Robust subnanometric plasmon ruler by rescaling of the nonlocal optical response.

We present the optical response of two interacting metallic nanowires calculated for separation distances down to angstrom range. State-of-the-art local and nonlocal approaches are compared with full quantum time-dependent density functional theory calculations that give an exact account of nonlocal and tunneling effects. We find that the quantum results are equivalent to those from classical approaches when the nanoparticle separation is defined as the separation between centroids of the screening charges. This establishes a universal plasmon ruler for subnanometric distances. Such a ruler not only impacts the basis of many applications of plasmonics, but also provides a robust rule for subnanometric metrology.

Superradiant optical emitters coupled to an array of nanosize metallic antennas.

We study the properties of an array of Au ring nanoantennas fed by an ensemble of coherent emitters. The luminescence of the emitters is strongly enhanced at certain wavelengths due to the excitation of two types of resonances-the diffractive Rayleigh anomalies associated with the opening of new diffraction orders and the localized surface plasmons of the nanoantennas. We show that the two families of resonances can spectrally overlap and lead to anticrossings or cumulative enhancements depending on the symmetries of the modes. This rich optical behavior induces marked changes in the linewidth, shape, and amplitude of the peaks and could be potentially used to tune the luminescence of superradiant sources with new flexibility.

Optical patch antennas for single photon emission using surface plasmon resonances.

Single photon sources can greatly benefit from specially designed structures that modify the properties of the photon emitter. Dielectric cavities are often discussed, but they require a compromise between the spectral width and Purcell factor. In this Letter, we introduce plasmonic cavities as promising alternatives. We first study how the emitter couples with the modes of such structures. We then show how a patch antenna configuration simultaneously presents a large Purcell factor, collection efficiency, and spectral width.

Huygens-Fresnel principle for surface plasmons.

We present an explicit form of the surface plasmon propagator. Its form has the structure of a vectorial Huygens-Fresnel principle. The propagator appears to be a powerful tool to deal with diffraction, interference and focusing of surface plasmons. In contrast with the scalar approximation used so far, the vectorial propagator accounts for near-field and polarization effects. We illustrate the potential of the propagator by studying diffraction of surface plasmons by a slit and focusing of surface plasmons by a Fresnel lens.