[Ou, Congjie; Fang, Wei; Chen, Ying; Yang, Yaping] Huaqiao Univ, Inst Syst Sci & Dept Phys, Coll Informat Sci & Engn, Xiamen, Peoples R China.
[Fang, Wei; Yang, Yaping] Tongji Univ, Sch Phys Sci & Engn, MOE Key Lab Adv Micro Struct Mat, Shanghai, Peoples R China.
[Zeng, Yali] Xiamen Univ, Dept Phys & Inst Elect Acoust, Xiamen, Peoples R China.
[Li, Gao-xiang] Huazhong Normal Univ, Dept Phys, Wuhan, Peoples R China.