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

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.