Spin-Symmetry Breaking Through Metasurface Geometric Phases

Studies of geometric phases arising in metasurfaces have focused on the Pancharatnam-Berry (PB) phase, locking spin states to a symmetric profile. This work shows how to realize instead the Aharonov-Anandan (AA) phase, by mimicking a single ballistic Aharonov-Bohm ring with metastructures. Spin-symmetry restriction is broken by combining the AA and PB phases, and the merged phase can impose a desired phase profile on an arbitrary polarization, enable manipulation of the photonic spin Hall effect, superpose spin-\textonehalf{} charges, and break the conjugate constraints of output orbital-angular-momentum modes. These results have significant potential for polarization control and spin-enabled optics.