Abstract-Stable and Scalable Multistage Terahertz-Driven Particle Accelerator

 

Heng Tang, Lingrong Zhao, Pengfei Zhu, Xiao Zou, Jia Qi, Ya Cheng, Jiaqi Qiu, Xianggang Hu, Wei Song, Dao Xiang, and Jie Zhang

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.074801?ft=1

Particle accelerators that use electromagnetic fields to increase a charged particle’s energy have greatly advanced the development of science and industry since invention. However, the enormous cost and size of conventional radio-frequency accelerators have limited their accessibility. Here, we demonstrate a miniaccelerator powered by terahertz pulses with wavelengths 100 times shorter than radio-frequency pulses. By injecting a short relativistic electron bunch to a 30-mm-long dielectric-lined waveguide and tuning the frequency of a 20-period terahertz pulse to the phase-velocity-matched value, precise and sustained acceleration for nearly 100% of the electrons is achieved with the beam energy spread essentially unchanged. Furthermore, by accurately controlling the phase of two terahertz pulses, the beam is stably accelerated successively in two dielectric waveguides with close to 100% charge coupling efficiency. Our results demonstrate stable and scalable beam acceleration in a multistage miniaccelerator and pave the way for functioning terahertz-driven high-energy accelerators.

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Abstract-Terahertz oscilloscope for recording time information of ultrashort electron beams

Lingrong Zhao, Zhe Wang, Heng Tang, Rui Wang, Yun Cheng, Chao Lu, Tao Jiang, Pengfei Zhu, Long Hu, Wei Song, Huida Wang, Jiaqi Qiu, Roman Kostin, Chunguang Jing, Sergey Antipov, Peng Wang, Jia Qi, Ya Cheng, Dao Xiang, and Jie Zhang

https://journals.aps.org/prl/accepted/d407dY16M5819b51b9d98708b359b7042e3e658c9

We propose and demonstrate a Terahertz (THz) oscilloscope for recording time information of an ultrashort electron beam. By injecting a laser-driven THz pulse with circular polarization into a dielectric tube, the electron beam is swept helically such that the time information is uniformly encoded into the angular distribution that allows one to characterize both the temporal profile and timing jitter of an electron beam. The dynamic range of the measurement in such a configuration is significantly increased compared to deflection with a linearly polarized THz pulse. With this THz oscilloscope, nearly 50-fold longitudinal compression of a relativistic electron beam to about 15 fs (rms) is directly visualized with its arrival time determined with 3 fs accuracy. This technique bridges the gap between streaking of photoelectrons with optical lasers and deflection of relativistic electron beams with radio-frequency deflectors, and should have wide applications in many ultrashort electron beam based facilities.

Abstract-Terahertz streaking of few-femtosecond relativistic electron beams

Lingrong Zhao, Zhe Wang, Chao Lu, Rui Wang, Cheng Hu, Peng Wang, Jia Qi, Tao Jiang, Shengguang Liu, Zhuoran Ma, Fengfeng Qi, Pengfei Zhu, Ya Cheng, Zhiwen Shi, Yanchao Shi, Wei Song, Xiaoxin Zhu, Jiaru Shi, Yingxin Wang, Lixin Yan, Liguo Zhu, Dao Xiang,  Jie Zhang,

https://journals.aps.org/prx/accepted/d8075K71A261f001129c7ce70c632d2221b6fd030

Streaking of photoelectrons with optical lasers has been widely used for temporal characterization of attosecond extreme ultraviolet pulses. Recently, this technique has been adapted to characterize femtosecond x-ray pulses in free-electron lasers with the streaking imprinted by far-infrared and Terahertz (THz) pulses. Here, we report successful implementation of THz streaking for time-stamping of an ultrashort relativistic electron beam of which the energy is several orders of magnitude higher than photoelectrons. Such ability is especially important for MeV ultrafast electron diffraction (UED) applications where electron beams with a few femtosecond pulse width may be obtained with longitudinal compression while the arrival time may fluctuate at a much larger time scale. Using this laser-driven THz streaking technique, the arrival time of an ultrashort electron beam with 6 fs (rms) pulse width has been determined with 1.5 fs (rms) accuracy. Furthermore, we have proposed and demonstrated a non-invasive method for correction of the timing jitter with femtosecond accuracy through measurement of the compressed beam energy, which may allow one to advance UED towards sub-10 fs frontier far beyond the $\sim$100 fs (rms) jitter.

Abstract-Strong Spatial Confinement of Terahertz Wave inside Femtosecond Laser Filament

Jiayu Zhao, Wei Chu, Zhi Wang, Yan Peng, Cheng Gong, Lie Lin, Yiming Zhu, Weiwei Liu, Ya Cheng, Songlin Zhuang, and Zhizhan Xu

ACS Photonics, Just Accepted Manuscript

DOI: 10.1021/acsphotonics.6b00512

Publication Date (Web): November 8, 2016

Copyright © 2016 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acsphotonics.6b00512

In this paper, a new experimental phenomenon is demonstrated. During the femtosecond laser filamentation, the generated terahertz (THz) pulse has been found to be strongly confined inside the plasma channel, reaching a spatial diameter of a few tens of micrometres. It has been attributed to the formation of a plasma negative dielectric waveguide induced by the transverse inhomogeneous plasma density distribution. The new experimental phenomenon will renew the understanding of the THz wave generation and propagation dynamics during the femtosecond laser and air plasma interaction. Due to this strong spatial confinement, THz electric field strength could be enhanced by orders of magnitude, potentially providing a new approach to perform THz nonlinear optics with low laser energy.

Abstract-A simple method to enhance terahertz radiation from femtosecond laser filament array with a step phase plate

Jiayu Zhao, Lanjun Guo, Wei Chu, Bin Zeng, Hui Gao, Weiwei Liu, and Ya Chen
https://www.osapublishing.org/ol/upcoming_pdf.cfm?id=236756

• Abstract: In this work, we experimentally demonstrate a 200% enhancement of terahertz (THz) wave amplitude generated by femtosecond laser filamentation in air. The experimental setup simply uses a semicircular phase plate to generate two parallel filaments. Temporally overlapped THz pulses from two filaments coherently add up, giving rise to significant enhancement of the THz pulse amplitude. It has been foreseen that further enhancement would be achieved if the design of phase plates could be optimized to generate filament array. This simple method makes full use of the laser energy and might potentially open a new approach to remotely enhance the THz emission in air.

Abstract-Terahertz Wave Guiding by Femtosecond Laser Filament in Air

Jiayu Zhao, Yizhu Zhang, Zhi Wang, Wei Chu, Bin Zeng, Ya Cheng, Zhizhan Xu, Weiwei Liu

http://arxiv-web3.library.cornell.edu/abs/1310.5435

(Submitted on 21 Oct 2013)

Femtosecond laser filament generates strong terahertz (THz) pulse in air. In this paper, THz pulse waveform generated by femtosecond laser filament has been experimentally investigated as a function of the length of the filament. Superluminal propagation of THz pulse has been uncovered, indicating that the filament creates a THz waveguide in air. Numerical simulation has confirmed that the waveguide is formed because of the radially non-uniform refractive index distribution inside the filament. The underlying physical mechanisms and the control techniques of this type THz pulse generation method might be revisited based on our findings. It might also potentially open a new approach for long-distance propagation of THz wave in air.