We present a fiber-based multichannel source of correlated photon pairs in the telecommunication O-band. Coincidence-to-accidental ratios >100 (≃1) are measured between the paired (unpaired) signal-idler channels.
We demonstrate an all-fiber photon-pair source with the highest coincidence-to-accidental ratio (CAR) reported to date in the fiber-optic telecom C-band. We achieve this through careful optimization of pairproduction efficiency as well as careful characterization and minimization of all sources of background photons, including Raman generation in the nonlinear fiber, Raman generation in the single-mode fiber, and leakage of pump photons. We cool the nonlinear fiber to 4 K to eliminate most of the Raman scattering, and we reduce other noise photon counts through careful system design. This yields a CAR of 1300 at a pair generation rate of 2 kHz. This CAR is a factor of 12 higher than previously reported results in the C-band. Measured data agree well with theoretical predictions.
We present a photon-pair source in a commercially available optical fiber that produces paired photons at telecommunication and near-infrared (NIR) wavelengths. The highly nondegenerate pairs are 700 nm apart: one in the 1500 nm E- and S-band telecommunication range and the other in the 830 nm NIR range. The high nondegeneracy means the photon pairs are far-detuned from Raman noise, resulting in a high coincidence-to-accidental ratio even while operating at room temperature. The source produces two spectrally and spatially distinct phase-matched processes with low spectral cross-talk, distinct transverse spatial modes in the NIR, and a single fundamental spatial mode in the telecommunication range. The source’s room-temperature operation, off-the-shelf materials, and multiplexing potential make it promising for deployment in quantum networks.
We present a fiber-based source of polarization-entangled photon pairs that is well suited for quantum communication applications in the 1.5μm band of standard telecommunication fiber. Quantum-correlated signal and idler photon pairs are produced when a nonlinear-fiber Sagnac interferometer is pumped in the anomalous-dispersion region of the fiber. Recently, we have demonstrated nonclassical properties of such photon pairs by using Geiger-mode InGaAs/InP avalanche photodiodes. Polarization entanglement in the photon pairs can be created by pumping the Sagnac interferometer with two orthogonally polarized pulses. In this case the parametrically scattered signal-idler photons yield biphoton interference with $>$90% visibility in coincidence detection, while no interference is observed in direct detection of either the signal or the idler photons.