A wide-range model for simulation of pump-probe experiments with metals

High precision pump-probe experiments can provide a valuable information about material states out of equilibrium. A wide-range numerical model is used for the description of material response on ultrashort laser action. The model is developed on the basis of two-temperature hydrodynamics with heat transport, ionization, plasma expansion, electron-ion collisions and two-temperature equation of state for an irradiated substance. Comparison of experimental findings with the results of simulation is used both for the numerical model verification and for calculation of plasma thermodynamic parameters that cannot be measured directly in experiment. An aluminum target is heated by an intense 400 nm (2ω) pump laser pulse that is incident normal to the planar target. Weak S- and P-polarized probe pulses with wavelength 800 nm (1ω) are used for diagnostics of the plasma. Both probe pulses illuminate the target at a 45° angle. Calculation of the reflectivity and phase shift of probe pulses with both polarizations are in good agreement with experiment.