1. Key Laboratory for Photonic and Electronic Bandgap Materials, Ministry of Education and College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin 150025, China
2. School of Physics and Technology, University of Jinan, Jinan 250022, China
3. Department of Physics, University of Houston, Houston 77004, USA
4. School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China