Optical fiber polarization-entangled photon pair source using intermodal spontaneous four-wave mixing in the visible spectral band

The theoretical and experimental investigation results of the generation of the polarization-entangled photon pairs operating at visible wavelengths are reported. The generation of polarization-entangled photon pairs was based on intermodal spontaneous four-wave mixing (IM-SFWM) using standard step-index few-mode fiber. It was shown theoretically that several combinations of IM-SFWM processes could occur depending on spatial modes of a pump beam. A polarization-entangled photon pair source based on Sagnac loop incorporating a segment of few-mode fiber were then experimentally created. A two-photon interference fringe visibility of our implemented photon pair source were 91.7% and 88.8% in H/V bases and D/A bases, respectively. A quantum state tomography was also conducted to reconstruct the density matrix of the generated state with a fidelity to a maximum entangled state of 93.1%.

Automated summary

This article reports the theoretical and experimental investigation results of generating polarization-entangled photon pairs at visible wavelengths. The generation was based on intermodal spontaneous four-wave mixing using standard step-index few-mode fiber. Theoretical analysis showed that different combinations of intermodal spontaneous four-wave mixing processes could occur based on the spatial modes of the pump beam. Experimental results demonstrated the successful creation of a polarization-entangled photon pair source by incorporating a segment of few-mode fiber in a Sagnac loop. The visibility of two-photon interference fringes of the implemented source was 91.7% and 88.8% in H/V bases and D/A bases, respectively. Furthermore, a quantum state tomography was conducted to reconstruct the density matrix of the generated state with a fidelity to a maximum entangled state of 93.1%.