We present both theoretical and experimental results on fluorescence of single defect centers in diamond nanocrystals embedded in a planar dielectric microcavity. From a theoretical point of view, we show that the overall fluorescence collection efficiency using moderate numerical aperture microscope objective can be enhanced by using a low quality factor microcavity. This could be used in particular for low temperature applications where the numerical aperture of collection microscope objectives is limited due to the experimental constraints. We experimentally investigate the control of the fluorescence spectrum of the emitted light from a single center. We show the simultaneous narrowing of the room temperature broadband emission spectrum and the increase of the fluorescence spectral density.
Photoluminescence (PL) spectra of single nitrogen vacancy (NV) centers in 50-nm diamond nanocrystals at the zero-phonon line (ZPL) were directly observed using a Fabry-Perot interferometer at cryogenic temperatures. The narrowest linewidth of ZPL was 1.2 GHz (1.9 ± 0.7 GHz on average), comparable to ZPL linewidths in PL spectra reported for NV centers in pure bulk diamond. This observation is important to the application of NV centers for use in quantum communication and computation devices, and in nano-sensing.
Quantum networks based on nitrogen-vacancy (N-
V) color centers in diamond will enable technology such as communication secured by the laws of nature, and blind quantum computation in the cloud. However, scaling to large distances and many nodes is hindered by the small coherent photon emission and collection from N-
V centers. By embedding a thin diamond membrane bearing coherent color centers into an open, tunable fiber-based optical microcavity, the authors demonstrate that the centers' emission can be enhanced in a fashion compatible with entanglement generation. This work is an important step toward employing N-
V centers in large-scale quantum networks with long coherence.