Ultra-Broadband Electromagnetically Induced Transparency in Metamaterial Based on Conductive Coupling

This paper proposes a structure composed of a horizontal metal strip resonator (SR) and four C-shaped ring resonators (CRR) to obtain a broadband electromagnetic induction transparency (EIT)–like effect. The SR and CRRs are divided into bright mode and dark mode according to whether they can be directly excited by the incident electromagnetic wave. The three-level Λ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Lambda$$\end{document}-type system and electric field are used to explain the mechanism of the EIT-like effect. Meanwhile, by decreasing the distance between the SR and CRRs, a transparency window with a relative bandwidth of 91.93% and a width of 1.4 THz is observed. It is found that when the bright and dark modes are directly contacted, the EIT window increases rapidly through conductive coupling, which can be explained by the surface current. Our work provides a new method for a wide band EIT-like effect, which has a certain value in the fields of slow light, filters, and non-linear optics.