Tunable Ultra-Broadband Terahertz Metamaterial Absorbers Based on Complementary Split Ring-Shaped Graphene

Abstract In the design of tunable broadband terahertz (THz) metamaterial absorbers based on graphene, simplifying the gating structure to control the Fermi energy of graphene is urgently required for practical applications. Pursuing this demand, we propose two kinds of tunable ultra-broadband THz metamaterial absorbers based on complementary split ring-shaped graphene. The first absorber can achieve an ultra-broadband absorption performance with absorptivity above 90% in the range of 2.06–4.24 THz and its relative absorption bandwidth is 69.2%. By varying the Fermi energy of graphene from 0 eV to 0.8 eV via bias voltage, the absorptivity can be dynamically tuned from 32.8–99.9%. The physical mechanism of ultra-broadband absorption is based on the surface plasmon polariton resonances excited by the surface charges of complementary split ring-shaped graphene. In addition, to further expand the absorption bandwidth, the first absorber structure is covered with another dielectric layer, resulting in the second absorber with enhanced relative absorption bandwidth of 108.27%. Our designed absorbers have many potential applications such as medical imaging, explosive detection, biological sensing and wireless communications.