A negative-phase-velocity condition derived by Depine and Lakhtakia [Microwave Opt Technol Lett 41 (2004) 315] for isotropic, homogeneous, passive, dielectric-magnetic materials is inapplicable as a negative-refraction condition for active materials.
When the electrically thin unit cell of a laminated composite material is made of two bianisotropic sheets whose constitutive properties in the thickness direction are decoupled from the constitutive properties in the interfacial planes, the laminate
d composite material can be homogenized into a material not all of whose constitutive parameters are independent of each other. This non-independence of the constitutive dyadics of the constituent materials and the homogenized composite material is captured by two simple constraints, which may not hold if even one of the two constituent materials has more complicated constitutive properties than stated above.
The solution of a boundary--value problem formulated for the Kretschmann configuration shows that the phase speed of a surface--plasmon--polariton (SPP) wave guided by the planar interface of a sufficiently thin metal film and a sculptured thin film
(STF) depends on the vapor incidence angle used while fabricating the STF by physical vapor deposition. Furthermore, it may be possible to engineer the phase speed by periodically varying the vapor incidence angle. The phase speed of the SPP wave can be set by selecting higher mean value and/or the modulation amplitude of the vapor incidence angle.
An equivalent-multishell approach for the approximate calculation of the characteristics of electromagnetic waves propagating in almost circular (azimuthally symmetric), closely packed bundles of parallel, identical, and metallic carbon nanotubes (CN
Ts) yields results in reasonably good agreement with a many-body technique, for infinitely long bundles when the number of CNTs is moderately high. The slow-wave coefficients for azimunthally symmetric guided waves increase with the number of metallic CNTs in the bundle, tending for thick bundles to unity, which is characteristic of macroscopic metallic wires. The existence of an azimuthally nonsymmetric guided wave at low frequencies in a bundle of a large number of finite-length CNTs stands in contrast to the characteristics of guided-wave propagation in a single CNT. The equivalent-multishell approach yields the polarizability scalar and the antenna efficiency of a bundle of finite-length CNTs in the long-wavelength regime over a wide frequency range spanning the terahertz and the near-infrared regimes. Edge effects give rise to geometric resonances in such bundles. The antenna efficiency of a CNT bundle at the first resonance can exceed that of a single CNT by four orders of magnitude, which is promising for the design and development of CNT-bundle antennas and composite materials containing CNT-bundles as inclusions.
