Subwavelength-Scale 3D Broadband Unidirectional Waveguides Based on Surface Magnetoplasmons at Terahertz Frequencies

Abstract

Unidirectional electromagnetic modes have significant potential for routing electromagnetic radiation and are highly desirable for various applications, such as isolators, splitters, and switches. In this study, we theoretically investigate surface magnetoplasmons (SMPs) in a four-layer structure consisting of a perfect magnetic conductor (PMC)–semiconductor–dielectric–metal, which exhibits complete unidirectional propagation. We extend this structure to a 3D model by decreasing the width of the PMC-semiconductor part to an appropriate value and demonstrate that the SMPs in the proposed 3D waveguide retain complete unidirectional propagation. Our findings indicate that the unidirectional SMPs are robust to backscattering caused by surface roughness and defects. Moreover, the proposed 3D waveguide can be efficiently coupled to conventional microstrip line waveguides. Our results (based on the numerical method) demonstrate that SMPs based on semiconductors offer a promising approach to creating devices with new functionalities in the terahertz regime below the diffraction limit.