Single-layer multiplexed metasurfaces with on-demand polarization encoding based on a symmetric Jones matrix.

Waveplates provide precise control over the state of polarization and are essential components in various technologies and scientific disciplines, greatly enhancing the performance of optical systems. Recently, advancements in metasurface technology have enabled the miniaturization of bulky optical components that manipulate polarization states while mitigating insertion loss. Nevertheless, generating vortex beams with specific topological charges within the desired polarization channels remains a significant challenge when utilizing versatile metasurface-based wave plates. This work presents a generalized design strategy for multifunctional metasurfaces, demonstrated through simulations and experiments, by varying the parametric conditions that facilitate the spin decoupling mechanism. Independent encoding of spin-polarized channels is achieved by integrating both geometric and propagation phase profiles into silicon pillar designs that exhibit birefringent effects. Meta-waveplates designed for operator computational mechanisms can effectively exhibit the behavior of orbital coupling from spin angular momentum (SAM) to orbital angular momentum (OAM) within a predetermined polarization channel. Also, OAM beams with topological charge evolution behavior in the longitudinal direction are further demonstrated, effectively enhancing the design freedom of multifunctional meta-waveplates. This research paves the way for developing multifunctional, high-performance, and ultra-compact terahertz meta-devices.