Pixelated Toroidal Metasurface Sensor with Broadband Terahertz Fingerprint Enhancement for Biochemical Trace Detection.

Terahertz (THz) trace fingerprint detection is essential for identifying the characteristic biomolecular absorption fingerprints from inherent molecular rotational and vibrational modes. Plasmonic THz resonance shows a way to enhance the recognition of biomolecular absorption fingerprint spectra. In this research, we experimentally demonstrate a broadband THz fingerprint metasensor based on a pixelated toroidal metasurface, showcasing excellent capabilities in biochemical trace detection. The design employs mirrored asymmetric double split-ring resonators to excite the toroidal resonance with a high quality (Q) factor and strong localized field enhancement. This high Q-factor resonance exhibits exceptional spectral resolution with spectral resolution less than 50 GHz for broadband fingerprint sensing, thereby capturing characteristic information. More importantly, the design allows for linear modulation of the split-ring resonator radius, which can be extended to cover a larger spectral region by adjusting geometric parameters to meet multifingerprints detection of various biochemical analytes. Utilizing fingerprint enhancement and multiplexing technology, the metasensor precisely detects trace glucose with a high sensitivity. The introduction of the metasensor significantly enhances the absorption characteristics of glucose films, demonstrating an outstanding broadband fingerprint sensing performance. This high-performance and flexible fingerprint metasensor has potential applications in enhanced broadband THz fingerprint sensing, providing a powerful and low-cost approach for advanced biochemical trace detection.