Ph. Emplit

Continuous wave photon pair generation in silicon-on-insulator waveguides and ring resonators

Silicon waveguides are promising chi(3)-based photon pair sources. Demonstrations so far have been based on picosecond pulsed lasers. Here, we present the first investigation of photon pair generation in silicon waveguides in a continuous regime. The source is characterized by coincidence measurements. We uncover the presence of unexpected noise which had not been noticed in earlier experiments. Subsequently, we present advances towards integration of the photon pair source with other components on the chip. This is demonstrated by photon pair generation in a Sagnac loop interferometer and inside a micro-ring cavity. Comparison with the straight waveguide shows that these are promising avenues for improving the source. In particular photon pair generation in the micro-ring cavity yields a source with a spectral width of approximately 150 pm resulting in a spectral brightness increased by more than 2 orders of magnitude.

Frequency Bin Entangled Photons

A monochromatic laser pumping a parametric down-conversion crystal generates frequency-entangled photon pairs. We study this experimentally by addressing such frequency-entangled photons at telecommunication wavelengths (around 1550 nm) with fiber-optics components such as electro-optic phase modulators and narrow-band frequency filters. The theory underlying our approach uses the notion of frequency-bin entanglement. Our results show that the phase modulators address coherently up to eleven frequency bins, leading to an interference pattern which can violate by more than five standard deviations a Bell inequality adapted to our setup.

Generation of correlated photons in hydrogenated amorphous-silicon waveguides

We report the first (to our knowledge) observation of correlated photon emission in hydrogenated amorphous-silicon waveguides. We compare this to photon generation in crystalline silicon waveguides with the same geometry. In particular, we show that amorphous silicon has a higher nonlinearity and competes with crystalline silicon in spite of higher loss.

Continuous wave photon pair generation in silicon-on-insulator waveguides and ring resonators: erratum

An error was made which is a basic calculation mistake. We have corrected this error and updated the prospects about ring cavity-based photon pair sources.

Nonlinear optical functions in crystalline and amorphous Silicon-on-Insulator nanowires

Silicon-on-Insulator nanowires provide an excellent platform for nonlinear optical functions in spite of the two-photon absorption at telecom wavelengths. Work on both crystalline and amorphous silicon nanowires is reviewed, in the wavelength range of 1.5 to 2.5 μm.

Integrated photon pair source for SOI-based quantum optics

Photon pair sources are an important building block for optics based Quantum Information Processing (QIP) such as Quantum Key Distribution (QKD) and Linear Optics Quantum Computing (LOQC) [1]. Beyond the demand for reliable and cheap photon pair sources for QKD, LOQC also requires interferometers that are mechanically stable and loss-free for which integrated photonics is particularly attractive [2]. In this context, photon pair generation (PPG) has been demonstrated via the third order nonlinear interaction between a silicon straight waveguide (Si-w) and a pulsed beam [3]. Such a source cannot be directly followed by other integrated components as photon pairs would be generated throughout the silicon chip. The solution we propose to suppress the pump beam consists of a Sagnac Loop Interferometer (SLI) in which photon pairs are generated and pump beam destructively interferes with itself, thereby allowing photon pairs to be generated in a localised part of the silicon chip. Furthermore, our study has been performed in a continuous instead of a pulsed regime, thereby avoiding any synchronization between detectors and laser and allowing for much cheaper laser sources. Our experimental setup is presented in Fig. 1. The experiment is performed at different pump power both in the a Si-w and the SLI. Results are presented in Fig. 2. The flux of generated pairs and the Signal-to-noise ratio are limited by the outcoupling loss and detector inefficiency. The photon flux is less than expected because the emitted spectrum is around 8nm (FWHM) broad instead of the expected 70nm. The performance of the SLI is not yet perfect: the pump suppression efficiency decreases with the pump power (from −22dB to −15dB) due to unexpected nonlinear behaviour in the directional coupler that changes the coupling ratio; and the Signal-to-Noise ratio is lower than in the Si-w which might be due to PPG in the broad (800nm) waveguide before the SLI.

Towards an Integrated Narrowband Source for Quantum Information: Photon Pair Generation in a Silicon Racetrack Resonator

We present evidences of time correlated photon pairs generated by the four-wave mixing process in a silicon racetrack cavity. A coincidence measurement and an emission spectrum are presented and discussed.