Luminescent Studies on Germanate Glasses Doped with Europium Ions for Photonic Applications

Abstract

Glass and ceramic materials doped with rare earth (RE) ions have gained wide interest in photonics as active materials for lasers, optical amplifiers, and luminescent sensors. The emission properties of RE-doped glasses depend on their chemical composition, but they can also be tailored by modifying the surrounding active ions. Typically, this is achieved through heat treatment (including continuous-wave and pulsed lasers) after establishing the ordering mechanisms in the particular glass–RE system. Within the known systems, silicate glasses predominate, while much less work relates to materials with lower energy phonons, which allow more efficient radiation sources to be constructed for photonic applications. In the present work, the luminescent and structural properties of germanate glasses modified with phosphate oxide doped with Eu3+ ions were investigated. Europium dopant was used as a “spectroscopic probe” in order to analyze the luminescence spectra, which characterizes the changes in the local site symmetries of Eu3+ ions. Based on the spectroscopic results, a strong influence of P2O5 content was observed on the excitation and luminescence spectra. The luminescence study of the most intense 5D0→7F2 (electric dipole) transition revealed that the increase in the P2O5 content leads to the linewidth reduction (from 15 nm to 10 nm) and the blue shift (~2 nm) of the emission peak. According to the crystal field theory, the introduction of P2O5 into the glass structure changes the splitting number of sublevels of the 5D0→7F1 (magnetic dipole) transition, confirming the higher polymerization of fabricated glass. The slightly different local environment of Eu3+ centers the results in a number of sites and causes inhomogeneous broadening of spectral lines. It was found that the local asymmetry ratio estimated by the relation of (5D0→7F2)/(5D0→7F1) transitions also confirms greater changes in local symmetry around Eu3+ ions. Our results indicate that modification of germanate glass by P2O5 allows control of their structural properties in order to functionalize the emissions for application as luminescent light sources and sensors.

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

“…Further studies revealed that modification of germanate glasses by P 2 O 5 allows control of their local structure and visible luminescence. The increase of P 2 O 5 content leads to the reduction of spectral linewidth and the shift of emission band of Eu 3+ ions in germanate glass to shorter wavelengths [ 23 ]. The effect of the spectroscopic properties of Tm 3+ ions for different compositions with varying Nb 2 O 5 /La 2 O 3 ratios has been studied and the optical concentration of glass components for efficient 1.8 µm near-infrared laser applications was determined [ 24 ].…”

Influence of Oxide Glass Modifiers on the Structural and Spectroscopic Properties of Phosphate Glasses for Visible and Near-Infrared Photonic Applications

“…It is generally known that the 5 D 0 → 7 F 1 is a magnetic dipole (MD) transition which is independent of local symmetry [ 73 ]. However, 5 D 0 → 7 F 2 is strongly influenced by the environment of europium ions and this electric dipole (ED) transition is said to be a hypersensitive transition [ 74 ]. For that reason, the ratio of the 5 D 0 → 7 F 2 to 5 D 0 → 7 F 1 transitions informs us about local asymmetry around the Eu 3+ ions in the glass host.…”

Experimental and theoretical studies on NIR luminescence of titanate‐germanate glasses doped with Pr3+ and Tm3+ ions

“…Furthermore, previously published results proved that the presence of modifier oxides has an important influence on the structural, thermal, and spectroscopic properties of low phonon glass systems containing rare-earth ions. [25][26][27] Among metal oxides that are components of glasses emitting NIR luminescence, titanium(IV) oxide (TiO 2 ) deserves particular attention. 28,29 The addition of TiO 2 increases the linear and non-linear refractive indices, increasing the radiative transition probabilities and improving the non-linear optical properties.…”

“…Furthermore, previously published results proved that the presence of modifier oxides has an important influence on the structural, thermal, and spectroscopic properties of low phonon glass systems containing rare‐earth ions 25–27 . Among metal oxides that are components of glasses emitting NIR luminescence, titanium(IV) oxide (TiO 2 ) deserves particular attention 28,29 .…”