High-Performance Labyrinth Circular Bragg Grating Design for Charge and Stark-Tunable Quantum Light Sources Spanning Visible to Telecom Wavelengths

TL;DR

This paper introduces an optimized labyrinth circular Bragg grating design that enables high-efficiency, electrically tunable quantum dot single-photon sources across visible to telecom wavelengths, overcoming previous limitations of optical performance degradation.

Contribution

It proposes a novel labyrinth CBG geometry with optimized design parameters that maintain high optical performance while allowing electrical integration for quantum light sources.

Findings

Achieved over 90% collection efficiency at three key wavelengths.

Demonstrated Purcell factors greater than 25 across wavelengths.

Designed a device layout with a barrier layer to prevent tunneling, maintaining performance.

Abstract

Semiconductor quantum dots embedded in circular Bragg gratings (CBGs) are among the most efficient integrated single-photon sources. However, the fully etched rings of conventional CBGs restrict the implementation of charge and Stark tuning via electrical contacts. To overcome this limitation, a labyrinth CBG geometry with four bridges has been proposed, yet the added bridges significantly degraded optical performance. In this work, we numerically demonstrate that a periodic labyrinth CBG design preserves both high coupling efficiency and strong Purcell enhancement while enabling electrical integration if optimized after introducing the bridges. We show three optimized designs at emission wavelengths of 780 nm, 930 nm, and 1550 nm, because these wavelengths are among the most relevant for quantum dots and show the general applicability of our approach. At all three wavelengths collection efficiencies exceeding 90% into a numerical aperture of 0.7 and Purcell factors greater than 25 are achieved. Furthermore, we propose a device layout incorporating a barrier layer that separates p- and n-doped semiconductor regions, which is incorporated to prevent tunneling of one of the charge carriers for selective charging. Also this design can be reoptimized to retain the performance of a device without tunnel barrier. These results establish labyrinth CBGs as a platform for electrically tunable quantum dot single-photon sources with high efficiency and scalability.