Intensity correlations in transmission and four-wave mixing signals intermediated by hot rubidium atoms

TL;DR

This study explores how atomic velocity distributions in hot rubidium affect intensity correlations in four-wave mixing and transmission signals, revealing oscillatory behaviors linked to Rabi oscillations and validated by a two-level stochastic model.

Contribution

It demonstrates the impact of atomic velocity groups on correlation signals and provides a theoretical model that aligns with experimental observations.

Findings

Correlation signals show oscillatory behavior dependent on incident power.

Atomic velocity groups significantly influence the system's response.

A stochastic two-level model accurately predicts experimental results.

Abstract

We investigate the influence of the distribution of atom velocities in a hot rubidium sample on the correlation between field-intensity fluctuations of two independently generated four-wave mixing signals and between the transmission signals. The nonlinear process is driven by a single cw laser in a pure two-level system due to the forward geometry with circular and parallel polarization of the input fields. The intensity cross-correlations of the four-wave mixing signals and the transmission signals present an oscillatory behavior with a clear dependence on the power of the incident fields, which indicates a connection with Rabi oscillations. A two-level theoretical model using stochastic differential equations to account for the mechanism of conversion of phase noise into amplitude noise shows good agreement with our experimental results. Moreover, we show how the response of the system is affected by the different atomic velocity groups.