1. Wuhan National Laboratory for Optoelectronics
2. Huazhong University of Science and Technology
3. Wuhan 430074
4. People's Republic of China
5. School of Information and Optoelectronic Science and Engineering
6. South China Normal University
7. Guangzhou 510006
8. Department of Physics
9. New Mexico State University
10. Las Cruces 88001
11. USA