Terahertz perfect absorber based on InSb metasurface for both temperature and refractive index sensing

In this paper, a terahertz perfect absorber (PA) made of all-dielectric metasurface with periodic sub-wavelength InSb micro-rod array in terahertz (THz) region was proposed, which can be functioned for temperature and refractive index (RI) sensing application simultaneously. Simulation results show that the absorbance of 99.9% at 1.757 THz and the Q-factor of about 53.24 under room temperature ( T = 295 K) can be obtained for this proposed PA. The perfect absorption is mainly contributed to the fundamental dipolar resonance inside the unit-cell structure. The resonance absorption properties of the PA can be adjusted by changing the geometric parameters of the structure. The proposed PA has a sensitivity of about 4.2 GHz/K since the electrical property of the InSb is highly dependent on the surrounding thermal radiation, which can be served as a temperature sensor. In addition, the PA also can be functioned as a RI sensor due to its higher Q-factor. As proofs of the RI sensing application, the sensitivity of the PA-based RI sensor about 1043.3 GHz/RIU at 295 K, and 920 GHz/RIU at 300 K can be obtained. Therefore, the narrow-band PA could be found promising applications on sensors, detectors, filters, and other optoelectronic devices in THz region. • Narrow-band tunable THz perfect absorber (PA) based on InSb metasurface was proposed. • The absorbance of PA is 99.9% at 1.757 THz and the Q-factor is about 53.24 when temperature 295 K. • Perfect absorption due to the fundamental dipolar resonance in the InSb metasurface. • The proposed PA can be served as both temperature and refractive index (RI) sensor.