Spectral and temporal dependence of the nonlinear refractive index of Graphene for use in integrated photonic devices

In this work, we measure the nonlinear refractive index (n(2)) of graphene using the Z-Scan technique as a function of varying spectral and temporal characteristics of the excitation laser. Recent works have worked to quantify the nonlinear index of refraction in graphene under various experimental conditions to only produce contradictory results. A laser source producing 100 fs pulses is tuned from 800-1050 nm and the n(2) is measured. Then the pulse is temporally expanded up to 500 fs using a prism pair stretcher at 900 nm and the n(2) is measured. The use of graphene in integrated nonlinear photonic devices such as all optical modulators, warrants the characterisation of the nonlinear behaviour in graphene for device design. In addition to that, the study gave us insight into the physics of the ultrafast and large nonlinear response in graphene, showing agreement with our theoretical model.