Spatial modulation on vortex FWM induced by the nonlinear Kerr effect

Abstract

Abstract We experimentally observe the interference patterns of vortex probe transmission signal (PTS) and vortex four-wave mixing (FWM). By changing the difference in the divergences of two optical beams, the spiral interference patterns of the probe beam and the reference Gaussian probe beam can be obtained. It is found that in the interference patterns of vortex PTS, the shifting of the fork can be regulated by blocking different dressing fields and tuning the probe frequency. When the two-photon resonance condition is satisfied, the shift of the fork is the weakest since the strongest probe field intensity induces the weak nonlinear phase shift. In addition, we realize that the relationship between the intensities of the vortex FWM signal and the probe field is not monotonic, because both the intensity of probe field and the dressing effect will affect the intensity of the vortex FWM signal. We also find that the spatial modulations including shifting and splitting are also regulated by the intensity of the probe field and the coupling field. Here, the explanation of these phenomena is presented by the transition of the nonlinear refraction index. Finally, we realize that the singularity overlap or separation between the linear probe and the third-order vortex FWM will lead to the change of fork quantity. Our research is helpful to understand and manipulate optical vortices and can be widely used in quantum computation and communication.