Fig. 5: Nonlinearity of the transient grating signal as a function of the pump intensity.

All X-ray TG signal intensity in transmission (blue) and diffraction (red) at Z = 7.3 mm and t = 2 fs as a function of the pump intensity. The shaded areas for each trace correspond to the signal including the standard deviation. Areas included in the vertical red/blue dashed lines represent the minimum and maximum intensities considered in the analysis of the quadratic behavior of the d/t-XTG signals. The blue trace shows outliers for low (below 10 μJ) and high (above 80 μJ) pump intensities (at the source), while the red trace shows a plateau at high pump intensities (above 40 μJ). This behavior is probably due to saturation of electron delocalization effects for high incident beam intensities. This effect does not affect the transmitted TG signal.