Electromagnetically induced transparency in terahertz asymmetric split-ring resonators driven by radiative and non-radiative losses

The classical analog of electromagnetically induced transparency (EIT), manifested using artificially structured materials known as metamaterials, has been a topic of significant interest for enabling slow and fast light propagation within a sharp transparency window. In metamaterials, the constituent resonators can be engineered to emulate a three-level quantum system, whose optical response is strongly influenced by the intrinsic losses of the system. These losses, both radiative and non-radiative, play a critical role in determining the linewidth and quality factor (Q-factor) of the EIT resonance. In this work, we investigate how material conductivity and structural asymmetry modulate the transparency window and loss dynamics over the 0.8–1.4 terahertz (THz) frequency range by employing a coupled oscillator model to decouple and quantify the individual contributions of radiative and non-radiative losses in a metamaterial configuration: the terahertz asymmetric split-ring resonator (TASR). By comparing TASRs constructed from aluminum and an ideal perfect electric conductor (PEC), we decouple and quantify the individual contributions of radiative and non-radiative losses in a well-known metamaterial configuration. The extracted Q-factors range from 10 to over 1000, with the PEC demonstrating ultrasharp EIT features at small asymmetry values due to its negligible ohmic loss. Our results provide important insights into optimizing metamaterial designs for high-Q performance in THz applications such as sensing, filtering, and slow-light devices.