Raman effects in Quantum Frequency Conversion using Bragg Scattering

TL;DR

This paper develops a quantum-mechanical model for fiber-based frequency conversion via four-wave-mixing Bragg scattering, analyzing the effects of Raman interactions and proposing methods to mitigate noise for improved quantum frequency conversion.

Contribution

It introduces a comprehensive quantum model for Raman-influenced frequency conversion and provides analytical and numerical tools for optimizing conversion efficiency and noise reduction.

Findings

Raman noise significantly affects conversion efficiency below 30 THz pump detuning.

Cross-polarized pumps and fiber cooling can mitigate Raman noise.

Closed-form expressions for efficiency and photon statistics are derived for continuous-wave pumps.

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.