Two-Color Optical Nonlinearity in an Ultracold Rydberg Atom Gas Mixture

TL;DR

This paper demonstrates strong two-color optical nonlinearity in an ultracold Rb atom mixture, showing cross-absorption modulation and tunability via isotope density ratios, with potential applications in multi-component light fluids.

Contribution

It provides the first experimental observation of two-color optical nonlinearity in a Rydberg atom mixture and develops coupled wave equations to describe the phenomenon.

Findings

Significant suppression of EIT resonance due to cross-absorption.

Nonlinearity can be tuned by adjusting isotope density ratios.

Potential for exploring multi-component strongly interacting light fluids.

Abstract

We report the experimental observation of strong two-color optical nonlinearity in an ultracold gas of $^{85}\mathrm{Rb}$-$^{87}\mathrm{Rb}$ atom mixture. By simultaneously coupling two probe transitions of $^{85}$Rb and $^{87}$Rb atoms to Rydberg states in electromagnetically induced transparency (EIT) configurations, we observe significant suppression of the transparency resonance for one probe field when the second probe field is detuned at $\sim1~\mathrm{GHz}$ and hitting the EIT resonance of the other isotope. Such a cross-absorption modulation to the beam propagation dynamics can be described by two coupled nonlinear wave equations we develope. We further demonstrate that the two-color optical nonlinearity can be tuned by varying the density ratio of different atomic isotopes, which highlights its potential for exploring strongly interacting multi-component fluids of light.