Terahertz sensors for next generation biomedical and other industrial electronics applications: A critical review

Principles of Measuring Thickness and Refractive Index of Thin Dielectric Film by Using Multiresonance Archimedean Spiral Metasurfaces with C Resonator in the Terahertz Frequency Range

“…Following our approach, we tried to find the parameters of the analyte with 𝑛 𝑎 (𝑓 𝑟𝑒𝑠 𝐼 ) = 𝑛 𝑎 (𝑓 𝑟𝑒𝑠 𝐼𝐼𝐼 ) = 1.74 RIU and precalculated values of thickness by using only the sensitivities from Table 1. Figure 4a shows the typical behavior of Equation (20) for various analyte thicknesses, whereas Figure 4b presents the thickness and refractive index values obtained by taking into account the error of the approximation model. According to Figure 4c, the error decreases with increasing thickness contrast and becomes minimal when the thickness is sufficiently far from the saturation mode and the linear operation mode of the sensor (𝑡 𝑎 ≪ 𝑡 𝑠𝑎𝑡 𝑥 ).…”

“…Tracking the position of the dip, one can measure and detect even minute amounts of the analyte. This feature, in addition to the unique properties of terahertz radiation, is optimal for label-free, selective thin-film sensing [19,20].…”

“…Many authors have reported on metasurface-based thin-film sensors. Most of these articles are devoted to split-ring resonators and their modifications, periodic slits in metallic foil, and sensors based on extraordinary transmission, BIC, or spoof localized surface plasmon resonance [15,[20][21][22]. Although these examples show good performance as sensing platforms, they usually exploit a single-resonance approach to measuring the characteristics of thin films.…”