1. Department of Materials Science and Engineering City University of Hong Kong Kowloon 999077 Hong Kong SAR
2. State Key Laboratory of Luminescence and Applications Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences Changchun 130021 China
3. State Key Laboratory of Terahertz and Millimeter Waves City University of Hong Kong Kowloon 999077 Hong Kong SAR
4. Key Laboratory of Advanced Materials Processing and Mold (Zhengzhou University) Ministry of Education Zhengzhou 450002 China
5. Institute for Materials Chemistry and Engineering Kyushu University Fukuoka 816–8580 Japan