Experimental investigations of two-photon absorption (TPA)
cross-section using nonlinear transmission (NLT) and a
new pump-probe mode-mismatched thermal lens (TL) scheme, in the picosecond regime are reported. Both methods are
used in a prospect of comparison. Values of the TPA coefficient and cross-section in perylenediimide derivatives (PDI)
at 532 nm and 1064 nm wavelengths are given.
We have developed a method which yields the real and the imaginary parts of third-order susceptibility of material media. We have applied this method to determine the nonlinear refractive index (n2) of new synthesized organic materials in the picosecond regime (30 ps pulse duration at 1064 nm wavelength). The results obtained show the efficiency of this technique for measuring low values of the nonlinear refraction coefficient n2 in diluted materials.
We report the quadratic hyperpolarizability βs of newly synthesized chirals carboxylates salts. These nonlinear optical coefficients have been measured using Hyper-Rayleigh scattering (HRS) technique in solution. Before nonlinear measurements, the different compounds under study were characterized by resonance magnetic nuclear of protons and absorption spectra. They were shown to be completely transparent to the absorption in the UV-Visible and near-infrared region of the spectrum: spectra of solutions in methanol, recorded on an ATI-UNICAM spectrometer in range 250 - 1100 nm show no absorption above 350 - 400 nm. HRS measurements are made by using methanol as solvent and the values of the nonresonant hyperpolarisabilities obtained are of the same order of magnitude that that of the paranitroaniline and are located beween 30x10-30 esu and 60x10-30 esu.
We have synthesized two chromophore monomers, starting from chloromethyl styrene and methyl methacrylate, and the corresponding homopolymer and copolymer. The obtained structures have been characterized by UV-Vis, IR and H-RNM. The molar fraction of the chromophore monomers in copolymers have been determined by H-RNM and elementary analysis. We have measured the NLO third order coefficients by the degenerated four wave mixing method and high values have been obtained.
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