Abstract

Graphene has unique properties, which makes it a very promising candidate for electronic and photonic devices [1]. In particular, its third-order nonlinear response has been widely investigated, notably at telecom wavelength and within integrated optics architectures, as graphene could be used to locally enhance the nonlinear response of dielectric waveguides by a few orders of magnitude [2,3]. However, despite some recent progress to model the graphene nonlinear response [4], the discrepancy between the values that have been experimentally measured in the literature is yet to be fully explained. We report here the observation of a strong spectral dependence of the nonlinear signature of graphene in hybrid graphene/Si₃N₄ waveguides. It manifests as a strong asymmetry in the conversion efficiency associated with four-wave mixing of spectrally close pump and probe pulsed signals. This unusual nonlinear behavior of graphene has not been observed to our knowledge, and does not seem to be fully described by current models.

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