Broadband enhancement and high extraction efficiency from single quantum dots embedded in microlenses coupled with a gold mirror

We present a broadband enhanced single photon source device of Gaussian-shaped GaAs microlens (ML) arrays coupled with a gold bottom mirror hybrid structure. The extrapolated light extraction efficiency of (60.6 ± 1.5)% at maximum (for collection numerical aperture = 0.45 and based on the an actually measured raw detection efficiency of ∼0.775%) and a broad spectral band of 890–960 nm were obtained. The ML-Au structure with embedded epitaxial quantum dots exhibits a high single-photon purity of (96.6 ± 0.7)% [g(2)(0) = 0.034 ± 0.003] under pulsed excitation with 20% saturation. Wet-etched microlenses with smooth surfaces achieve simultaneous enhancement of both XX and X exciton emissions, which is prerequisite for promising entangled photon pair generation. This work proposes the bright potential of integrated hybrid structures to enable further photon pair entanglement applications.