1. Institute of Theoretical Solid State Physics, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany
2. Department of Molecular Biophysics and Physics of Polymers, St. Petersburg State University, Ulyanovskaya ul. 1, 198504 St. Petersburg, Russia
3. Leibniz Institute of Photonic Technology, Albert-Einstein-Straße 9, 07745 Jena, Germany
4. Institute of Nanotechnology, Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe, Germany