Raman effects in Quantum Frequency Conversion using Bragg Scattering

Abstract: 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 crosspolarized pumps and on the anti-Stokes side, through cooling of the fiber.