Angle-multiplexed guided mode resonance metasurfaces for broadband terahertz fingerprint detection

Chiral enantiomers exhibit distinct pharmacological and pharmacokinetic properties, making the precise detection of chiral components crucial to avoid harmful effects on the human body. Terahertz (THz) spectroscopy, which resolves molecular structures by detecting intra- and intermolecular vibrational modes, has been enhanced through the integration with metasurfaces, extending its applications in biomedical and security detection. However, current methods face significant challenges in trace analysis and broadband detection of analytes. Here, we propose a novel metasurface-based approach for detecting molecular broadband fingerprint spectra, combining the simplicity of state-of-the-art THz angle-scanning methods with the specificity of molecular fingerprinting. Specifically, we designed a guided mode resonance (GMR) metasurface capable of providing localized electromagnetic field enhancement and continuous spectra between 0.95 and 1.45 THz. We demonstrate the enhanced detection of intrinsic absorption features of glutamic acid enantiomers by correlating the molecular absorption spectra with the reflectance spectra at each incident angle. This angle-scanning approach simplifies the identification process and spectroscopic system, offering the potential for miniaturization and field deployment of THz spectroscopic devices for molecular detection.