Thermalization of coupled atom-light states in the presence of optical collisions

TL;DR

This paper investigates the thermalization process of coupled atom-light states in the presence of optical collisions, combining theoretical modeling with experimental validation to understand how these states reach equilibrium.

Contribution

It introduces a model for atomic dressed state thermalization considering spontaneous emission and validates it through experiments with rubidium atoms under high-pressure buffer gas conditions.

Findings

Thermalization time depends on detuning and Rabi frequency.

Thermalization occurs in nanoseconds, much shorter than natural lifetime.

Detuning influences the saturated lineshape and sideband intensities.

Abstract

The interaction of a two-level atomic ensemble with a quantized single mode electromagnetic field in the presence of optical collisions (OC) is investigated both theoretically and experimentally. The main accent is made on achieving thermal equilibrium for coupled atom-light states (in particular dressed states). We propose a model of atomic dressed state thermalization that accounts for the evolution of the pseudo-spin Bloch vector components and characterize the essential role of the spontaneous emission rate in the thermalization process. Our model shows that the time of thermalization of the coupled atom-light states strictly depends on the ratio of the detuning and the resonant Rabi frequency. The predicted time of thermalization is in the nanosecond domain and about ten times shorter than the natural lifetime at full optical power in our experiment. Experimentally we are investigating the interaction of the optical field with rubidium atoms in an ultra-high pressure buffer gas cell under the condition of large atom-field detuning comparable to the thermal energy in frequency units. In particular, an observed detuning dependence of the saturated lineshape is interpreted as evidence for thermal equilibrium of coupled atom-light states. A significant modification of sideband intensity weights is predicted and obtained in this case as well.