High-Performance Terahertz Sensing at Exceptional Points in a Bilayer Structure
High-Performance Terahertz Sensing at Exceptional Points in a Bilayer Structure
复制标题
在双层结构的特殊点进行高性能太赫兹传感
DOI：
10.1002/adts.201800070
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发表时间：
2018
影响因子：
3.3
通讯作者：
Peiheng Wu
中科院分区：
文献类型：
--
作者：
Biaobing Jin;Wei Tan;Caihong Zhang;Jingbo Wu;Jian Chen;Shuang Zhang;Peiheng Wu
许多位于太赫兹（THz）频率的块体、粉末和薄膜中的分子内和分子间振动可以提供丰富的结构信息，可以通过常规的拉曼和傅里叶变换红外光谱来获取。然而，由于缺乏高质量的THz源和探测器，THz传感器的灵敏度远远达不到检测少量样品（如单层生物分子）所需的水平。这对超高灵敏度的THz生物传感器提出了迫切的需求。在这里，提出了一种理论设计，使用双层超颖表面来构造服从无源宇称时间对称并且具有例外点的双谐振器耦合系统。通过将耦合谐振器设计为具有正交激励取向并在偏振空间中恢复本征频率，可以区分甚至小于谐振线宽的本征频率分裂，从而获得超高THz灵敏度。电磁模拟表明，灵敏度（定义为分析物每微米厚度和每折射率单位（RIU）的频率变化）可以达到800 GHz RIU−1µm−1，比以前工作中报告的值高一个数量级。这种提出的高灵敏度方法可以为在太赫兹频率下检测单层分子开辟一条道路。
Many intra‐ and inter‐molecular vibrations lying at terahertz (THz) frequencies in bulk, powder, and thin film, which could provide rich structure information, can be accessed by conventional Raman and Fourier transform infrared spectroscopies. However, due to the lack of high‐quality THz sources and detectors, the sensitivity that has been demonstrated with THz sensors is far from the level needed to detect small amounts of sample, like monolayer biomolecules. This puts forward an urgent requirement for a THz biosensor with ultra‐high sensitivity. Here, a theoretical design is proposed using a bilayer metasurface to construct a two‐resonator coupled system that obeys passive parity time symmetry and that possesses an exceptional point. By designing the coupled resonators to have orthogonal excitation orientations and retrieving the eigenfrequencies in polarization space, eigenfrequency splitting even smaller than the resonance linewidth can be distinguished, and thus attain ultra‐high THz sensitivity. Electromagnetic simulations show that the sensitivity, defined as the frequency change per micrometer in thickness and per refractive index unit (RIU) of the analyte, can reach 800 GHz RIU−1µm−1, an order of magnitude higher than the values reported in previous work. This proposed high‐sensitivity approach could open a path toward the detection of monolayer molecules at THz frequencies.