1. Department of Physics, Guangdong University of Education, Guangzhou, 510303, China
2. Department of Applied Physics, South China Agricultural University, Guangzhou, 510642, China
3. Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, M5S-3G4, Canada
4. Department of Electronic Engineering, Dongguan University of Technology, Dongguan, 523808, China