Numerical design and simulation of a functionally switchable graphene metamaterial for high-sensitivity sensors and broadband terahertz absorbers

A computationally designed graphene-based terahertz metamaterial absorber (MMA) is proposed, with its geometrical configuration optimized via electromagnetic simulations using COMSOL Multiphysics. The metamaterial comprises a polyimide dielectric substrate as the bottom layer, overlaid by a periodic graphene pattern in the upper layer. The graphene unit cell architecture features three concentric rings and a central square resonator, which collectively facilitate strong localized electromagnetic scattering and resonance. This MMA exhibits multifunctional dynamic tunability, enabling switching between sensing and broadband absorption modes. Numerical simulations validate its application as a highly sensitive refractive index sensor, achieving a frequency sensitivity of 275 GHz/RIU and an absorptivity sensitivity of 64 at an analyte thickness of 45 μm without external optical pumping. With an applied external pump light source, the device operates as a broadband terahertz resonant absorber, demonstrating near-perfect absorption (approximately 0.97) at 0.43 THz when the graphene's Fermi level is modulated to 0.25 eV. This tunable response positions the device as a promising candidate for terahertz sensing and photonic switching applications.