Generation of MV/cm longitudinal terahertz electric fields from relativistic laser-solid interactions

We report on the generation and detection of longitudinal terahertz (THz) transient, with field strength of 1.5 MV/cm [1], at the focus of a radially polarized high-power terahertz beam generated at the rear surface of a thin metal foil irradiated by multi-terawatt laser pulse [2]. An f/1.5 off-axis parabolic mirror was used to focus the collimated THz beam. In addition to the longitudinal field, a transverse field, albeit off-axis, with amplitude in excess of 3 MV/cm was also measured.