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In this paper, we report on fabricating optical fibers with a controlled process of crystallization core during the drawing process. The research and synthesis of the core material of silica-germanium-antimony oxide glass were discussed. We also investigated the optical and luminescence properties were in relation to concentrating Eu 2 O 3 and P 2 O 5. Based on this investigation, we selected the most promising material for optical fiber core. In the next step, we drew optical fibers using a well-known rod-in-tube method. After drawing, we examine the optical fibers for luminescence shape changes. We observed a promising similarity between optical fibers and heat-treated samples with confirmed nanocrystals. Finally, XRD and TEM measurements confirm EuPO 4 nanocrystals at the core of the optical fiber. Highlighting the successful control of crystallization in the one-step method used to draw optical fibers. [ABSTRACT FROM AUTHOR]

LMA (Large Mode Area) optical fibers are presently under active investigation to explore their potential for generating laser action or broadband emission directly within the optical fiber structure. Additionally, a wide mode profile significantly reduces the power distribution density in the fiber cross-section, minimizing the power density, photodegradation, or thermal damage. Multi-stage deposition in the MCVD-CDT system was used to obtain the structural doping profile of the LMA fiber multi-ring core doped with Tm3+ and Tm3+/Ho3+ layer profiles. The low alumina content (Al2O3: 0.03wt%) results in low refractive index modification. The maximum concentrations of the lanthanide oxides were Tm2O3: 0.18wt % and Ho2O3: 0.15wt%. The double-clad construction of optical fiber with emission spectra in the eye-safe spectral range of (1.55–2.10 µm). The calculated LP01 Mode Field Diameter (MFD) was 69.7 µm (@ 2000 nm, and 1/e of maximum intensity), which confirms LMA fundamental mode guiding conditions. The FWHM and λmax vs. fiber length are presented and analyzed as a luminescence profile modification. The proposed structured optical fiber with a ring core can be used in new broadband optical radiation source designs. [ABSTRACT FROM AUTHOR]

In this study, a comprehensive analysis of emission in erbium-doped and erbium and ytterbium co-doped fluoroindate glasses has been presented. The luminescence of the erbium transitions and the effect of ytterbium co-doping under 488, 808 and 976 nm laser excitation have been discussed. Optimization of rare-earth (RE) ions doping concentration and the energy transfer processes related to the sensibilization effect in Er3+/Yb3+ co-doped fluoroindate glasses focusing on the reciprocal distribution of radiative transitions, energy transfer parameters, and lifetimes have been analyzed. The luminescence consists of several bands in the visible (525, 546 and 660 nm) and the infrared (1550 and 2700 nm) spectral regions that correspond to characteristic radiative energy transitions within the erbium ions. In glasses co-doped with the Er3+/Yb3+ system, an augmentation in the emission intensity was observed in the visible and at 1550 nm, while a decrease was observed in the 2700 nm infrared band. The increase of the Yb3+: 2F 5/2 lifetime under 488, 808 and 976 nm excitation showed significant Er3+: 4I 11/2 → Yb3+: 2F 5/2 back energy transfer. Based on the analysis of the available literature, it can be concluded that energy transfer upconversion and cooperative energy upconversion play a significant role in modulating luminescence intensity values within the examined emission bands. This effect is likely enhanced due to the incorporation in a low phonon energy glass matrix. As a result of the above optimization, a glass optical fiber co-doped with 0.8 YbF 3 /1.4 ErF 3 (in mol%) was drawn and characterized, showing a strong emission at 2.77 μm. The optimized Er3+/Yb3+ co-doped fluoroindate glass and glass optical fiber confirmed their ability to be used in the visible and near-infrared spectral regions as efficient optical fiber sources. [ABSTRACT FROM AUTHOR]

