High orbital angular momentum harmonic generation

TL;DR

This paper presents a novel mechanism for generating and amplifying high orbital angular momentum harmonics in plasma via stimulated Raman backscattering, enabling control over OAM spectra independently of other laser properties.

Contribution

It introduces a new high OAM harmonic generation method that preserves laser wavelength and allows tuning of harmonic orders based on initial OAM, supported by theory and simulations.

Findings

High OAM harmonics extend up to paraxial limit

Harmonic orders can be tuned via a selection rule

Generation demonstrated with plasma and Kerr media

Abstract

We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves. We illustrate the high OAM harmonics generation in a plasma using several examples including the generation of prime OAM harmonics. The process can also be realised in any nonlinear optical Kerr media supporting three-wave interactions.