Rigorous Signal Reconstruction in Terahertz Emission Spectroscopy

TL;DR

This paper introduces a rigorous method for accurate signal reconstruction in Terahertz emission spectroscopy, addressing practical errors and demonstrating its application in ultrafast magnetometry to recover detailed magnetization dynamics.

Contribution

The paper presents a new, experimentally validated reconstruction method that minimizes errors in THz emission spectroscopy, especially in line-of-sight geometries, enabling precise ultrafast magnetic measurements.

Findings

Optimal line-of-sight geometry for calibration

Successful reconstruction of ultrafast magnetization dynamics

Identification of key sources of reconstruction error

Abstract

Terahertz (THz) emission spectroscopy is a powerful method that allows one to measure the ultrafast dynamics of polarization, current, or magnetization in a material based on THz emission from the material. However, the practical implementation of this method can be challenging, and can result in significant errors in the reconstruction of the quantity of interest. Here, we experimentally and theoretically demonstrate a rigorous method of signal reconstruction in THz emission spectroscopy, and describe the main experimental and theoretical sources of reconstruction error. We identify the linear line-of-sight geometry of the THz emission spectrometer as the optimal configuration for accurate, fully calibrated THz signal reconstruction. As an example, we apply our reconstruction method to ultrafast THz magnetometry experiment, where we recover the ultrafast magnetization dynamics in a photoexcited iron film, including both its temporal shape and absolute magnitude.