Abstract-A megawatt-level surface wave oscillator in Y-band with large oversized structure driven by annular relativistic electron beam

Jianguo Wang, Guangqiang Wang, Dongyang Wang, Shuang Li,  Peng Zeng,

https://www.nature.com/articles/s41598-018-25466-w


High power vacuum electronic devices of millimeter wave to terahertz regime are attracting extensive interests due to their potential applications in science and technologies. In this paper, the design and experimental results of a powerful compact oversized surface wave oscillator (SWO) in Y-band are presented. The cylindrical slow wave structure (SWS) with rectangular corrugations and large diameter about 6.8 times the radiation wavelength is proposed to support the surface wave interacting with annular relativistic electron beam. By choosing appropriate beam parameters, the beam-wave interaction takes place near the π-point of TM01 mode dispersion curve, giving high coupling impedance and temporal growth rate compared with higher TM0nmodes. The fundamental mode operation of the device is verified by the particle-in-cell (PIC) simulation results, which also indicate its capability of tens of megawatts power output in the Y-band. Finally, a compact experimental setup is completed to validate our design. Measurement results show that a terahertz pulse with frequency in the range of 0.319–0.349 THz, duration of about 2 ns and radiation power of about 2.1 MW has been generated.

Abstract-A high-order mode extended interaction klystron at 0.34 THz

Dongyang Wang, Guangqiang Wang,   Jianguo Wang, Shuang Li, Peng Zeng, Yan Teng,

http://aip.scitation.org/doi/10.1063/1.4975649

We propose the concept of high-order mode extended interaction klystron (EIK) at the terahertz band. Compared to the conventional fundamental mode EIK, it operates at the TM31-2π mode, and its remarkable advantage is to obtain a large structure and good performance. The proposed EIK consists of five identical cavities with five gaps in each cavity. The method is discussed to suppress the mode competition and self-oscillation in the high-order mode cavity. Particle-in-cell simulation demonstrates that the EIK indeed operates at TM31-2π mode without self-oscillation while other modes are well suppressed. Driven by the electron beam with a voltage of 15 kV and a current of 0.3 A, the saturation gain of 43 dB and the output power of 60 W are achieved at the center frequency of 342.4 GHz. The EIK operating at high-order mode seems a promising approach to generate high power terahertz waves.

Abstract-Ultralow temperature terahertz magnetic thermodynamics of perovskite-like SmFeO3 ceramic.

Xiaojian Fu, Xinxi Zeng, Dongyang Wang, Hao Chi Zhang, Jiaguang Han, Tie Jun Cui

http://www.pubfacts.com/detail/26424488/Ultralow-temperature-terahertz-magnetic-thermodynamics-of-perovskite-like-SmFeO3-ceramic

The terahertz magnetic properties of perovskite-like SmFeO3 ceramic are investigated over a broad temperature range, especially at ultralow temperatures, using terahertz time-domain spectroscopy. It is shown that both resonant frequencies of quasi-ferromagnetic and quasi-antiferromagnetic modes have blue shifts with the decreasing temperature due to the enhancement of effective magnetic field. The temperature-dependent magnetic anisotropy constants are further estimated using the resonant frequencies, under the approximation of omitting the contribution of Sm(3+) magnetic moments to the effective field. Specially, the effective anisotropy constants in the ca and cb planes at 3 K are 6.63 × 10(5) erg/g and 8.48 × 10(5) erg/g, respectively. This thoroughly reveals the terahertz magnetic thermodynamics of orthoferrites and will be beneficial to the application in terahertz magnetism.

Abstract-Terahertz probes of magnetic field induced spin reorientation in YFeO3 single crystal

Xian Lin¹, Junjie Jiang¹, Zuanming Jin^1,2, Dongyang Wang³, Zhen Tian³,Jiaguang Han³, Zhenxiang Cheng^1,4 and Guohong Ma^1,a)


a) Author to whom correspondence should be addressed. Electronic mail: ghma@staff.shu.edu.cn
Appl. Phys. Lett. 106, 092403 (2015); http://dx.doi.org/10.1063/1.4913998
http://scitation.aip.org/content/aip/journal/apl/106/9/10.1063/1.4913998

Using the terahertz time-domain spectroscopy, we demonstrate the spin reorientation of a canted antiferromagnetic YFeO3 single crystal, by evaluating the temperature and magnetic field dependence of resonant frequency and amplitude for the quasi-ferromagnetic (FM) and quasi-antiferromagnetic modes (AFM), a deeper insight into the dynamics of spin reorientation in rare-earth orthoferrites is established. Due to the absence of 4f-electrons in Y ion, the spin reorientation of Fe sublattices can only be induced by the applied magnetic field, rather than temperature. In agreement with the theoretical predication, the frequency of FM mode decreases with magnetic field. In addition, an obvious step of spin reorientation phase transition occurs with a relatively large applied magnetic field of 4 T. By comparison with the family members of RFeO3 (R = Y³⁺ or rare-earth ions), our results suggest that the chosen of R would tailor the dynamical rotation properties of Fe ions, leading to the designable spin switching in the orthoferrite antiferromagnetic systems.

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