Waveguiding characteristics of a metal-clad dielectric grating for terahertz applications

Dielectric gratings (DGs) have recently been introduced as a new platform for guiding dielectric-based geometrically-induced surface plasmons (SPs) called spoof SPs (SSPs). In this paper, we report on the modal analysis of a metal-clad DG waveguide and compare its performance with other counterparts including the dielectric image guide (IG) and the metal grating (MG) waveguide. The proposed DG waveguide is made up of a periodic array of high-resistivity silicon (HR-Si) pillars on a metal plate with a metal cladding at a proper distance above the structure. By modal analysis of 2D and 3D structures, we show that the presence of the metal cladding enhances the modal field confinement without sacrificing the bandwidth. In addition, modal characteristics of the structure at hand in the presence of a thin substrate are studied. It is found that the lateral field confinement and bending loss can be impaired in the presence of a substrate. We also study the shape of dielectric pillars and show that nearly the same performance can be achieved by cubic and cylindrical pillars. Finally, some waveguide devices such as a bend, a directional coupler, and a ring resonator are also implemented and studied to assess the applicability of the proposed metal-clad DG waveguide.