Surface wave control via unidirectional surface magnetoplasmon waveguide arrays

Freely tailoring the wavefronts of surface waves (SWs), including surface plasmon polaritons (SPPs) and their equivalent counterparts, holds significant importance in the field of on-chip photonics. However, conventional diffraction-optics based devices often suffer from limited functionalities and low working efficiencies. Here, we present a novel concept of a unidirectional surface magnetoplasmon (USMP) waveguide array composed of carefully engineered subwavelength-spaced unidirectional waveguide slits. By utilizing the unique propagation properties of USMPs within these waveguides, the USMP waveguide array efficiently converts USMPs into SWs with predetermined wavefronts. As proof of the concept, we numerically demonstrate this new principle through the design of two microwave USMP waveguide arrays using a metal-air-YIG structure, which directly converts USMPs into SWs with the wavefronts of Bessel beam and focusing. Additionally, we extend this concept to the terahertz regime and achieve beam deflection of SWs using a metal-air-semiconductor waveguide array. These findings may inspire the development of highly miniaturized on-chip devices for integrated photonics applications.