1. Division of Physics and Applied Physics; School of Physical and Mathematical Sciences, Nanyang Technological University; 637371 Singapore
2. Division of Materials Technology; School of Materials Science and Engineering, Nanyang Technological University; 639798 Singapore
3. Key Laboratory of Luminescence and Applications; CIOMP, Chinese Academy of Sciences; No.3888 Dongnanhu Road Changchun 130033 People's Republic of China
4. Division of Chemistry and Biological Chemistry; School of Physical and Mathematical Sciences, Nanyang Technological University; Singapore 637371 Singapore
5. Centre for Disruptive Photonic Technologies; School of Physical and Mathematical Sciences, Nanyang Technological University; 637371 Singapore