Nonlinear optical characterization of tungsten disulfide and molybdenum disulfide via Z-scan technique

Abstract Two-dimensional (2D) materials have been widely used in optical applications due to their unique properties such as high transparency, strong light-matter interactions, and tuneable electronic and optical characteristics. In this context, transition metal dichalcogenide (TMD), tungsten disulfide (WS 2 ) and molybdenum disulfide (MoS 2 ) has been the subject of interest due to their direct bandgap monolayers properties. Previous studies were conducted under different parameters and conditions, where the results were not comparable. This comparative study investigates the optical nonlinearity of WS 2 and MoS 2 under identical experimental conditions. The primary objective is to determine superior nonlinear optical properties of these materials in the same environment, thereby identifying the more effective material for applications requiring high optical nonlinearity. In this context, the research employs Z-scan technique to measure the nonlinear refractive index and nonlinear absorption coefficients of both WS 2 and MoS 2 solutions. The Z-scan technique provided data on the third-order nonlinear refractive index (n 2 ) of the materials. Comparative analysis of the collected data revealed significant differences between the two materials’ optical responses under the same conditions. At a peak laser intensity of 29.2 MWm −2 , WS 2 exhibits a higher nonlinear refractive index of 37.02 × 10 −13 m 2 W −1 compared to MoS 2 of 5.58 × 10 −13 m 2 W −1 , indicating its superior performance in nonlinear refraction applications. Additionally, WS 2 also demonstrates high nonlinear absorption of 4.6 × 10 −6 mW −1 at 116.9 MWm −2 , which could be advantageous for optical limiting applications. In conclusion, this study highlights the distinct nonlinear optical properties of WS 2 and MoS 2 , providing critical insights for their application in photonic and optoelectronic devices.