Extended Data Fig. 7: Experimental setup used to measure the spatiotemporal evolution of the spherical electromagnetic wavefront.

a, A 3D schematic around the ZnTe crystal. The focused probe pulse passed through the hole with the diameter of 1 mm in the Al foil and was incident on the crystal with an incidence angle of 37° while the electron beam passed through the Al foil. b, A 2D schematic of the experimental setup. Abbreviations describing the setup are listed in the upper-right corner. The probe laser was focused on the ZnTe crystal by a lens, and the transverse electric field on the spot was measured. The polarization of the probe pulse was directed along the x-axis, and the QWP was adjusted to divide the probe pulse into two (p- and s-polarization) pulses with the same intensities. The spatiotemporal profile of the electric field was measured by moving two motorized stages for shifting the optics around the ZnTe crystal and the delay stage, respectively; they are surrounded by black rectangles in the figure, and the two-way arrows show the moving direction (dx and dt). The position of the Al foil was moved in the z-direction, and the distance D was adjusted.