Actively tunable and switchable electromagnetically induced transparency in hybrid metal-graphene metamaterials

Active control of the electromagnetically induced transparency (EIT) is highly desirable for advanced terahertz (THz) device applications. Currently, the EIT peak positions in the graphene-based metamaterials have been actively controlled by tailoring Fermi energy of graphene via electric doping. However, there is still a considerable challenge to realize active strength modulation of the EIT peak without frequency shifting. Here, a hybrid metal-graphene structure, consisting of the metal-based EIT metamaterial and patterning graphenes, is proposed at the THz frequencies. Through changing Fermi energy of graphene, the EIT peak strength can exhibit both active modulation and on-to-off switch without frequency shifting. Moreover, theoretical model and field distributions discover that the active response can be attributed to the increasing damping rate of the dark mode caused by the controllable conductivity of graphene. In addition, the controllable group delay is also achieved for the slow light applications. Therefore, this work provides the possibility for designing compact slow light devices in the information processing and telecommunication applications.