Identification of optical orbital angular momentum modes with the Kerr nonlinearity of few-layer WS ₂

Abstract Optical vortex beams (VBs), a structured light possessing helical phase—front and carrying orbital angular momentum (OAM), have recently emerged as a promising perspective in optical manipulation, optical tweezer and optical communication. In this contribution, by taking advantage of the strong light–matter interaction, a nonlinear diffraction method is demonstrated to identify OAM modes. The nonlinear diffraction device (NDD) composed of WS ₂ nanosheets is employed to excite the optical Kerr nonlinear effect. Owing to the large Kerr coefficient of layered WS ₂ , the spatial phase shift of VBs are readily regulated, resulting in controllable diffraction rings and tails, from which we can directly identify the magnitude and signs of OAM modes. The incident light intensity also expands the intensity distribution because the enhanced nonlinear phase shift will enlarge the diffraction rings, which provides an efficient way to identify the OAM and intensity of VBs simultaneously. It is anticipated that the optical nonlinearity might afford new opportunities for detecting structured lights and may have great potentials in designing all-optical OAM devices, etc.