Inverse Design Enables Large-Scale RGB-Achromatic Metalens and Metagrating

Metalenses with forward dispersion engineering promotes the correction of chromatic aberration. However, forward design of achromatic metalenses find the limitation of scale with the limited dispersion range of meta-atoms. There are many inverse design strategies of metasurface design. However, Inverse design remains very challenging for aperiodic large-scale meta-optics because of limitation of computation time and memory capacity. In this study, we utilize inverse-design framework for aperiodic large-scale complex meta-optics in three dimensions, which alleviates computational cost for both simulation and optimization via a fast-approximate solver and an adjoint method, respectively. We demonstrate an RGB-achomatic metalens with diameter up to 1 centimeter. The focusing efficiency is ~24% in simulation and ~15% in experiment. Furthermore, we demonstrate a metagrating which effectively deflects the light to the 1st order diffraction by using inverse design method. The maximum efficiency of our metagrating achieves up to 67% at large deflection angle (~70°), which is 32% higher than that with forward design in the literature [2]. Moreover, we demonstrate a future virtual-reality platforms by using our meta-eyepieces with a laser back-illuminated micro liquid crystal display. The inverse-design framework can be extended to design large-scale high efficiency multifunctionality metasurfaces.<br/>[1] Z. Li et al., Nature Communications 13, 2409 (2022).<br/>[2] D. Sell et al., Nano Letters 17(6), 3752-3757 (2017).