Graphene disks for frequency control of terahertz waves in broadband applications

The terahertz (THz) gap lying between the microwave and optical parts of the electromagnetic spectrum has attracted immense attention due to its applications between radiofrequency (RF)/microwave and photonic systems. A structure consisting of a graphene sheet sandwiched between two graphene disks is introduced herein to control the reflection, absorption, and transmission of THz waves. The proposed metamaterial structures are designed analytically using transmission line theory. Also, the dimensions of the structure and the electrical gating of the graphene are optimized utilizing a genetic algorithm. The structure is simulated using two different methods: (1) a circuit model based on transmission line theory and (2) commercial full-wave software based on the finite element method, which are verified by the agreement between their results. Finally, the proposed method is used to design a THz filter and THz wave absorber, which are in great demand for application in modulators, sensors, detectors, and imaging systems.