Application of Terahertz Metamaterials for Low-concentration Sensing of Premium Explosives like RDX and TNT

Mr. Rajesh Koalla
ACRHEM, University of Hyderabad, Hyderabad, India


The terahertz (THz) spectrum shows unique features such as high transmittivity, strong absorption, and low non-ionizing energy. THz metamaterials offer substantial advancements in detection technology and could be employed as fast, label-free chemical and biological sensors[1]. In the present study, we have investigated a parallel metal pair-based metamaterial for the low-concentration (10 mM) detection of two premium explosives such as RDX and TNT. The structure displays Fano resonance at 0.629 THz in reflection geometry in the 0.1 to 1 THz range. The structure consists of an asymmetric pair of aluminium metals rod-like structure deposited on a 400 μm intrinsic/undoped silicon wafer with resistivity >5000 Ω-cm, making up the metamaterial unit cell of dimensions Px= 110 μm and Py=120 μm. The structure's periodicity along the x and y coordinates is represented by Px and Py, respectively. The aluminium pair of rods lengths are 100 and 80 μm, the thickness is 80 μm, and the gap between the rods is 8 μm. We have also studied the refractive index-dependent sensitivity of the metamaterial. This excitation structure shows a sensitivity of S = 40 GHz/RIU when subjected to a 10 mM concentration of explosives (RDX and TNT). At a frequency of 0.629 THz, the refractive index for TNT is 1.61, and for RDX, it is 1.85. Consequently, this leads to resonance peak shifts of 0.012 THz and 0.029 THz from their respective resonance positions. Hence, these findings prove the advantages of metamaterials for low concentrations of explosives.