Terahertz Chiral Recognition Based on Metasurfaces

Chiral detection plays a crucial role in biomedicine and materials science, but traditional methods face challenges such as low sensitivity and complex operation. Utilizing a terahertz time‐domain spectroscopy (THz‐TDS) system for chiral sample detection leverages the advantages of terahertz radiation, including rich biological information and nonionizing properties. However, conventional THz‐TDS systems can only generate and detect linearly polarized terahertz radiation, requiring multiple measurements for chiral characterization. Here, we propose a novel terahertz chiral sensing method based on a multi‐layer metallic metasurface. Within the range of 0.65–0.75 THz, the metasurface can separate and focus the left‐handed and right‐handed circularly polarized components in the linearly polarized illuminating light into two focal points and convert them back into linear polarization for convenient measurement, thereby overcoming the technical bottleneck of traditional systems. Experimental results demonstrate that the double‐layer metasurface structure extends the operational bandwidth to 100 GHz through Fabry–Perot‐like resonance effects. The (R)‐(−)‐ibuprofen and (S)‐(+)‐ibuprofen enantiomers are measured to demonstrate the validity of proposed method. Compared to traditional THz‐TDS systems for chiral measurements, the efficiency of this method is significantly improved. This method provides a new approach for terahertz chiral recognition and demonstrates practical value in the field of pharmaceutical chiral analysis.