Graphene-based dual-broadband terahertz absorber with independent frequency and amplitude tunability

In the design of metamaterials, combining two active materials is acknowledged as an effective strategy for independently manipulating multi-band terahertz wave absorption. However, maneuvering two active materials requires a dual-physical field that is inherently complex and may reduce the modulation sensitivity due to hysteresis effects. In this paper, we present a design for a terahertz absorber based on a single active material that utilizes double-layer graphene arrays to achieve independently tunable dual-broadband absorption. The results show that dual-broadband with more than 90% absorption is obtained in the frequency ranges of 1.03-1.55 THz and 3.59-4.20 THz. Physical mechanistic analysis reveals that dual-broadband originates from hybridized plasmonic mode and localized surface plasmon resonance formed by the lower and upper graphene layers, respectively. Electrically controlling the corresponding graphene layer can implement independent active frequency and amplitude tunability of dual-broadband absorption, with modulation depths of 61.2% and 68.4%. The absorber exhibits polarization insensitivity and maintains dual-broadband absorption properties for a wide range of incidence angles. Moreover, the influence of slight dimensional variations in graphene patterns on absorption properties is also investigated. This dual-broadband absorber allows for independent active control of different parameters and could promote the practical applications of terahertz technology in modulators, detectors, and sensors.