Efficient out-coupling of high-purity single photons from a coherent quantum dot in a photonic-crystal cavity
Abstract
We demonstrate a single-photon collection efficiency of (44.32.1)\% from a quantum dot in a low-Q mode of a photonic-crystal cavity with a single-photon purity of g(2)(0)=(45)\% recorded above the saturation power. The high efficiency is directly confirmed by detecting up to 96246 kilocounts per second on a single-photon detector on another quantum dot coupled to the cavity mode. The high collection efficiency is found to be broadband, as is explained by detailed numerical simulations. Cavity-enhanced efficient excitation of quantum dots is obtained through phonon-mediated excitation and under these conditions, single-photon indistinguishability measurements reveal long coherence times reaching 0.770.19 ns in a weak-excitation regime. Our work demonstrates that photonic crystals provide a very promising platform for highly integrated generation of coherent single photons including the efficient out-coupling of the photons from the photonic chip.