Effect of quantum interference on the optical properties of a   three-level V-type atomic system beyond the two-photon resonance condition
  The effect of quantum interference on the optical properties of a pumped-probe three-level V-type atomic system is investigated. The probe absorption, dispersion, group index and optical bistability beyond the two-photon resonance condition are discussed. It is found that the optical properties of a medium in the frequency of the probe field, in general, are phase independent. The phase dependence arises from a scattering of the coupling field into the probe field at a frequency which in general differs from the probe field frequency. It is demonstrated that beyond the two-photon resonance condition the phase sensitivity of the medium will disappear. 
S. M. Mousavi, L. Safari, M. Mahmoudi and M. Sahrai
quant-ph physics.atom-ph