▎ 摘　　要

We evaluate the nonlinear coefficient of graphene-on-silicon waveguides through the coincidence measurement of photon-pairs generated via spontaneous four-wave mixing. We observed the temporal correlation of the photon-pairs from the waveguides over various transfer layouts of graphene sheets. A simple analysis of the experimental results using coupled-wave equations revealed that the atomically-thin graphene sheets enhanced the nonlinearity of silicon waveguides up to ten-fold. The results indicate that the purely chi((3))-based effective nonlinear refractive index of graphene is on the order of 10(-13) m(2)/W, and provide important insights for applications of graphene-based nonlinear optics in on-chip nanophotonics. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement