1. College of Materials Science and Opto-Electronic Technology
2. University of Chinese Academy of Sciences
3. Beijing 100049
4. China
5. College of Electronic Information and Optical Engineering
6. Nankai University
7. Tianjin 300071
8. School of Physics
9. Institute of Mineral Engineering
10. Division of Materials Science and Engineering
11. Faculty of Georesources and Materials Engineering
12. RWTH Aachen University
13. Aachen 52064