Figure 1.

Parametric four-wave mixing (FWM) and stimulated Raman scattering (SRS) gain curves. (a)–(c) Gain/loss per roundtrip vs (a) normalized power and (b) and (c) normalized detuning in the normal-dispersion regime. (a) Detuning (${\delta }_0$) is fixed at 0. No gain is present in the absence of modal interaction. Parametric gain can be created by introducing modal interaction ($\mathrm{\Delta }\omega >0$), which determines an amplitude and width of the gain envelope, and a threshold power. (b) Normalized power ($S$) is fixed at 4. Raman gain is not dependent on the frequency shift. Parametric gain is maximized at $a\approx 3$. (c) Parametric and Raman gains at different pump powers with a fixed frequency shift ($a\approx 2$). Raman gain increases linearly with the pump power, while parametric gain can be a function of both the pump power and additional frequency shift. (d)–(f) Difference between the FWM and SRS gains in 2D-parameter space. The FWM (SRS) dominant region is filled with red (blue). Red (blue) dashed line represents zero gain for FWM (SRS). Horizontal dashed arrows indicate excitation pathways explored in upcoming sections. The difference between the FWM and SRS gains is normalized by loss (α) with the chosen additional frequency shifts of (d) $a\approx 1$, (e) $a\approx 2$, and (f) $a\approx 4$. Cases (i)–(vi) shows parameters analyzed in the following sections. Note $b$ is assumed to be 1 in all calculations.