The high speed transfer of information in materials with dimensions below the sub-diffraction limit is essential for future technological developments. Metallic nanoparticle (NP) waveguides serve a unique role in efficient energy transfer in this size regime. Light may be confined to metallic structures and propagate along the surface of the waveguide via propagating plasmon waves known as surface plasmon polaritons (SPPs). Plasmon propagation of energy in metallic structures is not perfect however and damping losses from the waveguide material lead to a characteristic exponential decay in the plasmon near field intensity. This decay length is known as the propagation length and serves as an excellent metric to compare various waveguide materials and structures to one another at particular excitation wavelengths. This thesis presents recent work in the development of a novel measurement technique termed bleach imaged plasmon propagation (BlIPP). BlIPP uses the photobleaching property of fluorophores and far field fluorescence microscopy to probe the near-field intensity of propagating plasmons and determine the propagation length. The experimental setup, image analysis, conditions, and application of BlIPP are developed within this thesis and an in depth review of the 1-photon photobleaching mechanism is also investigated. The BlIPP method is used to investigate long plasmon propagation lengths along straight chains of tightly packed Au NPs through the coupling of light to sub-radiant propagating modes, where radiative energy losses are suppressed. The findings of this work reveal, experimentally, the importance of small gap distances for the propagation of energy. Complex chain architectures are then explored using BlIPP measurements of tightly packed straight and bent chains of spherical silver NPs. We observe the highly efficient propagation of energy around sharp corners with no additional bending losses. The findings of this thesis demonstrate the advantages and capabilities of using BlIPP propagation length measurement. Further, BlIPP is used to reveal the advantage of coupling light to sub-radiant modes of NP chains, which demonstrate the ability to guide light efficiently across long distances and around complex structures, bringing us a step closer to the goal of applying plasmonic devices and circuitry in ultra compact opto-electronic devices.

We have reported the optical properties of isolated gold nanowires and of nanowire arrays. Despite the advantages gold has to offer as it is less sensitive to oxidation and as an biocompatible metal, it has been scarcely studied than silver or semiconductors nanowires. We have made surface enhanced Raman spectroscopic (SERS) studies on the isolated nanowires and nanowire arrays. Single molecule regime is attained and has been proven with the aid of two dye molecules that are co-deposited. The propagation of surface plasmons in these nanowires and their evolution with the excitation wavelength have been studied. We report a propagation distance of 3.8 µm which is longer than the values previously reported in literature. Nanowire arrays have been investigated with two dyes again to disentangle the various factors contributing to SERS. Polarization studies and the evolution of enhancement in the nanowires with the wavelength have been reported and explained with the aid of simulations obtained by the discrete dipole approximation (DDA). The scanning near field optical microscopy (SNOM) has been done to investigate the local field enhancements on the nanowire arrays. Two different polarizations and two excitation wavelengths have been used. The original idea of the technique includes the use of two illumination modes which serves two purposes. One, to map the regions of enhanced field and the other to study the propagation effects seen on the nanowire.

Les études portent sur les propriétés optiques de nanofils d’or individuels et de réseaux de nanofils d’or. Malgré ses avantages, comme une sensibilité moindre à l’oxydation et sa biocompatibilité, les nanofils en or ont été peu étudiés par comparaison avec les nanofils en argent ou semiconducteurs. Les études sur ces substrats ont été réalisées par spectroscopie Raman exaltée de surface (SERS). Le régime de la molécule unique est atteint, ce que j’ai démontré en utilisant deux molécules différentes de colorant, co-déposées. J’ai étudié la propagation des plasmons de surface dans les nanofils ainsi que son évolution en fonction de la longueur d’onde. Une distance de propagation de 3,8 µm a été observée, plus grande que les valeurs précédemment rapportées. Les réseaux de nanofils ont également été étudiés en combinant la réponse de deux molécules pour démêler les différents processus contribuant au signal de la diffusion Raman. Les résultats obtenus par des études en polarisation et en fonction de la longueur d’onde sur l’évolution de l’intensité du signal SERS ont été confrontés aux résultats de simulations réalisées par la méthode de l’approximation des dipôles discrets (DDA). La microscopie de champ proche optique à balayage (SNOM) a été mise en œuvre pour étudier les effets d’exaltation locale sur les réseaux de nanofils. Ces études ont été réalisées avec deux polarisations croisées et à deux longueurs d’onde différentes. L’originalité des études SNOM repose sur l’utilisation de deux modes différents d’éclairement. L’un est utilisé pour cartographier l’exaltation des champs électromagnétiques, l’autre pour étudier les effets de propagation des plasmons dans les nanofils. / We have reported the optical properties of isolated gold nanowires and of nanowire arrays. Despite the advantages gold has to offer as it is less sensitive to oxidation and as an biocompatible metal, it has been scarcely studied than silver or semiconductors nanowires. We have made surface enhanced Raman spectroscopic (SERS) studies on the isolated nanowires and nanowire arrays. Single molecule regime is attained and has been proven with the aid of two dye molecules that are co-deposited. The propagation of surface plasmons in these nanowires and their evolution with the excitation wavelength have been studied. We report a propagation distance of 3.8 µm which is longer than the values previously reported in literature. Nanowire arrays have been investigated with two dyes again to disentangle the various factors contributing to SERS. Polarization studies and the evolution of enhancement in the nanowires with the wavelength have been reported and explained with the aid of simulations obtained by the discrete dipole approximation (DDA). The scanning near field optical microscopy (SNOM) has been done to investigate the local field enhancements on the nanowire arrays. Two different polarizations and two excitation wavelengths have been used. The original idea of the technique includes the use of two illumination modes which serves two purposes. One, to map the regions of enhanced field and the other to study the propagation effects seen on the nanowire.