Design framework for multifunctional on-chip waveguide-metasurface system for circularly polarized and spatially controlled beams

We present a design framework for an on-chip integrated multifunctional waveguide-metasurface system for the simultaneous control of polarization and spatial properties of free-space beams. The device combines a four-port waveguide arrangement with a binary metasurface optimized using a genetic algorithm. This approach enables unified control of beam shaping, steering, and circular polarization within a compact footprint of 2.24 × 2.24 μm². Full-wave 3D simulations demonstrate accurate beam formation up to 45° in polar angle, with polarization purity reaching up to 0.99. The results address the challenge of on-chip generation of circularly polarized, spatially defined beams, enabling fully integrated optical addressing in trapped-ion platforms.