Superradiant lasing in inhomogeneously broadened ensembles with spatially varying coupling

TL;DR

This paper investigates superradiant lasing in inhomogeneously broadened atomic ensembles with spatially varying coupling, analyzing how these factors influence laser power, linewidth, and stability.

Contribution

It introduces a second-order cumulant expansion method to study superradiant lasing considering inhomogeneous broadening and spatial coupling variations.

Findings

Conditions for collective atomic coherence buildup identified

Scaling laws for laser linewidth derived

Limitations due to inhomogeneous broadening discussed

Abstract

Theoretical studies of superradiant lasing on optical clock transitions predict a superb frequency accuracy and precision closely tied to the bare atomic linewidth. Such a superradiant laser is also robust against cavity fluctuations when the spectral width of the lasing mode is much larger than that of the atomic medium. Recent predictions suggest that this unique feature persists even for a hot and thus strongly broadened ensemble, provided the effective atom number is large enough. Here we use a second-order cumulant expansion approach to study the power, linewidth and lineshifts of such a superradiant laser as a function of the inhomogeneous width of the ensemble including variations of the spatial atom-field coupling within the resonator. We present conditions on the atom numbers, the pump and coupling strengths required to reach the buildup of collective atomic coherence as well as scaling and limitations for the achievable laser linewidth.