Near source fluorescence spectroscopy for miniaturized thermal atomic beams

TL;DR

This paper introduces a near-source fluorescence spectroscopy technique to characterize miniature thermal atomic beams close to their source, enabling detailed analysis of beam properties even under strong laser saturation conditions.

Contribution

It presents a novel NSFS method and a predictive recipe for fluorescence spectra, accounting for optical pumping and laser beam effects, validated by theory and experiments.

Findings

Accurate characterization of atomic beam angular distribution.

Agreement between theoretical models and experimental data.

Resolved beam details over three decades of flux variation.

Abstract

Miniature atomic beams can provide new functionalities for atom based sensing instruments such as atomic clocks and interferometers. We recently demonstrated a planar silicon device for generating well-collimated thermal atomic beams [Nat Commun 10, 1831 (2019)]. Here, we present a near-source fluorescence spectroscopy (NSFS) technique that can fully characterize such miniature beams even when measured only a few millimeters from the nozzle exit. We also present a recipe for predicting the fluorescence spectrum, and therefore, the source angular distribution, even under conditions of strong laser saturation of the probing transition. Monte Carlo simulations together with multi-level master equation calculations fully account for the influence of optical pumping and spatial extension of the Gaussian laser beam. A notable consequence of this work is the agreement between theory and experimental data that has allowed fine details of the angular distribution of the collimator to be resolved over 3 decades of dynamic range of atomic beam output flux.