Passive Polarization-Independent Nonreciprocal Magneto-Optical Chiral Metasurfaces for Decoupled Bidirectional Wavefront Manipulation

Nonreciprocal devices governed by broken Lorentz reciprocity are key technologies for advancing modern photonics, particularly for realizing photonic circulators and isolators essential to full-duplex communication, signal routing, and quantum information processing. Yet most passive nonreciprocal implementations are limited to unidirectional isolation and are often constrained by limited bandwidth and polarization sensitivity, lacking the capability to manipulate optical functionality independently in both propagation directions. Here, we report a passive and linear magneto‑optical chiral metasurface with a high isolation ratio that goes beyond isolation, enabling on-demand, polarization-independent bidirectional free‑space wavefront shaping with near-unity transmission efficiency. By combining gyrotropic magneto-optical responses with chiral bianisotropy, we engineer direction‑dependent interference that decouples the forward and backward optical paths. This mechanism enables the redistribution of energy between orthogonal linear polarizations without reducing total transmittance, thereby allowing for asymmetric polarization conversion and independent phase engineering in opposite directions. The metasurface offers a transmittance of up to 97.5% and an operating angle of ±50°, as validated through broadband bidirectional nonreciprocal beam routing and nonreciprocal metalens. Our findings uncover connections between symmetry-engineered photonics, bianisotropic photonics, and nonreciprocal flat optics, suggesting compact and versatile components for signal processing and routing, and protection of high-power laser cavities.