Tri-Band Terahertz Metamaterial Absorber Based on Structural Ti₃C₂Tₓ MXene for Enhanced Sensing Application

High-performance terahertz (THz) narrow-band metamaterial absorbers (MMAs) occupy a central position in sensing application. However, the majority of current MMAs for refractive index (RI) sensing typically only perform well within a single or dual-band range, or exhibit relatively low sensing performance. In this work, a tri-band MMA based on tri-cylindrical-shell (TCS) structure Ti3C2Tx MXene is proposed and investigated numerically for the enhanced RI sensing applications in THz region. The fundamental idea behind our approach lies in harnessing the unique electromagnetic (EM) properties of Ti3C2Tx MXene to achieve multiband absorption and enhanced sensing capabilities. A comprehensive numerical simulation analysis of the designed MMA was conducted using the finite element method (FEM) and the equivalent circuit method (ECM). The simulation results demonstrate that the proposed MMA achieves remarkably high absorbance levels of 99.97%, 94.54%, and 99.65% at 1.20, 1.55, and 1.91 THz, respectively. This strong absorption is attributed to the hybrid coupling effect between waveguide modes and surface plasmon polaritons (SPPs), as evidenced by the simulated EM fields and energy distributions. Notably, the tri-band absorption characteristics of our MMA can be easily tuned by adjusting the geometric parameters of its unit-cell. Moreover, the MMA exhibits exceptional sensing performance, with sensitivities of up to 1.79, 1.40, and 1.13 THz/RIU, respectively. This combination of straightforward design, robust absorption capabilities, and heightened sensitivity makes our MMA structure a promising candidate for applications in THz biosensing, material detection, and communication systems.