Electrical Detection of High-Order Optical Orbital Angular Momentum.

Abstract

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 an integrated silicon-based photodetector that enables direct electrical detection of light OAM. This photodetector can resolve vortex beams with topological charges from m = ±1 to ±9. With a single measurement, the OAM classification accuracy of the best-performing device can reach up to 99.92%. 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 device provides a compact and robust solution for integrated OAM detection in structured-light-based optical communication and computing systems.