▎ 摘　　要

A graphene-based meta-surface structure consisting of middle strip and side rings is proposed, which can achieve plasmon-induced transparency (PIT) effects by bright-dark mode coupling. By properly adjusting geometry parameters of the meta-surface and gradually varying Fermi energy level of graphene, the PIT window can be actively tuned in a wide range of transmission spectra, allowing for dynamically tunable group delay of the incident light. In this letter, by changing geometry parameters, we find that the value of group delay of light becomes greater when the coupling strength becomes weaker. In other words, the less the transmittance of the PIT window is, the slower the speed of light is. (C) 2018 Elsevier B.V. All rights reserved.