Fabrication, Characterisation and Nanophotonic Applications of Plasmonic Waveguides made of Metallic Nanorod Arrays

高度集成的光学器件和传感器，能够在纳米尺度上引导和操纵光，需要小于工作波长的结构元件，以纳米尺度控制分辨率设计。这种光学元件的基本组成部分之一，依赖于纳米级金和银粒子中的光子和电子之间的共振耦合。这些共振被称为局部表面等离子体激元（LSPs），可以通过光照射纳米粒子来激发，其频率由纳米粒子的大小和形状以及材料特性决定。在由纳米颗粒组成的线性链中，由于纳米颗粒之间的近场电磁相互作用，这些局部等离子体模式沿着链变得离域。这种相互作用允许电磁能量在链中的纳米颗粒之间有效地交换，从而使光从链的一端传播到另一端。这种金属纳米颗粒链被称为表面等离子体粒子波导（SPPW），它可以根据纳米颗粒的大小来引导光。SPPWs的使用为当前基于光子晶体和条纹表面极化子波导的波导特性的微尺度光子器件开辟了新的和独特的机会，因为在近场的相互作用过程中，引导表面等离子体模式是建立在其上的。这些近场过程仅与短距离（通常为几纳米）相关，因此，当寻求高密度器件集成时，对单颗粒尺度上波导内发生的突然方向变化并不十分敏感。迄今为止，波导内较差的近场耦合效率导致波导透射率低，并且昂贵的处理技术限制了该技术的发展和适用性。目前的研究计划将解决这两个限制因素，试图开发一种波导设计，既能提高金属纳米粒子波导的引导性能，又能实现适合工业的制造工艺。具体来说，我们提出了一种易于生产的基于模板的SPPW几何结构，由垂直于衬底的相互作用纳米棒制成。得到的SPPWs将被结构和光学表征，然后用于创建一个全光有源器件。

Highly integrated optical devices and sensors, which enable guidance and manipulation of light at the nanoscale, require structural elements smaller than the operating wavelength designed with a nanometer-scale-controlled resolution. One of the basic building blocks for such optical components relies on the resonant coupling between photons and the electrons residing in nanoscale gold and silver particles. These resonances are called Localized Surface Plasmons (LSPs) and can be excited by illuminating the nanoparticle with light at a frequency determined by the size and shape of the nanoparticle as well as by material properties. In linear chains made of nanoparticles, these localised plasmon modes become delocalized along the chain due to the near-field electromagnetic interaction between the nanoparticles. This interaction allows for electromagnetic energy to be efficiently exchanged between the nanoparticles in the chain and thus for light to propagate from one end of the chain to the other. This kind of metallic nanoparticle chain is called a Surface Plasmon Particle Waveguide (SPPW) and enables light guiding determined by the size of the nanoparticles.The use of SPPWs opens up new and unique opportunities over current microscale photonic devices based on waveguiding properties of photonic crystals and stripe surface polariton waveguides because of the near-field nature of the interaction processes on which the guided surface plasmon modes are built up from. These near-field processes are relevant at short distances only (typically a few nanometers) and are therefore not dramatically sensitive to abrupt directional changes that take place within the guide at the single particle scale when high-density device integration is sought. To date poor near-field coupling efficiencies within the waveguide, leading to low waveguide transmittance, and expensive processing techniques have limited the development and applicability of this technology.The present research proposal will address these two prohibiting factors in an attempt to develop a waveguide design that improves both the guiding properties of metal-nanoparticles waveguides and allows for an industry-suitable manufacturing process to be implemented. Specifically, we propose an easy to produce, templated-based SPPW geometry made from interacting nanorods grown perpendicular to a substrate. The obtained SPPWs will be characterized both structurally and optically to be then used to create one all-optical active device.