Terahertz GaAs Indicator Chip Based on High‐Q‐Factor Spoof Localized Surface Plasmons Resonator

Abstract Spoof localized surface plasmons (spoof LSPs, SLSPs) have recently emerged as high‐quality‐factor (Q‐factor) multipole electromagnetic resonant structures, showcasing considerable promise in the field of sensing. However, sensing in the terahertz band presents notable challenges. Here, a dual‐port coupled SLSPs resonator and a single‐port coupled SLSPs resonator are proposed with phase separated excitation, both exhibiting high‐Q‐factors in the terahertz band. The dual‐port coupled SLSPs can sustain both odd resonance mode and even resonance mode, whereas the single‐port coupled SLSPs can generate vortex wave resonance modes and asymmetric modes. In the measurement, the highest Q value of the dual‐port resonator is 69 at the frequency of 179.4 GHz. Equally noteworthy is the single‐port resonator, which reaches a groundbreaking Q‐factor of 405.4 at the frequency of 150 GHz, marking a significant advancement in the Q‐factors of passive devices. Biosensing for Bletilla, Fritillaria, Rhubarb, and glucose in the terahertz band is implemented, with the maximum frequency shift of 15.8 GHz for the dual‐port coupled SLSPs and 7.8 GHz for the single‐port coupled SLSPs. The maximum sensing figures of merits (FoM) are 4.1 and 12.9RIU −1 for the dual‐ and single‐port resonators, respectively, underscoring substantial potentials of this work in the realm of terahertz sensing.