Multi-fold geometric phase metasurface with versatile operations for transmission and reflection

We propose a high efficiency wideband three-fold geometric phase metasurface for versatile operation of transmission and reflection. The transmission coefficient as high as 87 % is achieved in the frequency range of f₁ (15.4–15.8 GHz), while equal transmission and reflection are achieved in two frequency bands represented by f₂ (14.6–15.2 GHz & 16–17 GHz) with maximum coefficient reaches 49 %. With geometric rotation, the phase shifts of the cross-polarized transmission and co-polarized reflection are six times the rotation angle within the frequency range of 14.6–17 GHz. Furthermore, by elaborately breaking the mirror symmetry while preserving rotational symmetry, interesting features of resonance frequency shift and mode splitting are observed, offering a more fruitful approach for versatile operations. To substantiate the proposed design, a metasurface prototype for vortex beam generation is fabricated and verified by microwave measurement.