1. Department of Physics and State Key Laboratory of Silicon Materials
2. Zhejiang University
3. Hangzhou
4. P. R. China
5. State Key Laboratory for Infrared Physics
6. Shanghai Institute of Technical Physics
7. Chinese Academy of Sciences
8. Shanghai
9. Faculty of physics & Material sciences center
10. Philipps University Marburg
11. D-35032 Marburg
12. Germany