Revealing the intrinsic nonlinear optical response of a single MoS_(2) nanosheet in a suspension based on spatial self-phase modulation

The reorientation of 2D materials caused by nonlocal electron coherence is the formation mechanism of 2D material spatial self-phase modulation under laser irradiation,which is widely known as the“wind-chime”model.Here,we present a method that provides strong evidence for the reorientation of 2D-material-induced spatial self-phase modulation.The traditional“wind-chime”model was modified by taking into account the attenuation,i.e.,damping of the incident light beam in the direction of the optical path.Accordingly,we can extract the nonlinear refractive index of a single MoS2 nanosheet,instead of simply obtaining the index from an equivalent MoS2 film that was constructed by all nanosheets.Our approach introduces a universal and accurate method to extract intrinsic nonlinear optical parameters from 2D material systems.