Tunable dual-band metasurface absorber utilizing electric dipole and magnetic loop in a DC-connected bilayer graphene stack: A theoretical approach

Abstract

This work proposes a dual-band tunable metasurface absorber (DBTMSA) having a unique design and simple construction based on a bilayer graphene stack. The design evolution of the metasurface has been inspired by the modal behaviour of two complementary types of resonators, i.e., electric dipole and magnetic loop. A dipole and loop mode is seamlessly combined at both bands to achieve excellent electromagnetic (EM) response with near-unity absorptivity $\left(A\left(f\right)\right)$ of 99.6 % and 99.9 % at 2.63 and 4.98 THz, respectively. Interconnection in the bilayer graphene stack allows for constant DC voltage distribution required to tune the chemical potential $\left({\mu }_c\right)$ practically. An increase in ${\mu }_c$ from 0.4 to 1 eV leads to the frequency sweep in the absorption peaks from 1.72 to 4.98 THz with an $A\left(f\right)$ $\ge$ 90 %. Thus providing an overall tuning range of 3.26 THz, corresponding to a fractional bandwidth of 97.31 %. The DBTMSA design is miniaturized, featuring a periodicity of ${\lambda }_0$/11.4 and a thickness of ${\lambda }_0$/38, with ${\lambda }_0$ calculated at 2.63 THz. Hence, MSA could be employed for size-constrained smart terahertz applications.