A Novel Miniaturized THz Refractive Index-Based Electric Permittivity Sensor

A novel miniaturized and highly sensitive terahertz (THz) sensor is designed and analyzed in this article. For material sensing applications, a unique resonator, consisting of spokes and a hexagonal rim, is proposed. The footprint of the designed resonator is
$0.67\lambda _{\text {eff}} \times 0.67\lambda _{\text {eff}}$
, where
$\lambda _{\text {eff}}$
represents the effective wavelength calculated at 7.16 THz. The sensitivity of the proposed metamaterial unit cell sensor is determined by analyzing its absorption characteristics. The proposed sensor demonstrates 99.9% absorptivity in free space and remains insensitive to polarization variations due to its geometry, which has rotational symmetry. The sensor is found to be angularly stable for oblique incidences up to 60°. Various analytes with different refractive indices are used to study the sensing performance, and the mean sensitivity is estimated to be 1.37 THz/refractive index unit (RIU). Furthermore, the impact of thickness of the analyte is examined, and the average deviation is estimated to be 59 GHz/
$\mu \text{m}$
. From the achieved results, it can be concluded that the proposed THz metamaterial unit cell is well suited for material sensing applications.