Hybrid nanocavities for resonant enhancement of color center emission in   diamond
  Resonantly enhanced emission from the zero phonon line of a diamond nitrogen-vacancy (NV) center in single crystal diamond is demonstrated experimentally using a hybrid whispering gallery mode nanocavity. A 900 nm diameter ring nanocavity formed from gallium phosphide, whose sidewalls extend into a diamond substrate, is tuned onto resonance at low-temperature with the zero phonon line of a negatively charged NV center implanted near the diamond surface. When the nanocavity is on resonance, the zero phonon line intensity is enhanced by approximately an order of magnitude, and the spontaneous emission lifetime of the NV is reduced as much as 18%, corresponding to a 6.3X enhancement of emission in the zero photon line. 
Paul E. Barclay, Kai-Mei C. Fu, Charles Santori, Andrei Faraon,   Raymond G. Beausoleil
quant-ph cond-mat.mes-hall