The effect of pulse duration on the interplay of electron heat conduction and electron-phonon interaction: Photo-mechanical versus photo-thermal damage of metal targets

Here we present a theoretical work on short pulse laser interaction with metal targets. With the help of Two Temperature Model we consider in detail the interplay of two competitive mechanism of the laser deposited energy dissipation: the fast electron heat conduction and the electron-phonon interaction processes. For a range of pulse durations the modelling included a complex description of these processes as the functions of the electron and phonon temperatures. It was shown that for transitional type of metals the maximum surface temperature determined for a range of pulse durations at fixed fluence exhibits peak behavior and the corresponding pulse duration is close to the electron-phonon relaxation time. In contrast, having complex deviation of heat conductivity from its linear growth with the electronic temperature, the group of noble metals shows different behavior in maximum surface temperature depending on the fluence regime. Based on the results, an experimental approach in measuring the electron-phonon relaxation time is suggested and a general tendency of photo-mechanical versus photo-thermal damage of metal targets is deduced. (C) 2009 Elsevier B.V. All rights reserved.