Zhiyi Wei, Institute of Physics, Chinese Academy of Sciences, Beijing, PR China; Heping Zeng, East China Normal University, Shanghai, PR China; Ya Cheng, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, PR China; Shaoqun Zeng, Huazhong University of Science and Technology, Wuhan, PR China; Xiaojun Liu, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, PR China; Qihuang Gong, Peking University, Beijing, PR China.