Faraday and Cotton-Mouton Effects of Helium at $\lambda = 1064$ nm

TL;DR

This study measures the Faraday and Cotton-Mouton effects of helium at 1064 nm using a high-finesse optical cavity, providing the first experimental Faraday value at this wavelength and confirming theoretical predictions for the Cotton-Mouton effect.

Contribution

First experimental measurement of the Faraday effect at 1064 nm and improved agreement with theory for the Cotton-Mouton effect in helium.

Findings

Faraday effect value at 1064 nm compatible with theory

Cotton-Mouton effect measurement agrees with predictions within 1σ

Optical cavity enhances measurement sensitivity by over 270,000 times

Abstract

We present measurements of the Faraday and the Cotton-Mouton effects of helium gas at $\lambda =~1064$\,nm. Our apparatus is based on an up-to-date resonant optical cavity coupled to longitudinal and transverse magnetic fields. This cavity increases the signal to be measured by more than a factor of 270\,000 compared to the one acquired after a single path of light in the magnetic field region. We have reached a precision of a few percent both for Faraday effect and Cotton-Mouton effect. Our measurements give for the first time the experimental value of the Faraday effect at $\lambda$=\,1064\,nm. This value is compatible with the theoretical prediction. Concerning Cotton-Mouton effect, our measurement is the second reported experimental value at this wavelength, and the first to agree at better than 1$\sigma$ with theoretical predictions.