The five-level Λ−Ξ system as an optical switch under different wavelength mismatching regimes, including one due to Rydberg transition

Abstract We investigate the influence of wavelength mismatching on the probe response of the medium in Λ − Ξ 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 Λ − Ξ 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, Λ − Ξ 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.