Regensburg 2010 – wissenschaftliches Programm
HL 60.12: Poster
Donnerstag, 25. März 2010, 18:00–20:00, Poster D1
Multiple Bragg diffraction in photonic crystals — •Georg Kropat, Rebecca Wagner, and Frank Cichos — Molecular Nanophotonics Group, University Leipzig, Linnéstr. 5, 04103 Leipzig
We investigated colloidal fcc crystals made of polystyrene spheres in air by angle resolved reflectivity measurements. Bragg reflections occur due to constructive interference of the light which is diffracted by the crystalline structure of the photonic crystal. For angles of incidence of around 35°, multiple reflection peaks are observed at points of intersecting planes. The dependence of this multiple reflection on the turning angle around the surface normal of the incident plane was checked. Simulated photonic band structures reveal that the multiple peaks are caused by simultaneous Bragg diffraction at (111) and (200) planes. We demonstrate that this leads to significant deviations from simple Bragg diffraction. As the emission of dye molecules inside the photonic crystal is also influenced by Bragg reflections, we expect this band repulsion also to be of importance for the modification of the angular emission of dye doped beads in photonic crystals.