[1] Nanjing Univ Posts & Telecommun, Sch Geog & Biol Informat, Nanjing 210023, Jiangsu, Peoples R China
[2] Nanjing Univ, Sch Elect Sci & Engn, Natl Lab Solid State Microstruct, Nanjing 210093, Jiangsu, Peoples R China
[3] Natl Univ Def Technol, Coll Optoelect Sci & Engn, Changsha 410073, Hunan, Peoples R China