1 - Metal-Dielectric Nanocomposites Based on Germanate and Tellurite Glasses

Abstract

Recent photoluminescence (PL) studies performed with metal-dielectric nanocomposites (MDNCs) based on germanate and tellurite glasses doped and undoped with rare-earth ions and silver (Ag) nanoparticles (NPs) are reviewed. The fabrication of the MDNCs and their optical characterization are described. The contribution of the NPs for the optical response of the samples is characterized, and comments on their possible technological applications are presented. The examples given are based on the glass compositions GeO2-Bi2O3, GeO2-PbO, TeO2-ZnO-Na2O-PbO, and TeO2-ZnO. The influence of Ag NPs on the optical properties of GeO2-Bi2O3 glasses is analyzed for excitation at 808nm by monitoring the strong PL band from 1000 to 1600nm, due to bismuth ions (Bi+). An increase of the PL by 100% was observed and attributed to the large local field on the Bi+ located in the vicinities of the Ag NPs. The use of Ho3+/Tm3+/Yb3+-doped GeO2-PbO glasses with Ag NPs for white-light generation (WLG) is also reviewed. In this case, an adequate combination of rare-earth ions and Ag NP concentrations was essential to obtain efficient WLG. The use of Nd3+-doped GeO2-PbO glasses with Ag NPs is also reviewed and shows that this MDNC has good prospect to be exploited as optical amplifiers at 1064nm. As another example, the enhanced PL from Tb3+-doped TeO2-ZnO-Na2O-PbO glasses with embedded Ag NPs is also discussed. By the appropriate heat treatment of the samples, the visible PL spectrum was intensified, and enhancement of ≈200% of the Tb3+ emission at 550nm was observed. Also reviewed is the improved behavior of silicon and gallium phosphide solar cells covered with TeO2-ZnO glass doped with Eu3+ and contained Ag NPs. The results show the improvement of the solar cell efficiencies thanks to enhanced downconversion emissions due to Eu3+ excited at 473nm. In all cases discussed here, the presence of metallic NPs was essential to improve the optical performance of the samples aiming the different photonic applications considered.