Low-frequency electromagnetic pulse radiation from metal targets irradiated by a short pulse laser*

A theoretical study of low-frequency radiation from a short laser pulse (\textless 1 ps) normally incident on metal targets is presented and applied to experiments at NRL. The laser field drives large time-varying currents (MA/cm$^{\mathrm{2}})$ in the skin layer of the metal, which emit radiation that peaks in the THz range, but have a significant component in the microwave band. A one-dimensional electrostatic model for Cu is coupled to a radiation model for an infinitely thin flat disc (thickness -- one skin depth, diameter -- laser focal spot size). The salient characteristics of the emitted radiation are calculated, which include radiated power, energy, and spectra as a function of laser energy and angle of observation. Work supported by the NRL Base Program.