Genetic algorithms designed ultra-broadband achromatic metalens in the visible

Chromatic aberration is a significant phenomenon in optical systems, and it significantly affects quality imaging. Intelligent algorithms provide a powerful new approach for complex optimization. Here, we propose a broadband achromatic polarization-insensitive metalens in the wide wavelength region from 400 nm to 740 nm using a genetic algorithm. The genetic algorithm can optimize the parameter space through selection, crossover, and mutation operations. The incident light is modulated by different diameters and side lengths of circular and square titanium dioxide nanopillars. Using a powerful genetic algorithm, various geometric parameters of the desired nanopillar can be optimized simultaneously and effectively to match the target phase compensation in a broad wavelength region. The focal lengths all converged to a record narrow location range in the whole wavelength range from 400 nm to 740 nm.