Towards a random laser with cold atoms

TL;DR

This paper explores the feasibility of creating a random laser using cold atoms by examining how scattering and stimulated emission can be combined, demonstrating potential gain mechanisms and thresholds for such a system.

Contribution

It introduces a novel approach to realize a random laser with cold atoms, analyzing gain mechanisms and thresholds, and providing experimental evidence of lasing in this context.

Findings

Efficient combination of gain and scattering in cold atoms.

Experimental demonstration of lasing using different gain mechanisms.

Evaluation of the random laser threshold with cold atoms.

Abstract

Atoms can scatter light and they can also amplify it by stimulated emission. From this simple starting point, we examine the possibility of realizing a random laser in a cloud of laser-cooled atoms. The answer is not obvious as both processes (elastic scattering and stimulated emission) seem to exclude one another: pumping atoms to make them behave as amplifier reduces drastically their scattering cross-section. However, we show that even the simplest atom model allows the efficient combination of gain and scattering. Moreover, supplementary degrees of freedom that atoms offer allow the use of several gain mechanisms, depending on the pumping scheme. We thus first study these different gain mechanisms and show experimentally that they can induce (standard) lasing. We then present how the constraint of combining scattering and gain can be quantified, which leads to an evaluation of the random laser threshold. The results are promising and we draw some prospects for a practical realization of a random laser with cold atoms.