arXiv:0906.0571 · Physical Review A
Electromagnetically induced transparency versus nonlinear Faraday effect: Coherent control of light-beam polarization
Rafael Drampyan, Szymon Pustelny, Wojciech Gawlik
Abstract
We report on experimental and theoretical study of the nonlinear Faraday effect under conditions of electromagnetically induced transparency at the $5{S}_{1/2}\ensuremath{\rightarrow}5{P}_{3/2}\ensuremath{\rightarrow}5{D}_{5/2}$ two-photon transition in rubidium vapor. These transitions realize the inverted $Y$ model which combines the $\ensuremath{\Lambda}$ and ladder systems. Strong nonlinearity allowing for large rotation angles of a probe beam tuned to the $S\ensuremath{\rightarrow}P$ transition was obtained by creation of quantum superpositions of magnetic sublevels (Zeeman coherences) in the rubidium ground state ($\ensuremath{\Lambda}$ scheme). Additionally, electromagnetically induced transparency was accomplished in a ladder scheme by acting with a second strong coupling laser on the $P\ensuremath{\rightarrow}D$ transition. Under conditions of a two-photon resonance the rotation was significantly reduced, which is interpreted as a competition between the coherent 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.