Triple-band graphene-based tunable electromagnetically induced transparency terahertz metamaterial with multi-frequency optical switching

A simple graphene-based terahertz metamaterial with the composite patterns of a π-shaped and a strip-shaped is proposed for realizing the electromagnetically induced transparency (EIT) effect. Three efficient transparent peaks with the average transparency strength of >85 % are achieved. The physical mechanism of the formation of the triple-band EIT effect is illustrated by the transmission spectra combined with the electric field diagrams of the transparent window and the transmission dip. Interestingly, upon changing the position of the strip-shape graphene and the distance between the vertical graphene, the triple-band EIT effect shifts to a dual-band and a single-band, respectively, illustrating the reason for the shifts using the electric field of peaks and dips. The Fermi energy level of graphene can be changed by biasing voltage to create a frequency shift of the resonance peaks of the transmission spectrum, and at the same time, six-frequency optical switching can be realized, which has a modulation degree of amplitude (MDA) of 94.6 %, 90.6 %, 98.1 %, 90.5 %, 97.6 %, and 89.4 %, respectively. These results indicate that the proposed multi-band terahertz metamaterials have great potential for applications in fields such as optical switching and sensing.