Design of a hybrid spoof plasmonic sub-terahertz waveguide with low bending loss in a broad frequency band.

The effect of dielectric cladding on the waveguiding characteristics of an array of metallic pillars on a metal plane in the sub-terahertz band is explored. Firstly, a 2D structure made up of a metallic grating of infinite lateral width with various dielectric overlays is analytically studied to get more insight into the problem. Then the ideas inferred from the 2D structure are applied to the realistic 3D structure that has a finite lateral width. It is shown that by proper design of the dielectric medium surrounding the metallic structure the modal field confinement can be enhanced in a broad frequency band resulting in a low bending loss. Especially, by integrating the pillars into a silicon channel of finite size and evacuating the spaces between them a highly confined spoof surface plasmon is supported and a considerable reduction in the bending loss over a broad bandwidth is observed. Due to small cross-sectional size, low bending loss and ease of fabrication, the proposed waveguide is a promising choice for millimeter-wave and terahertz integrated circuits; particularly those based on the silicon technology.