Experimental observation of optically generated unipolar electromagnetic precursors

It was recently predicted [Phys. Rev. A 95(6), 063817 (2017)] that an intense femtosecond laser pulse propagating in an electro-optic crystal and producing free carriers via multiphoton ionization can generate a unipolar electromagnetic precursor propagating ahead of the laser pulse. Here we report the experimental observation of this phenomenon in a GaP crystal excited by an amplified Ti:sapphire laser. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement