Spatial self-phase modulation in WS₂ and MoS₂ atomic layers

Abstract

Laser field-induced spatial self-phase modulation (SSPM) in WS 2 and MoS 2 atomic layer liquid suspensions displayed the diffraction profile of concentric rings at the far-field due to the coherent superposition of transverse wave vectors with characteristic spatial nonlinear phases. The evolution of the number of rings indicated the spatial alignment of anisotropic atomic layers in the liquid base solution. The intensity-dependent number of symmetric rings revealed the nonlinear refraction coefficients of MoS 2 and WS 2 atomic layers which were estimated to be ∼ −1.96 × 10 −16 m 2 /W and ∼ −1.11 × 10 −16 m 2 /W, respectively. The central interference profile and the diffraction pattern identified the negative polarity of nonlinear refraction. The vertically asymmetric diffraction ring indicates the phase distortion of optical field due to the heat convection.