1. School of Physics and Electronics , Hunan University , Changsha 410082 , China
2. Ministry of Industry and Information Technology Key Lab of Micro-Nano Optoelectronic Information System , Shenzhen Graduate School, Harbin Institute of Technology , Shenzhen , 518055 P. R. China
3. College of Physics and Optoelectronic Engineering , Shenzhen University , Shenzhen 518060 , China
4. School of Electronic Information and Electrical Engineering , Hunan University , Changsha 410003 , China