Upconversion nanoparticles are appealing to various applications due to their energy conversion capabilities. However, their potential is limited by low efficiency, reproducibility, and poor morphology control. In this work, the synthesis of NaYF4 co-doped with Yb3+ and Tm3+ ions using both thermal decomposition (TD) and microwave irradiation heating (MW) using non-polar solvent were explored. Finding that the samples obtained by MW irradiation not only reduced reaction time but also decreased particle size from micrometers to nanometers. Also, their particle size distribution and shape control improved. The upconverted emission obtained in both cases is in consistency with the characteristic emission band of thulium located at 360, 451, 476, 645, and 802 nm corresponding with 1D2→3H6, 1D2→3F4, 1G4→3H6, 1G4→3F4, and 3H4→3H6 transitions, respectively.
This study investigates the feasibility of inducing crystallization in tellurite-phosphate glass within the TeO2-P2O5-BaF2- ZnF2-Na2O-Er2O3 system by direct laser writing (DLW) technique using a femtosecond laser beam operating at 1030 nm with a pulse duration of 230 fs. Two irradiation modes were examined: stationary-mode (1 MHz repetition rate, 160 nJ pulse energy, 120 s exposure time, for dot patterning) and translational-mode (200 kHz repetition rate, 10 μm/s translation speed, 470 nJ pulse energy, for line patterning) of laser irradiation. Our results, validated by Raman spectroscopy and scanning electron microscopy, revealed the formation of barium fluoride and zinc barium phosphate crystals in the areas irradiated employing stationary-mode. However, only barium fluoride nanocrystals were detected in the lines induced by the fs-laser employing the translational-mode. SEM analysis of the morphology and size of the laser-induced crystals showcased intriguing findings. In stationary-mode, barium fluoride crystals were distributed across the entire dot pattern area (30 μm), while zinc barium phosphate crystals were predominantly located at the edges of the dot spheres (with a size of 10 μm). Interestingly, barium fluoride nanocrystals with a size below 100 nm were detected in the area of laser irradiation in translational mode. Further structural analysis revealed alterations in the tellurite (TeO4) and phosphate (Q0) structural units within the glass matrix of the fs-laser crystallized tellurite-phosphate system. Moreover, we discussed the changes in erbium emission across the UV-NIR region in both laser-induced crystals and the parent glass. Notably, a stronger emission of erbium ions was observed in the glass compared to the crystalline phases, which needs further investigations. These preliminary findings underscore the potential of fs-laser writing for the development of telluritephosphate glass-ceramics.
In the paper, the possibility of obtaining broadband NIR luminescence in germanate glasses and fibers doped with transition metals (Cr, Ni), bismuth (Bi), and rare-earths (RE) has been investigated. In bismuth-doped GGB glasses, the influence of Sb2O3 content on luminescence properties has been studied, and the possibility of drawing glass into fiber. Luminescence at 1.3 μm with FWHM=209 nm was observed for the glass doped with 3 mol% Sb2O3 and 1.5 mol% Bi2O3. In the next step, the spectroscopic properties of Cr3+ doped GGB glass and optical fiber were investigated. After drawing glass into fiber FWHM (full with at half maximum) at 1.0 μm increased from 202 nm to 234 nm compared to bulk glass. Obtained luminescence at 1.0 μm can be attributed to the 4T2 → 4A2 transition of Cr3+ ions. For multicore glass-ceramic optical fiber, broadband near-infrared emission in the range of 1.1 to 2.1 μm was obtained under 940 and 980 nm pump excitation as a superposition of luminescence bands of Ni2+, Er3+, Tm3+ and Ho3+ ions.
This study introduces constructions of the structural (multiring) doping profile for Large Mode Area fibers, incorporating Tm3+ and Tm3+/Ho3+ layer profiles. The presentation includes a numerical analysis of modal properties and beam shape. The chelate doping technology (CDT) of modified chemical vapour phase deposition (MCVD), known for its low attenuation active preforms fabrication method, was employed in optical fiber manufacturing. The multi-stage deposition in the MCVD-CDT system enables the fabrication of optical preforms with up to 20 layers. Concentrations of lanthanides were optimized to achieve broadband emission in the eye-safe spectral range of 1.55 to 2.10 µm. The fiber construction employed Tm3+ doping design used for a laser construction utilizing the Fabry-Perot resonator for single-mode laser beam generation at a wavelength of 1940 nm, with an M2 value of approximately 1.1.
Acknowledgments: The project was funded by the National Science Centre (Poland) granted on the basis of decision no. UMO-2020/37/B/ST7/03094.
