We present a theoretical model, using density matrix approach, to study theeffect of weak as well as strong probe field on the optical properties of aninhomogeneously broadened multilevel V-system of the $^{87}$Rb D2 line. Weconsider the case of stationary as well as moving atoms and perform thermalaveraging at room temperature. The presence of multiple excited states resultsin asymmetric absorption and dispersion profiles. In the weak probe regime, weobserve the partial transparency window due to the constructive interferenceoccurs between transition pathways at the line center. In a room temperaturevapour, we obtain an increased linewidth of the transparency window and steeppositive dispersion. For a strong probe regime, the transparency window withnormal dispersion switches to enhanced absorption with anomalous dispersion atthe line center. Here, we show how the electromagnetically induced transparency(EIT) depends on the polarizations of the applied fields. We also discuss thetransient behaviour of our system which agrees well with the correspondingabsorption and dispersion profiles. This study may help to understand opticalswitching and controllability of group velocity.
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