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Circular Bragg Gratings for Enhanced Emission and Spin Coherent Control of Silicon C Centers

Junchun Yang, Alessandro Puddu, Shuyu Wen, Sourav Dev, Shengqiang Zhou, Yonder Berencén, Kambiz Jamshidi

Published Jan 1, 2026• 0 citations
Publisher

Abstract

We design and simulate a circular-Bragg-grating (CBG) cavity simulation optimized for silicon C center (1571 nm) achieving 11× Purcell enhancement and 40% collection efficiency (NA=0.65).
DOI
10.1364/cleo_at.2026.jtu.135

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Efficient extraction of photons coming from solid-state spin systems is one of the main challenges when aiming to increase the size and complexity of quantum information protocols using these type of systems. An example of this is the read-out of photoluminescence from an NV centres in plain bulk diamond. Due to the refractive index contrast, only a fraction of the light coming from the defect can be collected. Several top-down fabrication strategies have been used in the past decade to fabricate structures such as lenses and cavities around NV centres in order to increase the extraction efficiency using bulk optics [1] . However to fully exploit the potential of color centres in diamond, integration with on-chip waveguides and cavities is necessary. Remarkable effort has been made to fabricate photonic structures on bulk diamond [2] yet the laborious diamond undercut methods and the reduced versatility of these top-down approaches limit the scope for scalability and integration.
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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.