Compact source of narrow-band counterpropagating polarization-entangled photon pairs using a single dual-periodically poled crystal

TL;DR

This paper introduces a compact, narrow-band, backward-wave polarization-entangled photon source using a dual-periodically poled crystal, offering high spectral brightness and stability for quantum communication applications.

Contribution

It presents a novel backward-wave SPDC scheme in a dual-periodically poled crystal, achieving narrow bandwidth and high brightness without state projection.

Findings

Bandwidth of 3.6 GHz with 2-cm crystal length

Spectral brightness exceeds 100 pairs/(s GHz mW)

Compatible with degenerate and non-degenerate cases

Abstract

We propose a scheme for the generation of counterpropagating polarization-entangled photon pairs from a dual-periodically poled crystal. Compared with the usual forward-wave type source, this source, in the backward-wave way, has a much narrower bandwidth. With a 2-cm-long bulk crystal, the bandwidths of the example sources are estimated to be 3.6 GHz, and the spectral brightnesses are more than 100 pairs/(s GHz mW). Two concurrent quasi-phase-matched spontaneous parametric down-conversion processes in a single crystal enable our source to be compact and stable. This scheme does not rely on any state projection and applies to both degenerate and non-degenerate cases, facilitating applications of the entangled photons.