Reconfigurable terahertz absorber with zigzag graphene ribbons: comprehensive mathematical analysis and performance characterization

This paper presents a comprehensive mathematical framework for analyzing a reconfigurable terahertz absorber based on periodic zigzag graphene ribbons. The proposed structure employs a silver back reflector, TOPAS polymer spacer, and electrically tunable graphene patterns to achieve dual-band perfect absorption. We develop a rigorous equivalent circuit model that accurately captures the electromagnetic behavior of zigzag graphene ribbons, incorporating both intra-band and inter-band conductivity contributions through the Kubo formalism. The absorber demonstrates exceptional performance with > 99% absorption in two distinct frequency bands (2.8–4.2 THz and 5.5–7.1 THz) while maintaining a compact profile of only 15 µm total thickness. Extensive parametric studies reveal remarkable robustness against geometrical variations, oblique incidence up to 60◦, polarization changes, and material parameter fluctuations. The mathematical model shows excellent agreement with full-wave simulations, validating the theoretical approach. This work establishes a fundamental framework for designing tunable graphenebased THz devices with enhanced performance characteristics.