Dynamic Control of Electromagnetically Induced Transparency in a Toroidal Planar Terahertz Metasurface

The dynamic control of terahertz (THz) transmission is crucial for next-generation devices, including sensors, modulators, and slow-light systems. This study investigates an actively tunable electromagnetically induced transparency (EIT) effect in a toroidal dipole-based THz metamaterial. Experimental and numerical analyses confirm toroidal excitation through surface current distributions, profiles of the magnetic field, and multipolar analysis. The metamaterials, fabricated on a flexible polyimide substrate, achieve tunable modulation of EIT using vanadium dioxide (VO$_{2}$). The terahertz time-domain spectroscopy in transmission mode reveals modulation efficiency of up to 50%. Additionally, active control of group delay is demonstrated, highlighting the versatility of the proposed design for advanced THz applications.