Electrical detection of high-order optical orbital angular momentum
The orbital angular momentum (OAM) of light provides an unbounded set of orthogonal modes for ultrahigh-capacity optical information processing. However, current OAM detection schemes typically rely on light interference or diffraction, which require bulky optical components and pose a major obstacle to on-chip integration. Here, we demonstrate a fully integrated silicon-based photodetector that enables direct electrical detection of light OAM. This photodetector can resolve vortex beams with topological charges from m = -9 to 9, achieving a record-high mode number resolution among on-chip devices. By integrating plasmonic gratings onto the device electrodes, incident vortex beams can be converted into surface plasmon polaritons with OAM-dependent splitting angles, which in turn produce photocurrents that vary monotonically with the OAM order. Further incorporation of a surface dielectric lens can enhance mode resolution, and a split-electrode architecture enables OAM chirality discrimination. Owing to its CMOS-compatibility and spectral scalability, this platform provides a compact and robust solution for integrated OAM detection, opening new opportunities for on-chip optical communication and computing systems based on structured light.