Abstract-High power THz coherent Cherenkov radiation based on a separated dielectric loaded waveguide

Shimin Jiang, Weiwei Li, Zhigang He, Ruixuan Huang, Qika Jia, Lin Wang, Yalin Lu,



https://www.sciencedirect.com/science/article/pii/S0168900219301202

In this paper, we propose a new type of dielectric loaded waveguide structure named separated dielectric loaded waveguide (SDLW), whose dielectric layer and metal layer are separated with each other. The characters of wakefield inside SDLW are studied in details by theory analysis and numerical simulation. Compared with the ordinary dielectric loaded waveguide, the peak power of Terahertz coherent Cherenkov radiation (CCR) excited by the short relativistic electron bunch can be enhanced by over one order. Therefore, this new structure offers a promising candidate for high power THz source

Abstract-Design of a Pre-Bunched THz Free Electron Laser

Ruixuan Huang, Weiwei Li,  Zhouyu Zhao, Heting Li, Jigang Wang, Tian Ma, Qiuping Huang, Zhigang He, Qika Jia, Lin Wang, Yalin Lu

https://www.mdpi.com/2571-712X/1/1/21/htm

Terahertz (THz) radiation has attracted much attention in new scientific and industrial applications. There has been significant recent progress in generating THz with accelerators. To investigate the collective behavior of electron dynamics, we have proposed a new high throughput material characterization system, which supplies a multiple light source. The system includes a pre-bunched THz free electron laser (FEL), which is a high-power narrow-band THz source with a wide tuning range of frequency. The physical design with the main components of the facility is introduced, and the simulation results are illustrated. Radiation of 0.5–3.0 THz is obtained by the fundamental wave of the pre-bunched beam, and radiation covering 3.0–5.0 THz is realized by second harmonic generation. As the simulation shows, intense THz radiation could be achieved in a frequency from 0.5–5.0 THz, with a peak power of several megawatts (MWs) and a bandwidth of a few percent.

Abstract-Multicolor Terahertz Frequency Mixer Using Multibunching of Free-Electron Beams

Weihao Liu, Linbo Liang, Qika Jia, Lin Wang, and Yalin Lu

https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.10.034031

We propose a free-electron-beam (FEB)-driven frequency mixer for generating terahertz-wave radiation. It employs an initial steady-current FEB to drive two cascaded gratings. On the first grating, the FEB is macrobunched by interacting with the self-stimulated backward slow waves. On the second grating, which operates at high harmonics of the first grating, it is further microbunched at high frequencies, producing mixed bunching components within the FEB. The multibunched FEB then generates a series of superradiant Smith-Purcell radiations from the second grating, achieving multicolor radiations in the terahertz region. The radiation can be tuned by adjusting the beam energy, covering the frequency range from 0.8 to 1.8 THz. It is a promising broad-tunable and multicolor terahertz source.

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Abstract-Two-dimensional reversed Cherenkov radiation on plasmonic thin-film

Weihao Liu, Linbo Liang, and Qika Jia

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-15-18216&origin=search

The reversed Cherenkov radiation is one of the most attractive research topics because of its unique characteristics and promising applications. It was generally believed that reversed Cherenkov radiations exist only in left-handed metamaterials (double negative mediums). In the present paper, we demonstrated that they can also be generated on plasmonic thin-films. Reversed Cherenkov radiations in the terahertz region and in the visible light region were achieved on the metamaterial thin-film and the metal thin-film, respectively. Their radiation frequencies and directions, which are interdependent with each other, are controllable. For the normal Cherenkov radiation, the wavelength on the thin-film increases with the frequency; whereas for the reversed Cherenkov radiation, the opposite is true. Theoretical analyses and simulations revealed that the normal or reversed Cherenkov radiation is generated depending on whether the forward or backward surface modes are excited on the plasmonic thin-film. Requirements of these reversed Cherenkov radiations were found out.

© 2017 Optical Society of America

Abstract-High-harmonic terahertz Smith-Purcell free-electron-laser with two tandem cylindrical-gratings

Linbo Liang, Weihao Liu, Qika Jia, Lin Wang, and Yalin Lu

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-3-2960

A modified Smith-Purcell free-electron-laser based on two tandem cylindrical-gratings is proposed. The preset grating with larger size, operating in the slow-wave condition, is to prebunch the initial continuous electron-beam, and the postpositive grating with smaller size, operating in the fast-wave condition, is used as the main radiator. Compared with traditional Smith-Purcell free-electron-lasers operating at the second harmonic of the bunched-beam, the present scheme operates at much higher harmonics, fifth and sixth harmonics have been achieved, and the radiation frequency is greatly increased consequently. And also the radiation power is enhanced by tens of times. Thus it could be developed as an efficient terahertz source with frequency being over 0.5 THz in practice.

© 2017 Optical Society of America

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Abstract-Harmonics generation of a terahertz wakefield free-electron laser from a dielectric loaded waveguide excited by a direct current electron beam

Weiwei Li, Yalin Lu, Zhigang He, Qika Jia, and Lin Wang
https://www.osapublishing.org/ol/abstract.cfm?uri=ol-41-11-2458

We propose to generate high-power terahertz (THz) radiation from a cylindrical dielectric loaded waveguide (DLW) excited by a direct-current electron beam with the harmonics generation method. The DLW supports a discrete set of modes that can be excited by an electron beam passing through the structure. The interaction of these modes with the co-propagating electron beam results in micro-bunching and the coherent enhancement of the wakefield radiation, which is dominated by the fundamental mode. By properly choosing the parameters of DLW and beam energy, the high order modes can be the harmonics of the fundamental one; thus, high frequency radiation corresponding to the high order modes will benefit from the dominating bunching process at the fundamental eigenfrequency and can also be coherently excited. With the proposed method, high power THz radiation can be obtained with an easily achievable electron beam and a large DLW structure.

© 2016 Optical Society of America

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Abstract-A multimode terahertz-Orotron with the special Smith–Purcell radiation

Weihao Liu1,a), Yalin Lu1, Lin Wang1 and Qika Jia1

1 National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, China

a) Electronic mail: liuwhao@ustc.edu.cn

Appl. Phys. Lett. 108, 183510 (2016); http://dx.doi.org/10.1063/1.4949015

http://scitation.aip.org/content/aip/journal/apl/108/18/10.1063/1.4949015

We proposed and investigated a terahertz Orotron, which is based on the recently revealed special Smith–Purcell radiation. It overcomes the main obstacles of the traditional Orotron in the terahertz region—unreachable high starting-current-density and low radiation power. With the experimentally available electron beam and facilities, its average output power can reach hundreds of milliwatts and even several watts in terahertz region, which is many orders of magnitude higher than that of the traditional Orotron. Additionally, it can be controlled to operate in ether the first or the second order mode, and the radiation frequency can extend from 0.1 THz to 1 THz. These remarkable advantages make it a promising terahertz source for practical applications.

Abstract-Broad-tunable terahertz source with over-mode waveguide driven by train of electron bunches

Weihao Liu, Yalin Lu, Zhigang He, Weiwei Li, Lin Wang, and Qika Jia

A broad-tunable free electron terahertz radiation source is proposed. In this source, a train of electron bunches with tunable bunching frequency is produced by a photocathode based DC-gun under excitation of a train of tunable laser pulses. These electron bunches are then applied to excite an over-mode waveguide, in which diverse guided modes are coupled into radiation with frequency determined by the bunching frequency. By this means, the tunable radiation with frequency extending from 0.1 THz to 1.2 THz can be obtained from one single structure model. In addition, compared with other sources, the proposed source is compact and easily achievable.

© 2016 Optical Society of America

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