1. Department of Optoelectronic Science; Harbin Institute of Technology at Weihai; Weihai 264209 China
2. School of Marine Science and Technology; Harbin Institute of Technology at Weihai; Weihai 264209 China
3. Department of Physics; Southeast University; Nanjing 211189 China
4. School of Materials Science and Engineering; Harbin Institute of Technology at Weihai; Weihai 264209 China