In situ spatial mapping of gouy phase slip with terahertz generation in strong laser field

We establish a one-to-one mapping between the local phase slip and the spatial position near the focus by scanning a thin jet along the propagation direction of laser beams. The measurement shows that the optimal phase of THz can be utilized to characterize in situ the spatially dependent relative phase of the two-color field and the carrier-envelope-phase of the few-cycle pulse. The result is of critical importance for any phase-dependent application of strong laser-field including high-order harmonic and terahertz generation.