Multi-frequency switch and excellent slow light based on tunable triple plasmon-induced transparency in bilayer graphene metamaterial

We propose a novel bilayer graphene terahertz metamaterial composed of double graphene ribbons and double graphene rings to excite a dynamically adjustable triple plasma-induced transparency(PIT) effect. The coupled mode theory(CMT) is used to explain the PIT phenomenon, and the results of the CMT and the finite-difference time-domain simulation show high matching degree. By adjusting the Fermi levels of graphene, we have realized a pentafrequency asynchronous optical switch. The performance of this switch, which is mainly manifested in the maximum modulation depth(MD = 99.97%) and the minimum insertion loss(IL = 0.33 dB), is excellent. In addition, we have studied the slow-light effect of this triple-PIT and found that when the Fermi level of graphene reaches 1.2 eV, the time delay can reach 0.848ps. Therefore, this metamaterial provides a foundation for the research of multi-frequency optical switches and excellent slow-light devices in the terahertz band.