Generation of Narrow-Band THz Radiation by Collision of Laser Wake Waves with a Small-Scale Transverse Structure in a Plasma

Abstract: A new method was proposed to generate high-power narrow-band terahertz radiation in the process of nonlinear interaction of counterpropagating laser wake waves, the potential profiles of which are modulated in the transverse direction and do not coincide locally with each other. It was shown that, to achieve a high efficiency of radiation at the doubled plasma frequency, the period of such modulation should coincide with the length of the generated electromagnetic wave. Each of the plasma waves with such a small-scale transverse structure was proposed to be created by a pair of interfering laser pulses propagating at a small angle to each other. Numerical simulation by the particle-in-cell method confirmed such a scheme can provide a narrow (2%) spectral emission line and a high energy conversion efficiency at a level of 1%. With the XCELS design parameters, the proposed method opens the way to achieving a record terawatt radiation power in the THz frequency range.