Narrow- and broadband single-photon sources using customised-tapered waveguides

Abstract

Presented here are the findings of a recent thorough investigation into spontaneous parametric four-wave mixing processes in third-order nonlinear waveguides with continuous tapering patterns. It has been previously shown that these tapered devices can be exploited to quasi-phase-match the four-wave mixing process and enhance its conversion efficiency by several orders of magnitude. I start with validating the developed quantum model by reproducing the existing results in the literature. Furthermore, through selection of different tapering profiles, I show that these devices can serve as efficient sources of heralded single-photons, with either narrow or broadband spectral widths and at on-demand frequencies. Simultaneously, I was able to use the aforementioned model to determine the fibre length at which the spectral purity, an important property for quantum information applications, is maximised.