We have observed optical birefringence in liquids induced by single-cycle THz pulses with field strengths exceeding 100 kV/cm. The induced change in polarization is proportional to the square of the THz electric field. The time-dependent THz Kerr signal is composed of a fast electronic response that follows the individual cycles of the electric field and a slow exponential response associated with molecular orientation.
@article{arxiv.0907.5081,
title = {Terahertz Kerr effect},
author = {Matthias C. Hoffmann and Nathaniel C. Brandt and Harold Y. Hwang and Ka-Lo Yeh and Keith A. Nelson},
journal= {arXiv preprint arXiv:0907.5081},
year = {2015}
}