Electromagnetically induced transparency and four-wave mixing in a cold atomic ensemble with large optical depth

TL;DR

This paper demonstrates significant optical pulse delay using electromagnetically induced transparency in cold atomic ensembles with high optical depth, analyzing the effects of four-wave mixing in different rubidium isotopes.

Contribution

It provides a detailed experimental comparison of EIT and four-wave mixing effects in rubidium 85 and 87, achieving high delay-bandwidth products and multimode delay capabilities.

Findings

Achieved a 50% efficiency delay with a single pulse in rubidium 87.

Observed four-wave mixing effects in rubidium 85 that enhance delay performance.

Demonstrated temporal multimode delay by compressing two pulses into the medium.

Abstract

We report on the delay of optical pulses using electromagnetically induced transparency in an ensemble of cold atoms with an optical depth exceeding 500. To identify the regimes in which four-wave mixing impacts on EIT behaviour, we conduct the experiment in both rubidium 85 and rubidium 87. Comparison with theory shows excellent agreement in both isotopes. In rubidium 87, negligible four-wave mixing was observed and we obtained one pulse-width of delay with 50% efficiency. In rubidium 85, four-wave-mixing contributes to the output. In this regime we achieve a delay-bandwidth product of 3.7 at 50% efficiency, allowing temporally multimode delay, which we demonstrate by compressing two pulses into the memory medium.