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

Abstract

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 10 at.%) 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 Cd 1?x Ni x S 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 2.48 eV to 2.23 eV. 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 10 at.%, the nonlinear absorption coefficient (?) are enhanced from 0.92 10 ?5 to 4.46 10 ?5 (cm W ?1 ), nonlinear refractive index (n 2 ) from 0.2967 10 ?9 to 0.1297 10 ?8 (cm 2 W ?1 ) and thereby the third-order NLO susceptibility (? (3) ) values also increased from 1.7075 10 ?6 to 7.4743 10 ?6 (esu). OL characteristics of the prepared films are studied at the experimental wavelength. The results propose that the Cd 1?x Ni x S film is a capable material for nonlinear optical devices at 532 nm and optical power limiting applications. 2019, Springer Science+Business Media, LLC, part of Springer Nature.