Broadband and Polarization‐Multiplexed Nonreciprocal Transmission Enabled by Magneto‐Optical Metasurface

Abstract The violation of Lorentz reciprocity through directional electromagnetic transmission constitutes a cornerstone for advancing next‐generation photonic architectures. While existing implementations predominantly exhibit nonreciprocal behavior limited to individual polarization bases with inherently constrained bandwidth. Here, a magneto‐optical nonreciprocal metasurface (NRM) is proposed to achieve concurrent polarization‐multiplexed functionalities: polarization‐dependent nonreciprocity for circularly polarized waves and unidirectional transmission for linear polarization. This dual functionality originates from coordinated spatiotemporal symmetry breaking across orthogonal electromagnetic eigenstates, enabling independent wavefront manipulation through tailored bi‐anisotropic responses. The proposed magneto‐optical metasurface comprises a thin layer of Yttrium Iron Garnet (YIG) integrated with a Magnesium‐Titanium Dielectric Ceramics resonator (MTDCR) rotated by 30° along the z ‐axis. The nonreciprocal transmission effect arises from the simultaneous breaking of two distinct symmetries: gyroscopic mirror symmetry and time‐reversal symmetry. Furthermore, the magneto‐electric coupling between Mie resonances excited within the MTDCR and Fabry‐Pérot modes sustained in the subwavelength YIG layer establishes a spectral broadening mechanism, achieving a record relative bandwidth of 12% across operational spectra. The NRM exhibits exceptional performance with 94% transmittance and maintains nonreciprocal functionality for incident angles up to 50°. This work establishes a universal platform for developing nonreciprocal photonic systems with applications in quantum communications and 6G full‐duplex radar.