High-Q terahertz sensor based on semiconductor material with annular geometry

This paper proposes a terahertz sensor incorporating an annular grating that enables strong absorption at 5.485 and 6.895 THz. The physical origin of the resonance peaks is elucidated by impedance matching theory together with the electric-field distribution. The tolerance of the device to structural-parameter variations is systematically evaluated, and its insensitivity to small changes in the incident angle is further verified. Furthermore, the sensing performance of the sensor is comprehensively analyzed, and the detectable refractive-index range is determined to be from 1.30 to 1.40. The sensor provides dual sensing channels, maintains the full width at half maximum below 0.013 THz, and exhibits maximum quality factor (Q-factor), sensitivity (S), and figure of merit (FOM) of 825.34, 1.6 THz RIU−1, and 224.88 RIU−1, respectively. In the biological detection, the refractive index of most analytes falls between 1.30 and 1.40. Owing to the simultaneously high Q-factor and FOM, the proposed sensor holds significant potential for biological detection.