1. School of Physics and Optoelectronics South China University of Technology Guangzhou 510640 China
2. State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials Guangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and Devices Guangdong Provincial Key Laboratory of Fiber laser Materials and Applied Techniques South China University of Technology Guangzhou 510640 China
3. Guangdong Engineering Technology Research and Development Center of High-performance Fiber Laser Techniques and Equipments Hengqin Firay Sci-Tech Company Ltd. Zhuhai 519031 China