This presentation explores the interdisciplinary realm of nanocomposite material design, integrating materials engineering, chemistry, and photonics. Focusing on the innovative use of nanocomposite glasses containing noble metal nanoparticles, the discussion delves into the novel opportunities these materials present for developing sensing structures based on LSPR (Localized Surface Plasmon Resonance). Additionally, transparent glass-ceramics are spotlighted as high-performing materials in functional photonic applications for optical fiber technology.
Fluoroindate glass is characterized by low phonon energy (500 cm-1 ), which enables most of the radiative transitions in the lanthanides to occur in the range VIS-NIR. It allows considering this matrix as a potential host glass for NIR emission and light sources. This work reports the fabrication and analysis of luminescence properties, and structure of the fluoroindate glasses and glass-ceramics (GC) co-doped with Eu3+ ions. The materials' microstructure and structure were analysed using X-ray diffraction (XRD) and Raman measurement techniques, respectively. It has been shown that the basic structural units in the glass network are [InF6] octahedrons tetrahedrons. The luminescence analysis was performed in the glass and glass-ceramics samples doped with EuF3 showing the excitation and emission properties and changes in the lifetimes. The excitation at 395 nm resulted in different emissions in blue, green, and red which correspond to the transitions from 5DJ (J=0 to 3) multiples to the 7FJ (J= 0 to 6), which is the effect of the low phonon energy of the matrix and is comparable with other low phonon materials. In the glass-ceramics, the effect of network ordering around the Eu3+ ions was noticed. The fluorescence intensity ratio R/O related to 5D0→7F2 and 5D0→7F1 transitions in Eu3+ decreased from 0.74 to 0.56 value. Obtained results allowed to consider this GC material as a potential host for luminescent material and possibly glass fiber sources.
The Large Mode Area (LMA) fibers are attractive in the field of new components in optical fiber technology in the field of sensing and novel radiation sources. The numerical analysis of multi-ring (multi trench) fiber construction is investigated for eye-safe transmission spectral range (1400-2100 nm). The optical fiber refractive profile construction of ∆n (0.001- 0.004) for different radial step ∆r (1.0-1.6 µm) is used for the investigation of linearly polarized modes (LP01 and LP11) propagation. The maximum mode field diameter (MFD) of LP01 was calculated. The results confirm the LMA propagation possibility in the presented fiber construction. The single-mode guiding was confirmed for different ∆n and ∆r parameters in the investigated spectral range. The cutoff wavelength <1400 nm and single-mode operation are possible for ∆n=0.001 and ∆r=1 µm.
Incorporating new optical materials as nanocrystals into glass fibres for new functionalities has recently become a hot research topic. Our team (funded by the European FET Open project NCLAS) investigates the introduction of nanoscale laser crystallites into the core of optical fibres using the glass powder doping method. Active Y2O3:Pr3+ nanocrystals (NCs) were prepared via different synthesis methods, and structurally and spectroscopically characterized. After modification of technological parameters, the optimised NCs have been proposed as a luminescence centres to embed into germanate and silicate glass hosts. Glasses were analysed in terms of optical (transmission, refractive index matching to NCs) and thermal (thermal stability, viscosity, thermal expansion coefficient) parameters. Crystallisation issues during fibre drawing were particularly investigated. In a first step, glass powder-NCs mixing techniques and fibre preform preparation were developed. It was shown that temperature cycle profiles including dwell time and heating/cooling ramp rates influenced the glass-NCs properties and can lead to glass crystallisation or NCs dissolution. The sintering investigations pointed out the melting temperature limits to preserve active NCs in the glasses. In germanate glasses, Y2O3:Pr3+ dissolution was noticed at 800°C. In the case of the silicate glass compositions these regions vary from 700°C to 1050°C. The results allowed to select optical fibre drawing conditions performed by the powder-in-tube method. Their distribution uniformity is not yet sufficient, requiring further optimisation of the drawing kinetics.
Fluoroindate glasses co-dopped with Er3+ at different concentrations were synthesized using the melting quenching technique, where it was observed that the emission peak located at 1.53 μm associated with 4I13/2→4I15/2 transition of Er3+ increases up to 11.5 times with increasing ErF3 content up to 1.4 mol. %. Such increase is significant due to their proximity with one of the most important telecommunication windows (1.55 μm) which the spite of all the studies around it, some challenges like its efficiency need to be optimized. The effect of sensitization of the Er3+ by Yb3+ ions was also evaluated. The increase in luminescence intensity (~19%) was obtained by co-doping of 1.4ErF3 glass by 0.8YbF3. This effect is related to the efficient Yb3+→ Er3+ energy transfer.
