Tunable bandwidth of double electromagnetic induced transparency windows in terahertz graphene metamaterial.

By patterning graphene on a SiO/Si substrate, in this paper, we design and numerically investigate double electromagnetic induced transparency (EIT) windows in a terahertz metamaterial based on a π-like graphene structure. The surface current distributions reveal that the double EIT windows arise from the destructive interferences caused by different asymmetric coupling modes. Moreover, the bandwidth of two transparency windows can be actively controlled by changing the asymmetric coupling strength. By shifting the Fermi energy of graphene, more interestingly, the bandwidth and frequency modulation depths of the two transparency windows is 38.4% and 36% respectively, and the associated group delay and delay bandwidth product (DBP) can also be actively tuned. Therefore, such EIT-like graphene metamaterials are promising candidates for designing slow-light devices and wide-band filters.