Selz, FelixFelixSelzKölbel, JohannaJohannaKölbelParies, FelixFelixPariesFreymann, Georg vonGeorg vonFreymannMolter, DanielDanielMolterMittleman, Daniel M.Daniel M.Mittleman2025-03-202025-03-202025-02-25https://publica.fraunhofer.de/handle/publica/48571110.1364/OE.546261Measuring terahertz waveforms in terahertz spectroscopy often relies on electro-optic sampling employing a ZnTe crystal. Although the nonlinearities in such zincblende semiconductors induced by intense terahertz pulses have been studied at optical frequencies, a quantitative study of nonlinearities in the terahertz regime has not been reported. In this work, we investigate the nonlinear response of ZnTe in the terahertz frequency region utilizing time-resolved terahertz-pump terahertz-probe spectroscopy. We find that the interaction of two co-propagating terahertz pulses in ZnTe leads to a nonlinear polarization change which modifies the electro-optic response of the medium at terahertz frequencies. We present a model for this polarization that showcases the second-order nonlinear behavior. We also determine the magnitude of the third-order susceptibility in ZnTe at terahertz frequencies, χ (3)(ω THz). These results clarify the interactions in ZnTe at terahertz frequencies, with implications for measurements of intense terahertz fields using electro-optic sampling.enterahertz waveformsZnTe crystal500 Naturwissenschaften und Mathematikjournal article