Observation of Gigawatt-Class THz Pulses from a Compact Laser-Driven Particle Accelerator

Abstract

We report the observation of subpicosecond terahertz ($T$-ray) pulses with energies $\ensuremath{\ge}460\text{ }\text{ }\ensuremath{\mu}\mathrm{J}$ from a laser-driven ion accelerator, thus rendering the peak power of the source higher even than that of state-of-the-art synchrotrons. Experiments were performed with intense laser pulses (up to $5\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$) to irradiate thin metal foil targets. Ion spectra measured simultaneously showed a square law dependence of the $T$-ray yield on particle number. Two-dimensional particle-in-cell simulations show the presence of transient currents at the target rear surface which could be responsible for the strong $T$-ray emission.