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

TL;DR

This paper extends the theory of electromagnetic emission from colliding laser wakefields in plasma to arbitrary angles, predicting angular distribution and efficiency, supported by particle-in-cell simulations.

Contribution

It generalizes existing models to include oblique collision angles, enabling better prediction of emission characteristics in practical setups.

Findings

Theoretical model predicts angular distribution of emitted radiation.

Simulation results qualitatively confirm theoretical predictions.

Efficiency of second harmonic generation depends on collision 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.