1 State Key Laboratory of Precision Spectroscopy, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China.
2 State Key Laboratory of Precision Spectroscopy, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China; Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China. Electronic address: sazhang@phy.ecnu.edu.cn.