Probing structural inhomogeneity of graphene layers via nonlinear optical scattering

Incoherent optical second harmonic generation (SHG) is studied from series of multilayer graphene samples of various thickness manufactured by chemical vapor deposition technique and deposited over 150 μm thick glass slides. Two different values of the correlation lengths are obtained from the linear and SHG indicatrices and reveal the existence of two types of optical scatterers. The first one is associated with homogeneous graphene areas, while the second one originates from wrinkles at the interdomain boundaries. Second harmonic imaging microscopy used to map the distribution of the second-order polarization at the nanoscale confirms the results of the nonlinear scattering data.