Phase conjugation and mode conversion in stimulated parametric down-conversion with orbital angular momentum: a geometrical interpretation

TL;DR

This paper explores how spatial modes with orbital angular momentum are converted during parametric down-conversion, using a geometric Poincaré sphere model to intuitively understand phase conjugation and topological charge conservation.

Contribution

It introduces a geometric interpretation of mode conversion in parametric down-conversion with orbital angular momentum, linking it to Poincaré sphere representations.

Findings

Demonstrated phase conjugation in OAM modes during down-conversion

Provided a geometric model for understanding mode conversion

Compared phenomena with optical parametric oscillators

Abstract

We report on an experiment that investigates the spatial mode conversion in the process of parametric down-conversion seeded by a light beam in a superposition of orbital angular momentum modes. This process is interpreted in terms of a geometric representation of first-order spatial modes in a Poincar\'e sphere, providing an intuitive image of the phase conjugation and the topological charge conservation. We also make a comparison with the analogous phenomenon for optical parametric oscillators.