Terahertz metasurface sensor and its applications

Terahertz waves, often referred to as far-infrared radiation, represent a unique band of high-frequency electromagnetic waves. In biosensing applications, terahertz waves possess extremely low photon energies—much lower than those of visible and near-infrared radiation—thereby ensuring the safety of biological detection. At the same time, their frequency range covers the characteristic spectral regions associated with collective vibrational modes and weak intermolecular interactions of biological macromolecules. In addition, terahertz waves exhibit strong penetrability through dielectric materials, and a single terahertz pulse can span an ultrabroad bandwidth ranging from the gigahertz to tens of terahertz. When integrated with metasurfaces, terahertz metasurface sensors can further enhance local electric fields, suppress background noise and interference, significantly improve the detection sensitivity, and enable high-sensitivity quantitative analysis of trace biomolecules. This review provides a comprehensive overview of terahertz metasurface sensors from multiple perspectives. It covers terahertz refractive index sensors based on various operating principles, metasurfaces fabricated from different materials—including metallic structures, doped semiconductors, and all-dielectric components—as well as hybrid designs incorporating two-dimensional materials like graphene. The article further categorizes sensors based on their specific application targets. Furthermore, it examines the different device architectures and modulation principles employed, analyzing their respective advantages, drawbacks, and future development trajectories.