Topology optimization enables nonlocal high-Q metasurfaces and matrix Fourier optics

In this invited talk, I will present our recent developments of topology-optimized nonlocal high-Q metasurfaces and matrix Fourier optics. In the first part, we demonstrate novel topology-optimized nonlocal metasurfaces, selectively enhancing or suppressing individual resonances at red, yellow, green, and blue wavelengths. Our metasurfaces, designed using higher efficiency techniques compared to traditional RWGs, demonstrate experimental efficiencies up to 59% with a Q-factor of 93. A 2D optimized metasurface successfully diffracts blue, green-, and red-light beams with peak efficiency, as observed in experimental results. In the second part, we combine a forward design approach with topology optimization to realize matrix Fourier optics, creating a single-layer metasurface that diffracts incident light of various polarizations to specific directions in the far field. Our freeform metasurface successfully processed six mixed polarizations aligning with the matrix Fourier optics concept, demonstrating a polarization contrast of up to 98% in numerical and 99% in experimental results.