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positive to negative. On the other hand, the steepest anomalous slope of dispersion occurs when 2 < Ω$_{c}$ < 3 and a strong enough indirect incoherent pump, popu- lates level | 3 〉 . Fig.5 is presented to see how an increase in r$_{1}$ causes the gain deeps to become more distinguish- able and consequently the anomalous slope of dispersion become steeper. In Fig.5a for r$_{1}$ = 1 . 2 (solid line) the slope of dispersion around zero probe field detuning is positive. With increasing the indirect incoherent pump rate to r$_{1}$ = 1 . 5 (dashed lines), the slope of dispersion becomes zero and it is negative for r$_{1}$ = 3 . 0 (dash dotted lines). In Fig.5b, the probe field absorption curves are plotted. It shows that the subluminal and superluminal light propagation around zero probe detuning is accom- panied by a considerable gain. It is time to investigate the optical response of the medium to populating level | 2 〉 while the transition | 1 〉 ↔ | 3 〉 is driven by the coher- ent field, and the population between levels | 1 〉 and | 3 〉 is inverted due to the indirect incoherent pump with a rate r$_{1}$ > γ . In Fig.6, the real (a) and imaginary (b) parts of χ are plotted versus probe field detuning. The common parameters are Ω$_{c}$ = 1 . 69 γ , and r$_{1}$ = 1 . 5 γ . The first plots (solid lines), corresponding to r$_{2}$ = 0, are pre- sented for comparison only. They show that the slope of dispersion is almost zero around zero probe field de- tuning and there is a considerable amount of gain due to 

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the partly combined gain deeps. By populating level | 2 〉 with rate r$_{2}$ = γ , (dashed lines), the slope of dispersion becomes negative around Δ$_{p}$ = 0. The absorption curve varies according to the probe field detuning, so that the maximum reduction in gain occurs around zero probe field detuning, while beyond Δ$_{p}$ = ± Ω$_{c}$ γ , the gain in- creases slightly. By increasing the value of r$_{2}$ to 2 . 43 γ 

