[1] Shenzhen Polytech Univ, Coll Elect & Commun Engn, Shenzhen 518055, Peoples R China
[2] Cent China Normal Univ, Coll Phys & Technol, Dept Nanosci & Technol, Wuhan 430079, Peoples R China
[3] Huazhong Univ Sci & Technol, Wuhan Natl Lab Optoelect, Wuhan 430074, Peoples R China