Toward Arbitrary Spin‐Orbit Flat Optics Via Structured Geometric Phase Gratings

Reciprocal spin-orbit coupling (SOC) via geometric phase with flat optics provides a promising platform for shaping and controlling paraxial structured light. Current devices, from the pioneering q-plates to recent J-plates, provide only spin-dependent wavefront modulation without amplitude control. However, achieving control over all spatial dimensions of SOC states requires corresponding complex amplitude, which remains challenging optics. Here, address this issue, new type flat-optics elements termed gratings is presented, that capable conjugated complex-amplitude orthogonal input circular polarizations. By using microstructured liquid crystal photoalignment technique, series engineered their excellent precision in arbitrary shown. This principle unlocks full-field light optics, providing way develop an information exchange processing units general photonic states, as well extra-/intracavity mode convertors high-precision laser beam shaping.