Dual-narrowband terahertz metamaterial absorber based on all-metal vertical ring array for enhanced sensing application

In this paper, a novel design of a dual-narrowband metamaterial absorber (MMA) was proposed for use as a high-performance refractive index (RI) sensor in the terahertz (THz) region. The proposed MMA is based on a vertical-ring-shaped (VRS) structure gold film array. Through numerical simulation, it was found that the MMA can achieve high absorption levels of 99.8% and 94.6% at 1.723 THz and 2.457 THz, respectively, which are consistent with the values obtained using coupling mode theory (CMT). The MMA also exhibits high Q-factor values of about 27.35 and 102.38, respectively, which are close to the CMT values of 29.94 and 98.34. The dual-band strong absorption of the MMA is attributed to the guided modes of the critical coupling resonance, and the absorption properties can be adjusted by changing the geometrical parameters of the unit-cell structure of the MMA. The proposed MMA has a narrowband and a higher Q-factor, making it suitable for RI sensing, with a sensitivity of about 1.66 and 1.88 THz/RIU, and a figure-of-merit (FOM) of about 259.4 and 659.7 RIU−1, respectively. These findings open up new opportunities for the development of highly efficient MMAs, which have potential applications in biochemical sensing and detection in the THz region.