1. Experimentelle Physik II, Universität Dortmund, D-44221 Dortmund, Germany.
2. Naval Research Laboratory, Washington, DC 20375, USA.
3. School of Computational Sciences, George Mason University, Fairfax, VA 22030, USA.
4. A. F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia.
5. Institute of Physics, St. Petersburg State University, 1908504 St. Petersburg, Russia.