In this work, Tm3+ doped and Tm3+/Ho3+ co-doped germanate glasses with various TiO 2 concentrations have been examined using optical spectroscopy. The broad emission bands corresponding to 3F 4 →3H 6 (1.8 μm) and 5I 7 →5I 8 (2 μm) transitions of thulium and holmium ions were registered, respectively. It was observed that the intensity of near-infrared emission bands significantly changes with increasing titanium oxide content in the glass composition. Furthermore, the energy transfer process from Tm3+ to Ho3+ ions in studied glass systems was confirmed and discussed. The dependence of spectroscopic parameters like full width at half maximum (FWHM) and energy transfer efficiency (η ET) on increased TiO 2 concentration in glass host was established. [ABSTRACT FROM AUTHOR]

This work presents an analysis of the spectroscopic properties of glass and glass ceramics co-doped with Ni2+ and Er3+ ions. Spectroscopic analysis showed the embedding of nickel ions in the gamma-gallium oxide nanocrystals as a result of heat treatment of the glass samples. Analysis of the luminescence properties of the obtained samples under 940 nm and 980 nm pump excitation allowed the selection of a proper Er3+ ions concentration for further optical fiber fabrication. Measured lifetime results of glass-ceramics samples confirm energy transfer from nickel ions to erbium. In the process of drawing the optical fiber, it was possible to create a transparent nanocrystalline glass-ceramic core, as confirmed by XRD results. The produced glass-ceramic optical fiber was characterized by broadband emission in the range from 1100 nm to 1650 nm corresponding to the 3T 2 (3F) →3A 2 (3F) (Ni2+) and 4I 13/2 → 4I 15/2 (Er3+) transitions for 940 nm and 980 nm pump excitation. The Er3+ to Ni2+ ions emission intensity ratio of the fabricated glass-ceramic fiber was estimated to be 0.84 and 7.14 for 940 nm and 980 nm optical pumps, respectively. [ABSTRACT FROM AUTHOR]

Double-clad optical fiber with a multi-ring core profile doped with thulium and holmium fabricated by Modified Chemical Vapor Deposition Chelate Doping Technology (MCVD-CDT) is presented. The measured Tm2O3 and Ho2O3 complexes' weight concentrations were 0.5% and 0.2% respectively. Numerical analyses show weakly guiding conditions and 42.2 µm of MFD LP01 at 2000 nm. The low NA numerical aperture (NA = 0.054) was obtained for the 20/250 µm core/cladding ratio optical fiber construction. The emission spectra in the range of 1.6–2.1 µm vs. the fiber length are presented. The full width at half maximum (FWHM) decreases from 318 to 270 nm for fiber lengths from 2 to 10 m. The presented fiber design is of interest for the development of new construction of optical fibers operating in the eye-safe spectral range. [ABSTRACT FROM AUTHOR]

Double-clad optical fiber with a multi-ring core profile doped with thulium and holmium fabricated by Modified Chemical Vapor Deposition Chelate Doping Technology (MCVD-CDT) is presented. The measured Tm2O3 and Ho2O3 complexes' weight concentrations were 0.5% and 0.2% respectively. Numerical analyses show weakly guiding conditions and 42.2 µm of MFD LP01 at 2000 nm. The low NA numerical aperture (NA = 0.054) was obtained for the 20/250 µm core/cladding ratio optical fiber construction. The emission spectra in the range of 1.6–2.1 µm vs. the fiber length are presented. The full width at half maximum (FWHM) decreases from 318 to 270 nm for fiber lengths from 2 to 10 m. The presented fiber design is of interest for the development of new construction of optical fibers operating in the eye-safe spectral range. [ABSTRACT FROM AUTHOR]

An investigation of fluoroindate glass and fiber co-doped with Yb3+/Er3+ ions as a potential temperature sensor was assessed using the fluorescence intensity ratio (FIR) technique. Analysis of thermally coupled levels (TCLs—2H11/2 and 4S3/2), non-thermally coupled levels (non-TCLs—4F7/2 and 4F9/2), and their combination were examined. Additionally, the luminescent stability of the samples under constant NIR excitation using different density power at three different temperatures was carried out. The obtained values of absolute sensitivity (0.003 K−1—glass, 0.0019 K−1—glass fiber 2H11/2 → 4S3/2 transition) and relative sensitivity (2.05% K−1—glass, 1.64% K−1—glass fiber 4F7/2 → 4F9/2 transition), as well as high repeatability of the signal, indicate that this material could be used in temperature sensing applications. [ABSTRACT FROM AUTHOR]

