1. State Key Laboratory of Luminescent Materials and Devicesand Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques, and Guangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and DevicesSchool of Materials Science and EngineeringSouth China University of Technology Guangzhou 510640 China
2. Department of PhysicsMaterials Science Program, and National High Magnetic Field LaboratoryFlorida State University Tallahassee FL 32306 USA
3. State Key Laboratory of Modern Optical InstrumentationCollege of Optical Science and EngineeringZhejiang University Hangzhou 310027 China
4. Centre for Optical and Electromagnetic ResearchSouth China Academy of Advanced OptoelectronicsSouth China Normal University Guangzhou 510006 China