Abstract

Parametric amplification in two coupled nonlinear waveguides has been proposed as a solution for signal amplification in optical communications featuring a broadband and flat gain profile with low noise figure [1,2]. Here we present a general theory of parametric amplification valid both for dual-core silica fibers and integrated coupled waveguides (e.g. silicon nitride) which takes into account the frequency dependency of the coupling strength and captures both phase-sensitive (PS) and insensitive (PI) regimes. We show that coupling dispersion can compensate for waveguide dispersion enabling a substantial control of the gain spectrum and amplification in the normal dispersion regime too. Our theory is based on the coupled nonlinear Schrödinger equations with fre-quency dependent coupling $C(\omega )={\displaystyle {\sum }_{n=0}^{\infty }{\left(\omega -{\omega }_0\right)}^n}{C}_n/n!$, where C_nis the n-th coefficient of the Taylor expan-sion of the coupling strength around the pump frequency ω₀

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