[1] Xidian Univ, Sch Tech Phys & Optoelect Engn, Xian 710071, Shaanxi, Peoples R China
[2] Chinese Acad Sci, Beijing Natl Lab Condensed Matter Phys, Inst Phys, Beijing 100190, Peoples R China
[3] China Univ Petr, Coll Sci, Qingdao 266580, Shandong, Peoples R China
[4] Chinese Acad Sci, Shanghai Inst Ceram, Key Lab Transparent & Optofunct Inorgan Mat, Shanghai 201800, Peoples R China