High Electric Field-Enhanced Terahertz Metamaterials with Bowtie Triangle Rings: Modeling, Mechanism, and Carbohydrate Antigen 125 Detection

Spatial overlap between the electromagnetic field and analytes is a key factor to improve the sensitivity of label-free optical sensors. However, the overlap and sensitivity are limited by the plasma local field or the decaying resonant mode outside the cavity. In this paper, by constructing a bowtie triangle ring (BTR) metal microstructure array, a high electric-field enhanced terahertz (THz) metamaterials (MMs) absorber is proposed and demonstrated. By tuning the length and splits of the BTR structure, the greatly confined electromagnetic fields could be obtained in the channel, resulting in a significantly enhanced interaction between the analytes and terahertz. The split BTR (S-BTR) generates an additional dipole resonant, and the maximum calculating sensitivity of 498 GHz/RIU is obtained. Meanwhile, two kinds of THz MMs biosensors are fabricated and used to detect the breast cancer marker carbohydrate antigen 125 (CA125). The S-BTR has a resonance shift of 46.8 GHz (20 mu g/mL), which is larger than the unbroken BTR (U-BTR). Therefore, the combination of electricfield enhancement with a dipole resonant could further improve the sensitivity of the MMs sensor. This BTR MMs sensor has great potential in the detection of proteins and small molecules.