Study on the Third-Order Nonlinear Optical Properties of Cd2+ Ion Doped Zns/PVP Nanocomposite FilmsB. Suresh1, S. Ramachandran1 and G. Shanmugam2

Abstract

Cd2+ ion doped ZnS/PVP nanocomposite films have been prepared using in-situ chemical method. XRD studies confirm the cubic structure of ZnS for all the films and the nanocrystallite size of ZnS is found to varying from 3.82 to 4.07 nm with Cd doping. The morphology of the films has been analyzed using SEM micrograph which shows the mono dispersion of ZnS nanoparticles in PVP matrix. The interaction between ZnS nanoparticles and PVP polymer matrix has been discussed using FTIR spectra. Optical absorption spectra of the films reveal the blue shift on the absorbance onset with the comparison of bulk ZnS and the estimated optical band gap energy decreases with increasing the concentration of Cd dopant. Photoluminescence spectra show a blue emission peak for all the films. The Z-scan results of three samples show a reverse saturation absorption process in open Z-scan experiment and self-focusing behavior in closed Z-scan experiment. Both ZnS/PVP and Cd2+ ion doped ZnS/PVP films exhibited the large optical nonlinearity and the value of nonlinear refractive index (n2), nonlinear absorption coefficient (β), third-order nonlinear optical susceptibility (χ(3)) and figure of merit (FOM) increase with Cd doping. The estimated n2, β, χ(3) and FOM values were found to be high for 6 mol% Cd doped ZnS/PVP nanocomposite film and they are about 1.771⋅10− 10 m2 W− 1, 4.148⋅10− 3 mW− 1, 1.603⋅10− 4 esu and 9.576⋅10− 6 esu m respectively. The experimental results clearly showed that the Cd2+ ion doped ZnS/PVP nanocomposite film is a worthy candidate for the future nonlinear optical device fabrication.