Abstract-High spatial resolution diffraction diagnostics for intense terahertz sources

Shang-Qing Li, Jing-Long Ma, Xiao-Jun Wu, Bao-Long Zhang, Chen Ou-Yang, Tian-Ze Wang, Dan Wang, Xuan Wang, Yu-Tong Li

https://arxiv.org/abs/1910.05714

We propose a high resolution spatial diagnostic method via inserting a millimeter-gap grating into the collimated terahertz beam to monitor the minute variation of the terahertz beam in strong-field terahertz sources, which is difficult to be resolved in conventional terahertz imaging systems. To verify the method, we intentionally fabricate tiny variations of the terahertz beam through tuning the iris for the infrared pumping beam before the tilted pulse-front pumping (TPFP) setups. The phenomena can be well explained by the the theory based on tilted pulse front technique and terahertz diffraction. We believe our observation not only help further understand the mechanism of intense terahertz generation, but also may be useful for strong-field terahertz applications.

Abstract-Highly efficient generation of 0.2 mJ terahertz pulses in lithium niobate at room temperature with sub-50 fs chirped Ti:sapphire laser pulses

Xiao-jun Wu, Jing-long Ma, Bao-long Zhang, Shu-su Chai, Zhao-ji Fang, Chen-Yi Xia, De-yin Kong, Jin-guang Wang, Hao Liu, Chang-Qing Zhu, Xuan Wang, Cun-Jun Ruan, and Yu-Tong Li

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-6-7107#top

We demonstrate generation of 0.2 mJ terahertz (THz) pulses in lithium niobate driven by Ti:sapphire laser pulses at room temperature. Employing tilted pulse front technique, the 800 nm-to-THz energy conversion efficiency has been optimized to 0.3% through chirping the sub-50 fs pump laser pulses to overcome multi-photon absorption and to extend effective interaction length for phase matching. Our approach paves the way for mJ-level THz generation via optical rectification using existing Ti:sapphire laser systems which can deliver Joule-level pulse energy with sub-50 fs pulse duration.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Demonstration of Coherent Terahertz Transition Radiation from Relativistic Laser-Solid Interactions

Guo-Qian Liao, Yu-Tong Li, Yi-Hang Zhang, Hao Liu, Xu-Lei Ge, Su Yang, Wen-Qing Wei, Xiao-Hui Yuan, Yan-Qing Deng, Bao-Jun Zhu, Zhe Zhang, Wei-Min Wang, Zheng-Ming Sheng, Li-Ming Chen, Xin Lu, Jing-Long Ma, Xuan Wang, and Jie Zhang

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.205003

Coherent transition radiation in the terahertz (THz) region with energies of sub-mJ/pulse has been demonstrated by relativistic laser-driven electron beams crossing the solid-vacuum boundary. Targets including mass-limited foils and layered metal-plastic targets are used to verify the radiation mechanism and characterize the radiation properties. Observations of THz emissions as a function of target parameters agree well with the formation-zone and diffraction model of transition radiation. Particle-in-cell simulations also well reproduce the observed characteristics of THz emissions. The present THz transition radiation enables not only a potential tabletop brilliant THz source, but also a novel noninvasive diagnostic for fast electron generation and transport in laser-plasma interactions.

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• Received 12 January 2016

DOI:http://dx.doi.org/10.1103/PhysRevLett.116.205003

Abstract-Backward terahertz radiation from intense laser-solid interactions

Chun Li, Guo-Qian Liao, Mu-Lin Zhou, Fei Du, Jing-Long Ma, Yu-Tong Li, Wei-Min Wang, Zheng-Ming Sheng, Li-Ming Chen, and Jie Zhang
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-4-4010

We report a systematic study on backward terahertz (THz) radiation generation from laser-solid interactions by changing a variety of laser/plasma parameters. We demonstrate a high-energy (with an energy flux density reaching 80 μJ/sr), broadband (>10 THz) plasma-based radiation source. The radiation energy is mainly distributed either in the >10 THz or <3 THz regions. A radial surface current formed by the lateral transport of low-energy electrons (LEE) is believed to be responsible for the radiation in the high-THz region (>10 THz), while high-energy surface fast electrons (SFE) accelerated along the target surface mainly contribute to lower frequency (<3 THz) radiation. The unifying explanation could be applied to backward THz radiation generation from solid targets with presence of relative small preplasmas.

© 2016 Optical Society of America

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Abstract-Role of resonance absorption in terahertz radiation generation from solid targets

Chun Li, Yun-Qian Cui, Mu-Lin Zhou, Fei Du, Yu-Tong Li, Wei-Min Wang, Li-Ming Chen, Zheng-Ming Sheng, Jing-Long Ma, Xin Lu, and Jie Zhang  »View Author Affiliations

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-10-11797

Optics Express, Vol. 22, Issue 10, pp. 11797-11803 (2014)
http://dx.doi.org/10.1364/OE.22.011797

The interaction of 100-fs laser pulses with solid targets at laser intensities 10¹⁶-10¹⁸ W/cm² has been investigated experimentally by simultaneous measurements of terahertz (THz) and second harmonic signals. THz yield at the front side of the target, which rises from the self-organized transient electron currents along the target surface, is found scaling linearly with the laser intensity basically. Measurements of specularly reflected light spectrum show clear evidence of resonance absorption. The positive effects of resonance absorption on surface current and THz radiation generation have been confirmed by two-dimensional (2D) particle-in-cell (PIC) simulations and angular-dependent experiments, respectively.

© 2014 Optical Society of America