Understanding the effect of bound excitons on two photon absorption process in anatase TiO2 nanospheres using ultrafast pulses

Abstract

Nanoparticles of Titanium dioxide [Formula: see text] with its unique optical and electronic characteristics is an important material for photochemical catalysis. The efficiency of catalytic activity of [Formula: see text] anatase nanostructures is greatly influenced by the photo-generated bound excitons. It is found that the interaction of bound excitons generated in [Formula: see text] enhances the cubic nonlinearity of the system due to strong oscillation of photo-generated bound excitons. The trapped electron hole pair concentration is directly proportional to the photocatalytic efficiency of the [Formula: see text] anatase nanostructures. In our report, we show how these photo-generated bound excitons play a significant role in origin of third-order optical nonlinearities. In particular, we have measured large phase shift and seen two photon absorption process through closed and open aperture Z-scan, respectively, using femtosecond pulses at 532[Formula: see text]nm.