Multimillijoule coherent terahertz bursts from picosecond laser-irradiated metal foils

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

doi:10.1073/pnas.1815256116

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 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.

Highlights

Ultrahigh-power terahertz (THz) radiation sources are essential for many applications, for example, THz-wave-based compact accelerators and THz control over matter
In this report, utilizing an ultraintense, picosecond laser pulse to irradiate a metal foil, we demonstrate the efficient generation of low-frequency (
The direct manipulation of target-rear sheath fields with a controllable prepulse provides direct evidence that the THz radiation mainly originates from the coherent transition radiation induced by energetic electrons transiting the target

Summary

Introduction

Ultrahigh-power terahertz (THz) radiation sources are essential for many applications, for example, THz-wave-based compact accelerators and THz control over matter. 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. Observation of THz-field-induced carrier multiplication in high-resistivity silicon is presented as a proof-of-concept application demonstration. The most prominent approaches toward generating high-power THz pulses are based on conventional electron accelerators [11,12,13], and ultrafast laser systems [14]. The former has output a THz pulse energy up to ∼600 μJ, the compromise between the electron bunch charge and bunch duration makes it difficult to enhance the THz energy. The direct manipulation of target-rear sheath fields with a controllable prepulse provides direct evidence that the THz radiation mainly originates from the coherent transition radiation induced by energetic electrons transiting the target

Methods

Results

Conclusion