School of Microelectronics, Shanghai University, Shanghai 200000, China.
Shanghai Key Laboratory of Chips and Systems for Intelligent Connected Vehicle, Shanghai University, Shanghai 200000, China.
Sensors (Basel). 2023 Jun 25;23(13):5902. doi: 10.3390/s23135902.
Terahertz (THz) waves, which fall between microwaves and infrared bands, possess intriguing electromagnetic properties of non-ionizing radiation, low photon energy, being highly sensitive to weak resonances, and non-polar material penetrability. Therefore, THz waves are extremely suitable for sensing and detecting chemical, pharmaceutical, and biological molecules. However, the relatively long wavelength of THz waves (303000 μm) compared to the size of analytes (1100 nm for biomolecules, <10 μm for microorganisms) constrains the development of THz-based sensors. To circumvent this problem, metasurface technology, by engineering subwavelength periodic resonators, has gained a great deal of attention to enhance the resonance response of THz waves. Those metasurface-based THz sensors exhibit high sensitivity for label-free sensing, making them appealing for a variety of applications in security, medical applications, and detection. The performance of metasurface-based THz sensors is controlled by geometric structure and material parameters. The operating mechanism is divided into two main categories, passive and active. To have a profound understanding of these metasurface-assisted THz sensing technologies, we review and categorize those THz sensors, based on their operating mechanisms, including resonators for frequency shift sensing, nanogaps for enhanced field confinement, chirality for handedness detection, and active elements (such as graphene and MEMS) for advanced tunable sensing. This comprehensive review can serve as a guideline for future metasurfaces design to assist THz sensing and detection.
太赫兹（THz）波位于微波和红外波段之间，具有非电离辐射、低光子能量、对弱共振高度敏感以及对非极性材料可穿透等有趣的电磁特性。因此，THz 波非常适合用于感测和检测化学、制药和生物分子。然而，THz 波的相对较长波长（303000μm）与分析物的大小（生物分子为 1100nm，微生物小于 10μm）相比，限制了基于 THz 的传感器的发展。为了解决这个问题，通过工程亚波长周期性谐振器的超表面技术引起了人们的极大关注，以增强 THz 波的共振响应。基于超表面的 THz 传感器具有针对无标记感测的高灵敏度，使其在安全、医疗应用和检测等各种应用中具有吸引力。基于超表面的 THz 传感器的性能受几何结构和材料参数控制。工作机制分为无源和有源两种主要类型。为了深入了解这些基于超表面的 THz 感测技术，我们根据它们的工作机制对这些 THz 传感器进行了综述和分类，包括用于频率移位感测的谐振器、用于增强场限制的纳米间隙、用于手性检测的手性以及用于高级可调谐感测的有源元件（如石墨烯和 MEMS）。这篇综述可以作为未来用于 THz 感测和检测的超表面设计的指南。
