Excitation-Dependent Features and Artifacts in 2-D Terahertz Spectroscopy

TL;DR

This paper investigates the origins of features and artifacts in 2D terahertz spectroscopy, using ZnTe as a model, and highlights potential sampling artifacts affecting spectral interpretation.

Contribution

It clarifies the origins of spectral features in 2DTS and identifies artifacts from electro-optic sampling that can mislead analysis.

Findings

Spectral features can originate from material properties or sampling artifacts.

Electro-optic sampling can produce spurious signals like rectified or second harmonic signals.

ZnTe exhibits featureless optical susceptibility at low terahertz frequencies.

Abstract

Recently, two-dimensional terahertz spectroscopy (2DTS) has attracted increasing attention for studying complex solids. A number of recent studies have applied 2DTS either with long pulses or away from any material resonances, situations that yield unconventional 2DTS spectra that are often difficult to interpret. Here, we clarify the generic origins of observed spectral features by examining 2DTS spectra of ZnTe, a model system with a featureless optical susceptibility at low terahertz frequencies. These results also reveal possible artifacts that may arise from electro-optic sampling in collinear 2DTS experiments, including the observation of spurious rectified or second harmonic signals.