A Femtosecond Magnetic Circular Dichroism Spectrometer

TL;DR

This paper presents a novel broadband femtosecond magneto-optical spectrometer capable of measuring static and transient magneto-optical spectra with high sensitivity, applicable to various samples using a simple setup.

Contribution

The development of a broadband femtosecond magneto-optical spectrometer with shot-to-shot referencing and high sensitivity, enabling detailed static and transient magneto-optical measurements.

Findings

Achieved static magneto-optical sensitivity of 5 mdeg.

Achieved transient magneto-optical sensitivity of 0.4 mdeg.

Demonstrated applicability to solution-based and thin-film samples.

Abstract

We describe the development of a broadband magneto-optical spectrometer with femtosecond temporal resolution. The absorption spectrometer is based on a white-light supercontinuum (ca. 320 - 750 nm) using shot-to-shot temporal and spectral referencing at 1 kHz. Static and transient absorption spectra using circularly polarised light are collected in a magnetic field. The difference spectra with respect to the external field direction give the static and transient magneto-optical Faraday rotation (magnetic optical rotary dispersion) and ellipticity (magnetic circular dichroism) spectra. An achromatic quarter-wave plate is used and the impact of the deviation from ideal retardance on the spectra is discussed. Results from solution-based and thin-film samples are used to demonstrate the performance and wide applicability of the instrument. The sensitivities for the static and time-resolved data were found to be 5 and 0.4 mdeg, respectively. The method presents a simple way to measure magneto-optical spectra using a transient absorption spectrometer and an electromagnet.