On-Chip Metasurface Enabling Simultaneous Four-Dimensional Transformation of Generalized Vortex Arrays

Multi-dimensional optical field manipulation is crucial for enhancing information capacity and advancing photonic functionality. However, traditional waveguide-based photonic integrated circuits suffer from limited two-dimensional spatial scalability and insufficient degrees of freedom, hindering on-chip complex optical field generation and manipulation. Here, we propose and experimentally demonstrate a single on-chip metasurface for generating generalized vortex beam (GVB) arrays, enabling four-dimensional modulation including angular momentum, diffraction order, and incident wave vector. By integrating judiciously engineered subwavelength meta-atoms on the waveguide, we tailor the local phase gradient along the azimuthal direction and incorporate Dammann optimization to experimentally generate GVB arrays. The resulting arrays exhibit diverse orbital angular momentum distributions and distinct intensity profiles among different diffraction orders. Furthermore, by utilizing incident excitation with different wave vectors, along the x, y, and z directions, we generate multiple GVB arrays with independent intensity profiles. With its potential for miniaturized integration, this on-chip scheme further expands the control dimensions and information capacity, thus opening up new avenues for near- to far-field transformation, particle manipulation, high-speed optical communication, and next-generation integrated photonic information processing platforms.