Electromagnetic emission due to nonlinear interaction of laser wakefields colliding in plasma at an oblique angle

Abstract

Head-on collision of laser-induced plasma wakefields with differing profiles of electrostatic potential has been recently found to be an efficient mechanism for generating high-power electromagnetic emission at the second harmonic of the plasma frequency [I.V.Timofeev et al. Phys. Plasmas 24, 103106 (2017)]. This mechanism is attractive for creating a source of tunable narrow-band coherent radiation in the terahertz frequency range. In this paper, we generalize the theory of electromagnetic emission produced by nonlinear interaction of two plasma wakes to the case of an arbitrary collision angle. Such a theory is used to evaluate the angular distribution of the second harmonic radiation as well as its total generation efficiency for parameters of the proof-of-principle experiment in which laser axes will be aligned with a small finite angle. Theoretical predictions are qualitatively confirmed by particle-in-cell simulations.