1. State Key Laboratory of Information Photonics and Optical Communications & School of Science
2. Beijing University of Posts and Telecommunications
3. Beijing 100876
4. China
5. Department of Physics
6. The State University of New York at Potsdam
7. Potsdam
8. USA
9. State Key Laboratory of Optoelectronic Materials and Technologies
10. School of Physics and Engineering
11. Sun Yat-Sen University
12. Guangzhou 510085
13. P. R. China