[1] Nanjing Univ Sci & Technol, Sch Elect Engn & Optoelect Technol, Nanjing 210094, Jiangsu, Peoples R China
[2] Chinese Acad Sci, Inst Chem, Beijing 100190, Peoples R China
[3] Natl Inst Metrol, Beijing 100013, Peoples R China
[4] Chinese Acad Sci, Purple Mt Observ, Nanjing 210008, Jiangsu, Peoples R China
[5] Arizona Radio Observ, Tucson, AZ 85721 USA