We demonstrate the detection of broadband intense terahertz electromagnetic pulses by Zeeman-torque sampling (ZTS). Our approach is based on magneto-optic probing of the Zeeman torque that the terahertz magnetic field exerts on the magnetization of a ferromagnet. Using an 8-nm-thick iron film as a sensor, we detect pulses from a silicon-based spintronic terahertz emitter with a bandwidth of 0.1–11 THz and a peak field of >0.1 MV/cm. A simple static magneto-optic calibration measurement provides access to absolute transient terahertz field strengths. We show the relevant added value of ZTS compared to electro-optic sampling (EOS): an echo-free transfer function with simple frequency dependence, linearity even at high terahertz-field amplitudes, the straightforward calibration of EOS response functions, and modulation of the polarization-sensitive direction by an external ac magnetic field. Consequently, ZTS has interesting applications even beyond the accurate characterization of broadband high-field terahertz pulses for nonlinear terahertz spectroscopy.

• Received 15 June 2023
• Revised 10 August 2023
• Accepted 17 August 2023

DOI:https://doi.org/10.1103/PhysRevApplied.20.034037

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

Published by the American Physical Society