Terahertz metamaterial and its sensing application

Spatial overlap between the electromagnetic fields and the analytes is a key factor for strong light-matter interaction leading to high sensitivity for label-free optical biosensors. Usually, the exponential fields of cavity modes or surface plasmon resonances are applied to monitor the refractive index variation from bio-reactions. The sensitivity is therefore limited by the influence of local index variation to the weak exponential field. In this paper, by constructing a metallic microstructure array-dielectric-metal (MDM) structure, a novel metamaterial integrated microfluidic (MIM) sensor is demonstrated in terahertz (THz) range, where the dielectric layer of the MDM metamaterial is hollow and acts as the microfluidic channel. Tuning the electromagnetic parameters of metamaterial, greatly confined electromagnetic fields can be obtained in the channel resulting in significantly enhanced interaction between the analytes and the THz wave. A record high sensitivity of 3.5 THz/RIU is predicted by numerical simulation. Normalized the sensitivity to the working frequency, the calculated and measured normalized sensitivity is 0.55/RIU and 0.31/RIU, respectively. The proposed idea to integrate metamaterial and microfluid with a large light-matter interaction can be extended to other frequency regions and has promising applications in biosensing and matter detection.