No abstract

The electro-optic (EO) effect in nanodisordered potassium tantalate niobate (KTN) crystal is quantitatively investigated. It is found out that the EO coefficient of nanodisordered KTN crystal depends not only on the cooling temperature but also on the cooling rate. A larger EO coefficient can be obtained by employing a faster cooling rate. A Kerr EO efficient (s(11) - s(12) = 6.94 × 10(-14) m(2)/V(2)) is obtained at a cooling rate of 0.45 °C/s. The enhanced EO efficient by employing a faster cooling rate will be greatly beneficial for a variety of applications such as laser Q switches, laser pulse shaping, high-speed optical shutters, and modulating retroreflectors.

Dendrimer metal nanocomposites are novel hybride materials that display unique physical and chemical properties as a consequence of the atomic/molecular level dispersion of inorganic and organic molecules. In their synthesis, dendrimers are used as templates to pre-organize metal ions followed by an in-situ reduction, which will immobilize and stabilize atomic domains of the reaction product(s). Size, shape, size distribution and surface functionality of these nanocomposites are determined and controlled by the dendritic macromolecules and may also be influenced by the encapsulated compounds. Solubility of these molecular nanocomposites is controlled by the polymer. Thus, it is possible to solubilize conventionally insoluble inorganic compounds in water or other solvents using dendritic hosts. Conceptually, these materials have enormous potential for applications such as catalysts or molecular devices.In this work, surface-modified poly(amido-amine) dendrimers were used to prepare {Cu(0)-PAMAM}, {Ag(0)-PAMAM} and {Au(0)-PAMAM} dendrimer-metal nanocomposites containing stable and solvent soluble zero valence metals. Characterization of the resulting nanocomposites has been carried out by TEM, UV-visible spectroscopy, and scattering techniques. Depending on the chemistry of ion preorganization in the dendrimer, internal (“I”), external (“E”) and mixed (“M”) type nanocomposite structures could be identified according to the varying location of the actual metal content.The effect of structural differences was found to be reflected in the optical properties of the nanocomposites.

The singlet excited-state lifetime of a bipyridyl platinum(II) complex containing two alkynyl-benzothiazolylfluorene units was determined to be 145+/-105 ps by fitting femtosecond transient difference absorption data, and the triplet quantum yield was measured to be 0.14. A ground-state absorption cross section of 6.1 x 10(-19) cm(2) at 532 nm was deduced from UV-visible absorption data. Excited-state absorption cross sections of (6.7+/-0.1) x 10(-17) cm(2) (singlet) and (4.6+/-0.1) x 10(-16) cm(2) (triplet) were obtained by using a five-level dynamic model to fit open-aperture Z scans at picosecond and nanosecond pulse widths and a variety of pulse energies. For this complex, the ratio of the triplet excited-state absorption cross section to the ground-state absorption cross section--long used as a figure of merit for reverse saturable absorbers--thus stands at 754, to our knowledge the largest ever reported at 532 nm wavelength.

The singlet excited-state lifetime of a terpyridyl platinum(II) pentynyl complex was determined to be 268+/-87 ps by fitting femtosecond transient absorption data, the triplet excited-state lifetime was found to be 62 ns by fitting nanosecond transient absorption decay data, and the triplet quantum yield was measured to be 0.16. A ground-state absorption cross section of 2.5 x 10(-19) cm(2) at 532 nm was deduced from UV-vis absorption data. Excited-state absorption cross sections of 3.5 x 10(-17) cm(2) (singlet) and 4.5 x 10(-17) cm(2) (triplet) were obtained by using a five-level dynamic model to fit open-aperture Z scans at picosecond and nanosecond pulse widths and a variety of pulse energies.