Terahertz narrowband perfect metasurface absorber based on micro-ring-shaped GaAs array for enhanced refractive index sensing

In this paper, a narrowband perfect metasurface absorber (MSA) based on micro-ring-shaped structure GaAs array was proposed and investigated theoretically in terahertz (THz) region, which can be applicable for the enhanced refractive index (RI) sensing. Simulation results show that the proposed perfect MSA can achieve an absorbance of 99.9% at 2.213 THz and the Q-factor of about 460.08, which can be confirmed efficiently by the coupling mode theory (CMT). The perfect absorption of the designed structure is mainly contributed to the guided mode of the critical resonance coupling. The absorption properties of the proposed structure can be adjusted by changing the geometrical parameters of GaAs structure. Owing to its higher Q-factor, the proposed MSA can enhance the RI sensing application, and the sensitivity of about 1.45 THz/RIU can be achieved. The research provides a new route for the construction of the highly efficient MSA with potential applications in sensing, detecting, and imaging in THz region.