Plasmon resonances have attracted a lot of recent research interest for their potential applications, including bio-sensing, sub-wavelength optics, negative refractive index metamaterials and their ability to produce massively enhanced electromagnetic fields. Localised surface plasmon resonances (LSPR) in metallic nanostructures can offer large electromagnetic field enhancements, and nanometre-scale localisation of electric fields. Their resonance wavelengths and properties can be tuned by variation of the nanostructure geometry and are sensitive to environmental refractive index. Coupling of localised plasmon resonances can: Create new hybrid modes that cannot be supported by individual nanostructures, overcome some of the limitations of individual LSPR, and open up possibilities for new applications and active control of plasmon resonances. This thesis contains results from samples exploiting near-field, far-field and resistive coupling of localised plasmon resonances to create novel resonance modes that may make them suitable for important applications. Firstly results are presented from samples exhibiting strong collective plasmon resonances at normal incidence, which could be used to improve the spatial resolution of, miniaturise and add new functionality to highly sensitive surface plasmon resonance based approaches to bio-sensing. A very high bio-sensing figure of merit is calculated for the nanostructure arrays fabricated.Results are also presented from samples designed to produce the highest quality factor resonances possible when excited with light at grazing incidence. The highest resonance quality factors measured were conservatively estimated to be >210, which to our knowledge are the highest values of quality factor measured in diffraction coupled arrays at the resonance wavelengths around 1.5 micro metre. Evidence for the existence of a presently largely unrecognised resistive coupling mechanism is also presented from an array of gold nanostripes covered with a graphene layer. If further work is successful, this could allow extremely rapid modulation of theoptical properties of a plasmonic array by application of gate voltage to the graphenelayer.Finally an improvement to the fabrication procedure for established near-field coupled composite plasmonic nanostructures that create a cascaded electromagnetic field enhancement effect is presented.
|Date of Award||1 Aug 2015|
- The University of Manchester
|Supervisor||Alexander Grigorenko (Supervisor) & Andre Geim (Supervisor)|