Efficient Collection of Light from Colloidal Quantum Dots with a Hybrid Metal-Dielectric Nanoantenna

We introduce a hybrid metal-dielectric nanoantenna consisting of a metallic bullseye nanostructure and a dielectric waveguide layer, for directing the photon emission of embedded colloidal nanocrystal quantum dots. This structure overcomes the intrinsic losses of plasmonic nanoantennas on one hand and is much more scalable than dielectric nanoantennas on the other. The experimental results demonstrate a very low divergence angle beam, allowing a collection efficiency of 30% of the quantum dot emission into a numerical aperture of 0.55. The experimental results are well reproduced by numerical simulations, which predict a maximal collection efficiency larger than 25% directly into a single mode fiber having a numerical aperture of 0.12 without the need for any additional optics. Such hybrid nanoantennas can significantly improve the performance of quantum dot based devices, from displays to single-photon sources.