Abstract
Nitrogen-vacancy (NV) centers feature outstanding properties such as a spin coherence time of up to 1 s as well as a level structure offering the possibility to initialize, coherently manipulate, and optically read-out the spin degree of freedom of the ground state. However, only about 3% of their photon emission is channeled into the zero phonon line (ZPL), limiting both the rate of indistinguishable single photons and the signal-to-noise ratio (SNR) of coherent spin-photon interfaces. We here report on the enhancement of the SNR of the optical spin read-out achieved by tuning the mode of a two-dimensional photonic crystal (PhC) cavity into resonance with the NV-ZPL. PhC cavities are fabricated by focused ion beam milling in thin reactive ion etched ultrapure single crystal diamond membranes featuring modes with Q-factors of up to 8250 at mode volumes below one cubic wavelength. NV centers are produced in the cavities in a controlled fashion by a high resolution atomic force microscope implantation technique. On cavity resonance, we observe a lifetime shortening from 9.0 ns to 8.0 ns as well as an enhancement of the ZPL emission by almost one order of magnitude. Although on resonance the collection efficiency of ZPL photons and the spin-dependent fluorescence contrast are reduced, the SNR of the optical spin read-out is almost tripled for the cavity-coupled NV centers.
Highlights
The nitrogen-vacancy (NV) center, a point defect in diamond consisting of a lattice vacancy and an adjacent nitrogen substitution, has attracted a lot of interest during the past years owing to its outstanding optical and spin properties.[1]
We here report on the enhancement of the signal-to-noise ratio (SNR) of the optical spin read-out achieved by tuning the mode of a two-dimensional photonic crystal (PhC) cavity into resonance with the NV-zero phonon line (ZPL)
We report on the SNR enhancement achieved by coupling NV centers to a two-dimensional PhC cavity
Summary
The nitrogen-vacancy (NV) center, a point defect in diamond consisting of a lattice vacancy and an adjacent nitrogen substitution, has attracted a lot of interest during the past years owing to its outstanding optical and spin properties.[1]. As visible from Eq (2), a large SNR of optical spin read-out requires both a large collected photon rate and a large contrast of spindependent fluorescence.[16]. The collection efficiency can be modified by coupling NV centers to whispering gallery,[36,39] photonic crystal (PhC),[40–44] or fiber-based cavities[45,46] as well as to plasmonic structures.[47,48]. By such a coupling, the local density of states at the emitter’s position and its spontaneous emission rate may be enhanced or, correspondingly, the spontaneous emission lifetime reduced by the Purcell-factor F.49. Successful coupling of NV centers to low mode volume, tunable cavities was recently demonstrated employing thin diamond membranes embedded into Fabry-Pérot microcavities.[45]. We experimentally measure and theoretically simulate the modification of spin-dependent fluorescence contrast C and SNR on resonance
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