红外超表面的角度敏感机理及生物分子探测器件研究

The metamaterial enhanced infrared absorption spectroscopy can be used to identify fingerprint absorptions of biomolecules, which has promising applications in medical diagnosis, national security, and industrial process monitoring, etc. To address the key issue of matching the frequency of metamaterial optical resonance with those of the molecular absorption lines, this project investigates the mechanism of angle-dependence of metasurfaces, and proposes a new class of optical biomolecular sensors based on angle-sensitive metasurfaces. By using the surface waves instead of conventional localized electrical or magnetic resonances, the resonant frequencies of the metasurfaces can be tuned over a large frequency range by varying the incident angle, and therefore the resonant optical field can be coupled to the multiple absorption lines of a single target molecule or multiple molecules. As compared with existing metamaterial molecular sensors, our proposed angle-scanned molecular sensors have the advantages of larger frequency bandwidth and relatively simpler operation. Taking the Octadecanethiol (ODT) and Bovine Serum Albumin (BSA) as representative detection targets, we will design and fabricate angle-sensitive metasurface biomolecular sensors. The physical mechanism of angle-sensitivity of the metasurfaces will be revealed, and the proof-of-concept monolayer biomolecular sensing will be demonstrated. Our proposed metasurface sensors are novel in their working mechanism, and pave a way towards fast and parallel sensing of multiple molecular species.

超材料增强的红外吸收光谱技术能够实现生物分子的灵敏识别，在医疗、安检和工业监控等方面具有广阔应用前景。针对超材料分子探测器件中共振光场与待检分子指纹吸收频率匹配的关键共性问题，本项目研究超表面的角度敏感机理，并研制基于角度特性的超表面分子探测器件。利用表面波模式，而不是常规的局域电共振或者磁共振，可以实现角度调控的超表面光场共振频率的大范围扫描，从而实现与单一检测目标的多个指纹谱线或者多个待检分子特征吸收谱线的匹配。相比现有基于尺寸控制或者可调材料的超表面分子探测器件，本项目提出的角度扫描超表面分子探测器件具有工作频带宽和操作简易的优点。项目以十八硫醇和牛血清白蛋白为典型检测对象，设计并制备角度敏感超表面分子探测器件，揭示超表面的角度敏感机理，演示角度扫描的单层生物分子检测。本项目提出的角度敏感超表面分子探测器件是检测方法的创新，有助于推动光学分子探测技术向多特征谱线快速检测的方向发展。

超表面增强的红外吸收光谱技术能够实现分子的灵敏识别，在无接触、非破坏性光学传感方面具有重要应用。针对超表面分子探测器件中共振光场与待检分子指纹谱线频率匹配的关键共性问题，本项目开展了角度敏感超表面的理论设计、样品制备、性能测试及机理分析等研究工作。利用漏波和波导模传播模式，项目研制了金属条和非对称“十”字棒等结构的角度敏感超表面，实现了角度调控的共振频率动态调谐，实验测试的共振频率扫描范围为中心频率的18-40.4%。基于所研制的角度敏感超表面，项目还实现了单分子层十八硫醇（ODT）和牛血清白蛋白（BSA）的特征指纹检测，实验测试的最大指纹信噪对比度为0.5-1.5%，展示了角度敏感超表面在分子检测方面的性能优势。项目研制的超表面具有常规超材料不具备的角度敏感性，通过入射角度的变化可以实现超表面共振频率的动态调谐，为超表面的模式调控提供了便利方法，在可调光学器件和超表面传感器件等方面具有应用前景。