Large-area, topology-optimized metasurfaces with facile fabrication parameters

Metasurfaces are flat optical platforms capable of unprecedented wavefront control. To push the limits of experimental device performance, scalable design methodologies that balance device performance and manufacturability are required. We introduce a reparametrized topology optimization framework for large-area freeform metasurfaces in which nanoscale elements are explicitly constrained to feature basic shapes. Despite the simplicity of the geometric features, these devices are able to utilize nonlocal near-field coupling to achieve highly efficient and extreme wavefront scattering beyond conventional design methodologies. Utilizing this approach, we design and experimentally demonstrate a series of large-area, multifunctional, high-numerical-aperture metadevices.