A triple-band metamaterial absorber for gas sensing and refractive index detection through enhanced FOM and Q-factor performance in the THz regime

In this paper, a new micro-arranged triple band interconnected oval-shaped split ring with an external split circle symmetrical metamaterial absorber (MMA) is discussed. This design contains three layers where lead glass is sandwiched between two copper layers as a resonator surface and ground, which has a strong ability to identify the variation of refractive index for different gas sensing through THz frequency spectral analysis. The working frequency of the proposed absorber is 9 to 10 terahertz (THz) where the three absorption peaks are having 99.95%, 96.42%, and 99.98% absorptions at 9.42 (f1), 9.86 (f2), and 10.03 (f3) THz, respectively. The figure of merit (FOM) of the proposed MMA having value of 15.45, 23.82, and 29.87shows progressively higher sensing application and precisely identify small changes in refractive index. To measure the Sensitivity, refractive index (n) has been varied from 1 to 1.05 and the results are 2.016, 2.556 and 1.41 THz per refractive index unit where these values indicate an effective sensitivity for detecting small changes in refractive index. The quality factors (Q-factors) of this triple band MMA are 72.53, 92.11, and 213.24 indicating sophisticated accuracy and better capability to spot and respond to minute changes in its environment. This MMA shows a great polarization independency as it has symmetrical construction. To explore the absorption and sensitivity property of this unique MMA, several parametric simulations have been done such as surface current, different gas layers and in addition permittivity and permeability are also analyzed. As a whole, this MMA shows versatility, with excellent FOM values and Q-factors, making it a reliable option for both wide-band sensing as well as high-precision sensing. This ability to react to changes in refractive index makes it a brilliant candidate for sensing applications in fields such as environmental monitoring, clinical examination, and chemical sensing.