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

An ultrathin, single-layer planar terahertz metamaterial absorber (MMA) is numerically demonstrated for chemical sensing applications. The fractal MMA consists of a 2nd order Cayley tree-shaped resonator deposited on a polyimide substrate. The designed absorber is polarization-insensitive and has six resonance frequencies at 3.376, 6.49, 6.92, 8.083, 8.227, and 9.36 THz. For the absorption peak at 3.376 THz, the proposed sensor has thickness of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.067 \ \lambda$</tex> and its largest dimension is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.38 \ \lambda$</tex>. The electric field map is analysed to interpret the fundamental characteristics of the six resonances. The refractive index based sensing is evaluated by placing an analyte on top of the absorber. The proposed sensor exhibits a good Quality factor (Q) value of 98.85 and its highest sensitivity is 1.35 THzIRIU. The designed MMA sensor is suitable for various chemical and bio sensing purposes.