Light propagation and localisation on periodic dielectric and metallic nanostructures

This thesis presents firstly a study in the light propagation in dielectric photonic crystal waveguides and secondly light propagation and localisation on arrays of metallic inverted pyramidal pits. As well as introducing the concept and properties of photonic crystals, the first part of the thesis concentrates on 2D photonic crystals and in particular the superprism effect. Experimental results demonstrate the angular dispersion experienced by wavelength close to the bandgap. Reflectivity measurements allowed the acquisition of dispersion diagram as a function of azimuthal angles, therefore permitting the experimental observation of dispersion surfaces which are then compared with results from plane wave simulation. The same reflectivity technique as been employed to measure arrays of gold coated inverted pyramidal pits with square apertures. These nano-patterned gold structures show clear evidence of propagating and localised plasmon as standing wave localised in the pits. Using a sample graded in depth, we showed that the localised plasmon resonance follows a simple interference model. This model is then confirmed using reflectivity data from a sample graded in depth and pitch, which also shows that the dip in reflectivity observed at normal incidence is independent of pitch. Repeating the measurements for different coating and comparing them with simulation results leads to an intuitive understanding of the coupling mechanism of the light to the pit. Surface enhanced Raman scattering is then used to probe the field localised in the pit and the surface enhanced Raman scattered signal from the pit array is found to be in agreement with the electric field enhancement predicted by a plasmon cavity model. Further correlation with simulation results paves the way to optimised plasmon cavity for applications such as surface enhanced Raman scattering or to enhance the interaction between light and matter.