Study on Structural Optimization of Axisymmetric Meta-Lenses by Function Expansion Method

Metasurfaces consisting of two-dimensional array of subwavelength structures can realize functions that are difficult to be achieved with original materials. Among them, meta-lenses, which can realize conventional lens functions in a 2D thin film, are also attracting a lot of attention. In this paper, considering meta-lens attached to the end of optical fibers, we study on an optimal design of axisymmetric meta-lenses. In our approach, the axisymmetric full-vectorial finite element method (Axi-FV-FEM) is employed to efficiently simulate the propagation behavior. Metasurface structures are represented by function expansion method, and the covariance matrix adaptation evolution strategy (CMA-ES) is used to optimize design variables.