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The optical response of growing silver thin films undergoes a transition dominated by three distinct plasmonic modes, two localized and one delocalized. Their admix as a function of added mass is analysed. The onset of the delocalized or Drude mode occurs before the sharp electrical percolation transition so optically the full insulator-metal transition is broadened. A scaling explanation supported by images shows Ag islands only have to link up over 200-300 nm to yield partial delocalization. The localized modes are (i) from silver nano-islands and (ii) a transitional anomalous mode, peaking near the dc critical percolation point, from islands surrounded by network. Growing silver within a multilayer oxide stack is compared with that on glass. The transition in thermal emittance matches that in the delocalized mode. Its broadening enables practical tuning of intermediate emittance by varying mass. © 2011 IOP Publishing Ltd.

Oxide coated metal nanoparticles buried within a thin metal layer support a surface plasmon resonance. A local dip occurs in spectral reflectance along with a switching off of the film's plasmonic response. Models are introduced in which these resonances are tunable by altering the ratio of oxide thickness to core particle radius. The optical response of two experimental examples is presented and modeled using effective medium theory. Beyond the resonance zone the doped layer switches back to the plasmonic response of a nanoporous version of the host metal whose effective plasma frequency arises only from the percolating component. © 2010 American Institute of Physics.

Anomalous strong resonances in silver and gold nanoporous thin films which conduct are found to arise from isolated metal nano-islands separated from the surrounding percolating metal network by a thin loop of insulator. This observed resonant optical response is modelled. The observed peak position is in agreement with the observed average dimensions of the silver core and insulator shell. As the insulating ring thickness shrinks, the resonance moves to longer wavelengths and strengthens. This structure is the Babinet's principle counterpart of dielectric core-metal shell nanoparticles embedded in dielectric. Like for the latter, tuning of resonant absorption is possible, but here the matrix reflects rather than transmits, and tuning to longer wavelengths is more practical. A new class of metal mirror occurring as a single thin layer is identified using the same resonances in dense metal mirrors. Narrow band deep localized dips in reflectance result. © 2010 IOP Publishing Ltd.

University of Technology, Sydney. Dept. of Applied Physics. Daylight is an abundant source of energy that, if used effectively for lighting in buildings, can improve quality of life and decrease the demand for electric lighting and air-conditioning, reducing energy consumption and costs. Various daylighting systems are available for daylighting the perimeter zones of buildings. However, it is more difficult to transport daylight to remote rooms. The few systems available for remote room daylighting are expensive or disruptive to the building design and rely heavily on direct sunlight. Luminescent Solar Concentrators (LSC’s) contain fluorescent dyes that absorb both direct and diffuse sunlight without tracking the sun, causing fluorescent emission in a specific wavelength range. LSC’s can potentially be used for daylighting, but the only previously demonstrated system is rather bulky and architecturally intrusive, and its output is yellow-green and difficult to control. A stack of three coloured LSC’s is proposed in this thesis, which produces a good white output of over 1,000 lumens under solar illumination of 100,000 lux. This output is transported to a remote room in narrow flexible polymer light guides. A theoretical model of the three-colour LSC stack was developed, which uses the absorption and emission spectra of the dyes to predict the LSC’s output spectrum and lumens. Studies with this model revealed the importance of highly accurate absorption tails data for good prediction of the stack performance. The model was used to determine the optimum size and dye concentration for each LSC. A simple experimental method was devised for characterising the optical performance of a fixed size LSC. Half of the emitted light is trapped at the end of the light guides, so a ‘light extractor’ is required to enable this light to escape. Ray tracing simulations were carried out for various light extractor designs, from which the optimal light extractor size, shape and configuration were determined for maximum optical gain. With a good light extractor design, a gain of 1.7-1.8 should be achievable, but with the current prototypes, the gain is limited to 1.2-1.3, limiting the output to around 1,100 lumens. The violet collector sheet in the LSC stack was also found to be problematic, so an alternative blue light source is proposed. Hence there is room for improvement in future prototypes.