Structural and optical properties of antimony-germanate-borate glass and glass fiber co-doped Eu3+ and Ag nanoparticles

Effect of Silver Nanoparticles on the Optical Properties of Double Line Waveguides Written by fs Laser in Nd3+-Doped GeO2-PbO Glasses

Nd³⁺-doped GeO₂-PbO glass with silver (Ag) nanoparticles (NPs) are produced with double line waveguides through fs laser processing for photonic applications. A Ti:sapphire fs laser at 800 nm was used to write the waveguides directly into the glass 0.7 mm beneath the surface. This platform is based on pairs of parallel lines with spacing of 10 µm, each pair being formed by two identical written lines but in two different configurations of 4 or 8 separately processed lines, which are coincident. The results of optical microscopy, absorbance measurements, refractive index change, beam quality factor (at 632 and 1064 nm), photoluminescence, propagation losses, and relative gain at 1064 nm are presented. The structural changes in the glass due to the presence of Ag NPs were investigated by Raman spectroscopy. At 632 and 1064 nm, x,y-symmetrical guiding was observed, and for both kinds of overlapping pulses, a refractive index alteration of 10^-3 was found in both directions. Photoluminescence growth of ~47% at 1064 nm was observed due to the plasmonic effect of Ag NPs. In dual waveguides containing Ag NPs, the relative gain obtained increased by 40% and 30% for four and eight overlapping lines, respectively, at 600 mW of 808 nm pump power, when compared to waveguides without those metallic NPs. We highlight the resultant positive internal gains of 5.11 and 7.12 dB/cm that showed a growth of ~40% and ~30%, respectively, with respect to the samples without Ag NPs. The increase in photoluminescence and relative gain were related to the local field growth produced by Ag NPs. The present results show that the addition of Ag NPs impacts positively on the optical performance at 1064 nm of double line waveguides processed by fs laser writing in Nd³⁺-doped GeO₂-PbO glass, opening news perspectives for photonics.

Transition Metals (Cr3+) and Lanthanides (Eu3+) in Inorganic Glasses with Extremely Different Glass-Formers B2O3 and GeO2

Glasses containing two different network-forming components and doped with optically active ions exhibit interesting properties. In this work, glass systems based on germanium dioxide and boron trioxide singly doped with lanthanides (Eu³⁺) and transition metals (Cr³⁺) ions are research subjects. Optical spectroscopy was the major research tool used to record excitation and emission spectra in a wide spectral range for studied systems. The emitted radiation of glasses doped with Cr³⁺ ions is dominated by broadband luminescence centered at 770 nm and 1050 nm (⁴T₂ → ⁴A₂). Interestingly, the increase of concentration of one of the oxides contributed to the detectable changes of the R-line (²E → ⁴A₂) of Cr³⁺ ions. Moreover, EPR spectroscopy confirmed the paramagnetic properties of the obtained glasses. The influence of molar ratio GeO₂:B₂O₃ on spectroscopic properties for Eu³⁺ ions is discussed. The intensity of luminescence bands due to transitions of trivalent europium ions as well as the ratio R/O decrease with the increase of B₂O₃. On the other hand, the increase in concentration B₂O₃ influences the increasing tendency of luminescence lifetimes for the ⁵D₀ state of Eu³⁺ ions. The results will contribute to a better understanding of the role of the glass host and thus the prospects for new optical materials.

Novel Multicomponent Titanate-Germanate Glasses: Synthesis, Structure, Properties, Transition Metal, and Rare Earth Doping

Novel multicomponent titanate-germanate glasses singly doped with transition metal (Cr³⁺) and rare earth ions (Eu³⁺) were synthesized and the glass transition temperatures and thermal stability parameters were determined using DSC measurements. X-ray diffraction analysis confirmed fully amorphous nature of the received samples. Their structural and optical properties were compared with germanate glasses without TiO₂. Correlation between local structure and optical properties in titanate-germanate glasses is well evidenced by FT-IR, Raman, EPR, and luminescence spectroscopy. In particular, luminescence spectra and their decays are examined for glass samples, where GeO₂ was partially substituted by TiO₂.

Vibrational spectroscopy and density of K2O-B2O3-GeO2 glasses with variable B/Ge ratio

Glasses of the K₂O-B₂O₃-GeO₂ system were studied by means of Raman and IR spectroscopy. The density of the samples was measured and the dependence of the molar volume and atomic density on composition was calculated. Curve-fitting of Raman spectra was applied to obtain a definition of the main structural units formed in the system. The conditions for highly-coordinated boron and germanium atoms were obtained. It was shown that potassium cations remain connected to germanate structural units at a B/Ge ratio of up to 1, whereas the explicit redistribution of borate and germanate structural groupings becomes most noticeable only at a B/Ge ratio > 2.