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In this Letter we introduce a novel route for achieving negative-group-velocity waveguiding at deep-subwavelength scales. Our scheme is based on the strong electromagnetic coupling between two conformal surface plasmon structures. Using symmetry arguments and detailed numerical simulations, we show that the coupled system can be geometrically tailored to yield negative-index dispersion. A high degree of subwavelength modal confinement, of λ/10 in the transversal dimensions, is also demonstrated. These results can assist in the development of ultrathin surface circuitry for the low-frequency region (microwave and terahertz regimes) of the electromagnetic spectrum.

The propagation of surface plasmon polaritons in dielectric loaded waveguides with randomly placed scatterers is studied using both numerical simulations and a simplified transfer matrix framework. Despite the importance of losses in this system, we find fingerprints of the localized behavior of one-dimensional disordered systems. Furthermore, losses amplify the impact of the necklace states on the transport properties for systems not much larger than the localization length. The system presented here also offers the possibility to use localization effects for engineering purposes by means of deliberately introduced disorder.

Enhanced polarization conversion in reflection for the Otto and Kretschmann configurations is introduced as a new method for hybrid-mode spectroscopy. Polarization conversion in reflection occurs when hybrid modes are excited in a guiding structure composed of at least one anisotropic medium. In contrast to a dark dip, in this case modes are associated with a peak in the converted reflectance spectrum, increasing the detection sensitivity and avoiding confusion with reflection dips associated with other processes, such as transmission.

We propose a metamaterial approach to route terahertz waves that features subwavelength confinement in the transverse plane. The guiding mechanism is based on geometrically induced electromagnetic modes sustained by corrugated metallic wedges, whose characteristics resemble those of wedge plasmon polaritons at telecom and optical frequencies. Additionally, frequency selective focusing and slowing down of terahertz radiation based on the proposed wedge waveguides are presented.

A theoretical study is presented on the optical transmission through square hole arrays drilled in optically thin films, where transmission may occur through both the holes and the metal layer. It is shown that, as the thickness of the metal film decreases, the coupling of light with short-range surface plasmons redshifts the extraordinary optical transmission peak to longer wavelengths. At the same time, the maximum-to-minimum transmittance ratio is kept high even for metal thicknesses as small as one skin depth.

We explore, both experimentally and theoretically, the existence in the millimeter-wave range of the phenomenon of extraordinary light transmission through arrays of subwavelength holes. We have measured the transmission spectra of several samples made on aluminum wafers by use of an AB Millimetre quasi-optical vector network analyzer in the wavelength range 4.2-6.5 mm. Clear signals of the existence of resonant light transmission at wavelengths close to the period of the array appear in the spectra.