1. State Key Laboratory of Luminescent Materials and Devices Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques Guangdong Engineering Technology Research and Development Centre of Special Optical Fiber Materials and Devices School of Materials Science and Engineering South China University of Technology Guangzhou 510641 China
2. School of Physics and Optoelectronics South China University of Technology Guangzhou Guangdong 510641 China
3. Lab of New Energy Materials and Devices School of Physics and Electronic Information Henan Polytechnic University Jiaozuo 454000 China
4. Diode Lasers and LED Systems Group Department of Electrical and Photonics Engineering Technical University of Denmark Roskilde 4000 Denmark