1 Femtosecond Laser Laboratory, Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University Changchun 130012 P. R. China yinghui_wang@jlu.edu.cn chixc@jlu.edu.cn.
2 State Key Laboratory of Superhard Materials, College of Physics, Jilin University Changchun 130012 P. R. China.