Spectrally pure photon pair generation in asymmetric heterogeneously coupled waveguides

TL;DR

This paper presents a novel design method for creating spectrally pure photon pairs using asymmetric heterogeneously coupled waveguides, leveraging mode coupling to achieve group velocity matching and improve single-photon source quality.

Contribution

The work introduces a new design strategy employing mode coupling in asymmetric waveguides to tailor group velocity, enabling high spectral purity in photon pair generation.

Findings

High spectral purity achieved in lithium niobate waveguides

Temperature tunability demonstrated for the photon sources

Versatile approach applicable to various waveguide materials

Abstract

In this work, we develop a design methodology to generate spectrally pure photon pairs in asymmetric heterogeneously coupled waveguides by spontaneous parametric down-conversion. Mode coupling in a system of waveguides is used to directly tailor the group velocity of a supermode to achieve group velocity matching (GVM) that is otherwise not allowed by material dispersion. Design examples based on thin film lithium niobate waveguides are provided, demonstrating high spectral purity and temperature tunability. This approach is a versatile strategy applicable to waveguides of different materials and structures, allowing more versatility in single-photon source designs.