Browsing by Subject "Colloids"

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    Femtosecond response of J aggregates adsorbed onto silver colloid surfaces
    (2003) Yaǧlioǧlu G.; Dorsinville, R.; Özçelik, S.
    The observation of stimulated emission from J aggregates adsorbed onto silver colloid surfaces using femtosecond excitation was reported. The stimulated emission was inferred from the excitation intensity and wavelength dependence of the emission band. The stimulated emission originated from the amplification of the one-exciton state emission by an induced transition from the two-exciton state to the one-exciton state.
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    Hard-core Yukawa model for charge-stabilized colloids
    (American Physical Society, 2000) Davoudi, B.; Kohandel, M.; Mohammadi, M.; Tanatar, Bilal
    The hypernetted chain approximation is used to study the phase diagram of a simple hardcore Yukawa model of a charge-stabilized colloids. We calculate the static structure factor, the pair distribution function, and the collective mode energies over a wide range of parameters, and the results are used for studying the freezing transition of the system. The resulting phase diagram is in good agreement with the known estimates and the Monte Carlo simulations. ©2000 The American Physical Society.
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    Near resonant third-order optical nonlinearities of colloidal InP/ZnS quantum dots
    (AIP Publishing, 2013) Wang, Y.; Yang, X.; He, T. C.; Gao, Y.; Demir, Hilmi Volkan; Sun, X. W.; Sun, H. D.
    We have investigated the third-order optical nonlinearities of high-quality colloidal InP/ZnS core-shell quantum dots (QDs) using Z-scan technique with femtosecond pulses. The two-photon absorption cross-sections as high as 6.2 × 103 GM are observed at 800 nm (non-resonant regime) in InP/ZnS QDs with diameter of 2.8 nm, which is even larger than those of CdSe, CdS, and CdTe QDs at similar sizes. Furthermore, both of the 2.2 nm and 2.8 nm-sized InP/ZnS QDs exhibit strong saturable absorption in near resonant regime, which is attributed to large exciton Bohr radius in this material. These results strongly suggest the promising potential of InP/ZnS QDs for widespread applications, especially in two-photon excited bio-imaging and saturable absorbing.
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    Superradiant lasing from J-aggregated molecules adsorbed onto colloidal silver
    (American Institute of Physics, 1998) Özçelik, S.; Özçelik, I.; Akins, D. L.
    The picosecond time-resolved emission spectrum of the cyanine dye 1,18-diethyl-3,38- bis-~3-sulfopropyl!-5,58,6,68-tetrachlorobenzimidazolocarbocyanine ~also known as BIC! adsorbed onto colloidal silver was examined as a function of laser pulse energy at room temperature. BIC is found to aggregate on colloidal silver, and the number of coherently responding molecules involved in the one-exciton state ~i.e., the coherence length! was estimated to involve 8–9 molecules. Lasing at a remarkably low incident pulse energy threshold was found for this system and explained in terms of a mechanism involving superradiant states created in coherently coupled adsorbed molecules that emit photons which stimulate emission from other spatially distributed superradiant states. © 1998 American Institute of Physics.