Design of Dual-Band Tunable THz Ultrasensitive Graphene Metamaterial Sensor

Terahertz metasurface sensors are sought after for their precision in detecting small refractive index shifts, which is vital for applications like environmental surveillance, medical testing, ensuring food quality, and biochemical examination. This work introduces a sensitive terahertz metasurface sensor designed with graphene-based metamaterials featuring adjustable dual-band responses. Composed of a silicon dioxide base and a graphene surface layer, the sensor's operation is explained through coupled-mode theory (CMT). Extensive simulations and evaluations using finite-difference time-domain (FDTD) methods confirm that the absorption and detection characteristics align with the predictions of the coupled-mode theory (CMT). The findings reveal two significant absorption maxima at 1.95 THz and 2.85 THz, both exceeding a 95% absorption rate. The sensor has sensitivities measured at 500 GHz/RIU and 540 GHz/RIU at these resonant frequencies. The stability and reliability of the design are assessed by analyzing the influence of structural parameters and the Fermi level on the absorption characteristics. Adjusting the Fermi level and graphene strip dimensions allows for precise tuning of the device's resonance peaks, expanding its effectiveness for a range of terahertz applications.