Double-pulse Model for the Study of Red-shifted Spectrum in Multi-frequency Raman Generation

Pumped by two frequency chirped pulses in the transient regime, the anti-Stokes orders from multi-frequency Raman Generation are spectrally broadened on the lower frequency side, causing each of the orders to have a broader spectrum with double-peak pattern. In this letter, a double-pulse model is introduced to analyze the measured spectrograms. We think the red-shifted spectrum comes from the linear Raman scattering between manifolds in the two-photon dressed states.