1. Technische Universität Kaiserslautern und Landesforschungszentrum OPTIMAS, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany.
2. Graduate School of Excellence Materials Science in Mainz, Staudinger Weg 9, 55128 Mainz, Germany.
3. Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
4. Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA.
5. Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305, USA.
6. Experimentelle Physik VI, Technische Universität Dortmund, 44221 Dortmund, Germany.
7. Georg-August-Universität Göttingen, I. Physikalisches Institut, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
8. Max Born Institute for Nonlinear Optics, Max-Born-Strasse 2A, 12489 Berlin, Germany.