Wideband Transparent Beam-Forming Metadevice with Amplitude- and Phase-Controlled Metasurface

Achieving simultaneous control of the amplitude and phase of a metasurface, especially in transmission geometry, is very essential in modern photonic research. An alternative strategy for manipulating the transmissive amplitude and phase is proposed by using a three-layered element. Two outer orthogonal gratings of the element can determine the transmissive polarization while the center modified I-shaped particle achieves a high-efficiency linear polarization conversion. We can control the transmissive phase by modulating the gap size of the modified I-shaped structure, and manipulate the transmissive amplitude by rotating the structure. As a proof of concept, we design a fan-shaped beam metasurface by using a genetic algorithm to obtain the optimal phase and amplitude distributions. The results show that the metasurface can generate a flat top (azimuthal angle range is -40 degrees to 40 degrees) beam under rectangular coordinates within 9.1-10.9 GHz. Our findings offer possibilities to realize arbitrary beam shapes, which not only widen the areas for shaping a wavefront by metasurfaces, but also offer an economical and simple alternative for a beam-forming array antenna.