里德伯电磁感应透明中的相位

Phase in Rydberg electromagnetically induced transparency

本文在典型的里德伯电磁感应透明系统中研究弱探测场在相互作用原子系统中的传播特性,重点关注基于偶极阻塞效应的探测场相位的合作光学非线性行为.通过与探测场透射率和光子关联作对比,发现相位的光学响应具有新特性:共振和Autler-Townes劈裂条件下相位对入射场强和初始光子关联不敏感,而在两者之间的频率范围内相位响应具有非线性特征,尤其在经典光频率处最显著.此外,提高主量子数和原子密度都会促进相位的非线性效应.综上,与探测场透射率和光子关联一样,相位可以作为合作光学非线性的另一个标识来刻画非线性现象,对里德伯电磁感应透明研究是一个有力的补充.

Transmission properties of a weak probe field traveling through a sample of interacting cold 87 Rb atoms driven into the three-level ladder configuration,which is a typical Rydberg electromagnetically induced transparency(EIT)system,are investigated.Rydberg atoms are considered to be a perfect platform in the research fields of quantum optics and quantum information processing due to some exaggerated properties of Rydberg atoms with high principal quantum number,especially,the dipole-dipole interaction between Rydberg atoms leads to the so-called dipole blockade effect accommodating at most one Rydberg excitation within a mesoscopic volume.The dipole blockade effect may be mapped onto the spectrum of EIT,and the EIT exhibits the cooperative optical nonlinearity which is usually characterized by two indicators,i.e.,the probe intensity and the photonic correlation.The cooperative optical nonlinearity is also found here in the phase of transmission spectrum,and the phase can be regarded as the third indicator of nonlinearity in Rydberg EIT.However,there are tremendous differences between the phase and probe transmission(photonic correlation)though they both originate from the conditional polarization.Specifically,the phase is not sensitive to neither the incident probe intensity nor the initial photonic correlation at the resonant probe frequency under the condition of the Autler-Townes(AT)splitting where two other indicators exhibit significant cooperative nonlinearity.The nonlinearity in phase spectrum occurs only in the regime between the resonant probe frequency and the AT splitting and especially is remarkable at the frequency where the probe field is classical.Finally,influence of the principal quantum number and the atomic density on the transmitted phase are examined.In the nonlinear regime,the absolute value of the phase becomes smaller and smaller as the principal quantum number and the atomic density are raised.This indicates that the nonlinearity is strengthened by increasing them.The probe phase provides an attractive supplement to study in depth the cooperative optical nonlinearity in Rydberg EIT and offers us the considerable flexibility to manipulate the propagation and evolution of a quantum light field.