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 P. R. China
2. Key Laboratory of Optoelectronic Technology and Systems (Ministry of Education) College of Optoelectronic Engineering Chongqing University Chongqing 400044 P. R. China
3. State Key Laboratory of Optoelectronic Materials and Technologies School of Electronics and Information Technology Sun Yat‐sen University Guangzhou 51006 P. R. China
4. School of Optoelectronic Engineering Guangdong Polytechnic Normal University Guangzhou 510665 P. R. China