Abstract
Complete control of spatially propagating waves (PWs) and surface waves (SWs) is an ultimate goal that scientists and engineers seek for, in which negative reflection of PW and negative surface wave are two exotic phenomena. Here, we experimentally demonstrate an anisotropic digital coding metasurface capable of controlling both PWs and SWs with a single coding pattern. On the basis of the digital description of coding metasurfaces, a simple coding method is proposed to allow dual functionalities (either PW or SW manipulations) under two orthogonal polarizations at arbitrarily oblique incidences, thus improving the adaptability of digital coding metasurfaces in more practical circumstances. With elaborately designed ellipse-shaped coding particles, we experimentally demonstrate various functions under oblique incidences, including the negative reflection of PW, negative SW, anomalous reflection and their arbitrary combinations, all having good agreements with theoretical and numerical predictions. We believe that the proposed method may enable the digital coding metasurfaces to have broad applications in radar detections, wireless communications and imaging.
Highlights
The unprecedented ability of metamaterials to manipulate electromagnetic (EM) waves in desired manners has provided a new route for designing strange devices, which has attracted much interest from both the physics and engineering communities
The real-time manipulation of wavefronts can be achieved by loading active components to these digital elements with their digital states being externally controlled by a field-programmable gate array (FPGA), realizing digital and programmable metasurfaces[29,32]
Independent controls of spatial waves with out-of-plane reflection and negative reflection We demonstrate the bi-functional performance of an anisotropic coding metasurface in controlling the PWs under oblique incidence. doi:10.1038/lsa.2018.8
Summary
The unprecedented ability of metamaterials to manipulate electromagnetic (EM) waves in desired manners has provided a new route for designing strange devices, which has attracted much interest from both the physics and engineering communities. Many exotic phenomena, such as negative refraction, subwavelength imaging and invisibility cloaking, have been experimentally demonstrated throughout the EM spectrum[1,2,3,4]. The arrays of subwavelength-spaced scatterers, distributed on an ultrathin metasurface with a certain phase gradient, provide an added gradient wave vector, and alter the direction of the refracted beam, as determined by the generalized Snell’s law[11,19,20].
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