Optical forces on atoms subject to higher-order Poincar\'e vortex modes

TL;DR

This paper investigates how higher-order Poincaré vortex modes of light influence atomic forces, revealing complex interactions depending on mode order, polarization, and atomic transitions, with analytical results for sodium atoms.

Contribution

It provides a comprehensive analytical framework for optical forces on atoms in higher-order Poincaré vortex modes, unifying polarization and mode order effects.

Findings

Optical forces vary with mode order and polarization.

Analytical expressions derived for sodium atom interactions.

Multiple physical scenarios depending on mode parameters.

Abstract

The interaction of atoms with higher-order Poincar\'e optical vortex modes of order $m\geq 0$ is explored for light close to resonance with atomic dipole transitions. It is well-known that atoms subject to optical vortex modes experience both translational and rotational forces acting on the atomic centre of mass, leading to atom dynamics and atom trapping. Here we consider the optical forces on atoms immersed in general paraxial higher-order Poincar\'e optical vector modes. The coupling to atoms gives rise to wide-ranging scenarios involving such modes in which any specific polarisation is within a spectrum of wave polarisation and all the interactions are treatable within a single formulation. We show that this gives rise to a variety of physical situations, governed by the mode order $m$, the polarisation represented by the angular coordinates of the mode on the surface of the unit Poincar\'e sphere, the atomic transitions involved, and their selection rules. We present the analytical steps leading to the optical forces on sodium atoms and display their variations in various situations.