Non-destructive shadowgraph imaging of ultracold atoms

TL;DR

This paper introduces a non-destructive, far-detuned shadowgraph imaging technique for Bose-Einstein condensates that enables high signal-to-noise ratio imaging without heating or atom loss, and can switch to resonant imaging dynamically.

Contribution

The authors present a novel non-destructive imaging method for ultracold atoms that generalizes to various species and allows dynamic switching to resonant imaging during experiments.

Findings

Achieved a signal-to-noise ratio of ~25 at 1 GHz detuning.

Demonstrated no observable heating or atom loss over 100 in-trap images.

Enabled observation of stochastic dynamics trajectories inaccessible to single shot imaging.

Abstract

An imaging system is presented that is capable of far-detuned non-destructive imaging of a Bose-Einstein condensate with the signal proportional to the second spatial derivative of the density. Whilst demonstrated with application to $^{85}\text{Rb}$, the technique generalizes to other atomic species and is shown to be capable of a signal to noise of ${\sim}25$ at $1$GHz detuning with $100$ in-trap images showing no observable heating or atom loss. The technique is also applied to the observation of individual trajectories of stochastic dynamics inaccessible to single shot imaging. Coupled with a fast optical phase lock loop, the system is capable of dynamically switching to resonant absorption imaging during the experiment.