Near-Infrared and Telecommunication-Wavelength Photon-Pair Source in Optical Fiber

Abstract

We present a photon-pair source in 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 non-degeneracy 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.

Figures (7)

• Figure 1: Experimental setup for generating and characterizing telecommunication-NIR photon pairs created via SFWM. The 1-meter-long 1550 nm PANDA PMF is pumped with 1064 nm fs-pulsed light from an OPO. The polarization is controlled by half waveplates (H) and a polarizing beam splitter (PBS) before spectral filtering with an interference filter (IF) and then coupling into the PMF via a collimation package (Col). The PMF produces photon pairs at 1490 nm and 830 nm and 1430 nm and 850 nm. After the PMF, the signal and idler photons are separated using a coarse wavelength division multiplexer (CWDM). They are further spectrally filtered in free space before being collected back into SMF or multi-mode fiber (MMF), and detected on the superconducting nanowire single-photon detectors (SNSPDs), avalanche photodiodes (APDs) or a spectrometer (SM). The coincidences are measured using a coincidence counter (CC).
• Figure 2: Joint spectral intensities (JSIs) of the photon pairs from stimulated four-wave mixing in the polarization-maintaining fiber. We obtain this JSI via stimulated emission through a tunable seed laser centered at (a) 830 nm for processs 1 and (b) 850 nm for process 2. The intensities are independently normalized to the maximum value for each process.
• Figure 3: Photon-pair statistics as a function of average pump power relative to the signal and idler for processes 1 and 2. (a) Cross-correlation $g^{(2)}$ of the photon pairs. The inset shows the coincidence-count histogram used to calculate the $g^{(2)}$ for process 1 at the maximum pump power. (b) Coincidence count rate. (c) Heralding efficiency. For a given pump power, process 1 produces higher rates and heralding efficiency than process 2.
• Figure 4: Example of the signal (NIR) spectrum we obtain from the PMF.
• Figure 5: Spectral intensity of stimulated emission with different combinations of input spatial modes for the process 1. The seed wavelength is set to 830 nm.