Generation of high-power terahertz radiation in the relativistic regime of laser-electron acceleration in a gas-cluster target

We report efficient (∼10^-4) generation of terahertz (THz) radiation under relativistic laser irradiation of nitrogen and oxygen gas-cluster targets. The relationship between the THz radiation yield and the process of laser-plasma generation of a megaelectronvolt electron beam, the divergence of which depends on the target density, has been studied. For a femtosecond laser beam intensity of ∼10¹⁹ W/cm², an energy of 20 μJ is recorded in the frequency range from 0.1 to 3 THz at an accelerated electron bunch charge of nanocoulomb units. Directionality and polarization of the THz pulse, as well as the dependence of its energy on the gas type, pressure, power, and duration of the pump pulse, are measured.