Measurements of terahertz electrical conductivity of intense laser-heated dense aluminum plasmas

We report the electrical conductivity of laser-produced warm dense aluminum plasmas measured using single-shot ultrafast terahertz (THz) frequency spectroscopy. In contrast with experiments performed at optical frequencies, measurements based upon THz probe reflectivity directly determine a quasi-dc electrical conductivity, and therefore the analysis does not require a free-electron Drude model based extrapolation to recover the near zero frequency conductivity. In fact, our experimental results indicate that the Drude model breaks down for warm (>0.6eV), moderate-dense (<1.6g/cm3) aluminum at THz frequencies. A calculation of THz reflectivity over a non-Fresnel boundary in dense plasmas is also presented.