1. Institute for Advanced MaterialsSouth China Academy of Advanced OptoelectronicsSouth China Normal University Guangzhou 510006 China
2. Guangdong Provincial Key Laboratory of Optical Information Materials and TechnologySouth China Academy of Advanced OptoelectronicsSouth China Normal University Guangzhou 510006 China
3. Department of Materials Science and EngineeringNational University of Singapore Singapore 117575 Singapore
4. School of Physical EngineeringZhengzhou University Zhengzhou 450001 China
5. State Key Laboratory of Low Dimensional Quantum Physics and Department of PhysicsTsinghua University Beijing 100084 China
6. National Center for International Research on Green OptoelectronicsSouth China Normal University Guangzhou 510006 China
7. Laboratory of Solid State Microstructures and Innovation Center of Advanced MicrostructuresNanjing University Nanjing 210093 China