Models for coherent anti-Stokes Raman scattering in Raman devices and in spectroscopy

We present our latest findings on the nature and behavior of CARS in active Raman devices, such as Raman converters and Raman lasers, which operate at exact Raman resonance. We demonstrate that the CARS mechanism in these devices actually comprises two opposite and competing interactions, which respectively create and annihilate phonons in the Raman-active medium. Furthermore, we show that both the phase mismatch of the CARS process and the level of pump depletion determine which of these two interactions takes place along the fields' propagation path in the Raman devices. Finally, we compare this CARS model with the model used by the CARS spectroscopy community, and explain that the difference between both models is mainly due to the fact that "CARS" in the context of Raman devices refers to Ramanresonant four-wave mixing, whereas "CARS" in the context of spectroscopy often denotes a two-step Raman interaction.