An on-going challenge within scalable optical quantum information processing is to increase the collection efficiency ε and the photon indistinguishability η of the single-photon source toward unity. Within quantum dot-based sources, the prospect of increasing the product [Formula: see text] arbitrarily close to unity was recently questioned. In this work, we discuss the influence of the trade-off between efficiency and indistinguishability in the presence of phonon-induced decoherence, and we show that the photonic “hourglass” design allows for improving [Formula: see text] beyond the predicted maximum for the standard micropillar design subject to this trade-off. This circumvention of the trade-off is possible thanks to control of the spontaneous emission into background radiation modes, and our work highlights the importance of engineering of the background emission in future pursuits of near-unity performance of quantum dot single-photon sources.

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In this paper, we introduce a quantum photonic device, which we term the photonic Bier-Glas cavity. We 1 discuss its fabrication and functionality, which is based on the coupling of integrated In(G(a)As quantum dots to a broadband photonic cavity resonance. By design, the device architecture uniquely combines the Purcell enhancement of a photonic micropillar structure with a broadband photonic mode shaping of a vertical, tapered waveguide, making it an interesting candidate to enable the efficient extraction of entangled photon pairs. We detail the epitaxial growth of the heterostructure as well as the necessary lithography steps to approach a GaAsbased photonic device with a height exceeding 15 μm, supported on a pedestal that can be as thin as 20 nm. We further describe its key performance parameters using a Fourier-modal method. Finally, we present an optical characterization, which confirms the presence of broadband optical resonances, in conjunction with amplified spontaneous emission of single photons.