Study on Changes in Spatial Self-Phase Modulation Pattern of Graphene Dispersion

Abstract

Changes in spatial self-phase modulation (SSPM) patterns have been studied when a laser beam passes through graphene dispersions and graphene dispersed gel. Interference rings are formed due to spatial self-phase modulation, which is induced by the change of the intensity dependent refractive index of graphene dispersions. The interference pattern of SSPM is found to be distorted rapidly for the graphene dispersions, while no distortion for the graphene dispersed gel. Experimental results show that thermal convection effect plays a dominant role for the distortion of the SSPM pattern. The distorted extent and area of the SSPM pattern depend on the speed and direction of convection in the graphene dispersions. Theoretical analyses have been given for the reason of the SSPM pattern distortion. Convection can effectively change the spatial symmetry distribution of polarized graphene sheets and non-linear refractive index in the beam cross section, thus making the interference rings distortion based on the spatial self - phase modulation.