Thesis (Ph.D.) - Cairo University - National Institute of Laser Enhanced Sciences - Department of Laser Sciences and Interactions

At surfaces, interactions of light with metal nanostructures can generate collective excitations in the form of localized surface plasmons (LSPs) or surface plasmon polaritons (SPPs). The latter interacts with quantum systems such as excitons (X) in a nearby semiconductor. The interactions of plasmon with excitons and light- pemitting systems can enhance or reduce their quantum efficiency. In this work, metal-dielectric heterostructures were used to generate surface plasmon amplification by stimulated emission of radiation (SPASERs). [1] The thesis studied the effect of a metal NPs and metal-dielectric NPs on optical properties of an active medium (CdTe semiconductor quantum dots QDs). The study was carried out for two nano-structures; mixture and heterostructure (nanocomposite (NC)) with Ag metal NPs. The factors affecting the lasing properties of CdTe QDs in case of heterojunction nanostructure have been investigated. Firstly, we prepared Ag NPs, Ag-SiO2 core-shell NPs and CdTe QDs.Thereafter; mixtures of different concentration of Ag NPs with CdTe QDs and Ag-SiO2 core-shell with CdTe QDs were prepared to investigate the photoluminescence (PL) of CdTe QDs in these two mixtures. While PL quenching was observed in presence of Ag NPs, PL enhancement was reported in presence of Ag-SiO2 core shell

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