1. College of Physics & Optoelectronics Technology, Baoji University of Arts and Sciences, Baoji 721016, China
2. School of Electrical and Electronic Engineering, Baoji University of Arts and Sciences, Baoji 721016, China
3. School of Sciences, Xidian University, Xi’an 710071, China
4. School of Physics and Electronic Engineering, Sichuan University of Science & Engineering, Zigong 643000, China