1. Key Laboratory for Physical Electronics and Devices of the Ministry of Education & Shaanxi Key Lab of Information Photonic Technique, School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, Shaanxi, P.R. China
2. Department of Applied Physics, Aalto University, FI-00076 AALTO, Finland
3. Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, Shaanxi, P.R. China
4. Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, P.R. China