1. Research Institute of Superconductor Electronics (RISE); School of Electronic Science and Engineering; Nanjing University; Nanjing 210093 China
2. State Key Laboratory of Millimeter Waves; Southeast University; Nanjing 210096 China
3. Institute of Modern Optics; Nankai University; Tianjin 300071 China
4. School of Electronic Science and Engineering; Nanjing University; Nanjing 210093 China
5. Cooperative Innovation Centre of Terahertz Science; University of Electronic Science and Technology; Chengdu 611731 China
6. Center for Integrated Nanotechnologies; Materials Physics and Applications Division; Los Alamos National Laboratory; Los Alamos NM 87545 USA
7. Terahertz Research Centre; School of Physical Electronics; University of Electronic Science and Technology of China; Chengdu Sichuan 610054 China