Experimental entangled photon pair generation using crystals with parallel optical axes

TL;DR

This paper introduces an optical design for generating polarization-entangled photon pairs using parallel-axis BBO crystals, improving collection efficiency and achieving high fidelity, which benefits quantum optics applications.

Contribution

The design enables higher photon pair rates and fidelity without extra compensators, advancing entangled photon source technology.

Findings

Photon pair rate of at least 65000 pairs/s/mW

Quantum state fidelity of 99.53%

Enhanced spatial mode overlap without additional compensators

Abstract

We present an optical design where polarization-entangled photon pairs are generated within two $\beta$-Barium Borate crystals whose optical axes are parallel. This design increases the spatial mode overlap of the emitted photon pairs enhancing single mode collection without the need for additional spatial walk-off compensators. The observed photon pair rate is at least 65000 pairs/s/mW with a quantum state fidelity of 99.53$\pm$0.22% when pumped with an elliptical spatial profile.