Observation of mechanical Faraday effect in gas media

TL;DR

This paper reports the first experimental observation of the mechanical Faraday effect in gases, where ultrafast molecular rotation induces polarization rotation of light, demonstrating optical control and robustness under ambient conditions.

Contribution

It provides the first experimental evidence of the mechanical Faraday effect in gas media using ultrafast molecular rotation induced by an optical centrifuge.

Findings

Observed polarization rotation angles of about 0.2 milliradians.

Demonstrated all-optical control of the polarization drag.

Showed robustness of the effect against molecular collisions.

Abstract

We report the experimental observation of the rotation of the polarization plane of light propagating in a gas of fast-spinning molecules (molecular super-rotors). In the observed effect, related to Fermi's prediction of "polarization drag" by a rotating medium, the vector of linear polarization tilts in the direction of molecular rotation due to the rotation-induced difference in the refractive indices for the left and right circularly polarized components. We use an optical centrifuge to bring the molecules in a gas sample to ultrafast unidirectional rotation and measure the polarization drag angles of the order of 0.2 milliradians in a number of gases under ambient conditions. We demonstrate an all-optical control of the drag magnitude and direction, and investigate the robustness of the mechanical Faraday effect with respect to molecular collisions.