Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing

Davide Grassani,Angelica Simbula,Daniele Bajoni,Matteo Galli,Michael Hochberg,Stefano Pirotta,Christophe Galland,Nicholas C Harris,Matteo Menotti,Tom Baehr-Jones,Marco Liscidini

doi:10.1038/srep23564

Abstract

Compact silicon integrated devices, such as micro-ring resonators, have recently been demonstrated as efficient sources of quantum correlated photon pairs. The mass production of integrated devices demands the implementation of fast and reliable techniques to monitor the device performances. In the case of time-energy correlations, this is particularly challenging, as it requires high spectral resolution that is not currently achievable in coincidence measurements. Here we reconstruct the joint spectral density of photons pairs generated by spontaneous four-wave mixing in a silicon ring resonator by studying the corresponding stimulated process, namely stimulated four wave mixing. We show that this approach, featuring high spectral resolution and short measurement times, allows one to discriminate between nearly-uncorrelated and highly-correlated photon pairs.

Highlights

We have experimentally demonstrated that a microring resonator integrated on a silicon chip can be driven to emit nearly uncorrelated or time-energy entangled photon pairs depending on the pump
This has been done by exploiting four-wave mixing (FWM) to directly and rapidly reconstruct the joint spectral density (JSD) of the generated photon pairs by the spontaneous process
The resolution we achieved is less than 10 pm[2], more than two orders of magnitude better than state-of-the art measurements based on single photon detection

Summary

Introduction

In the case of time-energy correlations, highly spectrally correlated photons result to be in an entangled state, while indistinguishable heralded single photons can be obtained from spectrally uncorrelated pairs, without the need for additional filtering stages[16] This capability to produce non-classical states of light for different applications, along with the possibility of mass production of integrated optical circuits, suggests the development of fast and reliable techniques to quickly characterise the quantum properties of these devices. This is a challenging task, as it requires the reconstruction of the biphoton wavefunction, which describes all the properties of the generated pairs, in the energy Hilbert space. The stimulated process is intrinsically much stronger and yields very high signal-to-noise ratios, leading to a fast and highly resolved two-photon state characterisation[19,20,21,22,23]

Methods

Results

Conclusion