Abstract

Pulse characterization in the vacuum-ultraviolet (VUV) region is not trivial. Since the photon energy is smaller than the ionization potentials, two-photon absorption is required to characterize a VUV waveform by the photo-electron spectroscopy. Recently, we developed an alternative method based on the time-resolved reflection spectroscopy [1]. In this plasma-mirror frequency resolved optical gating (PM-FROG) technique, ultrafast switching of the reflectivity of a plasma-mirror generated by focusing intense near-infrared (NIR) pulses on a solid target is used as a gate function. Since reflective optics is employed, this technique can be used for the characterization of broadband pulses. However, due to a damage of the solid target by laser ablation, the applicable repetition rate of PM-FROG was limited. In this study, we developed the time-resolved reflection spectroscopy with a liquid-sheet target to extend the application range, and demonstrated the eligibility of the waveform obtained by PM-FROG in a UV region. We also compared the obtained plasma-mirror reflectivity as a function of the time-delay with the FDTD calculation to understand underlying physics of plasma formation.

© 2019 IEEE