PARAMETRIC AMPLIFICATION OF SHORT PULSES IN OPTICAL-FIBER BRAGG GRATINGS

We study chi((3)) parametric amplification of a weak signal pulse tune d to a Bragg grating; through a series of numerical simulations. These simulations demonstrate that gratings permit strong signal amplificat ion for large wave vector mismatches between pump, signal, and idler, even though gain would be prohibited in the corresponding uniform medi um. The enhanced gain is explained in terms of a shift in the signal w ave vector due to the strong dispersion induced by the grating, an eff ect which is; well known from other frequency conversion processes. Fo r chi((3)) Parametric amplification, the pulsed regime introduces seve ral new effects, many of which are explained by simple arguments based on the cw dispersion relation of the grating. Notably, the gain exhib its a ''self-locking'' behavior, in that there is considerable freedom in the input frequency of the signal.