Electro-Optical Detection of Coherent Radiation Induced by Relativistic Electron Bunches in the Near and Far Fields

Coherent radiation produced by relativistic charged bunches is nowadays of great interest for user-oriented applications and high-resolution diagnostics. Here we present experimental results obtained by using a temporal monitor based on the electro-optical sampling that allows us to reveal the features of the radiation emitted in terahertz range by ultrashort electron bunches moving in proximity to a nonlinear crystal. We investigate the radiation properties both in near- and far-field conditions by employing electron beams accelerated by a conventional photoinjector and through laser-plasma interactions. Our results indicate that the emitted radiation moves collinearly with the beam in one case, while its properties resemble those of the classical Cherenkov radiation in a second case.