1. State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
2. Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany
3. Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
4. Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia