Highly efficient wavefront control through bianisotropic (Willis coupling) metasurfaces

Abstract

Recent advances in metasurfaces have shown that efficient wavefront transformation can be obtained by carefully controlling the bianisotropic response (Willis coupling) in the metasurfaces. However, applying such a scheme directly for complicated wavefront transformations will lead to nonreciprocal or nonlocal response, which is difficult to realize physically. Here we identify the local power conservation requirements and introduce several strategies to meet such requirements. Our strategies include designing surface waves into the scattered field, designing power-flow conformal metasurfaces, and combining coordinate transformation with bianisotropic metasurfaces. Based on such schemes, we develop a series of bianisotropic metasurfaces design approachs for near-perfect arbitrary wavefront control. These passive and reciprocal design approaches enable experimental demonstration of highly efficient, arbitrary wavefront transformation.