A High-Flux and High-Efficiency Setup for Magneto-Infrared Spectroscopy

TL;DR

This paper presents a highly efficient and flux-optimized magneto-infrared spectroscopy system that enhances measurement sensitivity and throughput in high magnetic fields, enabling detailed studies of subtle spectral features.

Contribution

The authors designed and implemented a novel setup with improved optical throughput and automation, significantly advancing broadband measurements in high magnetic fields compared to previous systems.

Findings

Achieved a noise level of 0.0061% in 2 minutes for a 40% reflectivity sample.

Enhanced collection efficiency by nearly an order of magnitude.

Demonstrated capability by resolving weak spectral features in EuCd2As2 and LaAlSi.

Abstract

We report the design and implementation of a high-flux, high-efficiency magneto-infrared spectroscopy system optimized for broadband measurements in high magnetic fields. The setup integrates a Fourier transform infrared spectrometer, a 12 T cryogen-free superconducting magnet, precision-polished and gold-plated light tubes, custom-designed reflective focusing modules for Faraday and Voigt geometries, and an external multi-detector chamber with motorized selection. Optical throughput is maximized by reducing light tube loss from 65.5%/m to 22.0%/m via abrasive flow and mechanical polishing followed by gold electroplating, and by adopting a single-on-axis parabolic-mirror Faraday module that increases the effective numerical aperture from 0.14 to 0.36, enhancing collection efficiency by nearly an order of magnitude. An eight-position motorized sample stage and fully automated control over magnetic field, temperature, optical path, and detector choice enable high-throughput measurements without repeated warm-ups. The optimized configuration achieves a root-mean-square noise level of 0.0061% in a 2-minute integration for a 40% reflectivity sample, corresponding to a signal-to-noise ratio exceeding 16000. System capabilities are demonstrated by resolving weak replica bands in EuCd2As2 and faint Landau level transitions in LaAlSi.