Novel Single-mode Narrow-band Photon Source of High Brightness for Hybrid Quantum Systems

TL;DR

This paper presents a high-brightness, single-mode photon source at 852 nm with narrow bandwidth, achieved through a novel mode-selection technique that enhances hybrid quantum system applications.

Contribution

Introduces a new birefringent element-based mode-selection method enabling single-mode operation without filters in cavity-enhanced SPDC.

Findings

Photon bandwidth of 10.9 MHz

Photon-pair rate exceeds 47 KHz at 10 mW pump power

Four-photon generation rate of 37 Hz at 20 mW pump

Abstract

Cavity-enhanced Spontaneous parametric down-conversion (SPDC) is capable of efficient generation of single photons with suitable spectral properties for interfacing with the atoms. However, beside the remarkable progress of this technique, multi-mode longitudinal emission remains as major drawback. Here we demonstrate a bright source of single photons that overcomes this limitation by a novel mode-selection technique based on the introduction of an additional birefringent element to the cavity. This enables us to tune the double resonance condition independent of the phase matching, and thus to achieve single-mode operation without mode filters. Our source emits single-frequency-mode photons at 852 nm, which is compatible to the Cs D2 line, with a bandwidth of 10.9 MHz and a photon-pair generation rate exceeding 47 KHz at 10 mW of pump power, while maintaining a low $g^{\left(2\right)}(0) =$ 0.13. The efficiency of our source is further underlined by measuring a four-photon generation rate of 37 Hz at 20 mW of pump power. This brightness opens up a variety of new applications reaching from hybrid light-matter interactions to optical quantum information tasks based on long temporal coherence.