Multifunctional coding metasurfaces based on polarization and propagation direction

With the continuous research on electromagnetic (EM) metasurfaces, it has been found that a variety of EM modulation functions can be realized by polarization multiplexing and frequency multiplexing, thus forming multifunctional EM metasurfaces. However, the inherent property of EM wave propagation direction has not been effectively utilized to realize multifunctional EM devices that depend on propagation direction. Here, a multifunctional coding metasurface is proposed based on Fourier convolution operation that can achieve different functions in opposite propagation directions. As a proof of concept, the proposed multifunctional metasurface is capable of achieving orbital angular momentum (OAM) beam with mode number l = 1 and divergence angle ± 6° in the upper half-space when a circularly polarized EM wave at 13 GHz is incident. On top of this the Fourier convolution operation is superimposed to achieve anomalous reflection of the OAM beam and OAM beam splitting. When X-polarized EM wave at 12.2 GHz is incident, beam splitting can be achieved in the lower half-space. The experimental results are in good agreement with the numerical results, and this multifunctional metasurface provides a new way for the development of new multifunctional devices and paves the way for their use in other fields such as antennas and communications.