[1] Xidian Univ, Sch Phys & Optoelect Engn, Xian 710071, Peoples R China
[2] Chinese Acad Sci, Inst Phys, Beijing Natl Lab Condensed Matter Phys, Beijing 100190, Peoples R China
[3] Chinese Acad Sci, Shanghai Inst Ceram, Key Lab Transparent & Optofunct Inorgan Mat, Shanghai 201800, Peoples R China