1. State Key Laboratory of Pulp and Paper Engineering, School of Light Industry and Engineering, South China University of Technology, 510641Guangzhou, Guangdong, China
2. State Key Laboratory of Luminescent Material and Devices, and Guangdong Provincial Key Laboratory of Fibre Laser Materials and Applied Techniques, Guangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and Devices, South China University of Technology, 510641Guangzhou, GuangdongChina