Mode hitching in traveling-wave optical parametric amplification

TL;DR

This paper investigates the classical transverse dynamics of traveling-wave optical parametric amplifiers, revealing a hitching phenomenon where beams tend to copropagate with fixed separation, impacting quantum imaging applications.

Contribution

It introduces the concept of hitching in OPAs, provides a theoretical model validated by simulations, and demonstrates experimentally how gain influences the hitching distance.

Findings

Beams tend to copropagate with fixed separation in thick OPAs.

The OPA gain significantly affects the hitching distance.

Experimental validation using four-wave mixing confirms the model.

Abstract

Optical parametric amplifiers (OPAs) in traveling wave configuration can generate localized spatial quantum correlations between a signal and an idler beam, a useful resource for quantum imaging. This study focuses on the classical transverse dynamics of the signal and idler beams when they propagate in a generic thick OPA at a nominally small angle. It shows that the beams tend to copropagate while maintaining a fixed separation, a phenomenon that we term hitching. We provide a model for hitching, validated by a numerical simulation, and we provide an experimental demonstration using four-wave mixing (4WM) in a hot atomic vapor. It shows that the OPA gain is the primary influence on the final hitching distance. These results have implications for the generation of multi-spatial-mode squeezed light for quantum imaging applications, where the exact spatial correspondence between the quantum fluctuations of the signal and the idler is of prime importance.