Spin noise spectroscopy of optical light shifts

TL;DR

This paper demonstrates that light-induced non-equilibrium spin noise spectroscopy can effectively reveal atomic level structures and coherent effects, including light shifts, through analysis of the spin noise spectrum in metastable helium.

Contribution

It introduces a combined theoretical and experimental approach to detect light shifts via spin noise spectroscopy, providing a simple method to measure and analyze atomic level structures.

Findings

Dual-peak spin noise spectrum observed around Larmor frequency

Light shifts cause the spectral splitting and depend on probe parameters

Modeling accurately reproduces the spectral features

Abstract

Light induced non-equilibrium spin noise spectroscopy is theoretically and experimentally shown to be an efficient technique to reveal the structure and the coherent effects in the probed transition. Indeed, using metastable helium, the spin noise spectrum is shown to exhibit a dual-peak structure around the Larmor frequency. This previously unobserved feature is due to the light shifts of the involved levels and strongly depends on the probe power, detuning, and polarization orientation. Both numerical and analytical models reproduce very well the details of the split spin noise spectra: this technique thus allows a simple and direct measurement of the light shifts, and its polarization dependence permits to reveal the level structure in a non ambiguous manner.