Enhancing the efficiency of quantum-dot-based single-photon source designs by suppressing background emission using concentric rings

In this paper, we theoretically demonstrate that a few-period circular Bragg reflector consisting of concentric rings placed around an infinite nanowire with an embedded quantum dot can increase the fraction of radiative emission into the fundamental ${\mathrm{H}\mathrm{E}}_{11}$ mode ($\beta ={\mathrm{\Gamma }}_{\mathrm{H}{\mathrm{E}}_{11}}\mathrm{/}{\mathrm{\Gamma }}_{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}}$) up to 0.999 due to enhanced suppression of the emission into radiation modes caused by a photonic bandgap effect. We then apply this strategy in the practically relevant case of the finite-sized single-photon source based on tapered nanowires and demonstrate that the collection efficiency can be improved. Additionally, we also show the beneficial effects of placing optimized rings around the micropillar single-photon source.