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Proceedings Paper

Large-area photonic crystals
Author(s): Tilmann Ruhl; Peter Spahn; Gotz P. Hellmann; Holger Winkler
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Paper Abstract

Materials with a periodically modulated refractive index, with periods on the scale of light wavelengths, are currently attracting much attention because of their unique optical properties which are caused by Bragg scattering of the visible light. In nature, 3d structures of this kind are found in the form of opals in which monodisperse silica spheres with submicron diameters form a face-centered-cubic (fcc) lattice. Artificial opals, with the same colloidal-crystalline fcc structure, have meanwhile been prepared by crystallizing spherical colloidal particles via sedimentation or drying of dispersions. In this report, colloidal crystalline films are introduced that were produced by a novel technique based on shear flow in the melts of specially designed submicroscopic silica-polymer core-shell hybrid spheres: when the melt of these spheres flows between the plates of a press, the spheres crystallize along the plates, layer by layer, and the silica cores assume the hexagonal order corresponding to the (111) plane of the fcc lattice. This process is fast and yields large-area films, thin or thick. To enhance the refractive index contrast in these films, the colloidal crystalline structure was inverted by etching out the silica cores with hydrofluoric acid. This type of an inverse opal, in which the fcc lattice is formed by mesopores, is referred to as a polymer-air photonic crystal.

Paper Details

Date Published: 15 September 2004
PDF: 9 pages
Proc. SPIE 5450, Photonic Crystal Materials and Nanostructures, (15 September 2004);
Show Author Affiliations
Tilmann Ruhl, German Institute for Polymers (Germany)
Peter Spahn, German Institute for Polymers (Germany)
Gotz P. Hellmann, German Institute for Polymers (Germany)
Holger Winkler, MERCK KGaA (Germany)

Published in SPIE Proceedings Vol. 5450:
Photonic Crystal Materials and Nanostructures
Richard M. De La Rue; Pierre Viktorovitch; Clivia M. Sotomayor Torres; Michele Midrio, Editor(s)

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