High-performance designs for fiber-pigtailed quantum-light sources based on quantum dots in electrically-controlled circular Bragg gratings

TL;DR

This paper numerically optimizes fiber-coupled quantum dot sources in circular Bragg gratings, achieving high efficiency, robustness to fabrication errors, and electrical control for wavelength tuning in relevant telecom and visible regimes.

Contribution

It introduces a Bayesian optimization-based design approach for high-performance, electrically tunable fiber-coupled quantum dot sources with robustness to fabrication tolerances.

Findings

Achieved >86% fiber coupling efficiency with Purcell factors >20.

Designed devices maintain >82% fiber efficiency despite fabrication variations.

Electrical fields for Stark tuning are feasible in the optimized designs.

Abstract

We present a numerical investigation of directly fiber-coupled hybrid circular Bragg gratings (CBGs) featuring electrical control for operation in the application relevant wavelength regimes around 930 nm as well as the telecom O- and C-band. We use a surrogate model combined with a Bayesian optimization approach to perform numerical optimization of the device performance which takes into account robustness with respect to fabrication tolerances. The proposed high-performance designs combine hCBGs with a dielectric planarization and a transparent contact material, enabling >86% direct fiber coupling efficiency (up to >93% efficiency into NA 0.8) while exhibiting Purcell Factors >20. Especially the proposed designs for the telecom range prove robust and can sustain expected fiber efficiencies of more than $(82.2\pm4.1)^{+2.2}_{-5.5}$% and expected average Purcell Factors of up to $(23.2\pm2.3)^{+3.2}_{-3.0}$ assuming conservative fabrication accuracies. The wavelength of maximum Purcell enhancement proves to be the most affected performance parameter by the deviations. Finally, we show that electrical field strengths suitable for Stark-tuning of an embedded quantum dot can be reached in the identified designs.