Description succincte
(Anglais)
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Opals can be created by the organisation of micron or sub-micron beads into highly ordered arrays using meniscus forces. These opals - and the inverse opals created by filling the opal's interstices and removing the beads - have unique optical properties, with potential applications in, for example telecommunications and sensing. These optical properties depend on both the refractive index contrast of the structure and the size of the beads. While a great deal of attention has been focussed on the stop bands of opals, fewer investigations have been carried out on the higher energy flat band region of the spectrum. This project, will concentrate on the flat band structure, the influence of coupled Mie resonances, and the extent to which the spectrum can be tuned by modifiying the degree of coupling between beads, the shape of the beads and the packing of the opal.
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Partenaires et organisations internationales
(Anglais)
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AT, BE, BG, CH, CY, CZ, DE, DK, ES, FI, FR, GR, HU, IE, IL, IT, LT, NL, PL, RO, SE, SK, UK
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Résumé des résultats (Abstract)
(Anglais)
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Opals can be created by the organisation of micro or sub-micron beads into highly ordered arrays using meniscus forces. The optical properties depend on both the refractive index contrast of the structure and the size of the beads. While a great deal of attention has been focused on the stop bands of opals, fewer investigations have been carried out on the higher energy flat band region of the spectrum. The main results achieved - (1) indentification of a novel stuctural colour arising from the symmetry properties of bead clusters. This gives dramatic colour effects for thin layers of opals. The effect predominates for low refractive index difference materials, for sphers larger than the wavelength of light. A patent has been published on this technology. (2) A range of deposition methods have been reporduced, new methods have been developed and all have been characterized. In particular, the routes to up-scalling the deposition process have been investigated. Currently full 3-inch wafers of close-packed beads with an amorphous domain orientation with hexagonal or cubic packing can be made routinely. (3) Novel transmission filters based on dense but random arrays of spheres have been developed. The deposition technique (adsporption) was applied to bead depoistion for the first time. The resulting filters have been fully chracterized experimentally and their optical properties can be predicted using a mix of singe scattering and multiple scattering techniques. Two patents based on the work in this project are at an advanced stage.
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