1. Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China
2. School of Electrical and Electronic Engineering, Nanyang Technological University, 639798 Singapore
3. School of Optoelectronic Engineering, Guangdong Polytechnic Normal University, Guangzhou 510665, China
4. State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 51006, China