1. Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China
2. Southwestern Institute of Physics, P. O. Box 432, Chengdu 610041, China
3. General Atomics, P. O. Box 85608, San Diego, California 92186-5608, USA
4. University of California, Irvine, California 92697, USA
5. Sichuan University of Arts and Science, School of Intelligent Manufacturing, Dazhou 635000, China