Both s-polarized and p-polarized phase resonances in one-dimensionally compound transmission gratings are analyzed, modeled, and measured. We demonstrate that s-polarized phase resonances occur with similar characteristics of p-polarized phase resonances, with narrow bandwidths, high Q values, and highly amplified fields. The phase difference of π radian between the fields in the coupled cavities produces light circulation and an inversion of the transmissivity/opacity of the structure. The dependencies of bandwidth and wavelength of the resonances on structural and material properties are described, as well as the way light flows in the structure when the phase resonances are excited.

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.

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