In this Letter we present the controlled coupling of a single nitrogen vacancy center to a plasmonic structure. With the help of an atomic force microscope, a single nanodiamond containing a single nitrogen vacancy center and two gold nanospheres are assembled step-by-step. We show that both the excitation rate and the radiative decay rate of the color center are enhanced by about 1 order of magnitude, while the single photon character of the emission is maintained. Hot spots between diamond and gold nanoparticles provide an efficient near-field coupling, despite the mismatch in size and shape. Our approach provides hybrid systems as important building blocks for novel nanophotonic light sources in advanced plasmonic devices stable even at room temperature.

The coupling of a quantum mechanical system to open decay channels has been theoretically studied in numerous works, mainly in the context of nuclear physics but also in atomic, molecular and mesoscopic physics. Theory predicts that with increasing coupling strength to the channels the resonance widths of all states should first increase but finally decrease again for most of the states. In this letter, the first direct experimental verification of this effect, known as resonance trapping, is presented. In the experiment a microwave Sinai cavity with an attached waveguide with variable slit width was used.PACS numbers: 03.65.Nk, 84.40.Az, 85.30.Vw Since more than ten years, interference phenomena in open quantum systems have been studied theoretically in the framework of different models. Common to all these studies is the appearance of different time scales as soon as the resonance states start to overlap see [1] and the recent papers [2] with references therein). Some of the states align with the decay channels and become short-lived while the remaining ones decouple to a great deal from the continuum and become long-lived (trapped). Due to this phenomenon, the number of relevant states will, in the short-time scale, be reduced while the system as a whole becomes dynamically stabilized. The phenomenologically introduced doorway states in nuclear physics provide an example for the alignment of the short-lived states with the channels [3]. Calculations for microwave resonators showed that the trapped resonance states can be identified in the time-delay function and that short-lived collective modes are formed at large openings of the resonator [4]. Resonance narrowing is inherent also in the Fano formalism [5]. Similar effects have been found in the linewidths in a semiconductor microcavity with variable strength of normal-mode coupling [6]. In spite of the many theoretical studies, the effect of resonance trapping has not yet been verified unambigously in an experiment. A theoretical study of neutron resonances in nuclei as a function of the interaction of a doorway state with narrow resonances [7] allowed only to draw the conclusion that resonance trapping is not in contradiction with experimental data. For a clear experimental demonstration of the trapping effect, the coupling strength to the decay channels should be tunable, which was not possible in all above mentioned experiments.The mechanism of resonance trapping can be illustrated best on the basis of a schematical model. In an open quantum system the resonance states are allowed to decay, i. e. their energies are complex,The Hamilton operator is non-hermitian,Here H 0 describes the N discrete states of the closed quantum system coupled to K decay channels by the N × K matrix V . H 0 and V V † are hermitian and α is a real parameter for the total coupling strength between the closed system and the channels. The complex eigenvalues of H give the energy positions E R and widths Γ R of the resonance states. Studies on the basis of this model were perfo...

Using a nanomanipulation technique a nanodiamond with a single nitrogen vacancy center is placed directly on the surface of a gallium phosphide photonic crystal cavity.A Purcell-enhancement of the fluorescence emission at the zero phonon line (ZPL) by a factor of 12.1 is observed. The ZPL coupling is a first crucial step towards future diamond-based integrated quantum optical devices.

We propose and demonstrate a hybrid cavity system in which metal nanoparticles are evanescently coupled to a dielectric photonic crystal cavity using a nanoassembly method. While the metal constituents lead to strongly localized fields, optical feedback is provided by the surrounding photonic crystal structure. The combined effect of plasmonic field enhancement and high quality factor (Q approximately 900) opens new routes for the control of light-matter interaction at the nanoscale.

In this paper we present a detailed comparison of experimentally observed modifications of the emission behavior of dye molecules embedded in colloidal photonic crystals with corresponding theoretical calculations of the optical mode density. For this purpose, angle-resolved measurements of emission spectra and timeresolved measurements were performed with a high spatial resolution using a confocal microscopy setup. The spectra reveal a strongly modified radiation pattern, including a highly directional fourfold intensity enhancement at the high frequency edge of the photonic stop band, while the radiative lifetime is only slightly affected. For the first time these experimental results are quantitatively compared to theoretical predictions based on calculations of the angle-dependent local density of optical states. It is demonstrated that the observed modifications can be explained by a spectral and angular redistribution of the optical mode density inside the photonic crystal, suggesting an altered radiation probability of the dye molecules for certain frequencies and directions. Furthermore, our calculations reveal a strong dependence of these modifications on the exact location of the dye molecules within the photonic crystal.