Femtosecond optical diagnostics and hydrodynamic simulation of Ag plasma created by laser irradiation of a solid target

Abstract

A combined experimental‐theoretical method of diagnostics of the plasma created on a surface of Ag target irradiated by intense femtosecond laser pulses is proposed. The method is based on semiempirical wide-range models of optical, transport and thermodynamic properties of Ag plasma. Numerical coefficients in these models are chosen so as to ensure the best accordance of simulations to measurements of a complex absorption coefficient of Ag plasma by means of femtosecond interference microscopy. A two-temperature hydrodynamic modelling of non-stationary laser-produced Ag plasma is carried out; calculated results are presented in comparison with experiments. Unexpectedly high values of the phase of the complex reflection coefficient at short (200 fs) time delay between pump and probe laser pulses are obtained experimentally; possible explanations of this phenomenon are discussed. (Some figures in this article are in colour only in the electronic version)