Review on terahertz polarization sensing based on metasurface sensor

Terahertz waves have a wide range of applications in the field of sensing because of their good coherence, high signal-noise ratio, low radiation energy, and non-ionization. In addition, THz sensing also has the advantages of real-time, non-contact, and label-free, so it has important application in biological sensing, especially in the sensing of active biological substances. But it also has some defects, such as low sensitivity, strong water absorption, limited detection information, and poor applicability. Herein, we propose a THz time-domain polarization spectroscopy (TDPS) sensing system. The metal metasurface structures are used as the sensor, and the transmission or reflection sensing method is used to detect the PVA thin film, tumor cell and amino acid solution respectively. The experimental results show that: compared with the traditional resonant sensing method, the quality (Q) factor and figure of merit (FoM) of polarization sensing method are improved by at least 4~5 times, so the sensing sensitivity is significantly improved. For tumor cell sensing, its minimum detection accuracy has reached 103 cells/ml. For amino acid solution sensing, the minimum detection accuracy is 10-5 g/ml magnitude. In addition, using the chiral metasurface structure as sensor, this method can also identify the difference between the chiral enantiomer solutions of amino acids.