Quantitative spin-orbit engineering enables subwavelength-scale programmable polarization states for versatile photonic functionalities
Precise and programmable control of optical polarization provides a versatile vectorial degree of freedom for light-matter interaction and optical information encoding. Existing polarization state generators (PSGs), however, suffer from poor switchability and modest fidelity at the micrometer scale, which severely constrains their practical applicability. To overcome these limitations, here we present a quantitative spin-orbit engineering that enables the dynamic synthesis of arbitrary polarization states at subwavelength dimensions. The core concept is to tailor conjugate optical vortices that independently address the orthogonal spin components of a vectorially polarized light. This spatial modulation scheme annihilates intrinsic topological charges and reshapes the spin-orbit interaction, thereby coherently constructing polarization ellipses on demand. Leveraging this mechanism, we experimentally synthesize diffraction-limited arbitrarily polarized beams spanning the entire Poincare sphere with fidelity over 99%. As proof-of-principle demonstrations, we apply the miniaturized PSG platform to Mueller-matrix polarization microscopy, pixel-level polarization encryption, and parallel polarization-information encoding, illustrating its broad utility of programmable polarization control for subwavelength polarimetric imaging and reconfigurable multiplexed polarization encoding. Compared with state-of-the-art PSGs, our approach uniquely integrates rapid programmability, high fidelity, and subwavelength localization in a single architecture. These multifunctional capabilities of this work position the platform as a promising route for advancing Mueller matrix polarization microscopy, multidimensional optical storage, and secure optical information processing, and beyond.