Ground-state Hanle effect based on atomic alignment

Abstract

We have studied the ground-state Hanle effect (GSHE) excited by linearly polarized laser light on the $D$${}_{1}$ line of cesium atoms. We have solved algebraically the Liouville equation using the irreducible tensor formalism, and derive an analytical expression for the resonance line shapes in a magnetic field of arbitrary direction. The model predictions are in excellent agreement with experimental observations in various field geometries. Our model is valid for arbitrary $F\ensuremath{\rightarrow}{F}^{\ensuremath{'}}$ transitions in the low-power limit. We discuss the relation between the GSHE and electromagnetically induced transparency or absorption. Our approach allows a full understanding of the mechanism of the GSHE and provides tools for quantifying the resonance contrast, a crucial parameter for metrological applications of level crossing resonances.