Abstract-Towards terawatt-scale spectrally-tunable terahertz pulses via relativistic laser-foil interactions

Guo-Qian Liao, Hao Liu, Graeme G. Scott, Yi-Hang Zhang, Bao-Jun Zhu, Zhe Zhang, Yu-Tong Li, Chris Armstrong, Egle Zemaityte, Philip Bradford, Dean R. Rusby, David Neely, Peter G. Huggard, Paul McKenna, Ceri M. Brenner, Nigel C. Woolsey, Wei-Min Wang, Zheng-Ming Sheng, Jie Zhang

https://journals.aps.org/prx/accepted/f9077Ka7Ta61f80ac4557eb8820820c019e7c6ab0

An ever-increasing number of strong-field applications, like ultrafast coherent control over matter and light, require driver light pulses that are of both high power and tunable spectra. However, the realization of such a source in the terahertz (THz) band has long been a formidable challenge. Here, we demonstrate, via experiment and theory, the efficient production of terawatt (TW)-level THz pulses from high-intensity picosecond laser irradiation on a metal foil. The THz spectra can be manipulated effectively by tuning the laser pulse duration or target size. An analytical model that well reproduces the experimental results is developed, and the spectral tunability stems from a hybrid THz generation mechanism driven jointly by both the high-current electron emission and the time-varying electron sheath at the target rear. In addition to being an ultrabright source (brightness temperature ~10^21 K) for extreme THz science, the THz radiation presented here also enables a unique in-situ laser-plasma diagnostic, and it has been employed to quantify the escaping electrons and the transient sheath, in good agreement with experimental measurements.

Abstract-Multimillijoule coherent terahertz bursts from picosecond laser-irradiated metal foils

Guoqian Liao, Yutong Li, Hao Liu, Graeme G. Scott, David Neely, Yihang Zhang, Baojun Zhu, Zhe Zhang, Chris Armstrong, Egle Zemaityte, Philip Bradford, Peter G. Huggard, Dean R. Rusby, Paul McKenna, Ceri M. Brenner, Nigel C. Woolsey, Weimin Wang, Zhengming Sheng, Jie Zhang

https://www.pnas.org/content/116/10/3994

Terahertz (THz) radiation, with frequencies spanning from 0.1 to 10 THz, has long been the most underdeveloped frequency band in electromagnetic waves, mainly due to the dearth of available high-power THz sources. Although the last decades have seen a surge of electronic and optical techniques for generating intense THz radiation, all THz sources reported until now have failed to produce above-millijoule (mJ) THz pulses. We present a THz source that enables a THz pulse energy up to tens of mJ, by using an intense laser pulse to irradiate a metal foil.

Abstract-Multimillijoule coherent terahertz bursts from picosecond laser-irradiated metal foils

Guoqian Liao, Yutong Li, Hao Liu, Graeme G. Scott, David Neely, Yihang Zhang, Baojun Zhu, Zhe Zhang, Chris Armstrong, Egle Zemaityte, Philip Bradford, Peter G. Huggard, Dean R. Rusby, Paul McKenna, Ceri M. Brenner, Nigel C. Woolsey, Weimin Wang, Zhengming Sheng, and Jie Zhang

https://www.pnas.org/content/early/2019/02/12/1815256116


Ultrahigh-power terahertz (THz) radiation sources are essential for many applications, for example, THz-wave-based compact accelerators and THz control over matter. However, to date none of the THz sources reported, whether based upon large-scale accelerators or high-power lasers, have produced THz pulses with energies above the millijoule (mJ) level. Here, we report a substantial increase in THz pulse energy, as high as tens of mJ, generated by a high-intensity, picosecond laser pulse irradiating a metal foil. A further up-scaling of THz energy by a factor of ∼4 is observed when introducing preplasmas at the target-rear side. Experimental measurements and theoretical models identify the dominant THz generation mechanism to be coherent transition radiation, induced by the laser-accelerated energetic electron bunch escaping the target. Observation of THz-field-induced carrier multiplication in high-resistivity silicon is presented as a proof-of-concept application demonstration. Such an extremely high THz energy not only triggers various nonlinear dynamics in matter, but also opens up the research era of relativistic THz optics.

Abstract->mJ terahertz radiation sources from intense laser-foil interactions

Yutong Li, Guoqian Liao, David Neely, Paul McKenna, Zhengming Sheng, and Jie Zhang

https://www.osapublishing.org/abstract.cfm?uri=ISUPTW-2018-TuE1

We have systematically studied strong THz radiation from solid targets driven by relativistic femtosecond and picosecond laser pulses. The THz generation is due to coherent transition radiation of relativistic laser-driven electron beams when they pass the solid-vacuum boundary. The THz radiation with pulse energy of >mJ has been observed with picosecond pulses. Such high energy THz pulses can not only trigger various nonlinear dynamics in matter, but also open up a new research field of relativistic THz optics.

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