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.