Bi-photon spectral correlation measurements from a silicon nanowire in the quantum and classical regimes

TL;DR

This paper demonstrates a fast, high-resolution method for characterizing spectral correlations in photon pairs generated by silicon nanowires using stimulated four-wave mixing, confirming its effectiveness across different pump pulse durations.

Contribution

It extends stimulated spectral correlation measurements to  sources in integrated waveguides, showing improved speed and resolution over traditional methods.

Findings

Stimulated four-wave mixing enables faster spectral correlation measurements.

Classical stimulated process accurately captures spectral entanglement.

Measurement consistency across different pump pulse durations.

Abstract

The growing requirement for photon pairs with specific spectral correlations in quantum optics experiments has created a demand for fast, high resolution and accurate source characterization. A promising tool for such characterization uses the classical stimulated process, in which an additional seed laser stimulates photon generation yielding much higher count rates, as recently demonstrated for a $\chi^{(2)}$ integrated source in A.~Eckstein \emph{et al.}, Laser Photon. Rev. \textbf{8}, L76 (2014). In this work we extend these results to $\chi^{(3)}$ sources, demonstrating spectral correlation measurements via stimulated four-wave mixing for the first time in a integrated optical waveguide, namely a silicon nanowire. We directly confirm the speed-up due to higher count rates and demonstrate that additional resolution can be gained when compared to traditional coincidence measurements. As pump pulse duration can influence the degree of spectral entanglement, all of our measurements are taken for two different pump pulse widths. This allows us to confirm that the classical stimulated process correctly captures the degree of spectral entanglement regardless of pump pulse duration, and cements its place as an essential characterization method for the development of future quantum integrated devices.