A Study on Optimal Design of Polarization-Independent Magneto-Metasurface Isolators Based on Multi-Material Topology Optimization

Metasurface has attracted a lot of attentions because they can realize properties that cannot be achieved with ordinary materials and are easy to be fabricated using established fabrication processes. In this paper, in order to design metasurface without requiring designer's experience and knowledge, we develop topology optimal design method for magneto-optic metasurfaces with periodic structure. A multi-material function expansion method is developed for representing device structures, and the full-vectorial finite element method is employed to evaluate device properties with arbitrary structures. To accurately treat the device structures expressed by multi-material function expansion method, we also develop finite element discretization scheme for them. To show the usefulness of our approach, we design polarization independent metasurface isolator.