Near-resonant optical forces beyond the two-level approximation for a continuous source of spin-polarized cold atoms

TL;DR

This paper introduces a novel method to generate a continuous, spin-polarized cold atom source using a three-level atomic system and optical forces beyond the two-level approximation, with potential applications in atom interferometry.

Contribution

It extends the dressed-atom model to three-level systems and demonstrates a practical setup for guiding spin-polarized atoms over centimeters.

Findings

Significant fraction of atoms can be guided over several centimeters

Atoms achieve output velocities of a few meters per second

Method enables continuous, collimated spin-polarized atom source

Abstract

We propose a method to generate a source of spin-polarized cold atoms which are continuously extracted and guided from a magneto-optical trap using an atom-diode effect. We show that it is possible to create a pipe-like potential by overlapping two optical beams coupled with the two transitions of a three-level system in a ladder configuration. With alkali-metal atoms, and in particular with $^{87}$Rb, a proper choice of transitions enables both the potential generation and optical pumping, thus polarizing the sample in a given Zeeman state. We extend the Dalibard and Cohen-Tannoudji dressed-atom model of radiative forces to the case of a three-level system. We derive expressions for the average force and the different sources of momentum diffusion in the resonant, non-perturbative regime. We show using numerical simulations that a significant fraction of the atoms initially loaded can be guided over several centimeters with output velocities of a few meters per second. This would produce a collimated continuous source of slow spin-polarized atoms suitable for atom interferometry.