Colloidal solutions of CdTe nanoparticles have been prepared by the "electropulse" technique. The diameters of the CdTe nanoparticles range from 5 to 30 nm. The goal of this work is to study the formation and evolution of the induced thermo-refractive index with a long-term goal of forming a thermal lens. An induced thermo-refractive index occurs when the CdTe solutions are irradiated with a strong laser beam. The experimental approach is derived from the Z-scan technique, a technique which is very sensitive to refractive index modulation in a sample. Thermo-optical coefficients, such as the thermal diffusivity, D, the characteristic build-up time of the thermal lens, t_c, and the induced thermo-refractive index can be determined from dynamic Z-scan curves. The thermo-optical coefficients have been determined at different wavelengths, beam powers, and for different nanoparticles sizes.

A third-order non-linear optical effect, the optical Kerr effect, was studied in DR l-doped sol-gel using the Z-scan method which allows studying both processes of non-linear absorption and refraction. The materials under study are sol-gel substrates, amorphous silica glasses doped by the azo-dye Disperse Red 1. Modifying the conditions of the sol-gel synthesis, in particular the pH of the catalytic medium, enabled us to vary the morphology of the sol-gel substrate. Non-linear effects of various amplitudes were observed in sol-gel substrates of various porosities, involving different non-linear mechanisms.

The third order nonlinear optical effect called the optical Kerr effect was studied in InP nanoparticles solutions. The synthesized InP nanoparticles have sizes ranging from 1.5 to 3.5 nm and each sample is characterized by its sizes distribution. The Z-scan technique was used to study nonlinear absorption and refraction. Different lasers were used, hence different nonlinear refraction effects were observed at different wavelengths (532, 633 and 1550 nm) and at different time scales (continuous and femtosecond).