# In-situ Raman gain between hyperfine ground states in a potassium magneto-optical trap

## TL;DR

This paper demonstrates in-situ Raman gain in a cold potassium gas within a magneto-optical trap, revealing stimulated Raman scattering between hyperfine ground states without extra fields, supported by a six-level model.

## Contribution

It presents the first observation of in-situ Raman gain in a MOT of potassium atoms, explaining the unique conditions enabling this gain compared to rubidium or cesium.

## Key findings

- Raman gain occurs during standard MOT operation without additional fields.
- The gain results from stimulated Raman scattering between hyperfine ground states.
- A six-level model accurately reproduces the experimental observations.

## Abstract

We study optical gain in a gas of cold 39K atoms. The gain is observed during operation of a conventional magneto-optical trap without the need for additional fields. Measurements of transmission spectra from a weak probe show that the gain is due to stimulated Raman scattering between hyperfine ground states. The experimental results are reproduced by a simplified six-level model, which also helps explain why such gain is not observed in similar experiments with rubidium or cesium.