B-centers in hexagonal boron nitride (hBN) are gaining significant research interest for quantum photonics applications due to precise emitter positioning and highly reproducible emission wavelengths at 436 nm. Here, we leverage the layered nature of hBN to directly measure the quantum efficiency (QE) of single B-centers. The defects were engineered in a 35 nm flake of hBN using electron beam irradiation, and the local dielectric environment was altered by transferring a 250 nm hBN flake on top of the one containing the emitters. By analyzing the resulting change in measured lifetimes, we determined the QE of B-centers in the thin flake of hBN. Additionally, we propose two approaches to quantify the QE of B-centers in thick flakes of hBN. Our results indicate that B-centers located in thin flakes can exhibit QEs higher than 40 %. Near-unity QEs are achievable under reasonable Purcell enhancement for emitters embedded in thick flakes of hBN, highlighting their promise for quantum photonics applications.

中文翻译：

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六方氮化硼B中心的量子效率


由于精确的发射器定位和 436 nm 处高度可重复的发射波长，六方氮化硼 (hBN) 中的 B 中心正在获得量子光子学应用的重大研究兴趣。在这里，我们利用 hBN 的分层性质来直接测量单个 B 中心的量子效率 (QE)。使用电子束辐照在 35 nm 六方氮化硼薄片中设计缺陷，并通过将 250 纳米六方氮化硼薄片转移到包含发射极的薄片顶部来改变局部介电环境。通过分析测量寿命的变化，我们确定了六方氮化硼薄片中 B 中心的 QE。此外，我们提出了两种方法来量化 hBN 厚片中 B 中心的 QE。我们的结果表明，位于薄片中的 B 中心可以表现出高于 40% 的 QE。对于嵌入六方氮化硼厚片中的发射器，在合理的 Purcell 增强下可以实现接近一致的 QE，这凸显了它们在量子光子学应用中的前景。