Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 21: Photonic Crystals I

HL 21.3: Vortrag

Montag, 26. März 2012, 17:30–17:45, EW 203

Fast structural analysis of photonic crystals — •Rebecca Wagner, Lars Heerklotz, and Frank Cichos — Molecular Nanophotonics, University of Leipzig, Germany

Photonic crystals (PCs) are materials where the dielectric constant varies periodically on the length scale of visible wavelengths. This results in the formation of a photonic band structure, which gives one the possibility to modify the propagation of light.

Inexpensive and simple methods for the production of 3D PCs are based on self assembly of colloidal beads, leading to close packed structures. However, these methods usually create polycrystalline structures, with differently stacked domains and other defects.

These stacking faults are hidden in the 3D structure and difficult to characterize experimentally. However, the PC's optical properties depend on its structure. Therefore a method to locally characterize the 3D order of the PC is desirable.

Here we present a method for fast microscopic characterization of PCs based on back focal plane (BFP) imaging. After local excitation by a focused laser the luminescence from inside the PC is collected by a high NA objective. The BFP of the objective contains information about the angel dependence of the emission. When imaging it onto a CCD for a selected wavelength, stop bands are visible for certain directions, showing the local symmetry of the PC. Thus, a fast determination of the orientation of domains is possible. The change between different kinds of stacking (twin structure) can be observed.