Trans-spectral orbital angular momentum transfer via four wave mixing in Rb vapor

TL;DR

This study demonstrates the transfer of orbital angular momentum from near-infrared pump lasers to blue light in rubidium vapor via four-wave mixing, enabling phase information transfer and complex mode excitation.

Contribution

It shows for the first time that orbital angular momentum can be transferred through four-wave mixing in atomic vapor, with implications for phase information storage.

Findings

Orbital angular momentum is fully transferred from pump to blue light.

Complex pump profiles excite specific spatial modes in the generated light.

Phase-matching conditions strongly influence mode excitation.

Abstract

We report the transfer of phase structure, and in particular of orbital angular momentum, from near-infrared pump light to blue light generated in a four-wave-mixing process in 85Rb vapour. The intensity and phase profile of the two pump lasers at 780nm and 776nm, shaped by a spatial light modulator, influences the phase and intensity profile of light at 420nm which is generated in a subsequent coherent cascade. In particular we oberve that the phase profile associated with orbital angular momentum is transferred entirely from the pump light to the blue. Pumping with more complicated light profiles results in the excitation of spatial modes in the blue that depend strongly on phase-matching, thus demonstrating the parametric nature of the mode transfer. These results have implications on the inscription and storage of phase-information in atomic gases.