Stimulated Raman and Brillouin backscattering of collimated beams carrying orbital angular momentum

TL;DR

This paper theoretically investigates how electromagnetic and electrostatic waves in plasma exchange angular momentum during stimulated Raman and Brillouin backscattering, introducing angular momentum states for plasmons and phonons, with potential applications in plasma diagnostics.

Contribution

It introduces angular momentum states for plasma waves and analyzes their excitation via nonlinear wave mixing in stimulated scattering processes.

Findings

Angular momentum states for plasmons and phonons are introduced.

Nonlinear wave mixing can excite these angular momentum states.

Derived equations and instability growth rates for the scattering processes.

Abstract

We study theoretically the exchange of angular momentum between electromagnetic and electrostatic waves in a plasma, due to the stimulated Raman and Brillouin backscattering processes. Angular momentum states for plasmon and phonon fields are introduced for the first time. We demonstrate that these states can be excited by nonlinear wave mixing, associated with the scattering processes. This could be relevant for plasma diagnostics, both in laboratory and in space. Nonlinearly coupled paraxial equations and instability growth rates are derived.