Guided atom laser: transverse mode quality and longitudinal momentum distribution

TL;DR

This paper investigates the outcoupling process of a Bose-Einstein condensate into a guide, analyzing how interactions affect the mode quality and momentum distribution of a guided atom laser, with implications for optimizing its coherence and flux.

Contribution

It provides a theoretical analysis of the outcoupling process considering non-adiabatic effects and interactions, offering strategies to improve the mode quality and flux of guided atom lasers.

Findings

Interactions limit the transverse mode quality of guided atom lasers.

Optimal outcoupling strategies can minimize longitudinal velocity dispersion.

The analysis aligns with experimental observations of low transverse excitations.

Abstract

We analyze the outcoupling of a matter wave into a guide by a time-dependent spilling of the atoms from an initially trapped Bose-Einstein condensate. This process yields intrinsically a breakdown of the adiabatic condition that triggers the outcoupling of the wave function. Our analysis of the time-dependent engineering and manipulation of condensates in momentum space in this context enables to work out the limits due to interactions in the mode quality of a guided atom laser. This study is consistent with recent experimental observations of low transverse excitations of guided atom lasers and suggests (i) an optimal strategy to realize such quasi-monomode guided atom lasers with, in addition, the lowest possible longitudinal velocity dispersion, or alternatively (ii) a strategy for engineering the atomic flux of the atom laser.