Ultrabright fiber-coupled ploarization-entangled photon source with spectral brightness surpassing 2.0 MHz/mW/nm

We present an ultrabright polarization-entangled photon source that is optimally coupled into single-mode fibers (SMFs). This study theoretically and experimentally examines the characteristics of spontaneous parametric down-conversion (SPDC) photons, including their spectrum, bandwidth, emission an...

Full description

Saved in:
Bibliographic Details
Published in:arXiv.org 2024-09
Main Authors: Park, Kyungdeuk, Lee, Jungmo, Dong-Gil Im, Kim, Dongkyu, Ihn, Yong Sup
Format: Article
Language:English
Subjects:
Brightness
Coupled modes
Crystals
Entangled states
Extreme values
Gaussian beams (optics)
Optimization
Photon beams
Photons
Polarization
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We present an ultrabright polarization-entangled photon source that is optimally coupled into single-mode fibers (SMFs). This study theoretically and experimentally examines the characteristics of spontaneous parametric down-conversion (SPDC) photons, including their spectrum, bandwidth, emission angle, and intensity, as functions of crystal length, temperature and beam waist condition. Notably, we measure the collinear spatial modes of photon-pairs and collection optics under various beam waist conditions and analyze them using a collinear Gaussian approximation model. By employing a simple mode-matching optical setup, we optimize the SMF coupling and heralding efficiencies of the photon-pairs. Consequently, we achieve a spectral brightness exceeding 2.0 MHz/mW/nm from a fiber-coupled entangled photon source, utilizing a 30-mm ppKTP crystal inside a polarization Sagnac interferometer. This represents the highest spectral brightness of SPDC photons generated using a CW laser pumped bulk crystal to date. Polarization entanglement was verified by a quantum state tomography and a polarization-correlation measurement. The fidelity of the entangled state is measured to be 97.8 % and the Bell-CHSH value S = 2.782 +- 0.04. The results obtained here provide practical insights for designing high-performance SPDC sources for satellite-based communication and long-distance optical links with extremely high-photon loss.
ISSN:2331-8422