Investigation of third-order nonlinear optical properties of nanostructured Ni-doped CdS thin films under continuous wave laser illumination

We report the third-order nonlinear optical (NLO) properties and optical limiting (OL) thresholds of pure CdS and Ni-doped CdS thin films have been investigated with the Z-scan technique under continuous wave laser excitation. Nanocrystalline CdS thin films with various doping concentrations of Ni (0%, 1%, 3%, 5% and 10at.%) are prepared by spray-pyrolysis technique. XRD patterns reveal that all the prepared films are polycrystalline and the incorporation of Ni does not lead to major changes in the crystalline phase of Cd1-xNixS thin films. The surface morphology of the prepared films is impacted by the Ni-doping and is indicated by Field Emission Scanning Electron Microscopy (FESEM) images. With an increase in Ni-doping concentration, the energy band-gap value decreased from 2.48eV to 2.23eV. From the Z-scan data, it is observed that the material show strong two-photon absorption (2PA) and with an increase in Ni-doping concentrations from 0 to 10at.%, the nonlinear absorption coefficient () are enhanced from 0.92x10(-5) to 4.46x10(-5) (cmW(-1)), nonlinear refractive index (n(2)) from 0.2967x10(-9) to 0.1297x10(-8) (cm(2)W(-1)) and thereby the third-order NLO susceptibility (((3))) values also increased from 1.7075x10(-6) to 7.4743x10(-6) (esu). OL characteristics of the prepared films are studied at the experimental wavelength. The results propose that the Cd1-xNixS film is a capable material for nonlinear optical devices at 532nm and optical power limiting applications.