High-Sensitivity Terahertz Sensor for Liquid Medium Detection Using Dual-Layer Metasurfaces

In this article, a metasurface-based liquid sensor combined with terahertz spectroscopy is proposed to detect various liquid mediums. The sensor consists of two intersecting resonant structures with identical geometry, offering high sensitivity and resolution for index sensing. The mechanism of intense resonance is investigated, and the impact of structural dimensions on device sensitivity is analyzed. Through experimental demonstrations, excellent detection performance is achieved with a sensitivity of 120.6 GHz/RIU and a Q-value of 82.3 for the proposed structure. The sensor is successfully applied to detect alcohol concentration, sucrose aqueous solution concentration and screen three common oils (castor, olive, and soybean oils). With its compact size and ease of fabrication, our design holds excellent potential for liquid sensing applications.