Funneling Electromagnetic Waves with PTD Symmetric Metastructures

This paper investigates a new class of metastructures for funneling electromagnetic energy within arbitrary narrow channels. This class is based on structures that are invariant under the Parity Time-reversal Duality (PTD) transformation. Such structures produce zero backscattering under the illumination of a plane wave at normal incidence for all incident polarizations. These reflectionless and arbitrary polarizations features are exploited to design metastructures for concentrating electromagnetic energy within subwavelength channels. Numerical results of the proposed metastructures are also discussed.