High-performance all-optical limiting based on nonlinear refraction of metal-doped PbS/PVA freestanding nanocomposite films

A modified Z-scan technique was used to define the nature of nonlinear refraction and absorption mechanisms with a single measurement. Undoped and metal (Zn, Mg, Cd)-doped PbS/PVA freestanding nanocomposite films were prepared using a simple chemical method with different doping concentrations. X-ray diffraction, scanning electron microscopy, and optical absorption spectroscopy were performed to characterize the prepared films. The crystallinity and optical band gap of the prepared metal-doped PbS/PVA were affected by Zn, Mg, and Cd doping concentration. All prepared samples showed a blue shift in the absorption edge, and the optical band gap increased with increasing doping concentration. The nanocomposite films displayed self-defocusing nonlinearity under the experimental conditions. Increasing the laser input power of the Zn-PbS/PVA sample yielded a higher optical nonlinearity as compared with the other prepared samples under a doping concentration of 0.008 M. The all-optical limiting performance of the metal-doped PbS/PVA prepared under different Zn, Mg, and Cd doping concentrations was investigated. The PbS/PVA sample doped with 0.008 M Zn realized all-optical limiting at a limiting threshold of 3 mW with an optical damage of 21 mW for a high dynamic range of 7.