Nonlinear characterisation of a silicon integrated Bragg waveguide filter

TL;DR

This paper demonstrates that stimulated FWM can effectively characterize the nonlinear response of silicon Bragg waveguide filters, showing that unwanted photon pairs are not a significant issue for integrated quantum sources.

Contribution

It introduces a method to use classical FWM measurements to predict quantum pair generation in integrated Bragg waveguides, validated by theory and experiment.

Findings

Good agreement between theory and experiment

Stimulated FWM accurately predicts pair generation

Unwanted photon pairs are not problematic for device operation

Abstract

Bragg waveguides are promising optical filters for pump suppression in spontaneous Four-Wave Mixing (FWM) photon sources. In this work, we investigate the generation of unwanted photon pairs in the filter itself. We do this by taking advantage of the relation between spontaneous and classical FWM, which allows for the precise characterisation of the nonlinear response of the device. The pair generation rate estimated from the classical measurement is compared with the theoretical value calculated by means of a full quantum model of the filter, which also allows to investigate the spectral properties of the generated pairs. We find a good agreement between theory and experiment, confirming that stimulated FWM is a valuable approach to characterise the nonlinear response of an integrated filter, and that the pairs generated in a Bragg waveguide are not a serious issue for the operation of a fully integrated nonclassical source.