Enhanced Broadband Terahertz Trace Fingerprint Spectrum Utilizing Multiunit Fano Metasurfaces

Terahertz (THz) spectroscopy can obtain characteristic fingerprint spectra by detecting the structural vibrations of molecules. Nanophotonic enhancement and subwavelength field confinement have expanded the application scope of this technology. However, current methods still require complex spectroscopic equipment and face obstacles in the trace analysis of analytes and broadband detection. Here, we introduce a novel metasurface design approach to detect the broadband absorption spectra of molecules, which combines the simplest detection method (transmission metasurface chipset) with the chemical specificity of THz spectroscopy. Specifically, we designed a metasurface chipset based on Fano resonance, capable of providing frequency-selective spectra and surface-sensitive resonances between 0.18 and 1.20 THz. We used this method to detect distinct absorption signatures of different interacting analytes, including l-tyrosine (5 and 10 mg/mL) and bovine hemoglobin. By combining the molecular absorption spectra with the transmission spectra of each metasurface chip, broadband detection was achieved through the design of the metasurface chipset, paving the way for the field-deployable applications of miniature THz spectroscopy devices.