Nanophosphors are widely used, especially in biological applications in the first and second biological windows. Currently, nanophosphors doped with lanthanide ions (Ln3+) are attracting much attention. However, doping the matrix with lanthanide ions is associated with a narrow luminescence bandwidth. This paper describes the structural and luminescence properties of co-doped LaPO4 nanophosphors, fabricated by the co-precipitation method. X-ray structural analysis, scanning electron microscope measurements with EDS analysis, and luminescence measurements (excitation 395 nm) of LaPO4:Eu3+/Nd3+ and LaPO4:Eu3+/Nd3+/Yb3+ nanophosphors were made and energy transfer between rare-earth ions was investigated. Tests performed confirmed the crystal structure of the produced phosphors and deposition of rare-earth ions in the structure of LaPO4 nanocrystals. In the range of the first biological window (650–950 nm), strong luminescence bands at the wavelengths of 687 nm and 698 nm (5D0 → 7F4:Eu3+) and 867 nm, 873 nm, 889 nm, 896 nm, and 907 nm (4F3/2 → 4I9/2:Nd3+) were observed. At 980 nm, 991 nm, 1033 nm (2F5/2 → 2F7/2:Yb3+) and 1048 nm, 1060 nm, 1073 nm, and 1080 nm (4F3/2 → 4I9/2:Nd3+), strong bands of luminescence were visible in the 950 nm–1100 nm range, demonstrating that energy transfer took place. [ABSTRACT FROM AUTHOR]

The effect of BaF2, MgF2, and AlF3 on the structural and luminescent properties of gallo-germanate glass (BGG) doped with erbium ions was investigated. A detailed analysis of infrared and Raman spectra shows that the local environment of erbium ions in the glass was influenced mainly by [GeO]4 and [GeO]6 units. Moreover, the highest number of non-bridging oxygens was found in the network of the BGG glass modified by MgF2. The 27Al MAS NMR spectrum of BGG glass with AlF3 suggests the presence of aluminum in tetra-, penta-, and octahedral coordination geometry. Therefore, the probability of the 4I13/2→4I15/2 transition of Er3+ ions increases in the BGG + MgF2 glass system. On the other hand, the luminescence spectra showed that the fluoride modifiers lead to an enhancement in the emission of each analyzed transition when different excitation sources are employed (808 nm and 980 nm). The analysis of energy transfer mechanisms shows that the fluoride compounds promote the emission intensity in different channels. These results represent a strong base for designing glasses with unique luminescent properties. [ABSTRACT FROM AUTHOR]

Glass-ceramic is semi-novel material with many applications, but it is still problematic in obtaining fibers. This paper aims to develop a new glass-ceramic material that is a compromise between crystallization, thermal stability, and optical properties required for optical fiber technology. This compromise is made possible by an alternative method with a controlled crystallization process and a suitable choice of the chemical composition of the core material. In this way, the annealing process is eliminated, and the core material adopts a glass-ceramic character with high transparency directly in the drawing process. In the experiment, low phonon antimony-germanate-silicate glass (SGS) doped with Eu3+ ions and different concentrations of P2O5 were fabricated. The glass material crystallized during the cooling process under conditions similar to the drawing processes'. Thermal stability (DSC), X-ray photo analysis (XRD), and spectroscopic were measured. Eu3+ ions were used as spectral probes to determine the effect of P2O5 on the asymmetry ratio for the selected transitions (5D0 → 7F1 and 5D0 → 7F2). From the measurements, it was observed that the material produced exhibited amorphous or glass-ceramic properties, strongly dependent on the nucleator concentration. In addition, the conducted study confirmed that europium ions co-form the EuPO4 structure during the cooling process from 730 °C to room temperature. Moreover, the asymmetry ratio was changed from over 4 to under 1. The result obtained confirms that the developed material has properties typical of transparent glass-ceramic while maintaining high thermal stability, which will enable the fabrication of fibers with the glass-ceramic core. [ABSTRACT FROM AUTHOR]

