Breaking Spin Locking for Full Circular Polarization Decoupling in a Dual‐Layer Metasurface

Polarization offers a rich yet underexploited dimension for encoding optical information. However, conventional metasurfaces—constrained by intrinsic symmetry—fail to decouple circular polarization channels, fundamentally limiting the capacity of polarization‐multiplexed systems. Here, we present a dual‐layer dielectric metasurface that breaks this spin locking through engineered interlayer diffraction coupling, enabling complete and independent control of the Jones matrix, including modulation along the elusive S 3 axis of the Poincaré sphere. Leveraging a neural‐network‐assisted inverse design framework, we co‐optimize local meta‐atom responses and global wavefront evolution. We demonstrate a six‐channel polarization‐multiplexed hologram with ∼30 dB signal‐to‐noise ratio (SNR), and further realize full circular polarization multiplexing (L‐L, L‐R, R‐L, R‐R) with SNRs above 21 dB. This platform unlocks full‐Poincaré polarization control in a CMOS‐compatible form, paving the way for high‐capacity holography, secure optical communication, and multidimensional photonic systems.