We study theoretically electromagnetic modes guided by metallic wedges at telecom wavelengths. These modes are found to exhibit superior confinement while showing similar propagation loss as compared to other subwavelength guiding configurations. It is also shown that mode focusing can be realized by gradual modification of the wedge geometry along the mode propagation direction.

We present a theoretical study, based on the finite difference time domain method, of the optical response of circular hole arrays drilled in several metal films (Ag, Au, Cu, Al, Ni, Cr, and W). Two series of structures are studied. In the first one, transmittance peaks are analyzed as all geometrical parameters defining the system are scaled, except for the metal thickness which is kept constant, showing good agreement with existing experimental data. In the second series, the metal thickness is also scaled. This allows a clear distinction in the behavior of different metals: Ag, Au, and Cu show even larger transmittance peaks than hole arrays in a perfect conductor with the same nominal parameters. This is due to both a larger effective hole area and smaller absorption. In the case of Ni and Cr, the transmittance is much smaller due to absorption. Band structure calculations confirm that surface electromagnetic modes sustained by the perforated metal film are responsible for the extraordinary optical transmission phenomenon.

We report on subwavelength plasmon-polariton guiding by triangular metal wedges at telecom wavelengths. A high-quality fabrication procedure for making gold wedge waveguides, which is also mass-production compatible offering large-scale parallel fabrication of plasmonic components, is developed. Using scanning near-field optical imaging at the wavelengths in the range of 1.43–1.52 µm, we demonstrate low-loss (propagation length ~120 µm) and well-confined (mode width ≅1.3 µm) wedge plasmon-polariton guiding along triangular 6-µm-high and 70.5°-angle gold wedges. Experimental observations are consistent with numerical simulations performed with the multiple multipole and finite difference time domain methods.

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A theory is presented of the negative refractive index observed in the so-called double-fishnet structures. We find that the electrical response of these structures is dominated by the cutoff frequency of the hole waveguide whereas the resonant magnetic response is due to the excitation of gap surface plasmon polaritons propagating along the dielectric slab. Associated with this origin, we show how the negative refractive index in these metamaterials presents strong dispersion with the parallel momentum of the incident light. DOI: http://dx.doi.org/10.1103/PhysRevLett.101.103902 © 2008 The American Physical Society