Gate Tunability of Third Harmonic Generation in CVD Graphene

One of the key features that has driven interest in graphene since its discovery is the ability to control its properties through electrostatic doping. It has been widely established that many optical properties of graphene, such as absorption and Raman scattering, can be tuned by applying a gate voltage to modulate the carrier concentration. We show that the nonlinear third order response of graphene can also be modulated by measuring third harmonic generation spectra in CVD graphene while controlling the doping level using ion gel gating. We measure the magnitude and relative phase change of the third harmonic light and compare our results to theories of the third order optical response in graphene.