Abstract:Solid-state quantum emitters, such as artificially engineered quantum dots or naturally occurring defects in solids, are being investigated for applications ranging from quantum information science and optoelectronics to biomedical imaging. Recently, these same systems have also been studied from the perspective of nanoscale metrology. In this letter we study the near-field optical properties of a diamond nanocrystal hosting a single nitrogen vacancy center. We find that the nitrogen vacancy center is a sensitive probe of the surrounding electromagnetic mode structure. We exploit this sensitivity to demonstrate nanoscale fluorescence lifetime imaging microscopy (FLIM) with a single nitrogen vacancy center by imaging the local density of states of an optical antenna.Controlled interaction of light and matter at the nanoscale requires a detailed understanding of the local electromagnetic mode distribution. It has been recognized for some time that, in contrast to the homogeneity exhibited by the vacuum electromagnetic modes in free space, surfaces and nanostructured environments can sculpt the local electromagnetic mode density or local density of optical states (LDOS). A manifestation of this modification, as first pointed out by Purcell [1], is that the excited state lifetime of a quantum object is not an immutable property, but depends sensitively on the system's . Important for the present work is that the NV center exhibits stable photoluminescence at room temperature (unlike most quantum dots that suffer from blinking) and the center's optical properties are preserved when the diamond host takes the form of a nanocrystal. In the following we exploit the previous features to demonstrate, for the first time, the suitability of the NV center for nanoscale FLIM by imaging a nanoscale optical antenna [28].The top panel of Fig. 1a presents an illustration of the FLIM concept. In the first modality a single quantum system (the "probe") is affixed to the vertex of a nanoscale tip and a sample to be interrogated (the "object") is scanned in close proximity to the emitter. The object perturbs the local electromagnetic environment of the probe and modifies its excited state dynamics that can be recorded as a function of the object's x-y coordinates to build an image. A second approach, followed in the present work, is to fix the probe in space, see bottom panel of Fig. 1a, and scan the object through the focus. Again, by monitoring the probe lifetime an image can be recorded. In our experiments a single NV center in a diamond nanocrystal is our probe of the nanoscale LDOS created by the object.

We study the near-field optical properties of a diamond nanocrystal hosting a single NV center. Using a single NV center as a probe of the electromagnetic mode structure, we demonstrate nanoscale fluorescence lifetime imaging microscopy.

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