Influence of polymer matrix on nonlinear optical properties and optical limiting threshold of polymer-ZnO nanocomposites

Polymer/ZnO nanocomposites have received a great interest in its linear and nonlinear optical properties because of their potential application such as optical switching and optical limiting devices. In the current work, four polymer/ZnO nanocomposites as a flexible foil have been prepared using casting method. Poly (methyl methacrylate) (PMMA), poly (vinylidene fluoride), polyvinyl alcohol and polystyrene were used as polymer matrices, while ZnO nanoparticles of different concentrations were used as filler. The composition of nanocomposites materials was confirmed by the energy dispersive X-ray (EDX), also a good spatial distribution of elements in the nanocomposites was showed by EDS mapping. The UV–Visible transmittance spectra of as-prepared samples showed low transmittance in the UV region and the peak absorption in the range of 370–377 nm depended on the polymer matrix. The optical absorptive and refractive nonlinearities parameters such as absorption coefficient and refractive index of the as-prepared sample were analyzed using an open and closed aperture single beam Z-scan technique via Q-switched Nd-YAG pulse laser at 532 nm. The nonlinear refractive index was in the order of 10⁻¹² cm²/W with a negative sign whereas the nonlinear absorption coefficient was in the order of 10⁻⁷ cm/W. In order to evaluate the suitability of the samples as optical limiting, the optical limiting threshold of the samples was measured by using transmittance technique. The results showed that the prepared nanocomposites can be considered as an excellent candidate for optical limiting devices. PMMA/ZnO with high concentration of ZnO nanoparticles showed low optical limiting threshold, which was equal to 70 Mw/cm².