<i>In situ</i> Measurement of Intense Optical Fields via Strong Field Ionization

Abstract This letter reports an all-optical measurement of laser electric field based on strong field ionization. By measuring the attosecond transient absorption spectra of krypton ions subjected to strong laser fields, we obtain the time-dependent effective valence-hole population, from which the driving laser waveform is retrieved with particle swarm optimization and genetic algorithm under strong-field approximation. Our in situ measurement approach underscores the capability of attosecond transient absorption spectroscopy (ATAS) to characterize intense laser fields accurately. This technique is pivotal for the analysis of electron dynamics in ATAS experiments, achieving a significant advancement in this field.