Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 24: Photonic crystals II

HL 24.9: Talk

Tuesday, February 26, 2008, 11:45–12:00, EW 202

Complex Liquid Crystal Director Fields Appearing in Photonic Crystals — Heinrich Matthias and •Heinz-Siegfried Kitzerow — Faculty of Science, University of Paderborn, Warburger Str. 100, 33098 Paderborn, Germany

It is well known that liquid crystals can be utilized to control the optical properties of photonic crystals. The frequencies of stop band edges and the resonance frequencies of microcavities embedded in photonic crystals can be tuned by changing the temperature or applying external fields [1]. However, the complex geometry of the cavities and the anchoring of the liquid crystal orientation at interfaces cause complicated director fields [2,3] rather than an ideal, uniform alignment of the liquid crystal molecules. In addition, chirality can induce a twisted director field thereby adding an additional spatial periodicity (given by the helix pitch) to the structure. In this contribution, we describe different director fields that have been observed in the pores of photonic crystals by means of fluorescence confocal polarization microscopy. The stability conditions of topologically different director configurations are discussed.

[1] H.-S. Kitzerow, A. Lorenz, and H. Matthias: phys. stat. sol. (a) 204, 3754 (2007). [2] H. Matthias, T. Röder, S. Matthias, R. B. Wehrspohn, S. Picken and H.-S. Kitzerow: Appl. Phys. Lett. 87, 241105 (2005). [3] H. Matthias, S. L. Schweizer, R. B. Wehrspohn, and H.-S. Kitzerow: J. Opt. A: Pure Appl. Opt. 9, 389 (2007).