All-optical mode conversion via spatially-multimode four-wave mixing

TL;DR

This paper demonstrates an all-optical method for converting Gaussian beams into non-Gaussian modes using spatially-multimode four-wave mixing in atomic vapor, supported by experiments, simulations, and analytical models.

Contribution

It introduces a novel all-optical mode conversion technique utilizing spatially-multimode four-wave mixing in atomic vapor, validated by experiments and theoretical analysis.

Findings

Successful conversion of Gaussian to Bessel-Gauss modes

Good agreement between experimental data and simulations

Potential for new mode conversion applications

Abstract

We experimentally demonstrate the conversion of a Gaussian beam to an approximate Bessel-Gauss mode by making use of a non-collinear four-wave mixing process in hot atomic vapor. The presence of a strong, spatially non-Gaussian pump both converts the probe beam into a non-Gaussian mode, and generates a conjugate beam that is in a similar non-Gaussian mode. The resulting probe and conjugate modes are compared to the output of a Gaussian beam incident on an annular aperture that is then spatially filtered according to the phase-matching conditions imposed by the four-wave mixing process. We find that the resulting experimental data agrees well with both numerical simulations, as well as analytical formulae describing the effects of annular apertures on Gaussian modes. These results show that spatially-multimode gain platforms may be used as a new method of mode conversion.