| The femtosecond and picosecond nonlinear optical properties of various nanostructures have been studied. The studied nanostructures are Gd2 doped metallofullerenes, TDBC 1,1′-diethyl-3,3 ′-bis(4-sulfobutyl)-5,5′,6,6′ -tetrachloro-benzimidazolo carbocyanine) J-aggregates on nanosized colloidal suspensions, Langmuir-Blodgett films of some aromathic polydiacetylenes, and Si nanocrystals into silica matrix. The observed dynamics are sensitive to the specific excited state dynamics of the sample, as well as to the experimental technique and the characteristics of the excitation, such as the wavelength and pulse duration.; Single-beam Z-scan and transient absorption experiments were carried out between 400 nm and 1000 nm in Gd2@C80 (Gd2 doped C80 metallofullerene) thin films and solutions. The third-order nonlinearity was large, negative, and strongly dependent on the pulse-duration and wavelength. Transient absorption results suggest that the fast nonlinear response is enhanced by two-photon-induced ground-state absorption and excited-state bleaching effects.; Femtosecond transient absorption experiments with white light continuum were conducted on TDBC J-aggregates on colloidal surfaces. The transient absorption spectra showed stimulated emission, which has not been seen in TDBC J-aggregates in water. The effects of the pump power, the probe power, and the pump wavelength on the transient absorption spectrum were investigated. The experimental results suggest that the transition from the two-exciton state to the one-exciton state stimulates the transition from the one-exciton state to the ground state.; The third order nonlinear optical properties of Langmuir-Blodgett films made from aromatic polydiacetylenes were studied for the first time by using the Z-scan technique. The values of the third order nonlinear optical susceptibilities of four different aromatic polydiacetylenes were substantially larger than the published values of aliphatic polydiacetylenes. The enhancement of the nonlinearity was attributed to the incorporation of the aromatic groups.; The nonlinear optical properties of silicon nanocrystals within a fused silica matrix were investigated systematically by the Z-scan technique. Nonlinear measurements at various wavelengths showed the role of three bands in the visible spectrum. Measurements at various laser pulse durations showed several time constants, which, illustrated the role of quantum confined and surface states. |
