Strong interaction between graphene layer and Fano resonance in terahertz metamaterials

Graphene has emerged as a promising building block in modern optics and optoelectronics due to its novel optical and electrical properties. In the mid-infrared and terahertz (THz) regime, graphene behaves like metals and supports surface plasmon resonances (SPRs). Moreover, the continuously tunable conductivity of graphene enables active SPRs and gives rise to a range of active applications. However, the interaction between graphene and metal-based resonant metamaterials has not been fully understood. In this work, a simulation investigation on the interaction between the graphene layer and THz resonances supported by the two-gap split ring metamaterials is systematically conducted. The simulation results show that the graphene layer can substantially reduce the Fano resonance and even switch it off, while leaving the dipole resonance nearly unaffected, which is well explained with the high conductivity of graphene. With the manipulation of graphene conductivity via altering its Fermi energy or layer number, the amplitude of the Fano resonance can be modulated. The tunable Fano resonance here together with the underlying physical mechanism can be strategically important in designing active metal-graphene hybrid metamaterials. In addition, the 'sensitivity' to the graphene layer of the Fano resonance is also highly appreciated in the field of ultrasensitive sensing, where the novel physical mechanism can be employed in sensing other graphene-like two-dimensional materials or biomolecules with the high conductivity.