1. Key Laboratory for Micro-/Nano-Optoelectronic Devices of Ministry of Education
2. School of Physics and Electronics
3. Hunan University
4. Changsha 410082
5. China
6. School of Physics and Technology
7. Wuhan University
8. Wuhan 430072
9. National Laboratory for Infrared Physics
10. Shanghai Institute of Technical Physics
11. Chinese Academy of Sciences
12. Shanghai 200083
13. Department of Materials Science and Engineering
14. City University of Hong Kong Tat Chee Avenue
15. Kowloon