Bright single-photon emission from a GeV center in diamond under a microfabricated solid immersion lens at room temperature

Abstract

We report on the metrological characterization of the emission from a germanium-vacancy center in diamond under a microfabricated solid immersion lens in a confocal laser-scanning microscope setup. Ge ions were implanted into a synthetic diamond at 3 MeV, and germanium-vacancy centers were then formed by subsequent annealing. Afterward, solid immersion lenses were fabricated in a focused ion beam scanning electron microscope. The photoluminescence was investigated at room temperature in terms of the spectral distribution, the excited state lifetime, the second-order correlation function, and the saturation behavior, proving simultaneous high single-photon purity and high brightness. Two methods were exploited to minimize the residual multi-photon probability: spectral filtering and temporal filtering. According to these results, we assume that Raman scattered photons and emission from neighboring color centers play an important role in the residual multi-photon emission probability. The system efficiency of the single-photon source was investigated and found to be in accordance with the value calculated from all sources of loss in the setup. The branching ratio of the germanium-vacancy center for the decay into the ground state and into metastable state was calculated. The results enable the usage of the single-photon source in future quantum radiometric experiments.

Structural formation yield of GeV centers from implanted Ge in diamond

“…It is frequently stated in the literature, e.g. [1,4,8,17,24,25,28,58], that thermal annealing with the aim of driving vacancies towards the implanted impurity would be an essential step in the formation mechanism of impurity-vacancy complexes in diamond. While this concept has proven valuable in what concerns formation of the nitrogen-vacancy complex, it is clearly not correct for the cases of Sn, Mg, Ge, and Ga since it was shown already that both SnV [30] and MgV [31] complexes are quite obviously already formed in significant amounts in the RT as-implanted state, as is also shown for GeV and GaV in this work.…”