Indexed by:Journal paper Journal:Appl. Phys. Lett. Affiliation of Author(s):Department of Physics, Technical University of Denmark, Building 309, 2800 Kongens Lyngby, Denmark Place of Publication:美国 Discipline:Engineering Funded by:自然科学基金 Document Type:J Volume:102 Issue:10 Page Number:4795015 Key Words:无 DOI number:10.1063/1.4795015 Date of Publication:2013-02-26 Abstract:We report on the observation of coupling a single nitrogen vacancy (NV) center in a nanodiamond crystal to a propagating plasmonic mode of silver nanowires. The nanocrystal is placed either near the apex of a single silver nanowire or in the gap between two end-to-end aligned silver nanowires. We observe an enhancement of the NV-centers’ decay rate in both cases as a result of the coupling to the plasmons. The devices are nano-assembled with a scanning probe technique. Through simulations, we show that end-to-end aligned silver nanowires can be used as a controllable splitter for emission from a dipole emitter. Nano-sized plasmonic structures support strongly confined electromagnetic fields at the nanometer scale. This leads to a variety of different effects such as surface enhanced Raman spectroscopy,1 the generation of higher harmonics,2 and the enhancement of fluorescence from emitters due to the Purcell effect.3 Moreover, plasmonic nanostructures can also be used as antennas, thereby tailoring the emission profile of nearby emitters.4 A variety of different emitters, including molecules,5,6 quantum dots,7 and nitrogen-vacancy (NV) centers in diamond8 have benefitted from these plasmonics properties—enhancement and directionality of emission. However, for some applications in quantum optics, for instance, single photon generation or absorption, efficient coupling between a single emitter and a single propagating mode is desirable.9 Plasmonic waveguides support the propagation of highly confined electromagnetic fields in the direction transverse to the propagation direction, and favor an efficient coupling to nearby emitters.10 This leads to an enhancement of the decay rate of the emitter, and channeling of its emission into a single propagating plasmonic mode.11–16 In particular, in Refs. 11 and 12, it was found that the coupling of a single emitter to the apex of a nanotip is particularly promising as in such a system a good compromise between losses and coupling is attained. The NV-center in a diamond has proven to be a serious candidate for quantum information processing due to its unique room-temperature properties. It emits single photons17 in the near infrared regime without blinking and its ground state forms a stable qubit with a long coherence time that can be easily initialized, manipulated, and read out.18,19 However, for advancing the NV technology, e.g., long distance communication20 or distributed quantum computing,21 the dipole moment of the NV-center must be efficiently coupled to a single propagating mode in order to direct the emitted photons in a specified direction. In this letter, we study the controlled coupling between single NV-centers and plasmonic waveguides. Using a scanning probe technique, we nano-assemble a system consisting of a nanodiamond with a single NV-center placed in the proximity of the apex of either a single silver nanowire (SNW) or two end-to-end aligned SNWs. We demonstrate efficient coupling of the NV dipole to the plasmonic mode supported by the SNWs, which is witnessed by an enhancement of the decay rate of the NV's dipole transition as well as channeling of the emitted light into the plasmonic mode. In Fig. 1, we present the schematic structure of the NV-SNW systems under consideration. The first system is an NV-center in a nanodiamond crystal coupled to the apex of a single SNW, whose side-view and top-view schematics are shown in Figs. 1(a) and 1(c), respectively. Similarly, Figs. 1(b) and 1(d) show the side-view and top-view schematics of the second system, which comprises an NV-center in a nanodiamond placed in between two end-to-end aligned SNWs. We note that in these figures the SNWs are cut short for presentational reasons. In the simulations and the experiments, the SNWs have a length of a few μm. In the simulations, the NV-center is modeled as a dipole emitter lying inside the nanodiamond. The material surrounding the dipole emitter also affects its decay rate.22 Therefore, we normalize the total decay rate Γ of the coupled systems to the decay rate Γ0 of a dipole emitter inside the nanodiamond without SNWs for different orientations and positions of the dipole. Note:无 Links to published journals:https://doi.org/10.1063/1.4795015