1. The MOE key laboratory of weak-Light Nonlinear Photonics,
School of Physics, Nankai University, Tianjin 300071, China
2. Research and Development Center for Semiconductor
Lighting, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
3. School
of Materials Sciences and Engineering, University of Science and Technology Beijing, Beijing 100083, China
4. College of Electronic Information and Optical
Engineering and Tianjin Key Laboratory of Photo-electronic Thin Film
Devices and Technology, Nankai University, Tianjin 300071, China