Efficient femtosecond pulse generation using a parabolic amplifier combined with a pulse compressor. I. Stimulated Raman-scattering effects

The effects of stimulated Raman scattering on femtosecond pulse generation using a parabolic amplifier and a grating-pair compressor are presented. We derive an explicit analytical form for the Stokes pulse evolution. We find that the evolution of the Stokes pulse can be divided into four regimes; small Gaussian Stokes pulse, small asymmetric Stokes pulse, signal depletion, and parabolic Raman pulse. To achieve efficient pulse compression, one should operate the parabolic amplifier in the small Stokes pulse regime where the signal pulse is not seriously distorted. We also derive an analytical expression to obtain a critical fiber length for the small Stokes pulse regime. The derived theory is applied to a realistic high-power femtosecond pulse generation process through a split-step Fourier numerical simulation. The pulse compression results confirm that our derived critical fiber length leads to the highest peak power and shortest width of compressed pulse.