Terahertz-Induced Nonlinear Response in ZnTe

TL;DR

This study investigates the nonlinear terahertz response of ZnTe using time-resolved spectroscopy, revealing second- and third-order nonlinearities that impact terahertz measurement techniques.

Contribution

It provides the first quantitative analysis of ZnTe's nonlinearities in the terahertz regime, including modeling and susceptibility measurements.

Findings

Nonlinear polarization change due to co-propagating terahertz pulses.

Model demonstrating second-order nonlinear behavior.

Quantified third-order susceptibility at terahertz frequencies.

Abstract

Measuring terahertz waveforms in terahertz spectroscopy often relies on electrooptic 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, $\chi^{\mathrm{(3)}}(\omega_\text{THz})$. These results clarify the interactions in ZnTe at terahertz frequencies, with implications for measurements of intense terahertz fields using electro-optic sampling.