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Journal of the Optical Society of America B

Correlated C-band photon-pair generation in a few-mode fiber with intermodal four-wave mixing

Seyedehnajmeh Montazeri, Mina Esmaeelpour

Published Jul 15, 2026• 0 citations

Abstract

We demonstrate intermodal spontaneous four-wave mixing in a 500 m graded-index few-mode fiber, generating correlated photon pairs in distinct spatial modes at room temperature and under cryogenic cooling. Two nondegenerate pumps at 1550 and 1551 nm are launched into the LP 01 and LP 11 spatial modes, enabling flexible phase matching and strong intermodal photon-pair correlations spanning the optical C band. Cooling the fiber to −160 ∘ C in a liquid-nitrogen-cooled cryogenic chamber substantially suppressed spontaneous Raman scattering without degrading the four-wave mixing process. Spectral and power-dependent measurements confirm quadratic photon-pair scaling with pump power and reduced linear Raman background at low temperature. Coincidence measurements show a coincidence-to-accidental ratio of 39±0.03 at −160 ∘ C, representing approximately a 40.8% improvement over room temperature. With photonic-lantern-based mode excitation and collection, the source exhibits low modal crosstalk and clean mode separation. This approach provides a practical route to low-noise, fiber-integrated photon-pair sources for scalable quantum photonics.

DOI: 10.1364/josab.600108

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We report our recent progress in generating and verifying entangled photon pairs in a telecommunication-length few-mode fiber using spontaneous four-wave mixing in a non-degenerate pump configuration. We demonstrate through seeding the desired four-wave mixing effect for pair production in the presence of a strong mode-coupling when using integrated mode multiplexers known as photonic lanterns. The mode content and phase-matching requirements were validated through computations and experiments. We discuss the challenges and requirements for phase matching and photon visibility without modifying the fiber structure. This work represents our first steps toward an efficient tunable source of entangled photons for space division multiplexing applications.