Adaptive model for the optical properties of excited gold

We investigate the optical properties of laser-excited gold within the Drude-Lorentz framework. Our approach extends the Drude-Lorentz model, initially fitted to experimental data for ambient conditions, to accommodate higher temperatures. It covers a wide range of excitation strengths and frequencies, Fermi-distributed electrons, as well as nonequilibrium scenarios. It is in good qualitative agreement with density functional theory--based calculations capturing key features of the reflectivity and, thus, provides a very efficient alternative to these numerically expensive calculations. When applied to thin films, we find a nonlinear dependence of reflection and absorption on electron temperature, accentuated at lower photon energies and under polarized light. Our highly efficient model can be particularly valuable when analyzing experiments investigating ultrafast processes as the pathways of energy relaxation in laser-excited samples.