Anomalies of Sub-Diffractive Guided-Wave Propagation along Metamaterial Nanocomponents
We describe our recent results on some of the anomalous propagation properties of subdiffractive guided modes along plasmonic or metamaterial cylindrical waveguides with core-shell structures, with particular attention to the design of optical subwavelength nanodevices. In our analysis, we compare and contrast the azimuthally symmetric modes, on which the previous literature has concentrated, with polaritonic guided modes, which propagate in a different regime close to the plasmonic resonance of the waveguide. Forward and backward modes may be envisioned in this latter regime, traveling with subdiffraction cross section along the cylindrical interface between plasmonic and nonplasmonic materials. In general, two oppositely oriented power flows arise in the positive and negative permittivity regions, consistent with our previous results in the planar geometry. Our discussion applies to a various range of frequencies, from RF to optical and UV, even if we are mainly focused on optical and infrared propagation. At lower frequencies, artificially engineered plasmonic metamaterials or natural plasmas may be envisioned to obtain similar propagation characteristics.