Perfect Anomalous Reflection with a Bipartite Huygens’ Metasurface

In this paper, we propose a new metasurface that is able to reflect a known incoming electromagnetic wave into an arbitrary direction, with perfect power efficiency. This seemingly simple task, which we hereafter call perfect anomalous reflection, is actually highly nontrivial because of the differing wave impedances and complex interference between the incident and reflected waves. Heretofore, proposed metasurfaces that achieve perfect anomalous reflection require complicated, deeply subwavelength and/or multilayer element structures, which allow them to couple to and from leaky and/or evanescent waves. In contrast, we demonstrate that using a bipartite Huygens’ metasurface (BHM)—a passive and lossless metasurface with only two cells per period—perfect anomalous reflection can be achieved over a wide angular and frequency range. Through simulations and experiments at 24 GHz, we show that a properly designed BHM can anomalously reflect an incident electromagnetic wave from θ_i = 50° to θ_r = −22.5°, with perfect power efficiency to within experimental precision.