Third-order optical nonlinearity of Ce-doped PbS/PEG self-standing nanocomposite films

Ce-doped PbS/PEG self-standing nanocomposite films have prepared using in situ chemical synthesis method. The formation of PbS nanoparticles with cubic phase structure was confirmed by X-ray diffraction studies. SEM images show that the PbS nanoparticles are well mono-dispersed in polymer matrix and the size of PbS nanoparticles decreases with increase in Ce concentration. UV–Vis optical absorption studies revealed the blue shift in absorption onset with respect to the bulk PbS. The values of optical band gap energy were calculated for all the films and found to increase with increase in Ce-dopant concentration. The photoluminescence spectra exhibit a single-emission peak which is attributed to red emission. The third-order nonlinear optical properties of all the films were analyzed using a Z-scan technique. All the self-standing films exhibit the negative value of nonlinear refractive index and nonlinear absorption coefficient. The third-order nonlinear optical susceptibility and figure of merit were estimated for all the self-standing films. These values are in the order of 10⁻⁵ esu and 10⁻⁹ esu m, respectively, for PbS/PEG film and they increase with increasing of Ce-dopant concentration. The calculated third-order nonlinear optical susceptibility and figure of merit are about three orders of magnitude greater than the value obtained for the substrate-supported thin films. From the results obtained here, it is concluded that the Ce-doped PbS/PEG self-standing nanocomposite films are good candidates for future opto-electronic devices.