Micrometric Kerr transient grating for in-situ ultrashort probe diagnostic

Ultrafast pump-probe imaging requires both an accurate synchronization of probe pulses with the pump and that the probe pulses are free from spatio-temporal distortions. However, characterizing weak probes inside transparent solids reveals to be particularly difficult. We report a new in-situ diagnostic for ultrashort probes using a micrometric-sized Kerr-based transient grating induced in the sample by a shaped pump pulse. Our configuration allows us to synchronize pump and probe pulses in-situ, to measure the ultrashort probe pulse duration, and to remove pulse front tilt of the weak probe. Our approach is valid for any probe wavelength and polarization.