Anisotropic terahertz response from a strong-field ionized electron-ion plasma

A microscopic theory is adapted to compute the time-resolved terahertz (THz) probe response of a dynamically evolving, strong-field ionized electron-ion plasma. The numerical solutions show that the relaxation of the initially highly anisotropic carrier distributions leads to a polarization dependent short-time THz response. This THz polarization discrimination gradually vanishes as the plasma approaches a thermodynamic equilibrium configuration via electron-electron and electron-ion scattering. The detailed carrier-relaxation dynamics causes a strongly nonmonotonic time-development of the THz absorption.