Active Control of Terahertz Toroidal Excitations in a Hybrid Metasurface with an Electrically Biased Silicon Layer

Abstract

The active control of artificially structured metasurfaces is a promising route for solving the operation bandwidth limitation of metasurfaces due to their resonant nature. Herein, the active tunability of the toroidal response in a terahertz hybrid metasurface is proposed and experimentally demonstrated. The top metallic layer of the metasurface has a toroidal configuration and is coupled to an electrically biased phase‐change silicon layer, whose conductive thickness and conductivity can be changed significantly when applying increased external current. The electrically biased hybrid metasurface shows high efficiency and complete electrical switching on the toroidal response in a broadband manner. Also, the optoelectronic metasurfaces modulated by biased currents are much easier to integrate in on‐chip optical devices. The hybrid metasurface taking advantage of the silicon layer with insulating‐state to conductive‐state transition in optical conductivity may facilitate the development of high‐performance active photonic applications in, for example, smart sensing in the terahertz regime.