Coherence time of a cold-atom laser below threshold

TL;DR

This paper experimentally investigates the coherence time of a below-threshold cold-atom Raman laser, demonstrating how gain control influences photon coherence and lifetime, with results aligning with a simple analytic model.

Contribution

It provides the first detailed experimental analysis of coherence time in a cold-atom laser below threshold, highlighting gain effects over dispersion.

Findings

Photon bunching correlation time varies with gain by two orders of magnitude.

Photon lifetime increases with gain, indicating enhanced coherence.

Results agree with a simple analytic model emphasizing gain dominance.

Abstract

We experimentally study the coherence time of a below-threshold Raman laser in which the gain medium is a gas of magneto-optically trapped atoms. The second-order optical coherence exhibits photon bunching with a correlation time which is varied by two orders of magnitude by controlling the gain. Results are in good agreement with a simple analytic model which suggests the effect is dominated by gain, rather than dispersion, in this system. Cavity ring-down measurements show the photon lifetime, related to the first-order coherence time, is also increased.