1. Guilin University of Electronic Technology, Institute of Electrical Engineering and Automation, No. 1 Jinji Road, Guilin 551004, China
2. Xi’an University of Technology, Departments of Applied Physics, No. 5 South Jinhua Road, Xi’an 710048, China
3. Xi’an Jiaotong University, School of Electronics and Information Engineering, Shaanxi Key Lab of Information Photonic Technique, Xianing-xilu 28, Xi’an 710049, China