Esmaeil Shahriari

Effect of particle size on nonlinear refractive index of Au nanoparticle in PVA solution

Nonlinear refractive index of Au nanoparticle suspended in PVA solution was measured using a single beam Z-scan technique. Measurements were carried out using a green CW laser beam operated at 532 nm as excitation source. Five nanoparticle samples with different particle sizes were prepa red by γ radiation method. The Au nano-fluid shows a good third order nonlinear response for particle sizes ranging from 7.0 nm to 18.7 nm. The sign of the nonlinear refractive index was found to be negative and the magnitude was in the order of 10-8 cm2/W. The results show that the nonlinear effect tends to be increased linearly with the increasing of particle sizes thus could be a good candidate for nonlinear optical devices.

Characterization of Electrosynthesized Conjugated Polymer-Carbon Nanotube Composite: Optical Nonlinearity and Electrical Property

The effects of multi-walled carbon nanotube (MWNT) concentration on the structural, optical and electrical properties of conjugated polymer-carbon nanotube composite are discussed. Multi-walled carbon nanotube-polypyrrole nanocomposites were synthesized by electrochemical polymerization of monomers in the presence of different amounts of MWNTs using sodium dodecylbenzensulfonate (SDBS) as surfactant at room temperature and normal pressure. Field emission scanning electron microscopy (FESEM) indicates that the polymer is wrapped around the nanotubes. Measurement of the nonlinear refractive indices (n2) and the nonlinear absorption (β) of the samples with different MWNT concentrations measurements were performed by a single Z-scan method using continuous wave (CW) laser beam excitation wavelength of λ = 532 nm. The results show that both nonlinear optical parameters increased with increasing the concentration of MWNTs. The third order nonlinear susceptibilities were also calculated and found to follow the same trend as n2 and β. In addition, the conductivity of the composite film was found to increase rapidly with the increase in the MWNT concentration.

Effect of Etching Time on Optical and Thermal Properties of p-Type Porous Silicon Prepared by Electrical Anodisation Method

The porous silicon (PSi) layers were formed on p-type silicon (Si) wafer. The six samples were anodised electrically with 30 mA/cm2 fixed current density for different etching times. The structural, optical, and thermal properties of porous silicon on silicon substrates were investigated by photoluminescence (PL), photoacoustic spectroscopy (PAS), and UV-Vis-NIR spectrophotometer. The thickness and porosity of the layers were measured using the gravimetric method. The band gap of the samples was measured through the photoluminescence (PL) peak and absorption spectra, then they were compared. It shows that band gap value increases by raising the porosity. Photoacoustic spectroscopy (PAS) was carried out for measuring the thermal diffusivity (TD) of the samples.