1. Laboratory of Optoelectronics Materials and Devices
2. School of Science
3. Beijing University of Posts and Telecommunications
4. Beijing 100876
5. China
6. Department of Physics
7. The State University of New York at Potsdam
8. New York 13676-2294
9. USA
10. Center for Optoelectronics Materials and Devices
11. Zhejiang Sci-Tech University
12. HangZhou