Generation of spatially pure photon pairs in a multimode nonlinear waveguide using intermodal dispersion

TL;DR

This paper demonstrates a method to generate spatially pure photon pairs in a nonlinear waveguide by exploiting intermodal dispersion, enabling high-quality entangled photon sources without additional filtering.

Contribution

It introduces a novel approach using intermodal dispersion in a waveguide to produce spatially pure photon pairs, enhancing quantum photonics applications.

Findings

Photon pairs produced in well-defined transverse modes

Violation of Bell's inequality with the generated entangled state

Potential for generating spatial and hyperentanglement

Abstract

We present experimental realization of type-II spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate (KTiOPO4) nonlinear waveguide. We demonstrate that by careful exploitation of intermodal dispersion in the waveguide it is feasible to produce photon pairs in well defined transverse modes without any additional spatial filtering at the output. Spatial characteristics is verified by measurements of the M2 beam quality factors. We also prepared a postselected polarization-entangled two-photon state shown to violate Bell's inequality. Similar techniques based on intermodal dispersion can be used to generate spatial entanglement and hyperentanglement.