Spatial dynamics of laser-induced fluorescence in an intense laser beam: experiment and theory in alkali metal atoms

TL;DR

This study combines experimental and theoretical approaches to understand the spatial and optical phenomena in intense laser fields interacting with alkali metal atoms, emphasizing the importance of intensity distribution modeling.

Contribution

It introduces a novel model dividing laser beams into concentric regions with tailored Rabi frequencies, accurately predicting magneto-optical resonance and fluorescence spatial profiles.

Findings

The model agrees well with experimental resonance curves up to 200 mW/cm².

Spatial fluorescence profiles match theoretical predictions qualitatively.

The approach improves understanding of laser-atom interactions in intense fields.

Abstract

We have shown that it is possible to model accurately optical phenomena in intense laser fields by taking into account the intensity distribution over the laser beam. We developed a theoretical model that divided an intense laser beam into concentric regions, each with a Rabi frequency that corresponds to the intensity in that region, and solved a set of coupled optical Bloch equations for the density matrix in each region. Experimentally obtained magneto-optical resonance curves for the $F_g=2\longrightarrow F_e=1$ transition of the $D_1$ line of $^{87}$Rb agreed very well with the theoretical model up to a laser intensity of around 200 mW/cm$^2$ for a transition whose saturation intensity is around 4.5 mW/cm$^2$. We have studied the spatial dependence of the fluorescence intensity in an intense laser beam experimentally and theoretically. An experiment was conducted whereby a broad, intense pump laser excited the $F_g=4\longrightarrow F_e=3$ transition of the $D_2$ line of cesium while a weak, narrow probe beam scanned the atoms within the pump beam and excited the $D_1$ line of cesium, whose fluorescence was recorded as a function of probe beam position. Experimentally obtained spatial profiles of the fluorescence intensity agreed qualitatively with the predictions of the model.