Terahertz hybrid metal-graphene metamaterials with tunable dual-band electromagnetically induced transparency

The electromagnetically induced transparency (EIT) effects in metamaterials have been widely studied due to their broad application prospects in the field of optical communications. Previous researchers focused mainly on the regulation of a single EIT effect. Here we proposed a structure containing two pairs of asymmetric C-shaped double-split ring resonators (DSRRs) placed on the two sides of cut wire (CW), and we studied the EIT effect of the structure. Furthermore, in order to tune the EIT peak, two graphene strips are placed on the two pairs of DSRRs. Simulation results show that, the EIT peak can be modulated by adjusting the Fermi level of the graphene strips and the modulation depths as high as 83 % and 87 % can be realized. Besides, slow light phenomenon accompanied by the EIT effect in the structure was investigated. Simulation results implied that, double group delays of 4.4 ps and 3.4 ps can be achieved in the design, and the delays can be adjusted by changing the graphene Fermi level. The physical mechanism of the tunable metamaterial was analyzed in terms of the three-oscillator model.