On-chip beam steering in gradient-index waveguide arrays

The ability to manipulate light propagation is crucial for the development of optical communication and information processing systems. Photonic integrated circuits have gained significant attention due to their ability to integrate a large volume of components and operate at high speeds, making them ideal for handling the increasing data capacity and rate. In this study, we proposed and experimentally demonstrated a novel method for beam steering using waveguide arrays with specific distributed spacing profiles. By analyzing the diffraction and coherence properties, we discovered that a single waveguide array can perform imaging and phase transformation functions, which are typically achieved using optical lenses. To further enhance this capability, we fabricated corresponding devices on a silicon nitride waveguide platform and investigated the light propagation process through the arrayed waveguide. We successfully achieved various forms of beam steering, including focusing, expansion, and collimation. This beam control method holds great potential for on-chip optical routing, ranging, sensing, and other applications. It offers high integration density and scalability, making it a promising solution for the development of advanced optical systems.