Near-total Faraday rotation by the Hall effect in a 2D electron gas

The rotation of electromagnetic wave polarization by a magnetized medium has been of interest in understanding light-matter interactions with broken time-reversal symmetry since Faraday's discovery of the effect. Faraday rotation is typically a weak effect, relying on light-matter interactions that are detuned from resonance to minimize absorption loss. Here we show that a Faraday rotation of 82° can be realized on a single pass through a high mobility two-dimensional electron gas approaching the ideal limit of 90°. Near-total rotation is achieved in the electron gas by the classical Hall effect. Cyclotron resonance loss is minimized and rotation enhanced by the combined effect of operating at frequencies where electron motion is inertial and introducing a reactive electromagnetic element to modify the light-matter coupling. Our work demonstrates that the classical Hall effect could be well suited for engineering non-reciprocal devices that realize uni-directional electromagnetic wave propagation.