Line waves Supported by Non-Hermitian Metasurfaces Satisfying Electromagnetic Duality

Line waves (LWs) represent unique electromagnetic (EM) modes occurring at the intersections of impedance surfaces in open space, fulfilling either electromagnetic duality or the parity-time symmetry. The line mode having singularity emerges within an extremely narrow one-dimensional channel, earning it the moniker "line waves". By employing both Hermitian and non-Hermitian impedance boundaries, LWs can be generated. However, the utilization of non-Hermitian surfaces has required maintaining the parity-time symmetry. In this study, three line-wave waveguides with non-Hermitian characteristics, founded upon the EM duality, have been introduced. We explore the advantages inherent in each structure. The capability to sustain unidirectional modes enhances structural performance along bent paths. In addition, preserving the EM duality provides the proposed waveguides with the capability to suppress backscattering so that our waveguides support non-reciprocal line modes.