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

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<0.1dB) and LP waves with an exceptional polarization extinction ratio (PER>50dB) 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.