Ultrathin All-Angle Hyperbolic Metasurface Retroreflectors Based on Directed Routing of Canalized Plasmonics

Abstract

Retroreflectors that can accurately redirect the incident waves in free space back along their original channels provide unprecedented opportunities for light manipulation. However, to the best of our knowledge, they suffer from either the bulky size, narrow angular bandwidths, or time-consuming postprocessing, which essentially limits their further applications. Here, a scheme for designing ultrathin all-angle real-time retroreflectors based on hyperbolic plasmonic metasurfaces is proposed and experimentally demonstrated. The physical mechanism underlying the scheme is the orthogonality between the traveling waves in free space and the canalized spoof surface plasmon on the hyperbolic plasmonic metasurfaces, which guarantee their high-efficiency and all-angle mutual conversion. In this case, the strong confinement characteristic that benefited from the enhanced light–matter interaction enables us to route and retroreflect the canalized spoof surface plasmon with extremely thin structures. As proof of the scheme, a retroreflector prototype with a thickness approximately equal to the central wavelength is designed and fabricated. Further experimental investigation obtains a half-power field of view up to 53° and a maximum efficiency of 83.2%. This scheme can find promising applications in target detection, remote sensing, and diverse on-chip light control devices.

Spin-decoupled excitation and wavefront shaping of structured surface waves via on-chip terahertz metasurfaces

“…Like propagating waves (PWs, freely traveling in space), surface waves (SWs) are another type of electromagnetic (EM) wave mode confined at metal/dielectric interfaces. 1 Due to the many unique properties of SWs, e.g., slow group velocity and local field confinement, a lot of extraordinary applications of SWs have been put forward, such as super-resolution imaging, 2 retroreflectors, 3 antennas, 4 second harmonic generation, 5 plasmonic vortex, 6 graded-index lenses, 7,8 spoof surface plasmon polariton switches, 29 and so on. Traditionally, prisms or gratings are used to excite and manipulate SWs.…”