中央研究院 原子與分子科學研究所

Single-shot ultrashort extreme-UV(EUV) pulse waveform measurement is demonstrated by utilizing strong field ionization of H₂ gas for transmission gating. A cross-propagating intense near-IR gate pulse ionizes the EUV absorbing H₂ molecules into EUV-non-absorbing H₂⁺⁺ (two protons) and creates a time sweep of transmission encoded spatially across the EUV pulse. The temporal envelope is then retrieved from the lopsided spatial profile of the transmitted pulse. This method not only measures EUV temporal envelope for each single shot, but also determines timing jitter and envelope fluctuation statistically, thus is particularly useful for characterizing low-repetition-rate fluctuating EUV/soft x-ray sources.