content_image/419413.jpg
(dashed-dotted lines) the region of anomalous dispersion becomes wider and its negative slope increases in abso- lute value. The absorption curve undergoes variations similar to those of the previous case ( r$_{2}$ = γ ). The value of the gain for the latter case ( r$_{2}$ = 2 . 43 γ ) vanishes at Δ$_{p}$ = 0. The proper value of r$_{2}$ resulting in zero gain around Δ$_{p}$ = 0 can be obtained by: 

Fig.7 displays the effect of incoherent and coherent pump fields on the group index. Fig.7a shows the group index versus indirect incoherent pump rate r$_{1}$ for Ω$_{c}$ = 1 . 0 (solid), 1 . 7 (dashed), 4 . 0 (dot-dashed), 6 . 0 (dotted), while r$_{2}$ = 0 . 0. Fig.7b displays group index versus co- herent pump field, Ω$_{c}$, for r$_{1}$ = 1 . 5 (solid), 2 . 0 (dashed), 3 . 0 (dash-dotted), and 5 . 0 (dotted), while r$_{2}$ = 0. In Fig.7c, the group index is plotted as a function of r$_{1}$ for Ω$_{c}$ = 0 . 5 (solid), 0 . 7 (dashed), 1 . 0 (dot-dashed), and 1 . 7 (dotted) while the second indirect incoherent pump has 

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<img src='content_image/419413.jpg'>

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## III. CONCLUSION 

