Browsing by Subject "conjugated polymers"

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    Lasing action and supercontinuum generation in nano- and micro-structures
    (2009) Akbulut, Duygu
    Supercontinuum generation is the substantial broadening of electromagnetic radiation due to nonlinear interactions with the transporting medium. It nds application in a wide range of areas, including spectroscopy, frequency metrology, optical coherence tomography and telecommunications. Whispering gallery mode microresonators con ne light in a micron scale area via total internal re ection mechanism. Among these structures, microtoroid is especially interesting since it combines ultrahigh quality factor and chip integrability. Applications of such structures include nonlinear and quantum optics, biological and chemical sensing, telecommunications and quantum electrodynamics. In the rst part of the present work, continuum generation from a nanostructured chalcogenide glass (As2Se3) core, high temperature polymer (polyethersulfone, PES) cladding ber was experimentally investigated. Simulation results for nonlinear interactions inside a microtoroid are also provided. In the second part, polymer coated toroidal microresonators were employed for observation of laser action. Owing to high quantum e ciency of the polymer, the observed lasing threshold has a very low value of 200 pJ/pulse despite free space excitation.
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    Novel design-based complex nanostructures in hybrid core-shell architectures for high-efficiency light generation
    (2010) Özel, İlkem Özge
    Recent developments in nanoscience and nanotechnology have given rise to the discovery of hybrid nanostructured multi-component materials that serve several tasks all at once. A very important and rapidly growing field of these materials is the development of highly efficient fluorophores to meet the urgent demand of low-energy consuming, high-quality light emitters for future solid-state lighting applications. Such hybrid nanomaterials are entailed to exhibit extraordinary optoelectronic properties compared to the bulk case of their single components such as enhanced quantum efficiency, tunable multi-color emission, and reduction of multiple processing steps. Herein, to address these requirements, we propose and demonstrate novel design-based complex nanomaterials in hybrid multi-shell architectures for high-efficiency light generation. These requirements are made possible by using the concept of hybrid core-shell-… nanostructures comprising at least two units, including hybrid metalcore/dielectric-shell nanoparticles furnished with an outer shell of semiconductor nanocrystals for enhanced emission and different conjugated polymers forming a single multi-polymer nanoparticle and emitting simultaneously at different wavelengths. In the first part of this thesis, we developed and demonstrated Au-silica core/shell nanoparticles that successfully assemble CdTe nanocrystals right on their silica shells for enhanced plasmonexciton interactions, while solving the common problems of lacking control in dielectric spacing and limited film thickness typically encountered in such plasmon-coupled nanocrystals. Here we present the synthesis and characterization results of this new set of multi-shell decorated nanoparticle composites with a tunable dielectric spacing thickness of silica shell precisely controlled by synthesis to optimize plasmon-exciton interactions for enhanced emission. Experimental data obtained from steady-state and time-resolved photoluminescence measurements together with extensive computational analysis clearly verify the strong plasmon-exciton interactions in these designbased multi-shell nanocomposites. In the second part, we construct bi-polymer nanoparticle systems in various architectures of core/shells, for each of which thorough investigations of the non-radiative energy transfer mechanisms are made. Here we present the synthesis and characterization results of these core/shell bi-polymer nanoassemblies. The flexibility of designing such bipolymer nanostructures allows for the optimization of maximum energy transfer efficiency. This concept of complex hybrid nanostructures for high-efficiency light generation opens up new paths for optoelectronic devices and nanophotonics applications including those in solid-state lighting.