Active and passive modulation of dual metamaterial induced transparency in terahertz regime

Metamaterial induced transparency (MIT) has shown great application potential in terahertz regime, which is of great significance in constructing photonic components such as slow light systems and tunable filters. The single or multiple transparent windows can be induced through near-field coupling via two or more resonant modes. Compared with the single MIT, multi-MIT effect can realize multiband sensing, communication, and storage applications. Here, we design a dual-MIT metastructure composed of three bright resonators including a cut-wire resonator (CWR), a pair of large toroidal split ring resonators (LTSRRs), and a pair of small toroidal split ring resonators (STSRRs). Dual-MIT windows can be induced through coupling between the electric dipole resonance and two inductance capacitance (LC) resonances. By optimizing and adjusting the geometric parameters of the metasurface, the resonant strength could be suppressed or enhanced. Thus, we can passively manipulate the frequency and amplitude of the dual-MIT windows and realize the switching between the two windows and single MIT. In addition, by actively tuning the conductivity of photosensitive Si introduced in the gap of the LTSRRs and STSRRs, we observe the LC resonance can be weakened to quench the dual-MIT windows. Our research provides an approach to explore the miniaturized, multi-functional, and switching components in terahertz regime.