Waveguide Coupler in Designer Surface Plasmon using Topological edge states

Photonic topological insulators has shown its ability to be immune to backscatter and defects in the two-dimensional waveguide structure. However, functional devices for PTIs applications are still lacking. In this work, we propose waveguide coupler that consists of two topological waveguides in designer surface plasmon working in the millimeter wave band. We can change the feed direction to adjust the coupling direction and the coupling strength can be adjusted by the distance between the two topological waveguides. At the same time, the proposed topological waveguide coupler using NaCl substrate is environmentally protection.