Extinction of Light and Coherent Scattering by a Single Nitrogen-Vacancy Center in Diamond

Coherently scattered light from a single quantum system promises to get a valuable quantum resource. In this letter an external laser field is efficiently coupled to a single nitrogen vacancy (NV-)center in diamond. By this it is possible to detect a direct extinction signal and estimate the NV's extinction cross-section. The exact amount of coherent and incoherent photons is determined against the saturation parameter, and reveals the optimal point of generating coherently scattered photons and an optimal point of excitation. A theoretical model of spectral diffusion allows to explain the deviation to an atom in free-space. The introduced experimental techniques are used to determine the properties of the tight focusing in an interference experiment, and allow for a direct determination of the Gouy-phase in a strongly focused beam.