1. State Key Laboratory of Optoelectronic Materials and Technologies; School of Physics; Sun Yat-Sen University; Guangzhou 510275 China
2. Department of Applied Physics; the Hong Kong Polytechnic University; Hung Hum Kowloon Hong Kong 999077 China
3. Institute of Optoelectronic Material and Technology; South China Normal University; Guangzhou 510631 China
4. Changchun Institute of Optics; Fine Mechanics and Physics; Chinese Academic Science; Changchun 130033 China
5. State Key Laboratory of Optoelectronic Materials and Technologies; School of Materials Science and Engineering; Sun Yat-Sen University; Guangzhou 510275 China