Spectral red-shifting of multi-frequency Raman orders

In this paper, the spectral characteristics of the anti-Stokes orders generated by multi-frequency Raman generation are investigated. In particular, we observe that the orders can be red-shifted from the expected Raman transition frequency. The experimental observations indicate that Stark shifting rather than four-wave mixing is responsible for the red-shift. Current numerical models are insufficient to reproduce the experimental observations of red-shifting of the anti-Stokes orders.