石墨烯纳米天线红外光谱增强机理研究

面向痕量分子检测这一重大需求，针对红外光波与分子相互作用极其微弱这一难题，基于石墨烯支持红外波段表面等离子体本征模式和自由电子密度可调谐等特性，提出激发石墨烯纳米天线局域电磁场模式实现对被测分子红外吸收光谱增强的新方法。采用第一性原理及有限元数值计算方法，研究石墨烯表面等离子体局域及调控特性；建立纳米天线局域电磁场耦合激发的物理模型；分析天线结构和外加电场对局域电磁场模式的空间能量分布及光谱特征的影响；发展宽光谱波段石墨烯纳米天线的设计方法；研究石墨烯纳米图形化的加工工艺；构建突破衍射极限的红外光谱增强测试实验及痕量分子探测实验。本项目发展的石墨烯纳米天线红外光谱增强方法，为突破现有红外光谱增强技术中金属纳米结构存在高损耗及窄带限制的瓶颈提供了新思路，为实现下一代超高灵敏度的红外光谱传感技术奠定基础。

Infrared(IR) spectroscopy offers a powerful tool for analysis and characterization of a wide range of molecular species via their distinct vibrational and rotational absorption resonance, often referred to as molecular fingerprints. However, the wavelength of light at these infrared frequencies is significantly larger than the absorption crosssection of the molecules of interest, making absorption spectroscopy of thin layers or nanoscale volumes challenging. In this project, we propose a new idea that exciting local electromagnetic field mode through graphene nanoantenna to enhance the infrared absorption spectrum of the molecule under tests, based on the graphene surface plasmon's eigen mode in infrared waveband and tunable free electron desity. First principles and finite element method are utilized to research the graphene surface plasmon's coupling and modulating properties. Then nanoatenna local electromagnetic field coupling excitation model is established. We further analyze the nanoatenna structures and external electric fields on the effects of local electromagnetic field mode's energy distribution and spectrum properties. Also, we'll develop the broadband graphene nanoantenna design method and graphene nanoctrsuture patterning technique. To verify our idea, infrared spectrum measuring experiment beyond the diffraction limits and trace meolecule detecting experiment are conducted. The infrared spectrum enhancement method with graphene nanoantenna developed in our study provide a new method to overcome the high loss and narrow bandwidth bottleneck connecting the local electric field mode on the metal surface, which will solve the extremely weak interaction between the wide-bandwidth infrared light waves and molecules at nanoscale, paving the way to next generation highly sensitive infrared spectrun sensing technology.