Engineering entangled photons for transmission in ring-core optical fibers

TL;DR

This paper demonstrates enhanced generation and coupling of entangled photon pairs into ring-core optical fibers using perfect vortex modes, enabling improved quantum communication with high-dimensional orbital angular momentum states.

Contribution

It introduces a method to increase photon pair coupling efficiency into ring-core fibers by using perfect vortex modes for pumping, advancing quantum state engineering.

Findings

Coupling efficiency increased by nearly three times using perfect vortex modes.

The two-photon orbital angular momentum spectrum remains nearly constant.

Superposition of vortex modes enables tailored quantum state generation.

Abstract

The capacity of optical communication channels can be increased by space division multiplexing in structured optical fibers. Radial core optical fibers allows for the propagation of twisted light--eigenmodes of orbital angular momentum, which have attracted considerable attention for high-dimensional quantum information. Here we study the generation of entangled photons that are tailor-made for coupling into ring core optical fibers. We show that the coupling of photon pairs produced by parametric down-conversion can be increased by close to a factor of three by pumping the non-linear crystal with a perfect vortex mode with orbital angular momentum $\ell$, rather than a gaussian mode. Moreover, the two-photon orbital angular momentum spectrum has a nearly constant shape. This provides an interesting scenario for quantum state engineering, as pumping the crystal with a superposition of perfect vortex modes can be used in conjunction with the mode filtering properties of the ring core fiber to produce simple and interesting quantum states.