分叉金属纳米线中表面等离激元螺旋波导机制的研究

Because of the ability of propagation beyond the diffraction limit, surface plasmon (SP) waveguide on metallic nanostructures has been seen as a key breakthough to fabricate the nanophotonic device. Nanophotonic basic logic devices and cascaded logic gates have already been sucessfully realized on branched metallic nanowires. Since the coherent superposition of different mode of SP, the electromagnetic energy of SP waveguide on individual metallic nanowire has been found propagating helically (helical SP waveguide). However, very little is known about the existence and mechanism of this helical SP waveguide on branched metallic nanowires, especially the influence of structure of branched nanowires (such as diameter, angle and position of branch). So, in this project, we plan to study both experimentally and theoretically the effects of incident light and structure on helical SP waveguide on branched Gold and Silver nanowires. To understand the phenomenon and mechanism of helical SP waveguide on branched metallic nanowires, the properties of the different mode of SP will also been studied. Since this project could provide design principle and necessary technique for the research of nanophotonic device and highly integrated photonic circuit, it is highly valuable for academic study and application.

金属纳米结构中表面等离激元波导可突破衍射极限，使其成为制备纳米光子元件的重要突破口。在分叉金属纳米线体系中，已成功制备了简单纳米光子逻辑器件并证明了其逻辑运算的可扩展性。由于表面等离激元不同振荡模式的相干叠加，处于均匀介质环境的单根金属纳米线中表面等离激元波导呈现能量螺旋传播的特征（螺旋波导）。但在分叉金属纳米线中，波导是否也存在螺旋特征以及该特征的变化规律，特别是关于分叉纳米线结构(直径、分叉的角度和位置等)影响规律的研究鲜见报道。因此，本项目拟以分叉金银纳米线为研究对象，从实验和理论上系统研究入射光和分叉纳米线结构对表面等离激元螺旋波导的影响，并通过分析在该体系中表面等离激元不同振荡模式的激发、传导以及耦合特性来深入理解螺旋特征的变化规律及其中的波导机制，为研发纳米光子元件以及更进一步的高集成光子芯片提供设计原则和技术积累，具有重要的研究和应用价值。

基于金属纳米结构中表面等离激元而实现的极大增强电磁场和突破传统衍射极限光波导，被广泛应用于诸如超灵敏检测、太阳能利用、表面催化和大规模光子芯片等光学领域。本项目主要从表面增强拉曼、等离激元波导、等离激元表面催化和Fano共振增强的等离激元圆二色性等四个领域，系统探究了表面等离激元的新奇现象及其影响规律，并通过理论仿真从局域表面等离激元的激发和耦合进行解释：（1）在等离激元波导方面，搭建了相应的光学检测装置，实现了基于金属纳米线中等离激元波导的远程表面增强拉曼散射技术，并撰写了相关综述。（2）在表面增强拉曼散射方面，自主搭建和完善了微区拉曼光谱仪，在金属纳米颗粒二聚体和薄膜体系中发现了电磁场重分布现象并以实现巨大的薄膜拉曼信号增强。系列工作证实该现象还可以拓展到介质薄膜和金属纳米线二聚体系统，对薄膜等二维材料的拉曼超灵敏检测有非常重要的意义。（3）在等离激元表面催化方面，系统研究了在金属纳米片和金属纳米颗粒薄膜体系中的选择性催化现象，研究结果表面等离激元的激发和耦合状态对该选择性催化有巨大的影响。（4）Fano共振增强的等离激元圆二色性方面，在金属纳米米体系中系统研究了等离激元Fano共振现象及其受结构和材料因素调制的规律，并从理论预言矩纳米异质二聚体在斜入射情况下会出现基于Fano共振增强的圆二色谱。