Dual-band 2-bit coding metasurface for multifunctional control of both spatial waves and surface waves

We present a reflection-type 2-bit digital coding metasurface to achieve dual-band functionalities in two different operating bands, independently. We aim to design various coding sequences to achieve the pre-desired functionalities, which no longer require time-consuming optimization of the distribution of reflection phases. Two main contributions are provided in this work. First, we show that by changing the operational frequency band between the lower (X-band) and higher (Ku-band) frequency bands, we can realize the beam switching between the opposite half planes. Second, the proposed dual-band 2-bit coding metasurface is further extended for conversion from the spatial waves to surface waves in one frequency band, and beam deflection/focusing in another band. Samples are fabricated to experimentally validate their frequency-dependent performances, which show high efficiency and good agreement with simulations results. We remark that the proposed concept can be readily extended to the terahertz and optical regimes, which may find potential applications in multifunctional metadevices with multispectral features. (C) 2019 Optical Society of America