1School of Physics and Optoelectronics, South China University of Technology, Guangzhou, Guangdong 510640, China
2State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, Guangdong 510640, China
3Guangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and Devices, Guangzhou, Guangdong 510640, China
4Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques, South China University of Technology, Guangzhou, Guangdong 510640, China