Low-profile linear polarization conversion metasurfaces using degenerate modes for high selectivity

In this paper, two ultrathin polarization conversion metasurfaces (PCMs) were designedfor linear polarization of electromagnetic waves. A method of controlling degenerate modes was applied for enhanced selectivity. The surface resonator is a square patch etched with orthogonal cross-slots. Adjustment of the cross-slot size is beneficial as it introduces a perturbation factor and controls the splitting of the degenerate modes. The constructed dual-mode single-band and four-mode dual-band PCMs with different pairs of degenerate modes can efficiently reflect linear polarized waves to the orthogonal polarization counterpart in the range of 5.89–6.4 GHz and 5.88–6.30 GHz/8.19–8.59 GHz, respectively. Current distribution and an equivalent circuit model were studied to reveal the polarization conversion mechanism. Finally, experiments were implemented to verify the near unity cross-polarization conversion efficiency at the corresponding bands. Given the PCM’s advanced performance of low profile and high selectivity, it has great potential applications in controlling the polarization state of microwaves.