Showing papers by "Habib Tajalli published in 2009"
TL;DR: The aggregate structures and the nature of the interacting pairs in these dyes were discussed using the exciton theory and the effect of molecular structure of the surfactants on the aggregative behavior of the rhodamine dyes was determined.
74 citations
TL;DR: In this article, the nonlinear optical properties of oxazine dyes, i.e., oxazine 720 (OX720) and oxazine 750 (OX750), in aqueous solution and in polyacrylamide hydrogel (PAA) matrix were studied by Z-scan technique using CW He-Ne laser at 632.8nm.
37 citations
TL;DR: In this article, the localized surface wave at the interface between an uniform right-handed material and a semi-infinite periodic multilayer structure containing alternate e-negative and the μ-negative layers was investigated, and it was shown that this system can only support TE or TM-polarized surface waves depending on the relative thicknesses of the ENG and the MNG layers.
Abstract: The localized surface waves at the interface between an uniform right-handed material and a semi-infinite periodic multilayer structure containing alternate e-negative (ENG) and the μ-negative (MNG) layers have been investigated. We demonstrated that this system can only support TE or TM-polarized surface waves depending on the relative thicknesses of the ENG and the MNG layers. These localized modes can have two different transverse structure related to the order of the ENG and the MNG layers; one with a hump at the interface between uniform material and the cap layer and the other one with a hump at the interface between the cap layer and the periodic multilayer structure.
18 citations
TL;DR: In this article, an experimental phase diagram for two types of nematic liquid crystals and their binary mixtures was established by polarised optical microscopy and differential scanning calorimetry methods.
Abstract: An experimental phase diagram for two types of nematic liquid crystals and their binary mixtures was established by polarised optical microscopy and differential scanning calorimetry methods. The mixtures comprised a tolane-base liquid crystal, 4-heptyl-3-fluoro-4-isothiocyanatotolane (7TOLF), and a biphenyl-base nematogen, 4-heptyl-3-fluoro-4-isothiocyanatobiphenyl (7BF). The static Kerr effect and third-order non-linearity were investigated for 7TOLF and 7BF and their nematic mixtures within the isotropic phase. Both the compounds have a positive and large Kerr constant. The second-order phase-transition temperatures, T∗, were determined for these mixtures. The linear dependence of (T - T∗)− 1 on the Kerr constant is found to be in good agreement with the predications of the Landau–de Gennes model. The third-order non-linear susceptibility,χ(3), values were determined for these mixtures.
5 citations
TL;DR: The static Kerr effect and third order nonlinearity were investigated for mixtures of the tolane-base liquid crystals within the isotropic phase in the neighborhood of the nematic phase as discussed by the authors.
Abstract: The static Kerr effect and third order non-linearity were investigated for mixtures of the tolane-base liquid crystals within the isotropic phase in the neighborhood of the nematic phase. The nematic mixtures are characterized by components having similar molecular structure, i.e., the mixtures comprised by 4′-pentyl-3-fluoro-4-isothiocyanatotolane (5TOLF) and 4′-heptyl-3 fluoro-4-isothiocyanatotolane (7TOLF) which have a positive and large Kerr constant. The nematic to isotropic transition temperatures and nematic to crystalline temperatures for these mixtures were measured using DSC and polarizing microscopy methods. The nematic mixture of M3 (%50 5TOLF + %50 7TOLF) shows the largest nematic range. The linear dependence of (T − T*)−1 on the Kerr constant is found to be in good agreement with the predications of the Landau-De Gennes model. The hypothetical second order phase transition temperatures and susceptibility values were determined for these compounds.
5 citations
TL;DR: In this paper, the nonlinearity of a guest-host system can be affected by control of phototautomerism and incident light modulation, and the results indicate that the variation of nonlinearities can be stable, so it can generate a stable refractive index pattern.
3 citations