RESUMO
A series of novel Er3+-doped bismuth-germanate glasses containing different tungsten concentrations with a molar composition of 97.5[(75 - x)GeO2-25Bi2O3-(x)WO3]-2Sb2O3-0.5Er2O3 (x = 5, 10, 15, 20, and 25 mol%) were fabricated. Their thermal properties are measured by differential scanning calorimetry. A structural investigation by Raman spectroscopy suggested that changes occurred in the glass network by WO3 incorporation. By laser excitation at 980 nm, a strong emission from Er3+ ions at 1532 nm is observed, while the WO3 addition caused changes in the emission spectra. The emission cross-section spectra of Er3+ are calculated by both McCumber and Füchtbauer-Ladenburg theories and their comparison showed these theories yielded slightly different results, but in both cases, the calculations showed that a gain signal in L-band can be achieved when 30% of the Er3+ ions are at the excited state. This study proves that the Er3+-doped bismuth-germanate glasses are suitable for optical fiber amplifier applications operating at C- and L-band.
RESUMO
Glass and glass-ceramics containing nanocrystals of Bi2Te4O11 cubic phase co-doped with Er3+ and Yb3+ were prepared by heat treatment of the precursor tellurite glass and investigated for optical applications. Lanthanide doped tellurite glass and glass-ceramics have been extensively investigated because of their optical and photoluminescence performance for technological photonic applications. Er3+ and Er3+/Yb3+ doped TeO2-GeO2-K2O-Bi2O3 tellurite glass compositions were prepared by the conventional melt-quenching method. Photoluminescence results showed the important role played by Yb3+ ions when co-doping with Er3+ ions in comparison with the Er3+ single-doped glass. Due to their larger absorption cross-section, Yb3+ species significantly absorbs 980 nm photons and effectively transfers them to Er3+ ions via a set of mechanisms including ground-state absorption (GSA), excited-state absorption (ESA), and energy transfer upconversion (ETU). Er3+/Yb3+ co-doped sample was chosen for the synthesis of transparent glass-ceramics by controlled heat treatment above Tg for 5 to 120 min. X-ray diffraction patterns, high-resolution transmission electron microscopy (TEM) images, and selected area electron diffraction (SAED) from Er3+/Yb3+ co-doped glass-ceramic samples were used to verify the nanocrystal precipitation, crystalline phase, and chemical nature. The structural change resulting from the crystallization of Bi2Te4O11 nanocrystals was evaluated by the Raman shift of the bands between 300-500 cm-1, which are assigned to the formation of Bi-O-Te linkages and the reduction of [TeO3] depolymerized units. The effects of HT time on the glass-ceramic's optical and upconversion photoluminescence properties were studied in the visible range under excitation at 980 nm in terms of the energy transfer mechanisms from Yb3+ to Er3+. Results indicate that Er3+/Yb3+ co-doped tellurite glass and glass-ceramics are potential candidates for photonic applications in lighting, energy conversion, and luminescent solar cell concentrators.
RESUMO
Erbium-doped tellurite glass containing copper nanoparticles showed multi-band emission of one particular transition (4I9/2â4I15/2, at 980 nm) due to electron-lattice coupling. The present study reports the vibronic transitions of intraconfigurational 4fn transitions of Er3+ ions in a tellurite host matrix at room temperature for the first time. The mechanisms of multiphoton transitions and the effect of laser heating are discussed here. This unprecedented behavior enables the design of a plethora of different applications spanning from tunable emission in the near infrared, such as lasers for bioimaging and biomedical fields, to energy conversion by thermophotovoltaic conversion of thermal radiation.
