Optimization for Si Nano-Pillar-Based Broadband Achromatic Metalens

An innovative optimization algorithm, named the hybrid particle swarm and genetic algorithm (PSO_GA), is proposed for designing broadband achromatic metalenses. A database is first constructed by scanning the parameters of the unit cell of the metalenses using FDTD software, mapping each unit cell to its phase modulation capability. The PSO_GA is then utilized to identify the optimal phase matrix that minimizes chromatic aberration for a metalens operating within a specific wave band. Using the PSO_GA, a broadband achromatic metalens is designed and its performance is validated by simulation. The results reveal that the designed metalens successfully focuses light in a wide band (1000 nm∼1250 nm), achieving a mean focusing efficiency of up to 58%. This metalens design method offers a solution for the intelligent design of flat optical devices.