Terahertz Anapole-Mode Metasurface for Highly Sensitive Refractive Index Sensing

Terahertz metasurface sensing has attracted tremendous attention in biomedical applications due to its advantages of label-free, non-invasive, and non-destructive detection. However, the sensing sensitivity needs to be further improved to achieve the sensing of trace samples. Here, we proposed a non-radiating anapole mode metasurface to enhance light-matter interaction and achieve highly sensitive refractive index sensing properties. The proposed metasurface consists of two E-shaped structures which can induce electric dipole and toroidal dipole simultaneously and their destructive interference caused the anapole mode. The electromagnetic field distribution and the multipole scattering theory indicated the excitation of the anapole mode. The refractive index sensing properties of the designed metasurface is tested which shows a high sensitivity of 416 GHz/GIU (refractive index unit). Our work provides a new design strategy for metasurface sensing devices and demonstrates its effectiveness in refractive index sensing applications.