title: Generation of frequency degenerate twin photons in pulse pumped fiber optical parametric amplifiers: influence of background noise.
abstract: Using a Sagnac fiber loop functions as a deterministic splitter of photon pairs produced by the frequency degenerate four wave mixing, we show that the background noise of the degenerate photon pairs is contributed by both Raman scattering and frequency non-degenerate four wave mixing. To improve the purity of photon pairs in the high gain regime, in addition to suppressing the noise photons by cooling the nonlinear fiber and by optimizing the detuning between the frequencies of the pump and photon pairs, the walk-off effect of the two pulsed pump fields should be mitigated by managing the dispersion of the fiber. Our investigation is not only the first step towards the generation of multi-mode squeezed vacuum in fiber optical parametric amplifiers pumped with pulsed lights, but also contributes to improving the purity of the fiber sources of degenerate photon pairs.
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.forename: Fengwei
authors.initials: F
authors.lastname: Sun
authors.forename: Ningbo
authors.initials: N
authors.lastname: Zhao
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Li