Inverse design of metamaterials for wideband multi-beam former

Abstract

The demand for compact beam-steering solutions has driven interest in gradient-index (GRIN) lenses, which shape wavefronts via spatially varying dielectric properties. Additive manufacturing enables their fabrication, but a central challenge remains: solving the inverse problem of determining the volumetric permittivity distribution for a desired field transformation. Unlike voxel-by-voxel topology optimization requiring thousands of full-wave simulations, our approach targets smooth GRIN profiles for propagation-based devices, reducing optimization to minutes on a standard computer. Here, we present an inverse-design framework that optimizes the geometrical optics propagation equations directly. We experimentally demonstrate the method by realizing a multi-feed GRIN lens based on a three-dimensional gyroid architecture fabricated via additive manufacturing. The device enables continuous beam scanning over a ±35 ∘ range with 33% fractional bandwidth, low scan loss, and excellent beam fidelity. Our results establish a direct pathway from electromagnetic functionality to manufacturable metamaterial devices, enabling scalable wavefront engineering