Revealing the intrinsic nonlinear optical response of a single MoS2 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. (C) 2020 Chinese Laser Press