Nitrogen-Vacancy centers coupled to fiber-based optical micro-cavities

We present our efforts to couple nitrogen-vacancy centers (NVs) embedded in micron-thin, ultra-smooth diamond membranes to the optical modes of a fiber-based microcavity. We take advantage of the membrane-based approach to channel the NVs emission to low-loss modes and show cavity finesses up to 20000 for the operational platform. In addition, the cavity can be tuned to modify the NV spectrum over a wide spectral range (ar. 650 to 710 nm). At room temperature and for our typical cavity mode volume, phonon-induced linewidth broadening of the NV spectrum prevents modification of the radiative lifetime (the Purcell effect). However if the cavity length can be reduced down to a few microns, a phonon-assisted process helps increasing the fraction of emitted photon in the cavity mode beyond simple spectral filtering. We discuss progress toward the observation of cavity-funneling with the membrane-based approach. This first step in the direction of coupling broad transitions to "good cavities" is essential for the realization of tunable single-photon sources with high indistinguishability at room temperature.