Dynamically tunable terahertz passband filter based on metamaterials integrated with a graphene middle layer**Project supported by the National Natural Science Foundation of China (Grant Nos. 61701434, 61735010, and 61675147), the Open Fund of the Key Laboratory of Optoelectronic Information Technology, Ministry of Education (Tianjin University), China, the Key Laboratory of Optoelectronic Information Functional Materials and Micro-Nano devices in Zaozhuang, China,

Abstract

The dynamic tunability of a terahertz (THz) passband filter was realized by changing the Fermi energy (EF) of graphene based on the sandwiched structure of metal–graphene–metal metamaterials (MGMs). By using plane wave simulation, we demonstrated that the central frequency (f0) of the proposed filter can shift from 5.04 THz to 5.71 THz; this shift is accompanied by a 3 dB bandwidth (Δf) decrease from 1.82 THz to 0.01 THz as the EF increases from 0 to 0.75 eV. Additionally, in order to select a suitable control equation for the proposed filter, the curves of Δf and f0 under different graphene EF were fitted using five different mathematical models. The fitting results demonstrate that the DoseResp model offers accurate predictions of the change in the 3 dB bandwidth, and the Quartic model can successfully describe the variation in the center frequency of the proposed filter. Moreover, the electric field and current density analyses show that the dynamic tuning property of the proposed filter is mainly caused by the competition of two coupling effects at different graphene EF, i.e., graphene–polyimide coupling and graphene–metal coupling. This study shows that the proposed structures are promising for realizing dynamically tunable filters in innovative THz communication systems.