Spatial modes in waveguided parametric down-conversion

TL;DR

This paper investigates how higher-order spatial modes in nonlinear waveguides affect photon pair emission, revealing impacts on entanglement and spectrum, with strategies to optimize fundamental mode pair production.

Contribution

It provides a theoretical and experimental analysis of higher-order mode effects in waveguided parametric down-conversion, including conditions for pair creation and mitigation strategies.

Findings

Higher-order modes influence the spectral and spatial correlations of photon pairs.

Experimental observations confirm the theoretical predictions of mode propagation effects.

Strategies are proposed to enhance fundamental mode pair production and reduce detrimental effects.

Abstract

The propagation of several spatial modes has a significant impact on the structure of the emission from parametric down-conversion in a nonlinear waveguide. This manifests itself not only in the spatial correlations of the photon pairs but also, due to new phase-matching conditions, in the output spectrum, radically altering the degree of entanglement within each pair. Here we investigate both theoretically and experimentally the results of higher-order spatial-mode propagation in nonlinear waveguides. We derive conditions for the creation of pairs in these modes and present observations of higher-order mode propagation in both the spatial and spectral domains. Furthermore, we observe correlations between the different degrees of freedom and finally we discuss strategies for mitigating any detrimental effects and optimizing pair production in the fundamental mode.