Electro-optic sampling at 90 degree interaction geometry for time-of-arrival stamping of ultrafast relativistic electron diffraction

In this paper we study a new geometry setup for electro-optic sampling (EOS) where the electron beam runs parallel to the $⟨110⟩$ face of a ZnTe crystal and the probe laser is perpendicular to it and to the beam path. The simple setup is used to encode the time-of-arrival information of a 3.5 MeV<10 pC electron bunch on the spatial profile of the laser pulse. The electric field lines inside the dielectric bend at an angle due to a relatively large (n~3) index of refraction of the ZnTe crystal. We found theoretically and experimentally that the EOS signal can be maximized with a proper choice of incoming laser polarization angle. We achieved single-shot nondestructive measurement of the relative time of arrival between the pump and the probe beams thus improving the temporal resolution of ultrafast relativistic electron diffraction experiments.