In this work, it is shown how the shapes of surface plasmon dispersion curves can be engineered by manipulating the distribution of the electromagnetic fields in multilayer structures, which themselves are controlled by the free electron density in metal-like materials, such as doped semiconductors in the THz spectral range. By having a nonuniform free electron density profile, reduced relative to that in typical bulk metals, the electromagnetic fields of surface plasmons are distributed in different metallic materials that have different complex dielectric permittivities. As the in-plane component of surface plasmon's wave-vector increases, they become more confined to a particular layer of the multilayer structure and have energies that are predictable by considering the permittivity of the layer in which the fields are most concentrated. Unusual and arbitrary shapes of surface plasmon dispersion curves can be designed, including stair steps and dovetails shapes.

Phase resonances in compound gratings are studied in the frequency and time domains, with the gratings having two dissimilar grooves within the unit cell that each support waveguide cavity modes that couple. Described in this work are the dependence of the phase resonances' Q on the degree of difference between the grooves in the unit cell, their optical properties, a closed-form expression describing their dispersion, their excitation, and the extraction of energy from the phase resonances into free space and into a waveguide. Application to optical filters and corrugated surface antennas are discussed.

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Abstract-In this work, an anisotropic zero index material is designed for use in Vivaldi antennas. The metasurface structures are placed within the aperture of a Vivaldi antenna to improve the directivity and gain of the emitted radiation. The range of operation is in the ultrahigh frequency (UHF) range, between 300 MHz and 3 GHz. Two approaches are presented: a type of resonant metallic metamaterial that belongs to the larger class of anisotropic zero index metamaterials and a non-resonant material. A technique for lowering the dimensions of the resonant metamaterial unit cell is presented and applied. The work presented consists of simulation results obtained with HFSS modelling software from ANSYS.