We report the experimental observation of strong two-color optical nonlinearity in an ultracold gas of ${}^{85}\mathrm{Rb}\text{−}{}^{87}\mathrm{Rb}$ atom mixture. By simultaneously coupling two probe transitions of ${}^{85}\mathrm{Rb}$ and ${}^{87}\mathrm{Rb}$ 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 $\sim 1\mathrm{GHz}$ 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 develop. 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 multicomponent fluids of light.

中文翻译：

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超冷Rydberg原子气体混合物中的双色光学非线性

我们报告了在超冷气体中强双色光学非线性的实验观察 ${}^{85}b\text{-}{}^{87}b$原子混合物。通过同时耦合两个探头转换${}^{85}b$ 和 ${}^{87}b$ 电磁感应透明（EIT）构型中的原子转变为Rydberg态，我们观察到当第二个探测场在失谐状态下对一个探测场的透明共振具有明显的抑制作用 $〜\mathrm{1个}\mathrm{兆赫}$并击中其他同位素的EIT共振。这种对光束传播动力学的交叉吸收调制可以通过我们开发的两个耦合的非线性波动方程来描述。我们进一步证明，可以通过改变不同原子同位素的密度比来调整双色光学非线性，这突出了其探索强相互作用的光多组分流体的潜力。