Abstract-Electric and magnetic terahertz nonlinearities resolved on the sub-cycle scale

Alexej Pashkin¹, Alexander Sell¹, Tobias Kampfrath² and Rupert Huber^3,4

^{http://iopscience.iop.org/1367-2630/15/6/065003}

¹ Department of Physics and Center for Applied Photonics, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
² Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
³ Department of Physics, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany
⁴ Author to whom any correspondence should be addressed. 

Table-top sources of intense multi-terahertz (THz) pulses have opened the door to studies of extreme nonlinearities in the previously elusive mid- to far-infrared spectral regime. We discuss two concepts of fully coherent coupling of phase-locked THz pulses with condensed matter. The first approach demonstrates two-dimensional multi-THz spectroscopy of the semiconductor material InSb. By phase- and amplitude-sensitive detection of the nonlinear optical response, we are able to separate incoherent pump–probe signals from coherent four-wave mixing and reveal extremely non-perturbative nonlinearities. While this class of interactions is mediated by the electric field component of the THz pulse, the second approach is complementary, as it demonstrates that, alternatively, the magnetic THz field may be exploited to selectively control the spin degree of freedom in antiferromagnetic NiO.