四能级Tripod原子系统中相干增强的非线性效应

Coherently Enhanced Nonlinear Effect in a Four-level Tripod Atomic System

大的交叉Kerr非线性(又称交叉相位调制(XPM))在量子信息处理中有着非常重要的应用。在热铷原子D1线构建的四能级Tripod系统中,开展了交叉Kerr非线性增强效应的研究,首先通过理论计算和数值模拟出耦合光使探针光和触发光同时产生的电磁感应透明(Electromagnetically Induced Transparency)窗口,即双EIT窗口;然后模拟了当有无触发光(探针光)时,探针光(触发光)的吸收和色散随探针光频率失谐的变化曲线,结果显示当触发光(探针光)的频率失谐接近或者等于耦合光频率失谐的时候,EIT窗口会出现一个显著的变化,即在此处实现了明显的交叉Kerr非线性增强效应。相比已有工作,特点在热的原子气体中,通过选取合适的能级,构建了四能级Tripod型系统,在此系统中计算得到了探针光和触发光同时产生的EIT窗口,并理论模拟了探针光和触发光之间基于该双EIT窗口的交叉Kerr非线性增强效应。

Large cross-Kerr nonlinearity of optics （ cross-phase modulation XPM ） has a very important role in quantum information processing. The enhanced cross-Kerr nonlinearity in a four-level tripod system of D1 line of 87Rb atoms was investigated. For the first time, the simultaneous EIT windows （Double EIT） for probe and trigger fields induced with coupling beam were observed by theoretical calculations and Numerical Simulation. Then simulation shows that ： with and without trigger beam （ probe b e am） , the absorption spectrum and dispersion spectrum of probe beam （ trigger beam ） have a variation trend with the frequency detuning of the probe beam. It turned out that when the frequency detuning of the trigger beam was near or equal to that of the coupling beam, the total depth of the EIT dip created by the coupling beam clearly became larger, whch achieved obvious cross- Ken- nonlinear effect.