The activation of non-linear optical response in ZnO@Ag nanocolloids under an external highly intense electric field

An extensive theoretical and experimental study of the non-linear optical properties of bare and silver-decorated zinc oxide (ZnO and Ag@ZnO) nanostructures, prepared by laser-generated plasmas in water and in water/polyvinyl alcohol (PVA) solutions, is reported. The z-scan technique was used to monitor the activation of the non-linear optical mechanisms, focusing an intense laser radiation through the nanocolloids under study. A classical formalism was adopted to explain the z-scan data of these anisotropic materials and to describe the influence of radiation torque and forces on the optically activated nanostructures. This modelling approach includes effects of nanoparticles rearrangements, also taking into account plasmonic effects. An interesting coupling between the nature of the optical limiting response and the nanostructures reorganization under the high-power laser excitation, used during the z-scan measurements, was found and, for the first time to our knowledge, was explained using a classical theoretical approach.