Dynamic transmission control based on all-dielectric toroidal dipole metasurfaces

All-dielectric metasurfaces that support resonators with multiple dipole resonances offer a versatile and effective approach for controlling electromagnetic fields at the nanoscale. Toroidal dipoles, as a peculiar component of multipole resonances, have attracted significant attention due to their unique ability to facilitate light–matter interactions, enabling enhanced absorption, amplified nonlinear responses, advanced data processing and storage capabilities, and highly sensitive sensing applications. The active control of toroidal dipoles in all-dielectric metasurfaces holds great significance for the development of adaptable photonic devices. However, achieving tunable toroidal dipoles in all-dielectric metasurfaces remains challenging due to the volumetric mode property of toroidal dipoles. To address this challenge, we propose a solution by integrating a thin layer of indium tin oxide (ITO) into the all-dielectric metasurfaces. Active modulation of the transmittance amplitude in toroidal dipole-based all-dielectric metasurfaces is achieved by precisely tuning the coupling between the metasurface modes and the ITO thin film. Furthermore, a tunable diffractive grating has been developed based on these findings, demonstrating its prospects for beam direction control applications.