.We experimentally study the generation of correlated pairs of photons through four-wave mixing (FWM) in embedded silicon waveguides. The waveguides, which are designed to exhibit anomalous group-velocity dispersion at wavelengths near 1555 nm, allow phase matched FWM and thus efficient pair-wise generation of non-degenerate signal and idler photons. Photon counting measurements yield a coincidence-to-accidental ratio (CAR) of around 25 for a signal (idler) photon production rate of about 0.05 per pulse. We characterize the variation in CAR as a function of pump power and pump-to-sideband wavelength detuning. These measurements represent a first step towards the development of tools for quantum information processing which are based on CMOS-compatible, silicon-on-insulator technology.
.We experimentally study the generation of correlated pairs of photons through four-wave mixing (FWM) in embedded silicon waveguides. The waveguides, which are designed to exhibit anomalous group-velocity dispersion at wavelengths near 1555 nm, allow phase matched FWM and thus efficient pair-wise generation of non-degenerate signal and idler photons. Photon counting measurements yield a coincidence-to-accidental ratio (CAR) of around 25 for a signal (idler) photon production rate of about 0.05 per pulse. We characterize the variation in CAR as a function of pump power and pump-to-sideband wavelength detuning. These measurements represent a first step towards the development of tools for quantum information processing which are based on CMOS-compatible, silicon-on-insulator technology.
Correlated single photons provide a means to drive applications such as quantum computing and quantum communications. Correlated single photons can be generated via parametric down conversion in second–order nonlinear media or spontaneous four–wave mixing in third–order nonlinear media. In particular, complementary metal–oxide–semiconductor (CMOS) technology allows for seamless integration with electronics, providing the potential for a completely on-chip solution for quantum information processing. Ultra–silicon–rich nitride platform is a backend CMOS compatible platform, that has already been used to obtain high gain optical parametric amplification, wideband supercontinuum and enhanced nonlinearity in photonic crystal waveguides due to its large nonlinearity. In this work, we demonstrate correlated photon pair generation based on spontaneous four–wave mixing using ultra-silicon-rich nitride waveguides for the application in CMOS–based optical quantum technologies. A CW pump at a wavelength of 1555.747nm amplified using an EDFA is filtered through five wavelength division multiplexers (WDM) with a bandwidth of 1.2nm, providing 175dB suppression of EDFA induced pump sideband noise. The filtered quasi–TE pump, adjusted using a fiber polarization controller, is coupled into an ultra–silicon–rich nitride waveguide using a lensed fiber. A SiO2 cladded waveguide with a width of 550nm and height of 300nm possesses a high nonlinear parameter of 530W^-1/m with anomalous dispersion necessary for spontaneous four-wave mixing. The waveguide output is coupled into a lensed fiber and 7 cascaded WDMs are used to provide 245dB of residual pump filtration. The pump–suppressed output is spectrally separated into signal/idler part using WDMs. We refer to lower (higher) frequency photon as the signal (idler). The spontaneously generated signal and idler photons are filtered using cascaded tunable band pass filters (OTF) centered at 1571.24nm and cascaded WDMs centered at 1540.56nm, respectively. The bandwidth of the tunable OTF and WDM is 0.5nm and 1.2nm, therefore the correlated signal/idler photons are observed within the bandwidth window of 0.5nm induced by the OTF. The signal and idler photons are measured using InGaAs/InP avalanche photodetectors. The time correlation between signal and idler photons is obtained using a time interval analyzer with a detection efficiency of 20% and dead time of 15μs.The time bin is set to 81ps and the photon collection time is 240s. The coincidence peak is located ~11ns in the time–bin histogram due to the optical-path difference between the tunable OTF and WDM at respective signal and idler sides. The experimental raw coincidence counts (Hz), calculated by subtracting the accidental rate from the coincidence peak, show a quadratic increase with respect to coupled pump power. At the maximum coupled power of 5mW, the raw coincidence count is ~1Hz. We achieve a raw coincidence–to–accidental ratio (CAR) of up to 3. Therefore, we succeeded to observe correlated photon pair generation based on spontaneous four–wave mixing using the ultra–silicon–rich-nitride waveguide as a CMOS compatible platform, for future applications in quantum technologies.
