Structured beams invariant to coherent diffusion

TL;DR

This paper demonstrates that certain structured non-diffracting laser fields, such as Bessel beams, are also immune to diffusion effects, with experiments mapping their phase and magnitude onto atomic coherence.

Contribution

It introduces the concept that non-diffracting fields can be invariant to diffusion, supported by experimental mapping onto atomic states and quantitative analysis.

Findings

Non-diffracting fields are immune to diffusion effects.

Diffusion invariance is linked to the phase structure of the fields.

Flattened phase patterns lose diffusion invariance.

Abstract

Bessel beams are renowned members of a wide family of non-diffracting (propagation-invariant) fields. We report on experiments showing that non-diffracting fields are also immune to diffusion. We map the phase and magnitude of structured laser fields onto the spatial coherence between two internal states of warm atoms undergoing diffusion. We measure the field after a controllable, effective, diffusion time by continuously generating light from the spatial coherence. The coherent diffusion of Bessel-Gaussian fields and more intricate, non-diffracting fields is quantitatively analyzed and directly compared to that of diffracting fields. To elucidate the origin of diffusion invariance, we show results for non-diffracting fields whose phase pattern we flatten.