Polarization-resolved terahertz metasurface sensor for concentration sensing and isomer recognition of chiral molecules

The paper presents a terahertz polarization sensing method based on a metasurface for concentration and isomer recognition of chiral molecules with high sensitivity. By designing a metasurface sensor with a spiral square ring structure and combining it with a polyvinyl alcohol-proline thin film coating, the circular dichroism and optical rotation signals of the sample are extracted using a terahertz polarization-resolved time-domain spectroscopy system. The experimental results show that the metasurface significantly improves the chiral signal detection sensitivity (4.57 GHz/(μg/cm2)), and its figure of merit (0.0354 cm2/μg) is superior to previous ring structure sensors. Further analysis shows the polarization ellipse angle and polarization rotation angle of different chiral molecules (D/L-proline) exhibit differentiated characteristics. This method provides a strategy for the precise detection of ultra-weak chiral signals in the terahertz radiation.