1. School of Electronic and Optical Engineering Nanjing University of Posts and Telecommunications Nanjing 210023 China
2. Jiangsu Province Engineering Research Center for Fabrication and Application of Special Optical Fiber Materials and Devices Nanjing 210036 China
3. School of Chemistry and Physics and QUT Centre for Materials Science Queensland University of Technology (QUT) Brisbane QLD 4000 Australia
4. CSIRO‐QUT Joint Sustainable Processes and Devices Laboratory P.O. Box 218 Lindfield NSW 2070 Australia