Electromagnetically induced transparency in inhomogeneously broadened Lambda-transition with multiple excited levels

TL;DR

This paper investigates how multiple excited levels in alkali-metal atoms affect electromagnetically induced transparency (EIT) in hot vapors, revealing that multiple levels reduce transparency but can be mitigated through optical pumping.

Contribution

It introduces a theoretical model accounting for multiple excited levels in EIT and demonstrates how optical pumping can recover transparency in alkali-metal vapors.

Findings

Multiple excited levels significantly reduce EIT transparency.

Optical pumping can restore transparency effectively.

The model aligns with experimental observations in hot vapors.

Abstract

Electromagnetically induced transparency (EIT) has mainly been modelled for three-level systems. In particular, a considerable interest has been dedicated to the Lambda-configuration, with two ground states and one excited state. However, in the alkali-metal atoms, which are commonly used, hyperfine interaction in the excited state introduces several levels which simultaneously participate in the scattering process. When the Doppler broadening is comparable with the hyperfine splitting in the upper state, the three-level Lambda model does not reproduce the experimental results. Here we theoretically investigate the EIT in a hot vapor of alkali-metal atoms and demonstrate that it can be strongly reduced due to the presence of multiple excited levels. Given this model, we also show that a well-designed optical pumping enables to significantly recover the transparency.