Coherent Optical Processes on Cs D$_2$ line Magnetically Induced Transitions

TL;DR

This paper investigates magnetically-induced transitions in cesium vapor using thin cells, demonstrating how specific polarization configurations enable electromagnetically induced transparency, with implications for miniaturized atomic sensors.

Contribution

It reveals the polarization-dependent conditions for EIT involving MI transitions in Cs vapor, highlighting the role of magnetic circular dichroism in these processes.

Findings

EIT occurs only with specific circular polarizations for MI transitions.

High magnetic field slopes enable sensitive EIT resonances.

Magnetic circular dichroism influences EIT in thin vapor cells.

Abstract

The increased spectral resolution allowed by the use of extremely thin vapor cells has led to the observation of interesting behaviour of alkali transitions when placed in a magnetic field. Particularly, transitions obeying an apparent $F_e-F_g\equiv\Delta F =\pm2$ selection rule, referred to as magnetically-induced (MI) transitions, have their probabilities largely increase in the intermediate interaction regime while being null at zero and higher magnetic fields. With an 800 nm-thick Cs vapor cell placed in a field up to 1.5 kG, we show here that the generation of electromagnetically induced transparency (EIT), realized in $\Lambda$-systems involving $\Delta F =- 2$ MI transitions, is only possible when both the coupling and probe beams are $\sigma^-$-circular polarized, demonstrating that EIT is affected by magnetic circular dichroism. A similar rule of thumb can be extrapolated for $\Delta F =+2$ MI transitions and $\sigma^+$ polarization. Because of the high frequency shift slope (typ. 4 MHz/G), the generation of EIT resonances involving MI transitions is interesting, especially in the context of growing attention towards micro-machined alkali vapor cell sensors.