  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.
