Decoherence due to XPM-assisted Raman amplification for polarization or wavelength offset pulses in all-normal dispersion supercontinuum generation

Feehan, James S. and Price, Jonathan H. V. (2020) Decoherence due to XPM-assisted Raman amplification for polarization or wavelength offset pulses in all-normal dispersion supercontinuum generation. Journal of the Optical Society of America B, 37 (3). pp. 635-644. ISSN 0740-3224

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    Abstract

    We report the importance of cross-phase modulation (XPM) on the coherence of a low-energy probe pulse co-propagating with a high-energy pump pulse that generates incoherent supercontinuum in all-normal dispersion (ANDi) fiber due to Raman amplification of quantum noise. By investigating numerous fiber and pulse parameters, we show consistently that for weak probe pulses, the XPM from the pump is the dominant influence on the degradation of the probe coherence. We show that the faster decoherence at the pump leading edge means that the probe coherence is reduced more significantly when the probe has a higher group velocity, i.e., when an orthogonally polarized probe is aligned to the fast (lower refractive index) axis of the fiber or when a co-polarized probe has a longer central wavelength. Simulations show that this effect occurs for both polarization-maintaining (PM) and non-PM ANDi fibers and can result in a probe decoherence rate that is higher than that of the pump. These previously unreported results extend our earlier scalar simulations showing incoherent supercontinuum within a single pulse.