Multimode photon pair generation with high purity in vortex fiber

To enhance communication capacity, quantum communication has been integrated with the traditional optical fiber communication network using mode-division multiplexing (MDM) techniques. Vortex fiber has been demonstrated to be a reliable transmission medium in fiber communication network using MDM technique, where the stable orbital angular momentum (OAM) mode can be used to encode quantum bit. We theoretically demonstrate multimode photon pairs generation with high spectral purity in the designed vortex fiber through the multi-modal spontaneous four-wave mixing (SFWM). The purity can reach 0.9 for all four vector fiber modes including HE₁₁, TE₀₁, TM₀₁, and OAM₁₁. When changing the pump wavelength from 1550nm to 1310nm, the photon pairs generated around two telecom-bands remain a high purity. As the proposed indistinguishable telecom-band photons from different eigen-modes are based on the vortex fiber, it has the potential to become a crucial component in future MDM quantum fiber internet.