Germanium oxide glass based metal-dielectric nanocomposites: fabrication and optical characterization: a review of new developments
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We review recent experimental results with germanate glasses containing rare-earth ions (RE) and silver nanoparticles (Ag-NPs) nucleated by appropriate heat-treatment of samples. In one study, the photoluminescence (PL) due to an infrared-to-visible frequency upconversion (UC) process was investigated in Bi2O3–GeO2 (BGO) glasses co-doped with ytterbium (Yb3+) and erbium (Er3+) ions when low concentration of AgNO3 was added to the starting glass composition. By exciting the samples at 980 nm, in resonance with the Yb3+ transition, we investigated the influence of the Ag-NPs on the UC process. The Er3+ PL was enhanced, up to 100%, due to the increased local-field sensed by the RE and to the efficient Yb3+ → Er3+ energy-transfer. In another set of experiments, we studied the behavior of BGO glasses containing thulium ions (Tm3+) and Ag-NPs. The role of energy-transfer from bismuth centers to Tm3+ was investigated. PL and relative gain enhancements of ≈ 56% and 500%, respectively, were observed due to the influence of Ag-NPs. Using a pump laser operating at 808 nm (6 W) and a probe laser at 1470 nm (0.6 mW) the relative gain measured at 1470 nm was 4.5 dB/cm. The results from the two sets of experiments indicate that Yb3+/Er3+ co-doped BGO glass with Ag-NPs is an efficient upconverter and Tm3+ doped BGO glass with Ag-NPs can be used as efficient optical amplifier in the short-wave infrared region.
We thank the financial support from the Brazilian Agencies: Conselho Nacional de Desenvolvimento Científico e Tecnológico - Grant: INCT/CNPq 465.763/2014 (Instituto de Fotônica), Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco - FACEPE: APQ 0409-1.05/17, and Coordenação de Aperfeiçoamento de Pessoal de Ensino Superior (CAPES) - PROEX 534/2018, grant: 23038.003382/2018-39. This work was performed in the framework of the PRONEX- Center of Excellence Program. The Nanotechnology National Laboratory (LNNano) of the CNPEM-Campinas/Brazil, is also acknowledged for the TEM measurements.
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