1. Ludwig-Maximilians-University of Munich, Faculty of Physics, Am Coulombwall 1, 85748 Garching, Germany.
2. Physics and Astronomy Department, College of Sciences, King Saud University, Riyadh 11451, Saudi Arabia.
3. Max Planck Institute of Quantum Optics, Hans-Kopfermann-Str. 1, 85748 Garching, Germany.