Raman effects in quantum frequency conversion using Bragg scattering

We present a quantum-mechanical model that describes fiber-based frequency conversion by four-wave-mixing Bragg scattering in the presence of Raman interactions. In the case of continuous-wave pumps, we find closed-form expressions for the conversion efficiency and photon statistics characterized by the second-order correlation function. For pulsed pumps, we derive a highly general model based on Green functions and provide a numerical solution method using a split-step scheme. In both cases, we find that noise from spontaneous Raman scattering can pose a serious challenge to this type of frequency conversion if the pumps are less than 30 THz from the quantum fields. However, this impact can be mitigated with cross-polarized pumps and, on the anti-Stokes side, through fiber cooling.