Prospects for a mHz-linewidth laser

TL;DR

This paper proposes a novel laser source using alkaline-earth atoms in an optical lattice to produce ultra-narrow linewidth light in the mHz range, significantly enhancing clock stability.

Contribution

It introduces a new collective emission scheme for ultra-narrow linewidth lasers based on atomic ensembles in optical cavities.

Findings

Linewidths in the mHz range achievable

Power levels around 10^{-12} W demonstrated

Potential to improve clock stability by two orders of magnitude

Abstract

We propose a new light source based on having alkaline-earth atoms in an optical lattice collectively emit photons on an ultra-narrow clock transition into the mode of a high Q-resonator. The resultant optical radiation has an extremely narrow linewidth in the mHz range, even smaller than that of the clock transition itself due to collective effects. A power level of order $10^{-12}W$ is possible, sufficient for phase-locking a slave optical local oscillator. Realizing this light source has the potential to improve the stability of the best clocks by two orders of magnitude.