Spin noise spectroscopy under resonant optical probing conditions: coherent and non-linear effects

TL;DR

This paper investigates how resonant and non-resonant optical probing affect spin noise in rubidium atoms, revealing coherent and collective effects through advanced spectroscopy and extended Bloch equation modeling.

Contribution

It provides new insights into spin noise behavior under resonant conditions, highlighting the role of coherent coupling and collective effects in excited states.

Findings

Clear signatures of coherent electronic level coupling in spin noise spectra

Spin noise from excited states shows collective effects at high intensities

Extended Bloch equations explain the observed spectral features

Abstract

High sensitivity Faraday rotation spectroscopy is used to measure the fluctuating magnetization noise of non-interacting rubidium atoms under resonant and non-resonant optical probing conditions. The spin noise frequency spectra in dependence on the probe light detuning with respect to the D2-transition reveals clear signatures of a coherent coupling of the participating electronic levels. The results are explained by extended Bloch equations including homogeneous and inhomogeneous broadening mechanisms. Our measurements further indicate that spin noise originating from excited states are governed at high intensities by collective effects.