Switchable Metasurface with Electromagnetically Induced Transparency and Absorption Simultaneously Realizing Circular Polarization‐Insensitive Circular‐to‐Linear Polarization Conversion

Abstract

AbstractA metasurface (MS) with switching features from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) is theoretically investigated in the terahertz (THz) range by incorporating vanadium dioxide (VO2) when circular polarization‐insensitive circularly polarized waves are incidents, which can also simultaneously realize circular‐to‐linear polarization conversion well. While the VO2 ring is in an insulator state, two new transparent EIT windows both are gained between 0.97 THz and 1.16 THz because of destructive interference between the two metal rings that are seen as bright modes. Once the VO2 ring is tuned to the metallic state, a perfect EIA phenomenon is observed between 0.824 THz and 1.233 THz, achieving the transition from the EIT to EIA behavior well. The received electromagnetic waves are radiated to left‐handed circularly polarized (LCP) or right‐handed circularly polarized (RCP) waves with identical phases and amplitudes through the radiation patches when the LCP or RCP ones are incident. Whereby, a resultant linearly polarized wave is obtained between 0.9 THz and 1.2 THz, and relative bandwidth reaches 29%. The outcomes of maximal group index and group delay both are 1934 and 488 ps at 1.08 THz, and maximal absorption is 90.3% at 1.06 THz.