Enhanced structural tunability and high sensitivity of a THz metasurface absorber for precise automotive fuel characterization.

This paper introduces a metasurface absorber (MSA) sensor designed for fuel adulteration detection in the sub-terahertz (THz) range. The MSA features mirror-symmetric separated half-circle (MSSHC)-shaped resonators, a gold ground plane, and a dielectric layer, operating effectively within the 4.4-5.4 THz frequency range. It achieves notable absorption peaks at 4.94 THz. The resonance frequencies can be finely tuned by adjusting the geometric dimensions, ensuring optimal absorption. The MSA detects various additives in diesel, gasoline, and octane by monitoring shifts in resonance frequencies corresponding to changes in the oil's refractive index (RI). The absorber demonstrates a Q-factor of 304.35, a figure of merit (FOM) of 7.15 RIU, and a maximum sensitivity of 120 GHz/RIU in diesel detection. This innovative concept holds significant potential as an efficient fuel oil sensor within the automotive industry. Its structural tunability, high sensitivity, and practical design render it a promising sensor for chemical detection and biosensing applications in the THz regime.