Superradiant atomic recoil lasing with orbital angular momentum light

TL;DR

This paper investigates how cold atoms collectively scatter light with orbital angular momentum, leading to atomic rotation and phase bunching, revealing new dynamics in light-matter interactions involving angular momentum transfer.

Contribution

It derives coupled equations for atomic motion under orbital angular momentum light, showing how collective recoil induces rotation and phase bunching in atomic ensembles.

Findings

Atoms become rotationally bunched due to orbital angular momentum transfer.

The system exhibits instability leading to atomic rotation and phase bunching.

The dynamics depend on the pump azimuthal index and ring radius.

Abstract

We analyze the collective light scattering by cold atoms in free space of a pump laser beam possessing orbital angular momentum. We derive a set of coupled equations for the atomic motion in which the vacuum-mode field is adiabatically eliminated. The resulting equations describe collective recoil as due to either transfer of linear momentum or orbital angular momentum. For a transverse annular atomic distribution the initial equilibrium with uniform atomic phases and no scattered field, is unstable. The atoms are set in rotation and bunched in phase at different harmonics depending on the pump azimuthal index l and on the ring radius.