[1] Univ Texas Arlington, Dept Phys, POB 19059, Arlington, TX 76019 USA
[2] Guangdong Univ Technol, Sch Phys & Optoelect Engn, Guangzhou, Guangdong, Peoples R China
[3] South China Univ Technol, Sch Mat Sci, Guangzhou, Guangdong, Peoples R China
[4] Harbin Normal Univ, Sch Phys & Elect Engn, Harbin, Peoples R China