Design of a tunable terahertz metamaterial absorber for compact multifunctional communication and biosensing platforms

Abstract This paper investigates three novel four-blade fan-shaped structure (BFSS)-based tunable terahertz metamaterial absorbers (TMMAs). The proposed absorbers provide ultra-wideband (UWB), narrowband (NBW), and multiband (six-band) absorption characteristics through a metal–dielectric–metal layered architecture. The UWB behavior is achieved through strong resonant coupling and distributed surface currents induced by the BFSS geometry. A narrowband response is obtained by compressing the central gap into a lens-shaped region, which enhances localized field confinement and sharpens the resonance. By expanding the lens-shaped gap, a smooth and controllable transition from narrowband to UWB absorption is realized. For multiband operation, a wavy-edge resonant structure is introduced at the center of the BFSS, resulting in multiple discrete absorption peaks across the THz range. The proposed UWB TMMA achieves absorption greater than 90% over the frequency range of 2.5–9 THz, corresponding to a 7.5 THz quasi-continuous broadband response with a −10 dB bandwidth. Full-wave simulations performed using CST Microwave Studio evaluate the electromagnetic response, revealing a sharp resonance at 2.43 THz with 99.35% absorption. The narrowband TMMA is further analyzed for noninvasive blood glucose sensing, where it demonstrates excellent performance, including a high figure of merit (FOM) of 61.62, a low detection limit (DL) of 0.005 RIU (Refractive Index Unit), a signal-to-noise ratio (SNR) of 11.72, a dynamic range (DR) of 11.21 Mm, and a sensitivity of 6.78 THz RIU −1 . The sensing capability is validated using Debye and Cole–Cole biological tissue models by accounting for variations in glucose concentration, refractive index, and permittivity. Additionally, a six-band TMMA is developed, achieving near-unity absorption at 0.5, 1.5, 3, 4.5, 6.5, and 8 THz. The structures exhibit polarization insensitivity and maintain stable performance for incidence angles ranging from 0° to 80°, owing to the symmetric BFSS geometry. These results demonstrate that the proposed TMMAs offer strong potential for diverse terahertz applications, including imaging, biological sensing, and broadband electromagnetic control systems.