We present a recent numerical analysis investigating spontaneous parametric four-wave mixing in third-order nonlinear waveguides with different tapering patterns. We find that these devices could lead to efficient highly-pure single-photon sources.
In this paper, we present a thorough investigation for a spontaneous parametric four-wave mixing process in third-order nonlinear waveguides with various continuous tapering patterns. It has been previously shown that these devices can quasi-phase-match the four-wave-mixing process and enhance its conversion efficiency by orders of magnitude. By altering the tapering profile curve we found that these devices can enable single-photon sources with either narrow or broadband spectral widths at on-demand frequencies. Using our model, we were also able to identify the waveguide length at which the single-photon spectral purity is maximised.
In this paper, we present a thorough investigation for a spontaneous parametric four-wave mixing process in third-order nonlinear waveguides with various continuous tapering patterns. It has been previously shown that these devices can quasi-phase-match the four-wave mixing process and enhance its conversion efficiency by orders of magnitude. By altering the tapering profile curve we found that these devices can enable single-photon sources with either narrow or broadband spectral widths at on-demand frequencies. Using our model, we were also able to identify the waveguide length at which the single-photon spectral purity is maximized.
Third-order nonlinear processes require phase matching between the interacting fields to achieve high efficiencies. Typically in guided-wave χ(3) platforms this is achieved by engineering the dispersion of the modes through the transverse profile of the device. However, this limits the flexibility of the phase matching that can be achieved. Instead, we analyze four-wave mixing in a pair of asymmetric waveguides and show that phasematching may be achieved in any χ(3) waveguide by coupling of a nondegenerate pump from an adjacent waveguide. We demonstrate the additional flexibility that this approach yields in the case of photon-pair generation by spontaneous FWM, where the supermode dispersion may be modified to produce pure heralded single photons -- a critical capability required for example by silicon platforms for chip-scale quantum photonics.
Single photon sources are a key building block for quantum information processing. A common approach uses spontaneous emitters based on parametric down conversion and four wave mixing. In 2005 experiments on the first spectrally engineered four wave mixing sources in fibre were published [1,2]. A primary obstacle for photonics to realize quantum-enhanced applications is loss. Designing single photon sources matched to single mode optical fibres greatly reduces coupling losses [3]. In addition, tailoring the phase matching properties of the sources to generate factorable photon pairs makes strong spectral filtering obsolete and thereby avoids the degradation of photon number correlations due to loss.
Heralded single photon sources, based on probabilistic non-linear interactions, currently serve as the de-facto standard for performing multi-photon quantum interference experiments. Already, interesting phenomena may be explored with a handful of such sources [1], whilst in the future, large arrays of identical sources could be multiplexed with a switching network to achieve a truly scalable, near-deterministic emission [2]. However, fabricating such a large number of indistinguishable, pure, heralded single photon sources, operating with low-loss, remains an open challenge. Spontaneous four-wave mixing (SFWM) in a silica waveguide is a promising route to building such a source. The low-loss and excellent mode-matching to optical fibre of silica waveguides allows high preparation efficiency. Guided-wave photonics also allows the precise control of the optical modes needed to engineer emission of photons into a single pair of Schmidt modes: allowing heralded photons of high purity without narrowband filtering [3].