Spatial division multiplexed monolithic phase mask for OAM detection

The orthogonality of orbital angular momentum (OAM) modes provides additional degrees of freedom in optical systems, with broad applications in high-capacity optical communication and other fields. Thus, simple yet efficient methods for OAM detection are equally essential. However, efficient detection remains challenging due to bulky setups, limited integrability, and inherent flaws in existing methods. Here, we propose a monolithic phase mask architecture for OAM detection based on spatial division multiplexing (SDM), partitioning the mask into angular sub-regions each embedding conjugate helical, tilt, and focusing phases. Integrated into a single structure (e.g., metasurfaces), it enables single-shot parallel detection without cascaded elements. Angular spectrum diffraction simulations demonstrate 16-channel parallel detection with high fidelity, as shown by the OAM transmission matrix with strong diagonal dominance. Its integrability, robustness, and scalability suit high-capacity communication, vector field detection, and advanced imaging, paving the way for scalable high-dimensional optical field detection in emerging photonics.