High-Q Color Selectivity Metasurface with 2D Topology Optimization for AR Applications

Wan-Tzu Kuo^1*, Chih-Yao Hsu¹, Huan-Teng Su¹, Wei-Zhe Li¹, Yao-Wei Huang¹

¹Department of Photonics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Wan-Tzu Kuo, email:melody0315.ee13@nycu.edu.tw

Nonlocal metasurfaces with high-Q responses, such as resonant waveguide gratings
(RWGs), are typically limited by geometric constraints and weak energy coupling, making efficient
and selective wavelength control difficult. Here, we employ adjoint-based topology optimization to
extend grating design into freeform layers, enabling greater flexibility in wavelength selection.
Using non-symmetric gratings to manipulate momentum in two dimensions, we realize an RGB
metasurface with a Q-factor up to 2657 at red light while suppressing other modes. Integrated into
a visual system, this design demonstrates high efficiency and superior color purity for augmented
reality.

Keywords: Resonant waveguide grating, Nonlocal metasurfaces, Topology optimization, High quality factor, RGB channels