Ultrafast Dynamics of Coulomb Electric Field Contraction by Relativistic Electron Bunch

In special relativity, the Lorentz transformation of electromagnetic potentials has never been directly demonstrated in experiments. Here, we show the spatiotemporal electric field profiles around a highly energetic electron beam with a sub-picosecond temporal resolution obtained by electro-optic sampling. We observe the Coulomb field contraction in the propagation direction of the beam under the Lorentz transformation. We investigated the dynamical behavior of the Coulomb field after passing the beam through a metallic plate. The contraction of the electric field around a beam of highly energetic electrons predicted by the special relativity is experimentally visualized for the first time.