1. State Key Laboratory of Luminescent Materials and DevicesSchool of Materials Science and EngineeringSouth China University of Technology Guangzhou 510640 China
2. Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied TechniquesGuangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and Devices Guangzhou 510640 China
3. State Key Laboratory of Crystal Materials and Institute of Crystal MaterialsShandong University Jinan 250100 China
4. Department of Applied PhysicsThe Hong Kong Polytechnic University Kowloon Hong Kong P. R. China
5. College of Optical Science and EngineeringZhejiang University Hangzhou 310027 China