1 Key Laboratory of Opto-electronic Information Technical Science of Ministry of Education, School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China
2 Key Laboratory of Integrated Opto-electronic Technologies and Devices in Tianjin, School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China
3 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
4 Department of Materials Engineering, University of Tokyo, Tokyo 113-8656, Japan
5 College of Optics and Photonics, CREOL and FPCE, University of Central Florida, Orlando, Florida 32816, USA