Experimental demonstration and in-depth investigation of analytically designed anomalous reflection metagratings

Abstract

We present the design, fabrication and experimental investigation of a printed circuit board (PCB) metagrating (MG) for perfect anomalous reflection. The design follows our previously developed analytical formalism, resulting in a single-element MG capable of unitary coupling of the incident wave to the specified (first order) Floquet-Bloch (FB) mode while suppressing the specular reflection. We characterize the MG performance experimentally using a bistatic scattering pattern measurement, relying on an original beam-power integration approach for accurate evaluation of the coupling to the various modes across a wide frequency range. The results show that highly-efficient wide-angle anomalous reflection is achieved, as predicted by the theory, with a relatively broadband response. In addition, the MG is found to perform well when illuminated from different angles, acting as a multichannel reflector, and to scatter efficiently also to higher-order FB modes at other frequencies, exhibiting multifunctional capabilities. Importantly, the merits of the introduced beam-integration approach, namely, its improved resilience to measurement inaccuracies or noise effects, and the implicit accommodation of different effective aperture sizes, are emphasized, highly relevant in view of the numerous recent experimental reports on anomalous reflection metasurfaces. Finally, we discuss the source for losses associated with the MG; interestingly, we show that these correlate well with edge diffraction effects, rather than (commonly assumed) power dissipation. These experimental results verify our theoretical synthesis scheme, showing that highly-efficient anomalous reflection is achievable with a realistic fabricated MG, demonstrating the practical applicability and potential mutifunctionality of analytically designed MGs for future wavefront manipulating devices.