We report the characterization of correlated photon pairs generated in dispersion-engineered silicon slow-light photonic crystal waveguides pumped by picosecond pulses. We found that taking advantage of the 15-nm flat-band slow-light window (vg~c/30), the bandwidth for correlated photon-pair generation in 96- and 196-μm-long waveguides was at least 11.2 nm, while a 396-μm-long waveguide reduced the bandwidth to 8 nm (only half of the slow-light bandwidth due to the increased impact of phase matching in a longer waveguide). The key metrics for a photon-pair source: coincidence to accidental ratio (CAR) and pair brightness were measured to be a maximum 33 at a pair generation rate of 0.004 pair per pulse in a 196- μm-long waveguide. Within the measurement errors, the maximum CAR achieved in 96-, 196-, and 396-μm-long waveguides is constant. The noise analysis shows that detector dark counts, leaked pump light, linear and nonlinear losses, multiple pair generation, and detector jitter are the limiting factors to the CAR performance of the sources.
Correlated photon pairs at 1.5μm are generated in a silicon wire waveguide (SWW) with a length of only 1.6mm. Experimental results show that the single-side count rates on both sides increase quadratically with pump light, indicating that photons are generated from the spontaneous four-wave mixing (SFWM) processes. The quantum correlation property of the generated photons is demonstrated by the ratio between coincident and accidental coincident count rates. The highest ratio measured at room temperature is to be about 19, showing that generated photon pairs have strong quantum correlation property and low noise. What is more, the wavelength correlation property of the coincident count is also measured to demonstrate the correlated photon pair generation. The experimental results demonstrate that SWWs have great potential in on-chip integrated low-noise correlated photon pair sources at 1.5 μm.
In this paper, correlated photon pairs at 1.55μm are generated in a silicon wire waveguidewith a length of 1.6 mm. The ratio between coincidence count rate and accidental coincidence count rate under room temperature is 19, showing the property of low Raman noise and strong quantum correlation. Moreover, the experiment shows that photon pair generation isstrongly dependent on pump polarization direction. Using quantum perturbation theory, we analyze the contribution of scalar and vectorspontaneous four-wave mixing processes to the generated photon pairs. Due tohigh nonlinear coefficient and high coupling efficiency, the generation rate in quasi-TE mode is much larger than that in quasi-TM mode.The combination of calculated photon pair generation rates through scalar and vector spontaneous four-wave mixing processes agrees well with the experimental result.
In this paper, correlated photon pairs at 1.55μm are generated in a silicon wire waveguidewith a length of 1.6 mm. The ratio between coincidence count rate and accidental coincidence count rate under room temperature is 19, showing the property of low Raman noise and strong quantum correlation. Moreover, the experiment shows that photon pair generation isstrongly dependent on pump polarization direction. Using quantum perturbation theory, we analyze the contribution of scalar and vectorspontaneous four-wave mixing processes to the generated photon pairs. Due tohigh nonlinear coefficient and high coupling efficiency, the generation rate in quasi-TE mode is much larger than that in quasi-TM mode. The combination of calculated photon pair generation rates through scalar and vector spontaneous four-wave mixing processes agrees well with the experimental result.
Sources of quantum correlated photons pairs bridging the 3um-4um Mid-infrared (MIR) band and Telecom/Near-Infrared/Visible band are of high importance for quantum technologies. Spontaneous Parametric Down Conversion is generally used for realizing such sources, but requires costly implementation platforms with reduced versatility. Here, we explore the potentialities of Spontaneous Four-Wave Mixing (SFWM) in all-solid Silicon On Insulator (SOI) waveguides thanks to an experimentally validated model and propose designs ensuring the production of correlated photon pairs bridging the 3um-4um Mid-infrared band and Telecom C-band. Choosing a pump with a wavelength in the range 2100nm-2210nm and a pulse duration of 5ps, we quantitatively performed simulations targeting a probability of photon pair generation per pulse of 0.05, and we found realistic conditions of utilization (2cm-length straight waveguides, intra-modal Four Wave Mixing with the fundamental TE00 mode) with a pump peak power in between 9.2mW and 32mW. A first design (wCOM) reaches a signal wavelength as high as 3.905um, which is situated in an atmospheric transparency window, while maintaining an idler in the Telecom C-band, making it of high interest for atmospheric Quantum Key Distribution. Two other designs wCH4 and wNO2 aim precise CH4 and NO2 gas sensing with a signal wavelength of 3265nm and 3461nm respectively. In terms of signal/idler wavelength separation, wCOM attains the value of 2364nm which is well above the current record of ~1125nm obtained in quantum regime with SFWM in all-solid SOI waveguides.