Optically‐Induced 90° Dynamic Polarization Rotation via Phase‐Transition Optical Activity in Metasurfaces

Dynamic polarization control is pivotal for advanced photonic applications. In this work, we demonstrate a novel approach for all‐optical dynamic polarization switching, enabled by phase‐transition optical activity (PTOA) in chiral metasurfaces. Leveraging the extreme sensitivity of phase transitions near the transition point, we achieve a 90 nonlinear optical polarization rotation with an exceptionally small control power variation of 0.2 mW. Our approach not only enables low‐power and highly responsive polarization control but also establishes a promising strategy with significant potential for both fundamental studies and practical applications in polarization imaging, optical metrology, and integrated photonic systems.