1 Shenzhen Key Laboratory of Laser Engineering, Key Laboratory of Advanced Optical Precision Manufacturing Technology of Guangdong Higher Education Institutes, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China
2 University Research Facility in Materials Characterization and Device Fabrication, The Hong Kong Polytechnic University, Hong Kong 999077, China
3 Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong 999077, China
4 Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
5 e-mail: zhangwf@szu.edu.cn
6 e-mail: scruan@szu.edu.cn