Twisted-ligth--ion interaction: the role of longitudinal fields

TL;DR

This paper demonstrates that longitudinal electric field components are crucial for accurately describing the interaction of twisted light with matter, especially in inhomogeneous fields, by comparing experimental data with a complete model.

Contribution

It introduces a comprehensive model including longitudinal fields to explain twisted light interactions, surpassing the traditional paraxial approximation.

Findings

Complete model matches experimental data within 11 standard deviations.

Longitudinal field components are essential for accurate light-matter interaction descriptions.

Paraxial approximation fails for strongly inhomogeneous or shaped light fields.

Abstract

The propagation of light beams is well described using the paraxial approximation, where field components along the propagation direction are usually neglected. For strongly inhomogeneous or shaped light fields, however, this approximation may fail, leading to intriguing variations of the light-matter interaction. This is the case of twisted light having opposite orbital and spin angular momenta. We compare experimental data for the excitation of a quadrupole transition in a single trapped $^{40}$Ca$^+$ ion by Schmiegelow et al, Nat.\ Comm.\ 7, 12998 (2016), with a complete model where longitudinal components of the electric field are taken into account. Our model matches the experimental data and excludes by 11 standard deviations the approximation of complete transverse field. This demonstrates the importance of all field components in the interaction of twisted light with matter.