Shaping Electromagnetic Fields with Irregular Metasurface

The electromagnetic scattering of an object is directly related to its physical geometry and material properties. While metasurfaces show excellent performances in mimicking material properties almost at well by flexibly designing meta-atoms with arbitrary electromagnetic responses, their physical geometries are generally in a regular manner. The break of a metasurface's geometry will inevitably affect its electromagnetic scattering that introduces uncertainty in wavefront manipulation. Here, a general approach for highly efficient wavefront manipulation with irregular shaped metasurfaces is proposed. Such an approach establishes a universal iterative modulation relation between the metasurface and scattered field by introducing boundary constraints at the aperture, enabling to deal with the electromagnetic scattering from a metasurface with arbitrary spatial shape. In this way, the desired wavefront form can be engineered using meta-atom sequences with arbitrarily shaped aperture. As a proof of concept, a flower-shaped metasurface operating in the reflection mode is designed and experimentally demonstrated for reconstructing four random focuses with uniform and high-efficiency intensity distribution at near-field region, while the flower shaped field pattern can be extracted near the aperture plane. Such a method may pave a new route for advanced wavefront manipulation and electromagnetic concealment/camouflage applications.