High-Efficiency Dual-Band Metasurface with Independent Multifold Geometric Phases

The concept of geometric phase has attracted enormous interest in the metasurface community for achieving phase variation with simple geometrical rotation. Here, this work demonstrates for the first time a highly efficient dual-band metasurface with independent phase responses for structures with different-fold rotational symmetries. For proof of concept, a hybrid unit cell structure with nested resonators of different-fold (single-fold and threefold) is proposed, where geometric rotation independent phase shifts of two times and six times the rotation angle are achieved in lower and higher bands, respectively. By rotating the resonators within the unit cell, highly efficient independent full phase controls can be achieved with circularly polarized incident waves. The co-polarized reflection efficiency exceeds 90% at the frequency domain from 10.95 to 11.75 GHz (corresponding to the inner resonator) and exceeds 80% between 14.10 and 14.43 GHz (corresponding to the outer resonator), with peak values of 94.7% at 11.55 GHz and 85.5% at 14.23 GHz, respectively. To validate the versatility of the design paradigm, a metasurface porotype is fabricated and experimentally tested by generating independent holographic images.