Perfect linear-to-circular polarization interconversion via intra-structural coupling modulation in split-ring resonators

Abstract This study proposes a broadband LP-CP interconversion metasurface based on symmetrically quarter-split ring resonators. By precisely tailoring the near-field coupling within the rings, complete polarization conversion is realized. CP waves with an ultra-low axial ratio (AR < 0.1 dB) and LP waves with an exceptional polarization extinction ratio (PER > 50 dB) are achieved across an ∼18% fractional bandwidth. Furthermore, the structure exhibits P-B phase characteristics under CP illumination. Through phase coding, this enables ideal separation of LCP/RCP waves, along with equal-power splitting of cross-polarized components.