Pure narrowband photon-pair generation in a monolithic cavity

TL;DR

This paper introduces a monolithic cavity-based heralded single-photon source optimized for high spectral and spatial purity, achieving high heralding efficiency and low multi-photon contamination at 1540 nm.

Contribution

The work demonstrates a novel monolithic cavity design for pure photon-pair generation with enhanced spectral purity and efficiency, advancing quantum photonic source technology.

Findings

Heralded single photons at 1540 nm with 70% efficiency.

Spectral purity increased to 96.2% using an etalon.

Theoretical upper bound on purity is 79.4%.

Abstract

Photonic quantum technologies require efficient sources of pure single photons. We present a heralded single-photon source based on spontaneous parametric down-conversion in a monolithic cavity optimized for high spectral and spatial purity. The source heralds single photons at a wavelength of 1540 nm and a spectral bandwidth of 168 MHz, with a maximum heralding efficiency of 70% including all transmission and detection losses, while keeping the multi-photon contamination below 3%. The cavity enhancement predominantly generates photons into the central cavity mode, with a theoretical upper bound on the spectral purity of 79.4% arising from nonzero overlap with adjacent cavity modes. Spectral isolation of the central cavity mode with an etalon yields an increased measured spectral purity of (96.2 $\pm$ 2.7)%.