The flux of coherent photons emitted by single NV centres in diamond is very low on account of three problems: (i) only a small percentage are emitted into the zero-phonon-line (ZPL); (ii) the extraction efficiency out of the high-index diamond host is small; and (iii) the radiative lifetime is large. All three problems can be solved by embedding a single NV centre into a high-Q-factor, low mode-volume microcavity tuned to the ZPL. In our paper just published in Physical Review X, we show that this concept can be implemented using a tunable, highly-miniaturised microcavity. The ZPL fraction increases from ∼3% to close to 50%.

Schematic of a diamond membrane embedded in a highly miniaturised Fabry-Perot cavity