In this work, we propose a pseudospin-polarized closed waveguide whose walls are formed by dual electromagnetic boundary conditions.  The structure has a very wide bandwidth so that it covers an extremely wide electromagnetic spectrum.  The proposed waveguide supports one-way pseudospin states resulting from the establishment of dual relationships at the waveguide boundaries, and hence the establishment of mirror reflection symmetry. This provides the proposed waveguide with the ability to suppress backscattering.  The boundary conditions of the proposed structure consist of complementary metasurfaces which have dual surface impedances.  The presence of these boundary conditions leads to forming a pseudospin-polarized waveguide having the ability to suppress and filter the backward modes that may be excited along bent paths or discontinuities.  To the best of our knowledge, this is the widest bandwidth waveguide that has been proposed so far, so that the isolation of the waveguide in the frequency range of 7- 350 GHz is above -0.5 dB.  In addition, we use a very precise method based on the variational method to calculate the surface impedance of the metasurfaces forming the waveguide boundaries so as to increase the accuracy of the obtained results.

Line waves are modes that propagate along a line connecting two-dimensional impedance surfaces with dual electromagnetic responses. In general, line waves can be implemented using complementary impedances or impedances with a gain-loss effect. On the other hand, if the two impedance surfaces are non-complementary, they can support a different type of mode called a “quasi-line wave”. We propose a different configuration to implement quasi-line waves. Indeed, non-dual structures with purely inductive impedances are used in order to drive the mode. We investigate the implementation of quasi-line modes using multilayer graphenes. This mode has a wide bandwidth in the terahertz range and a significant propagation length. The proposed structure guides one-way modes in which the fields are highly concentrated around the edges of two inductive impedance structures. Furthermore, incorporating graphene into the proposed waveguide allows for control of bandwidth and transmission characteristic of the waveguide.