Kopylovsky M. Investigation of nonlinear optical response of dielectric matrixes with incorporated nanostructures based on TiO2, Si/SiO2, Al2O3 under resonant excitation.

Nonlinear optical (NLO) response of dielectric matrices with nanostructures based on metal-oxide nanoparticles (NPs) was studied. It was shown that excitation of surface states of nanoscale subsystems gives the possibility to control the NLO properties of the composite system. The main objects of research are: the KDP crystals with incorporated anatase nanoparticles; anisotropic porous silicon films and nanostructured samples of ultraporous amorphous alumina. For the optical characterization and the investigation of NLO response, the following experimental techniques have been used: spectroscopy, scattering, spatial profile analysis technique based on self-action of continuous and pulsed (pico- and femtosecond ranges) laser radiation in different temperature ranges, second harmonic generation. The photoinduced variations of absorption coefficient and refractive index in the KDP:TiO2 crystals under self-action of laser radiation were investigated. The TiO2 NPs concentration has a strong impact on the magnitude and sign of the cubic NLO response of KDP:TiO2 single crystals. The possibility to control the cubic NLO response of the composite material KDP:TiO2 through the selection of NPs concentration and growth sector of the crystal was shown. For the first time the enhancement of SHG efficiency was obtained in optically "thick" KDP:TiO2 crystals relatively to pure KDP under picosecond laser excitation (?=1064 nm). The effect was explained by the internal self-focusing of laser beam in "thick" crystals KDP:TiO2. The mesoporous silicon films and nanostructured amorphous alumina were studied as promising subsystems for enhancement of the KDP crystals NLO response.