The phase shift induced by a single atom in free space

TL;DR

This paper theoretically investigates how a single atom in free space causes a measurable phase shift on a coherent light beam, highlighting the roles of focusing geometry and radiation overlap in the interaction.

Contribution

It introduces a semiclassical model to analyze the phase shift induced by a single atom, including saturation effects and Kerr non-linearity considerations.

Findings

Phase shift depends on solid angle and radiation overlap.

Saturation effects influence the phase shift magnitude.

Kerr-type non-linearity is associated with the atomic response.

Abstract

In this article we theoretically study the phase shift a single atom imprints onto a coherent state light beam in free space. The calculations are performed in a semiclassical framework. The key parameters governing the interaction and thus the measurable phase shift are the solid angle from which the light is focused onto the atom and the overlap of the incident radiation with the atomic dipole radiation pattern. The analysis includes saturation effects and discusses the associated Kerr-type non-linearity of a single atom.