Determining the dynamics of electrons and ions emitted from a target material during laser ablation is crucial for desirable control of laser processing. However, these dynamics are still challenging to understand because of a lack of ubiquitous spectroscopic tools to observe tangled-up dynamics appearing at ultrafast timescales. Here by harnessing highly sensitive single-shot terahertz time-domain spectroscopy using an echelon mirror, we investigate pulse-to-pulse temporal profile of terahertz radiation generated from the material surface. We clearly found that the carrier–envelope phase and the electric field amplitude of the terahertz waveform systematically vary between the pre- and post-ablation depending on the laser fluence and irradiated pulse numbers. Our results provide a stepping-stone towards perception of Coulomb explosion occurring throughout the laser ablation process, which is indispensable for future laser processing applications.

We implemented the single-shot terahertz spectrometer using an echelon mirror coupled with the phase-offset electro-optic sampling method. The single-shot sensitivity of the terahertz waveform approaches 1 V/cm, which opens a new possibility of detecting terahertz waveforms from various irreversible phenomena. Spectroscopy under pulsed high-magnet, terahertz spectral line imaging, and the terahertz spectroscopy of laser ablation processes are demonstrated. Pulse-to-pulse detection of the terahertz waveforms could bring new information on the ultrafast dynamics of materials and material processing.

Terahertz waveform was detected in time-domain using chirped-pulse up-conversion spectroscopy combined with dispersion compensation. Terahertz waveforms were accurately measured without any distortion due to the spectral interference, providing a scheme for single-shot terahertz time-domain spectroscopy.

Chirped-pulse up-conversion was applied to detect an accurate terahertz waveform. The waveform distortion was suppressed by using dispersion compensation via the chirped-pulse up-conversion, providing a scheme for terahertz time-domain spectroscopy on a single-shot basis.