Polarization Transfer from the Twisted Light to an Atom

TL;DR

This paper investigates how twisted light with orbital angular momentum transfers polarization to atoms, revealing a one-to-one correspondence for dipole transitions and complexities for higher multipolarity transitions.

Contribution

It introduces a parameterization of twisted light's polarization and derives formulas for atomic response, highlighting differences between dipole and higher multipolarity transitions.

Findings

Atomic polarization matches incident light for dipole transitions.

Higher multipolarity transitions show deviations from simple polarization transfer.

Longitudinal electric field contributions are significant in atomic transition matrix elements.

Abstract

When polarized light is absorbed by an atom, the excited atomic system carries information about the initial polarization of light. For the light that carries an orbital angular momentum, or the twisted light, the polarization states are described by eight independent parameters, as opposed to three Stokes parameters for plane waves. We use a parameterization of the spin-density matrix of the twisted light in terms of vector and tensor polarization, in analogy with massive spin-1 particles, and derive formulae that define atom's response to specific polarization components of the twisted light. It is shown that for dipole ($S\to P$) atomic transitions, the atom's polarization is in one-to-one correspondence with polarization of the incident light; this relation is violated, however, for the transitions of higher multipolarity ($S\to D$, $S\to F$, etc.) We pay special attention to contributions of the longitudinal electric field into the matrix elements of atomic transitions.