Synthesis, Characterization, Luminescent and Nonlinear Optical Responses of Nanosized ZnO.

In this study, we report soft and solvothermal methods for synthesis of zinc oxide nanoparticles (ZnO NPs). Both methods involve a precursor and are carried out at the middle low-temperature regime. The effect of different solvents on the ZnO NPs properties was studied. The nonlinear optical (NLO) response of the NPs was analyzed by the self-action of picosecond laser pulses at 1064 nm and by second harmonic generation (SHG) of a femtosecond laser pulses pump at 800 nm. The luminescence was studied within UV-visible ranges. It was shown that the NLO response efficiency significantly depends on the solvent. The obtained SHG efficiency of small (~2 nm) ZnO NPs is comparable to the one obtained for large (~150 nm) commercial ZnO NPs. The observed results are important for the application of the ZnO NPs in biolabeling.

Impact of Water Adsorption on Nonlinear Optical Properties of Functionalized Porous Silicon.

The porous silicon (PS) surface modification diagnostics due to functionalization and water adsorption/desorption processes were provided by the self-action effects of picosecond range pulsed laser radiation at 1064 nm. It was shown that the PS surface functionalization-oxide removal, alkylation, and oxidation-resulted in a refractive nonlinear optical (NLO) response sign turn to self-focusing (Δn>0) versus the self-defocusing (Δn<0) observed in the aged PS. The sensitivity of the proposed technique was revealed to water adsorption/desorption from the chemically oxidized PS interface. For the dried PS, the self-defocusing effect with corresponding NLO cubic susceptibility Re(χ (3))∼-4.7·10-9 esu was observed versus the self-focusing one (∼5·10-8 esu) for the PS positioned in saturated water vapor at room temperature. The obtained results demonstrate high sensitivity and wide versatility of the proposed readout technique based on pulsed laser radiation self-action at 1064 nm to the PS surface modification monitoring/diagnostics applications.

Photoinduced refractive index variation within picosecond laser pulses excitation as the indicator of oxyorthosilicates single crystals composition modification.

For the first time, the diagnostics of oxyorthosilicates single crystals based on self-action of picosecond range laser pulses at 1,064 nm (1.17 eV) has been performed. High sensitivity of the photoinduced refractive index variation to the substitution of the Lu atoms by Gd in the LSO/LGSO crystalline host as well as to the admixture of Ce was found. The effect can be explained with different electron detrapping-recombination process efficiencies due to the resonant electron excitation from the deep traps in the gap attributed to intrinsic oxygen vacancies.