We investigate the influence of wavelength mismatching on the probe response of the medium in $\Lambda -\Xi$ configuration. The density matrix formulation is invoked to analytically derive the probe coherence term for stationary as well as moving atoms. Our numerical results manifest that by simply altering the strength of switching field, light pulses can be slowed down at multiple frequency regions. It is found that for stationary atom case, EIT depth falls off with decrease in lifetime of topmost excited state of $\Lambda -\Xi$ system. Further, we substantiate that after inculcation of Doppler effect, subluminal propagation on resonance steadily switches to superluminal propagation as wavelength mismatching increases. The variation of group index with probe detuning and switched field’s strength is then examined and the results turned out to be in complete agreement with EIT spectra. Moreover, it is established that for sufficiently large strength of switching field, $\Lambda -\Xi$ system involving Rydberg state produces maximum delay in probe propagation for stationary as well as moving atoms. Our theoretical analysis evidently suggest the utilization of our considered system in storage of infrared (IR) signals and optical switching applications.

我们调查波长不匹配对介质探针响应的影响。 $\Lambda -\Xi$组态。调用密度矩阵公式来分析得出固定原子和移动原子的探针相干项。我们的数值结果表明，只需改变开关场的强度，就可以在多个频率区域减慢光脉冲。发现对于静止原子情况，EIT深度随着最高激发态寿命的减少而降低。$\Lambda -\Xi$系统。此外，我们证实了在注入多普勒效应之后，随着波长失配的增加，共振下的腔内传播稳定地切换为超腔传播。然后检查了基团指数随探针失谐和开关场强度的变化，结果与EIT光谱完全一致。此外，已经确定，对于足够大的开关场强度，$\Lambda -\Xi$涉及Rydberg态的系统对固定原子和移动原子产生最大的探针传播延迟。我们的理论分析显然表明，我们所考虑的系统可用于存储红外（IR）信号和光交换应用。