Multichannel Detection of Hybrid Spin-Orbital Mode Pairs

A photon in a vortex beam with a circular polarization state simultaneously carries an orbital angular momentum (OAM) and a spin angular momentum (SAM). A hybrid spin-orbital mode pair (HSOMP) refers to two beams with opposite topological charges and circular polarization states. It plays a crucial role in generating and manipulating more complex structured beams such as cylindrical vector beams. To meet the requirement of miniaturization and integration, a compact and efficient approach for HSOMP detection is urgently needed. A metalens approach is proposed for detecting multiple HSOMPs across different channels. Each detection position is designed to identify a predefined HSOMP. The patterns of bright spots indirectly confirm the incident OAM modes, while the orientation direction of the neighboring arc-shaped patterns (upward or downward) reveals their SAM states. The simulation and experiments show that this approach can realize precise detection of OAM modes and SAM states. This approach can significantly enhance the functionality density of compact devices, enable multiple detection tasks and improve the detection capability of the HSOMP sorters.