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(a) Schematic of evanescent coupling of single photons emitted by a single nitrogen vacancy center (hosted in a diamond nano-crystal) to a single guided mode of a TOF. Inset: FDTD simulation of the intensity distribution of a radiating NV-center coupled to the nano-fiber. (b) Schematic diagram of the experimental setup. An inverted optical confocal scanning microscope is used to analyze the fluorescence properties of individual diamond nano-crystals. In addition, an AFM is employed for in-situ nano-manipulation of individual crystals. Operating both microscopes at the same time allows to position a diamond nano-crystal (hosting only a single NV-center) on demand onto the apex of the optical nano-fiber.
(a) Schematics of the on-demand positioning of single fluorescing diamond nano-crystals onto the apex of an optical nano-fiber. (b) Topography and (c) optical scan before pick-up, after pick-up, and after placing onto the optical fiber (from left to right).
Second-order correlation function of fluorescence light emitted by a single NV-center for different excitation powers P = (0.5,1.0,1.5,2,3,4,5,6,8,10) mW (from bottom to top), coupled to an optical nano-fiber of 260 nm diameter. The NV-center is excited perpendicular to the optical fiber via a confocal microscope. Fluorescence photons are collected (a) via the objective of the confocal microscope and (b) via coupling to the guided mode of the optical nano-fiber. The anti-bunching dip at zero detection time difference demonstrates the non-classical character of the fluorescence light as well as the coupling of the NV-center emission to the optical nano-fiber. For better discrimination, the curves are shifted vertically by increments of 1.5.
(a) Second-order correlation function at detection time difference , (b) detected count rate, and (c) fit-parameter as a function of the excitation power P. Blue data points stem from confocal collection, whereas green data points stem from nano-fiber collection, respectively.
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