In-situ Attosecond Probing of Strong-Field Ionization Dynamics via a Transient Plasma Grating

We demonstrate an all-optical technique for in-situ monitoring of strong-field ionization (SFI) dynamics. The method relies on coherent scattering of a probe pulse from a transient plasma grating (TPG) formed by two interfering femtosecond pulses in a gas target. The diffracted signal provides a real-time, relative measure of the ionization yield. We demonstrate the method’s sensitivity by resolving the attosecond-scale coherent control of the ionization rate. Unlike conventional diagnostics that directly measure charged particles, our ensemble-based optical method is non-invasive and particularly suited for non-vacuum environments. To demonstrate its utility, we apply the technique to investigate the relationship between ionization and terahertz (THz) generation in a two-color (ω+ 2ω) field. We measure a phase offset of (0:18 ± 0:05)π between the maxima of the ionization yield and the THz emission. This result provides a quantitative benchmark for theoretical models and establishes the TPG technique as a practical tool for probing SFI dynamics in ensemble systems.