Coupling of a single nitrogen vacancy colour centre in diamond, to a planar microcavity

Single negatively charged nitrogen-vacancy (NV^-) defect centres in diamond are attractive systems for the implementation of solid state quantum information processing (QIP) and quantum key distribution (QKD). In both approaches, the coupling of an individual NV^- centre to a resonant microcavity is of interest: it would improve the optical readout of the NV ^- centre electron spin state in QIP and enhance the collection efficiency of the single photon fluorescence in QKD while increasing the coherence length of the emission. We theoretically demonstrate that, at room temperature, the coupling to a single-mode Fabry-Perot microcavity can be used to obtain a fluorescence spectrum narrowing without loss of total intensity. We also experimentally demonstrate the control of the fluorescence spectrum of a single NV^- centre by adjusting the thickness of the microcavity. Finally, we report a doubling of the emission spectral density with respect to the single mirror configuration.