Broadband-Enhanced Terahertz Metasurface Biosensor Enables Molecular Fingerprint Trace Detection via Single-Shot Acquisition

Enhancing light–matter interactions to reveal the fingerprint properties of trace molecules is of great significance for terahertz (THz) absorption spectroscopy, which provides vital information about inter- and intramolecular vibrations. The construction of gradient narrow-resonance metasurfaces offers an effective solution to amplify the weak response caused by the significant mismatch between the THz wavelength and the molecular scale. Nevertheless, numerous tests and complex data processing pose considerable challenges to their practical implementation. Herein, we propose a broadband-enhanced THz metasurface biosensor based on the electromagnetically induced transparency effect that achieves an average electric field intensity enhancement of up to 77.61 across a 200 GHz bandwidth. This capability enables highly sensitive detection of molecular fingerprint information through single-shot acquisition. Furthermore, by employing a parameter scaling strategy, we achieve linear tuning of the resonance frequency for each module, thereby expanding the operating bandwidth. As a proof of concept, we demonstrate the coupling responses of two biomolecules using the proposed sensor, achieving both qualitative and quantitative detection based on response intensity and interaction frequency, with a detection limit of 1.76 μg/mm2. As far as we know, it also represents the first instance of detection of two THz fingerprint absorption peaks of the same analyte using a single resonant peak of a metasurface, enabled by single-shot acquisition. This advancement provides novel insights into label-free, high-sensitivity sensing and molecular identification, thereby significantly advancing the application of the THz technology in biosensing.