High-performance achromatic metalens in the long-wavelength infrared regime

In recent decades, metasurfaces have shown remarkable advancements in the development of integrated and miniaturized optical devices. Among these, metalenses have emerged as a prominent and significant area of research. In this paper, a broadband achromatic metalens is designed to operate across a wide wavelength range, specifically from 9.6 μm to 11.6 μm. To efficiently achieve the optimization of initial metalens parameters, we employ an envelope-based layering strategy that divides the sample space into multiple adjacent floors. This approach effectively reduces the loss rate and computational burden in a comprehensive manner. An enhanced Archimedes optimization algorithm is utilized to obtain the optimal solution. It incorporates the opposition-based learning with Sine map and elite retention strategy to enhance the search capability and avoid getting trapped in local optima. Following the optimization process, the proposed metalens achieves an average focusing efficiency of 53.64 %, with chromatic aberration correction accomplished at a coefficient of variation of only 2.27 %. This accomplishment signifies a substantial advancement in the field of achromatic metalenses.