1. The School of Optoelectronic Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China
2. The State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Microelectronics and Solid-State Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
3. Electronic Information and Networking Research Institute, Collaborative Innovation Center for Information Communication Technology, Chongqing University of Posts and Telecommunications, Chongqing 400065, China