Terahertz polarization and chirality sensing for amino acid solution based on chiral metasurface sensor

The detection and identification of chiral materials, especially chiral biochemical samples, have a wide range of applications. Terahertz (THz) sensing has obvious advantages in online real-time non-contact and label-free biochemical detection, but it is difficult to detect the chiral solution samples. Herein, we propose a new THz sensing method based on THz reflective time-domain polarization spectroscopy (RTDPS) system and a chiral metasurface sensor. The chiral enantiomers of three kinds of amino acids aqueous solution were measured by this sensing method, which improves sensitivity and detection accuracy for amino acid aqueous solutions compared with the traditional THz resonance sensing. The sensing accuracies of the different amino acid samples are all in the order of 10−5 ∼ 10−4 g/mL, and the minimum value reaches 1 × 10-5 g/mL. Moreover, the D- and L- enantiomers with the same concentration can be distinguished by the significant difference in THz polarization parameters at the characteristic frequency. This method is not only suitable for amino acid aqueous solutions, but also other chiral biochemical solutions. Therefore, THz polarization spectroscopy and chiral metasurface sensor have great potential for high-sensitive quantitative detection and chirality identification in the analysis of biochemical materials.