Multichannel Metasurfaces with Frequency‐Direction Multiplexed Amplitude and Phase Modulations.

Electromagnetic wave multiplexing within a compact ultrathin device is pivotal for high‐capacity communications, wireless power transfer, and other applications. Among them, the independent amplitude and phase (AP) control is necessary, and the decoupling of full‐space scattering channels such as reflection (R) and transmission (T) is favoured for high capacities of information processing. This is yet extremely challenging, even at a single frequency, because A and P are essentially correlated and the R‐T channels are usually coupled. Here, a triband multichannel metasurface is proposed and demonstrated, with a frequency‐direction multiplexed paradigm for on‐demand control of both AP across three independent R‐T channels. For practical realization with high efficiency, a judiciously engineered four‐layer compound meta‐atom is proposed. Such a sophisticated multiplexing can facilitate powerful capability in wavefront control and significantly enrich the capacity as well as degrees of freedom for design. For verification, a proof‐of‐concept metadevice has been devised and experimentally demonstrated at microwave frequency, showcasing transmissive and reflective dual‐vortex beams along x and y directions at 7 and 10.2 GHz, respectively, while transmissive dual focusing at 15.7 GHz. This strategy opens a new avenue for circularly‐polarized AP control toward the capacity limit of frequency and direction and for novel functional metadevices with high integration. [ABSTRACT FROM AUTHOR]