1. Hunan Key Laboratory of Nanophotonics and Devices, School of Physics and Electronics, Central South University, 932 South Lushan Road, Changsha, Hunan 410083, China
2. Department of Applied Physics, School of Microelectronics and Physics, Hunan University of Technology and Business, Changsha 410205, China
3. College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China