On the theory of ps and sub-ps laser pulse interaction with metals I. Surface temperature

A model is proposed describing the interaction of short laser pulses with metals. It is shown that a generalized nonlocal heat flow in time leads to an equation of heat conduction with additional terms involving the time derivative of both the laser intensity and the coupling of the electrons to the phonons. The importance of the coefficient of heat exchange for the temperature distribution in metals and the different influence of its main parts, the electron phonon coupling and the averaged square phonon frequencies, is pointed out. For a laser pulse length of 1 ps the electron and phonon surface temperatures for Al, Cu, Nb and Pb are evaluated using a double temperature model with a nonlocal heat flow. This is compared with the results of a local heat flow approach and with the conventional theory.