Abstract-A magnetically tunable non-Bragg defect mode in a corrugated waveguide filled with liquid crystals

Lu Zhang, Ya-Xian Fan,  Huan Liua, Xu Han, Wen-Qiang Luc, Zhi-Yong Tao,

https://www.sciencedirect.com/science/article/pii/S0375960118301737

A magnetically tunable, non-Bragg defect mode (NBDM) was created in the terahertz frequency range by inserting a defect in the middle of a periodically corrugated waveguide filled with liquid crystals (LCs). In the periodic waveguide, non-Bragg gaps beyond the Bragg ones, which appear in the transmission spectra, are created by different transverse mode resonances. The transmission spectra of the waveguide containing a defect showed that a defect mode was present inside the non-Bragg gap. The NBDM has quite different features compared to the Bragg defect mode, which includes more complex, high-order guided wave modes. In our study, we filled the corrugated waveguide with LCs to realize the tunability of the NBDM. The simulated results showed that the NBDM in a corrugated waveguide filled with LCs can be used in filters, sensors, switches, and other terahertz integrated devices.

Abstract-Terahertz superconducting metamaterials for magnetic tunability

Dongyang Wang1, Zhen Tian1, Caihong Zhang2, Xiaoqing Jia2, Biaobing Jin2, Jianqiang Gu1, Jiaguang Han1 and Weili Zhang1,3

http://iopscience.iop.org/2040-8986/16/9/094013

jiaghan@tju.edu.cn weili.zhang@okstate.edu

1 Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology, Tianjin 300072, People's Republic of China
2 Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, People's Republic of China
3 School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, USA 

We present the magnetic tunability of a metamaterial made from superconducting niobium nitride film. The inductive-capacitive resonance excited by a normally incident terahertz wave was found to be continuously modulated through an external magnetic field at temperatures below the superconducting transition point. A giant resonance modulation was observed due to a strong magnetic effect, where the variation of the magnetic field alters the intrinsic conductivity of the superconducting film. The high sensitivity of the metamaterial allows us to observe the temperature-dependent magnetic effect, and the magnitude of resonance modulation decreases with increasing temperatures. This work demonstrates that a strong magnetic effect could be implemented as an active control modality in superconducting integrated devices functioning at terahertz frequencies