An Ultrathin Terahertz Tri-Band Fractal Meta-Absorber for Liquid Chemical Sensing Applications

An ultrathin, single-layer planar terahertz meta-material absorber (MMA) is numerically demonstrated for sensing applications. The tri-band fractal MMA consists of a Cayley tree-shaped resonator deposited on a polyimide substrate. The designed absorber is polarization-insensitive and has three resonance frequencies at 3.997, 6.98, and 8.795 THz. For the absorption peak at 3.997 THz, the proposed sensor has thickness of 0.08 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$A$</tex> and its largest dimension is 0.45 A. The electric field map is analysed to interpret the fundamental characteristics of the three resonances. The refractive index based sensing is evaluated by placing a container on top of the resonating surface that holds the analyte. The proposed sensor exhibits a good Quality factor (Q) value of 97.7 and its highest sensitivity is 0.44 THz/RIU. The designed MMA sensor is suitable for various chemical and bio sensing purposes.