substrate material. This is more pronounced in the early heating period. The constant properties predict excessive electron temperature rise in the surface vicinity of the substrate material.