1. State Key Laboratory of Integrated Optoelectronics and College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
2. Department of Materials Science and Engineering, and Centre for Functional Photonics (CFP), City University of Hong Kong, Kowloon, Hong Kong S.A.R.
3. Beijing Institute of Technology, School of Materials Science and Engineering, Beijing 100081, China