1. School of Semiconductor Science and Technology, South China Normal University, Foshan 528225, P.R. China
2. Guangdong Provincial Key Laboratory of Chip and Integration Technology, Guangzhou 510631, P.R. China
3. Hangzhou Institute of Optics and Fine Mechanics, Hangzhou 311421, P. R. China
4. Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China