1. State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics & Engineering, Sun Yat-sen University, Guangzhou 510275, People’s Republic of China
2. Department
of Physics, Shantou University, Shantou
515063, People’s
Republic of China
3. Institute
of Optoelectronics, Shenzhen University, Shenzhen 518060, People’s
Republic of China