Absorption enhancement of tunable terahertz hybrid graphene-metal antenna with stacked graphene configuration

Abstract

Gate tunable graphene-metal hybrid nanoantenna is proposed here with detailed numerical simulations carried out to evaluate the absorption of multi-layer graphene nanoantenna at terahertz frequencies, specifically at far-infrared. The investigated graphene nanoantenna composes of multi-layer graphene stack formation, which is placed above the gold hexagon radiator to efficiently couple activated graphene plasmons. The efficient coupled plasmons between graphene layers and gold hexagon increase the absorption of the antenna. Furthermore, the relationship between the absorption and multi-layer graphene is analysed by changing the Fermi energy of the graphene sheet, thus providing tunability of broadband absorption at a wide range of frequencies. The investigated nanoantenna has a resonant frequency at 30.5 THz with a bandwidth of 0.6 THz, while the trilayer graphene nanoantenna results in better absorption almost reaching 100% with a bandwidth of 2.5 THz. The simulation of the graphene-metal antenna is performed in CST studio by using an FDTD solver. The designed antenna has various utilizations in the field of photonics i.e. terahertz imaging, sensing, and spectroscopy applications.