Collective plasmonic oscillations in gold nanostrips arrays.

Excitation of collective plasmonic modes and their effect on optical behavior are experimentally and theoretically studied in 1D arrays of gold nanostrips in comparison with continuous gold films with periodically modulated profile. In strips, the angular dependence of the reflectivity demonstrates a peak at the resonance condition as opposed to a dip observed in continuous sine wave gratings. In addition, an extremely narrow feature in the reflection is observed in strips and tentatively ascribed to the bright Wood-Rayleigh anomaly. Theoretical calculations based on the combined transfer-matrix coupled-wave analysis and coordinate transformation method are shown to fit the experimental angular and spectral behavior of the plasmonic resonances. The effects are also discussed in terms of a simple equivalent circuit model.

Hyperbolic resonances of metasurface cavities.

We propose a new class of optical resonator structures featuring one or two metasurface reflectors or metacavities and predict that such resonators support novel hyperbolic resonances. As an example of such resonances we introduce hyperbolic Tamm plasmons (HTPs) and hyperbolic Fabry-Perot resonances (HFPs). The hyperbolic optical modes feature low-loss incident power re-distribution over TM and TE polarization output channels, clover-leaf anisotropic dispersion, and other unique properties which are tunable and are useful for multiple applications.

Spontaneous emission of electric and magnetic dipoles in the vicinity of thin and thick metal.

Strong modification of spontaneous emission of Eu(3+) ions placed in close vicinity to thin and thick gold and silver films was clearly demonstrated in a microscope setup separately for electric and magnetic dipole transitions. We have shown that the magnetic transition was very sensitive to the thickness of the gold substrate and behaved distinctly different from the electric transition. The observations were described theoretically based on the dyadic Green's function approach for layered media and explained through modified image models for the near and far-field emissions. We established that there exists a "near-field event horizon", which demarcates the distance from the metal at which the dipole emission is taken up exclusively in the near field.