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 p roblem. Consequently, the present study compares the predictions of one-equ ation (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 phys ical significance of the predictions are described and the discrepancies am ong the findings are discussed. It is found that all the models employed in the present study predict similar temperature profiles in the substrate fo r 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 temperatu re rise in the surface vicinity; however, two-equation and kinetic theory m odels predict similar temperature profiles. In this case, electron temperat ure rises rapidly while the lattice temperature increase slows down.