Multichannel Metasurfaces with Frequency-Direction Multiplexed Amplitude and Phase Modulations

Abstract

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.