Enhanced third-order optical nonlinearity in Ce3+ ion-doped zinc sulfide–polyvinyl alcohol freestanding nanocomposite films

Abstract

Undoped, 0, 2, and 5 mol% Ce-doped ZnS–PVA nanocomposite films have been prepared using in situ chemical method. X-ray diffraction patterns confirm that the prepared nanocomposite films are in cubic structure of ZnS. UV–Vis optical absorption spectra of Ce3+-doped ZnS–PVA films exhibit the red-shifted phenomenon with the increasing Ce dopant concentration in ZnS. Scanning electron microscope images reveal the morphology changes in the films with Ce doping. The high values of real and imaginary parts of dielectric constant at low frequencies are attributed to the space charge polarization, whereas the loss tangent of Ce-doped ZnS–PVA nanocomposite films at low frequency with the increasing Ce dopant concentration indicates the enhancement of optical quality of the films. The Z-scan technique exhibits a reverse saturable absorption process in nonlinear absorption studies and self-focusing optical nonlinearity in nonlinear refractive studies under the experimental conditions. The highest nonlinear optical parameters such as nonlinear absorption coefficient, nonlinear refractive index, and third-order nonlinear optical susceptibility are found to be about 9336.6 cm/GW, 1.782 × 10−4 cm2/GW, and 2.103 × 10−5 esu, respectively, for 5 mol% Ce3+-doped films. The estimated third-order nonlinear optical susceptibility is eight orders of magnitude larger than that of bulk ZnS, and four–five orders of magnitude higher than those of the some representative materials reported. Hence, the Ce3+-doped ZnS–PVA nanocomposite films investigated here emerge as promising candidates for the development of nonlinear optical devices.