In the paper, 1.4 – 2.2 μm broadband emission under 796, 808, 980 nm laser diode excitation in low phonon energy germanate glass system co-doped with 0.7Er2O3/0.35Tmo2O3 (1st core) and 0.7Tm2O3/0.15Ho2O3 (2nd core) were investigated. Next, double-core, double-clad optical fiber has been developed by the modified rod-in-tube technique. Amplified spontaneous emission (ASE) in double-clad optical fiber with 3dB bandwidth was measured to be 346 nm and 677 nm for - 10 dB. ASE spectrum is a result of the partial donor-acceptor energy transfer and superposition of Er3+: 4I13/2 → 4I13/2, Tm3+: 3F4 → 3H6, 1.8 μm and (Ho3+:5I7 → 5I8) 2 μm emission bands. Excellent spectroscopic properties indicate that the developed germanate optical fiber is a promising active element for construction compact, broadband ASE sources.
Eu3+ - doped oxyfluoride tellurite-germanate glass-ceramics were fabricated by the controlled crystallization method. The microstructure and structure of samples were analysed using x-ray diffraction (XRD), transmission electron microscopy (TEM), and infrared spectroscopy (IR). The EuF3 introduction caused the rise of the non-bridging oxygens/fluorides in glass network in a consequence of the [TeO,F4] and [GeO,F4] structural units transformation into the [TeO,F3]/[TeO,F3+1], and [GeO,F6], respectively. These changes were caused by Eu3+ ions, which played the role as a network modifier and led to the new non-bridging oxygens/fluorides Te–O,F− Eu3+O,F−–Te, and Ge– O,F−Eu3+O,F−–Ge, linkages formation and the ZnTe crystalline phase. The structure changes caused by the Eu3 + ions incorporation in the crystalline phase have been discussed in accordance to analysed the photoluminescence (PL) spectra and decay curves. It was showed a significant increase of the 5D0 → 7F1 magnetic-dipole transition intensity and decay times for transparent glass-ceramics sample. It confirmed the migration of Eu3+ ions from the amorphous network into ZnTe nanocrystals.
In this work, thermal and luminescent properties of lithium-borate glass and glass-ceramics co-doped with Eu3+/Dy3+ and Eu3+/Tb3+ ions have been investigated. The parent borate glasses were synthesized by the standard melt-quenching method. The amount of crystallites grown in the glass was controlled by the appropriate choice of annealing time and temperature. Stronger luminescence has been observed for glass-ceramics than for glass in each case. Zinc lithium borate (LiBZnF) glass-ceramics co-doped with 0.25Eu and 0.5Tb had the strongest luminescence under 388 nm laser excitation. The energy transfer mechanisms between Tb3+ and Eu3+ ions and Dy3+ and Eu3+ ions were discussed. Also, the influence of the molar ratio of active ions on the colour coordinates (CIE-1931) have been investigated.
In the article, the effect of samarium ions doping on the spectroscopic and biological properties of 45S5 Bioglass® was presented. The luminescence spectra of doped glasses have been analyzed in the visible range under 405 nm laser excitation. The in vitro method for testing the apatite-forming ability of bioactive glasses was used. Crushed to 100μm fractions bioactive glasses were immersed in Simulated Body Fluid (SBF) prepared by the Kokubo method. The material was incubated at 37°C for 3 days and then the measurements of ions (Ca, Na, Si) release in SBF were carried out. The bioactivity test indicated that Sm3+ ions affect not only on the luminescent properties of the bioactive glasses but also their capability of creating the hydroxycarbonate-apatite (HCA) layer.
The article presents the use of Eu3+ ions as a spectroscopic probe to measure changes in glass structure without interfering with the tested material. The aim of the work is to obtain bioactive glass-ceramics structure with increased mechanical properties. Examined 45S5 Bioglass® was annealed at 620°C for 8h. XRD measurements indicate the formation of the glass-ceramics structure with nanocrystals (Na4CaSi3O9). Despite the additional heat treatment, the bioactivity of the glass has been preserved. The changes of luminescence profile of Eu3+ - doped glass was determined. Decreasing value of fluorescence intensity radio parameter after annealing indicates symmetry around europium ions and thus the arrangement of the glass structure.
Structural and optical properties of Eu3+ doped barium-gallo-germanate glasses modified with antimony and tellurium oxides were investigated. Barium ions are gradually replaced by antimony and tellurium ions to create two glass series. Structural properties of prepared series were established with help of FT-IR spectroscopy, X-ray diffraction method and observation under Scanning Electron Microscope (SEM). MIR spectra of studied glasses indicate a tendency to glass structure polymerization through the observed shift of main band assigned to Ge-O-Ge and Ge-O bonds vibrations. Simultaneously luminescence spectrum of Eu3+ ion (Electric/Magnetic – ED/EM dipole transition intensity ratio) for both glass series presented the increasing tendency to ordering of Eu3+ local environment. It was also proved that tetrahedral [TeO4] units were created in glass structure which were modified with TeO2 when addition exceed 10 mol%. The result indicates decrease of ED/MD ratio as a function of TeO2 content above its 10 mol%.
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