基于Fano共振型超材料的表面增强单分子CARS光谱研究

等离激元共振超材料在光谱探测和生物传感等领域具有重要的作用，利用其在共振条件下巨大的电磁场增强可以实现对弱信号的有效探测，甚至可以达到单分子灵敏度。本项目利用具有Fano共振效应的超材料作为巨大场增强芯片来实现对生物单分子相干反斯托克斯拉曼散射（CARS）信号的放大和探测，探索和解决其中光与物质相互作用的基本科学问题。首先，设计合适的超材料金属非对称结构单元，使其Fano共振峰（暗模式）与泵浦光源的波长相匹配，不同的亮模式分别与斯托克斯光及反斯托克斯光对应，以便实现最大的信号增强；其次，研究光－等离激元－非线性拉曼信号之间内在关联和相互影响，探讨利用超材料不同共振模式实现单分子拉曼探测的物理机制和有效途径，以及增强非线性拉曼信号和分子探测灵敏度的关键因素。通过本项目的研究将为弱信号条件下的未知分子探测和高灵敏度传感提供实验支持和借鉴。

Plasmonic metamaterials have prominent applications in spectroscopies and biological and chemical sensing. The weak signals (even single-molecule signals) can be effectively detected due to its huge resonant plasmon field enhancement. In this application, we will use plasmonic metamaterials with Fano resonances to enhance and amplify single-molecule CARS spectra, and explore and solve the basic scientific problems of the light-matter interaction among them. Firstly, we will design the metamaterials with asymmetric substructures. In order to obtain the maximum signal enhancement, the Fano resonance (dark mode) peak should match with the wavelength of pump light, and different bright modes correspond to the Stokes and anti-Stokes signals; Secondly, we will study on the transformation and interaction among the light, plasmon and nonlinear Raman signals, and investigate the physical mechanism and effective method to realize the single-molecule Raman detection and key points to enhance the nonlinear Raman signal and probing sensitivity. This work will provide experimental support and reference for probing weak signals of unknown molecules and high sensitive sensing.