Strong and tunable chirality based on magnetic grating metasurfaces of magneto-optical materials

Abstract The enhancement and dynamic control of optical chirality via strong light-matter interactions in metasurfaces and metamaterials has attracted considerable attention in recent years. However, most reported metasurfaces (MS) rely on fixed geometric parameters, limiting their ability to achieve tunable chiral responses. In this work, we propose a magnetically tunable metasurface composed of a one-dimensional grating structure based on the magneto-optical material InSb, designed to enhance and control chirality under both normal and oblique incidence. The interplay between the magneto-optical effect of InSb and the geometry-induced electro-optical response of the MS enables a significant enhancement and modulation of optical chirality. Using effective medium theory and classical electromagnetic simulations, we systematically investigate the Kerr rotation angles, Faraday rotation angles, and circular dichroism under different incident configurations. Our results show that the anisotropy introduced by the grating structure substantially strengthens optical activity, while the observed circular dichroism mainly stems from the magneto-optical properties of the InSb film. Moreover, we demonstrate that the degree of chirality and optical rotation can be dynamically tuned by varying the external magnetic field, rotation angle, and incidence angle. This study offers a theoretical framework for the realization of metasurfaces with strong and tunable optical chirality.