VO2-Enabled Nanogap Metasurface for Active Terahertz Sensing

Terahertz (THz) sensing has attracted widespread attention for its superior performance, such as label-free detection and non-ionizing radiation. However, the relatively long wavelength of THz waves leads to weak electromagnetic responses for tiny biomolecules. Advanced metasurface technology is a promising solution to this problem. In this paper, we proposed a tunable nanogap metasurface operating at 1 THz for efficiency-enhanced biosensing. The sensor employed the phase-change material vanadium dioxide (VO 2 ), which enables a metal-insulator transition to achieve abrupt and reversible tunability. Furthermore, we narrowed the gaps of the resonators to the nanometer level, which is only a thousandth of a unit-cell size, generating a huge field enhancement locally. It allows precise capture and ultra-sensitive sensing of microorganisms. The sensor also produces electromagnetically induced transparency (EIT) phenomenon because of its novel asymmetric resonant structure. The active and highly sensitive properties of the metasurface make this biosensor promising to detect various microorganisms on the nano-scale, such as viruses, fungi, etc.