Nonlinear optical studies of tungsten disulphide (WS₂)/gold nanoparticles (AuNPs) using infrared femtosecond laser

We report on the observation of the nonlinear optical properties of tungsten disulphide (WS₂) in the infrared (IR) region, along with the enhancement in the nonlinearity achieved by integrating gold nanoparticles (AuNPs) in WS₂. WS₂ was synthesized using liquid phase exfoliation (LPE) and the spray pyrolysis technique, with layers integrated of AuNPs synthesized using de-wetting process. All samples were characterized using FESEM-EDX, AFM, UV-Vis, and Raman Spectroscopy to analyze their properties including their morphology and linear absorption, in addition to band-gap and vibrational analyses. The nonlinear optical (NLO) measurements and analysis were conducted using the Z-scan technique with a 1560 nm femtosecond laser with both on open and closed apertures to determine the nonlinear absorption coefficient (β) and nonlinear refractive index (n₂).Samples of WS₂ and AuNPs-WS₂ were compared for their coefficient values. AuNPs-WS₂ obtained higher values of β_{avg_}S1= (2.30 ± 0.06) ×10^− 9m/W and β_{avg_}S2= (4.45 ± 0.07) ×10^− 9 m/W resulting in a higher nonlinear optical susceptibility of χ ⁽³⁾ = 10.20 × 10^− 12 esu, which is double that of WS₂-only sample. This enhancement could be significant contribution in optical devices application.