A generalized Drude–Smith model for ultrafast pump-and-probe experiments and its application for studying of electronic dynamic properties of polycrystalline diamond

Abstract

In this work, we generalize the Drude–Smith model (DSM) proposed for optical conductivity in frequency-domain to the case of ultrafast pump-and-probe experiments, where the results are measured in time-domain. The generalized DSM (GDSM) considers the optically induced electronic backscattering or localization effect, and can be utilized for studying the electronic dynamics induced by pulsed radiation field in time-domain. By applying the optical-pump and terahertz-probe (OPTP) technique via normal reflection measurement, we study the electronic dynamic properties of polycrystalline diamond (PCD) on Si substrate and examine the validity of the proposed GDSM. We find that this model can lead to a better fitting between the experimental and theoretical results and can reasonably reflect the information about time resolution of the measurement system and the energy relaxation time for free carriers in PCD. For PCD subjected to 800 nm wavelength fs laser irradiation, the effect of carrier backscattering decreases and the electronic energy relaxation time increases with increasing pump radiation fluence. We hope that the GDSM from this work can be helpful for understanding the electronic dynamics in electronic and optoelectronic materials measured by, e.g., ultrafast pump-and-probe experiments.