Solids with Novel Symmetry Properties
This research area was active in our research group until 2007, but it has still an influence on the on-going research.
A prerequisite for an efficient „molding the flow of light“ by photonic crystals is the molding of materials in desired nanostructures. Very often, conventional materials and processing techniques cannot fulfill the theoretical requirements for the materials and structures. Sol-gel methods enable material processing in opal pores and the controlled introduction of pores into materials. The porosity can be used for lowering the refractive index, for soft processing of the materials and for stress relaxation. Examples for this approach are ultra-low refractive index films used as supports for 2D photonic crystals, inverse opals with a skeleton-like unit cell filling and ferroelectric films with high transparency. Especially we are able to fabricate mesoporous silica films with a refractive index of 1.14 for use in 2D photonic crystal waveguide systems. Important achievements are described in the following papers:
Magdalena Stempniewicz, Ahmed S. G. Khalil, Michael Rohwerder, and Frank Marlow:
Diffusion in Coiled Pores - Learning from Microrelease and Microsurgery.
J. Am. Chem. Soc.129 (2007) 10561
F. Marlow, A. S. G. Khalil, M. Stempniewicz:
Circular mesostructures: Solids with novel symmetry properties. Invited Feature.
J. Mater. Chem. 17 (2007) 2168-2182
A. S. G. Khalil, D. Konjhodzic, F. Marlow:
Hierarchy Selection, Position Control, and Orientation by Patterned Surfaces.
Adv. Mater. Vol 18, (2006) 1055.