Terahertz Liquid Sensing With Spoof Surface Plasmons Based on High-Contrast Gratings

High-contrast gratings (HCGs) have been reported to support the spoof surface plasmon (SSP). However, HCGs have not been applied in liquid sensing in the THz range. We propose a SSP sensor based on HCGs with Otto prism coupling. First, the investigation results show that our structure can achieve higher sensitivity than the all-metal SSP sensor with the same geometry parameters in the liquid crystal sensing scenario. Second, the influence of the geometry parameters such as the period and the gap depth on the sensitivity is also discussed. After the necessary optimization, the sensitivity of our structure achieves the highest sensitivity up to 412.6 GHz/RIU with a resolution of 0.002 RIU around 384.5 GHz. The suggested structure demonstrates a novel method for terahertz sensing applications.