Greater Than 1 THz Bandwidth High Sensitivity On-Chip Terahertz Sensing Achieved Using Spoof Surface Plasmon Polaritons for Trace Substance Analysis

Terahertz (THz) spoof surface plasmon polaritons (SSPPs) can play a key role in ultrasensitive fingerprint sensing of trace substances by the enhanced confinement of the electric field that they provide. However, achieving both high sensitivity and broadband detection simultaneously in such structures remains a significant challenge owing to the necessary trade-off between field confinement and bandwidth. This study demonstrates a sensing chip based on an artificial THz SSPP slow-light waveguide that simultaneously achieves broad bandwidth (up to 1 THz) along with highly sensitive detection achieved by enhancing both field confinement strength and the effective light-matter interaction distance. We use α-lactose monohydrate as a model analyte and show that our SSPP-integrated THz sensing chip detects its characteristic rotational mode at 0.53 THz at concentrations as low as 18 μg/μL, which represents a 4-fold improvement in the detection limit over previous sensors. Repeat measurements show reliable stability and reproducibility for the chip. In operating up to 1 THz, a frequency range of significant interest for the study of quantum excitations in condensed matter systems as well as for terahertz studies of molecular dynamics in polycrystalline materials, our scalable platform is ideal for the study of light–matter interactions in a wide range of advanced material systems.