Multi-millijoule coherent terahertz bursts from picosecond laser-irradiated metal foils

Liao, Guoqiang and Li, Yutong and Liu, Hao and Scott, Graeme G. and Neely, David and Zhang, Yihang and Zhu, Baojun and Zhang, Zhe and Armstrong, Chris and Zemaityte, Egle and Bradford, Phil and Huggard, Peter G. and Rusby, Dean R. and McKenna, Paul and Brenner, Ceri M. and Woolsey, Nigel C. and Wang, Weimin and Sheng, Zhengming and Zhang, Jie (2019) Multi-millijoule coherent terahertz bursts from picosecond laser-irradiated metal foils. Proceedings of the National Academy of Sciences, 116 (10). pp. 3994-3999. ISSN 1091-6490

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    Abstract

    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 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 new research era of relativistic THz optics.