Laser short-pulse heating of surfaces

The Fourier theory of heating is not applicable to the short-pulse type of laser heating due to the assumptions made in the theory. On the other hand, two-equation and kinetic theory models offer an improved solution to the problem. Consequently, the present study compares the predictions of one-equation (Fourier heating model), two-equation, and kinetic theory models for the laser heating pulses of 10^-9, 10^-10 and 10^-11 s lengths. The physical significance of the predictions are described and the discrepancies among the findings are discussed. It is found that all the models employed in the present study predict similar temperature profiles in the substrate for a nanosecond laser heating pulse. As the pulse length shortens such as to 10^-10 and 10^-11 s, the one-equation model predicts excessive temperature rise in the surface vicinity; however, two-equation and kinetic theory models predict similar temperature profiles. In this case, electron temperature rises rapidly while the lattice temperature increase slows down.