A broad-band planar-microcavity quantum-dot single-photon source with a solid immersion lens.

The integration of single quantum dots (QDs) into a planar Fabry–Pérot microcavity has been established as a direct and viable approach to vertically steer photons emitted from the quantum emitters, resulting in a strong increase in the source brightness, which becomes particularly evident when a lens with a low numerical aperture is used. However, the spectral bandwidth of QD–microcavity structures is limited and determined by their intrinsic quality factor; these structures are, thus, not ideal for the extraction of entangled photon pairs or for studies of exciton dynamics. We have found that, when a deterministic low-index solid immersion lens is placed on top of the QD in a QD–microcavity structure, the structure exhibits an enhancement in the bandwidth to 27 nm and a source brightness of 23%. The solid immersion lens is deterministically fabricated via two-photon absorption and can be remade several times without perturbing the QD, ensuring that the QD's intrinsic properties are preserved and ensuring its long-term reliability. [ABSTRACT FROM AUTHOR]