Nonlinear spectroscopy of nanostructured materials

Full text: Nanostructured materials present optical properties that are generally different from the corresponding bulk materials because of quantum phenomena and dielectric confinement effects. Presently a large variety of photonic materials is available and some of their properties can be controlled in the nanoscale. For instance, the appropriate modification of materials allows the change of their phonon density of states, the control of the electron dynamics as well as enhancement of energy transfer processes among luminophores embedded in a host medium. Our approach to this area is based on the exploitation of nonlinear (NL) optical techniques to investigate different composites. In this communication recent experiments performed at Recife with nanostructured systems will be reported. Particular emphasis will be given to processes related to NL refraction, NL absorption and NL light scattering. Experiments based on the use of lasers with pulse duration in the nano-, pico- and femto-second range will be described. Measurements of the NL optical response will be presented for colloids containing metallic or dielectric nanocrystals, luminescent ceramics containing metallic nanoparticles and polymers with silver nanostructures. The optical response of the materials is controlled changing the nanoparticles filling fraction. The materials investigated exhibit properties that make them useful for devices such as optical sensors, random lasers, optical limiters and all-optical switches