Double Rectangular Enclosed Hexagram Shape Metamaterial Absorber for Refractive Index Sensor Applications.

This work introduces a metamaterial absorber in the THz region, specifically designed as a double rectangular enclosed hexagram shape, to operate as a refractive index sensor. The dimensions of the structure are $32 \mu \mathrm{~m}$ in width and height. The substrate material employed between the two gold layers is PTFE. The absorption coefficient for this structure is exceptionally high, measuring $99.99 \%$ at a frequency of 7.28 THz. This structure is likewise unaffected by variations in polarization angle and different simulation modes, such as TE, TM, and TEM. The sensor’s performance is also analyzed, and this structure is susceptible to variations in the refractive index. The study investigates the sensing performance by analyzing refractive index values ranging from 1 to 1.10. The sensitivity obtained is $1.68 \mathrm{Thz} /$ RIU. The Q factor and figure of merit (FOM) value are 48.53 and 11.2, respectively. In addition, the analysis also includes examining the electric field (E-field), magnetic field (Hfield), and surface current. Furthermore, to verify the design, the equivalent circuit created and the results obtained from ADS were compared with the results from CST. The inquiry focuses on a refractive index sensor that utilizes a terahertz metamaterial absorber. Given its tiny size, cost-effectiveness, high absorption, and high sensitivity value, this option is highly suitable for a refractive index sensor.