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 Optoelectronic Engineering and CQUPT‐BUL Innovation Institute Chongqing University of Posts and Telecommunications Chongqing 400065 China
3. School of Physics and Optoelectronics South China University of Technology Guangzhou 510641 China