Electromagnetically Induced Transparency versus Nonlinear Faraday Effect. Coherent Control of the Light Beam Polarization

TL;DR

This paper explores the interplay of electromagnetically induced transparency and nonlinear Faraday effect in rubidium vapors, demonstrating coherent control of light polarization through experimental and theoretical analysis of quantum superpositions and magnetic field effects.

Contribution

It presents a combined experimental and theoretical study of EIT and nonlinear Faraday effect in rubidium, revealing how two-photon resonance influences polarization rotation and coherence control.

Findings

Large polarization rotation achieved via Zeeman coherences.

EIT reduces Faraday rotation at two-photon resonance.

Potential for coherent control of light polarization in quantum optics.

Abstract

We report on experimental and theoretical study of the nonlinear Faraday effect under conditions of electromagnetically induced transparency at the 5$S_{1/2} \to 5P_{3/2} \to 5D_{5/2}$ two-photon transition in rubidium vapors. These transitions realize the inverted Y model which combines the $\Lambda$ and ladder systems. Strong nonlinearity allowing for large rotation angles of a probe beam tuned to the $S\to P$ transition was obtained by creation of quantum superpositions of magnetic sublevels (Zeeman coherences) in the rubidium ground state ($\Lambda$ scheme). Additionally, electromagnetically induced transparency was accomplished in a ladder scheme by acting with an additional strong coupling laser on the $P\to D$ transition. Under conditions of a two-photon resonance the rotation was significantly reduced, which is interpreted as a competition between the two processes. The effect was observed in sub-Gauss magnetic fields and could be used for efficient coherent control of generation of the ground-state coherences, e.g. for controlling the polarization state of the probe light.