Ticking terahertz wave generation in attoseconds

TL;DR

This paper demonstrates a method to measure terahertz wave generation with attosecond precision by correlating it with high-order harmonic generation, revealing the critical role of electron rescattering in the process.

Contribution

It introduces a joint measurement technique that correlates THz and harmonic generation, highlighting the importance of electron rescattering in THz wave production.

Findings

THz wave generation occurs in tens of attoseconds.

Electron rescattering is crucial for THz generation.

Rescattering dynamics can be characterized using this method.

Abstract

We perform a joint measurement of terahertz waves and high-order harmonics generated from noble atoms driven by a fundamental laser pulse and its second harmonic. By correlating their dependence on the phase-delay of the two pulses, we determine the generation of THz waves in tens of attoseconds precision. Compared with simulations and models, we find that the laser-assisted soft-collision of the electron wave packet with the atomic core plays a key role. It is demonstrated that the rescattering process, being indispensable in HHG processes, dominant THz wave generation as well but in a more elaborate way. The new finding might be helpful for the full characterization of the rescattering dynamics.