Manipulation over Surface Waves in Bilayer Hyperbolic Metasurfaces: Topological Transition and Multidirectional Canalization

Spoof surface plasmon-polariton is a type of surface wave propagating at the artificially engineered structures in microwave and terahertz ranges. These surface waves are highly important in planar photonic and on-chip devices, integrated circuits, lenses, sensors, and antennas applications. However, it is still a challenge to control the propagation regime of such surface waves including the wavefront shapes and propagation directions. In this letter, we study the surface waves in bilayer hyperbolic metasurfaces and show that interplay between two layers allows to manage their regime of propagation. We demonstrate the switching between angle and number of propagation directions of surface waves at the same frequency. Finally, we demonstrate experimentally the tunable multidirectional in-plane canalization of surface waves by adjusting directions of their propagation with angular range from 0 to 12.8 degrees. The discovered rotation-mediated interlayer coupling of hyperbolic metasurfaces paves way towards efficient in-plane transfer of localized electromagnetic signal.