Topology optimization enables high-Q metasurface for color selectivity

Huan-Teng Su^1*, Lu-Yun Wang¹, Po-Cheng Yang¹, Jhih-Hao Huang¹, Yao-Wei Huang¹

¹Department of photonics, national yang ming chiao tung university, Hsinchu, Taiwan

* Presenter:Huan-Teng Su, email:suhuanteng.ee11@nycu.edu.tw

Local and nonlocal metasurfaces offer unique attributes for manipulating light at the nanoscale. Local metasurfaces, exemplified by phase-gradient metasurfaces, rely on individually placed metaunits to control the phase of incident light, referencing precomputed optical responses. In contrast, nonlocal metasurfaces, such as resonant waveguide gratings, spatially configure optical wavefronts through extended resonant modes. Unlike traditional methods that depend on precomputed optical responses, inverse design techniques for nonlocal metasurfaces enable similar functionalities without these references. However, traditional forward design techniques for resonant waveguide gratings have efficiencies lower than 10%. So, we present a metasurface composed of titanium dioxide resonant waveguide gratings on a glass substrate, simultaneously operating at red, yellow, green, and blue wavelengths. Through adjoint-based topology optimization, while considering nonlocal effects, we significantly enhance the diffraction efficiency of the metasurface resonant waveguide gratings. This groundbreaking achievement results in remarkable efficiencies, reaching up to 77%, accompanied by outstanding Q-factors, which reach as high as 1367. Our investigation represents a significant advancement in metasurface technology with the potential to revolutionize applications in see-through optical combiners and augmented reality platforms, solidifying metasurfaces as a cornerstone of future optical technologies.

Keywords: non-local metasurfaces, Gratings, Color selection, Beam steering, Topology optimization