Distinguishing nonlinear processes in atomic media via orbital angular momentum transfer

TL;DR

This paper introduces a method to distinguish nonlinear optical processes in atomic media by analyzing orbital angular momentum transfer, demonstrated through experiments with rubidium vapors and laser beams carrying topological charge.

Contribution

It presents a novel technique using orbital angular momentum transfer to identify specific nonlinear processes in atomic media, validated through experiments with rubidium vapors.

Findings

Emission at 1.37 μm results from a four-wave mixing process involving one laser field.

Orbital angular momentum transfer reveals the dominant nonlinear process.

Experimental analysis of intensity and phase profiles confirms the method's effectiveness.

Abstract

We suggest a technique based on the transfer of topological charge from applied laser radiation to directional and coherent optical fields generated in ladder-type excited atomic media to identify the major processes responsible for their appearance. As an illustration, in Rb vapours we analyse transverse intensity and phase profiles of the forward-directed collimated blue and near-IR light using self-interference and astigmatic transformation techniques when either or both of two resonant laser beams carry orbital angular momentum. Our observations unambiguously demonstrate that emission at 1.37 {\mu}m is the result of a parametric four-wave mixing process involving only one of the two applied laser fields.