Relativistic terahertz radiation generated by direct-laser-accelerated electrons from laser-foil interactions

Abstract

A scheme for generating powerful terahertz (THz) radiation based on laser-solid interactions is proposed. When a p-polarized femtosecond laser impinges obliquely on a plane solid target and the target partially blocks the laser energy, surface electrons are extracted to the vacuum and accelerated by the laser fields, forming a low-divergence electron beam. A half-cycle THz radiation pulse is emitted simultaneously as the beam passes by the edge of the target, due to a mechanism similar to coherent transition radiation. Our particle-in-cell simulations show that a relativistic THz pulse can be obtained with an energy of a few tens of millijoule and a conversion efficiency above 1%, with existing joule level femtosecond laser sources.