Efficient fiber coupling of telecom single-photons from circular Bragg gratings

TL;DR

This paper investigates and compares different fiber coupling methods for quantum dot single-photon sources at telecom wavelengths, demonstrating improved efficiency and stability crucial for quantum communication networks.

Contribution

It systematically evaluates fiber coupling performance with various optical configurations, highlighting a method that increases efficiency and stability for fiber-coupled quantum light sources.

Findings

End-to-end efficiency increased by up to 3 times with optimized fiber optics.

Less than 50% count rate drop with several micrometers misalignment.

Quantified spatial tolerance for stable fiber-cavity coupling.

Abstract

Deterministic sources of quantum light are becoming increasingly relevant in the development of quantum communication, particularly in deployed fiber networks. Therefore, efficient fiber-coupled sources at telecom wavelength are highly sought after. With this goal in mind, we systematically investigate the fiber coupling performance of quantum dots in optical resonators under three experimental configurations. We quantify coupling efficiency and sensitivity to spatial displacement for single-mode fibers with 3D printed optics on their tip, and benchmark their behavior over a commercial cleaved-cut fiber and a standard optical setup. The reduction of the required optical elements when operating with a lensed or a bare fiber allows for an increased end-to-end efficiency by a factor of up to 3.0 +/- 0.2 over a standard setup. For the perspective of realizing a mechanically stable fiber-coupled source, we precisely quantify the spatial tolerance to fiber-cavity misalignment, observing less than 50 % count rate drop for several micrometers displacement. These results will play a key role in the future development of fiber-coupled sources of quantum light.