Efficient single photon sources based on nanodiamonds on a plasmonic platform

We report on an efficient room-temperature source of single photons based on single nitrogen-vacancy centers in nanodiamonds (NDs) placing on a large-area plasmonic platform formed by crystalline gold flakes covered with a thin dielectric layer. Due to the strongly confined plasmonic fields in the thin dielectric layer, the NDs show a large enhancement in the fluorescence intensity without significant degradation in single photon purity. According to the deduced fluorescence lifetime from g⁽²⁾ measurements, the Purcell factor is estimated to be ~1.4. The plasmonic platform is very ideal for large-area fluorescence enhancement without the needs of sophisticated nanopositioning schemes for locating NDs at local hot spots in conventional plasmonic nanostructures.