Ultrafast Electron Temperature Dynamics in Spintronic Terahertz Emitters Studied by Optical-Pump Terahertz-Probe Spectroscopy

TL;DR

This study uses optical-pump terahertz-probe spectroscopy to measure ultrafast electron temperature dynamics in spintronic terahertz emitters, providing insights into thermal effects that influence their performance and damage thresholds.

Contribution

It introduces a novel method to directly measure electron temperature dynamics in STEs, enhancing understanding of thermal relaxation without additional heating from the probe.

Findings

Electron temperature changes can be monitored via terahertz transmission.

The two-temperature model effectively describes electron-lattice relaxation.

This method helps assess cumulative heating effects in STEs.

Abstract

Spintronic terahertz emitters (STEs) pumped by femtosecond lasers have become a widely used source of broadband terahertz radiation. However, the strength of the emitted field is limited in part by the optical damage threshold at the pump wavelength. Thermal management of STEs can be improved by understanding electron temperature relaxation in the spintronic metal layer. Here, we present a measurement of electron temperature dynamics on a picosecond timescale using optical-pump terahertz-probe spectroscopy. We observe that the optical pump induces a change in terahertz transmission through the STE. By analyzing the resulting signal with a two-temperature model, we extract the dynamic electron temperature of the STE. This approach offers an advantage over other methods by avoiding additional heating of the sample by the probe pulse, making it particularly suitable for studying cumulative heating effects, which are believed to contribute to optical damage under MHz repetition rate pumping.