The method of the analysis of luminous flux diffusion on the lateral surface of an optical fiber as a basis for designing and manufacturing of side-hole optical fibers is presented. The idea of the controllable emission of the luminous flux by formation of the fiber lateral surface is described. The presented method was verified by manufacturing an optical fiber with controllable emission from the shaped lateral surface. [ABSTRACT FROM AUTHOR]

Er3+-doped glass based on TiO 2 –GeO 2 –BaO–Ga 2 O 3 has been examined for mid-IR luminescence applications. Mid-IR luminescence corresponding to the 4I 11/2 → 4I 13/2 transition of Er3+ is enhanced in the presence of TiO 2. These effects are stronger for mid-IR emission at 2727 nm than near-IR emission at 1533 nm related to the 4I 13/2 → 4I 15/2 transition of Er3+. The gain bandwidth for the 4I 11/2 → 4I 13/2 transition of Er3+ is relatively large (σ em × FWHM = 8.14 × 10−26cm3), which imply that glass with TiO 2 might be a promising candidate for efficient sources emitting mid-IR radiation. • Titanate-germanate glass doped with Er3+ has been studied for mid-IR emission. • Mid-IR luminescence at 2700 nm is enhanced significantly in the presence of TiO 2. • The relatively large gain bandwidth for the 4I 11/2 → 4I 13/2 transition of Er3+ is observed. [ABSTRACT FROM AUTHOR]

This work reports on the analysis of structural and spectroscopic properties of the fluoroindate glasses co-doped with Er3+/Ho3+. Structural analysis showed that erbium and holmium ions were modifier ions and depolymerizedof the fluoroindate glass network. The energy transfer processes between rare - earth ions in fluoroindate glasses pumped by and 980 nm laser diode have been also examined. Due to partial Er3+ → Ho3+ energy transfer and superposition of Er3+: 4I 11/2 → 4I 13/2 (2.77 μm)+ Ho3+: 5I 6 → 5I 7 (2.85 μm) radiative transitions in fluoroindate glass co-doped with 0.8ErF 3 /1.6HoF 3 , a broadening 3 μm luminescence (Δλ= 201 nm) was obtained. The overall energy transfer efficiency η ET1 + η ET2 was calculated to be 95% indicating efficient sensitization of the holmium ions by erbium. [ABSTRACT FROM AUTHOR]

• Optical properties of titanate-germanate glasses doped with Ho3+ ions were studied. • Near-IR emission spectra of Ho3+and their decays were examined with TiO 2 content. • Spectroscopic parameters for Ho3+ ions in titanate-germanate glass were determined. • Higher concentrations of TiO 2 are preferred for near-IR luminescence at 2 µm. Holmium-doped titanate-germanate glasses have been investigated for optical applications. Near-infrared luminescence at 2 μm due to 5I 7 → 5I 8 transition of holmium ions has been examined in function of TiO 2 concentration. Several spectroscopic parameters for holmium ions such as emission linewidth and lifetime, stimulated emission cross-section and quantum efficiency were determined based on absorption and luminescence experiments and calculated using the Judd-Ofelt theory. Systematic studies demonstrate that holmium-doped titanate-germanate glasses with higher TiO 2 concentration show excellent optical properties. Multicomponent glasses with molar ratios GeO 2 :TiO 2 = 1:2 and 1:3 are recommended for near-infrared luminescence at 2 μm. [Display omitted] [ABSTRACT FROM AUTHOR]

The influence of Cr3+ concentration on near-infrared emission of Ho3+ in barium gallo-germanate glass has been studied. Near-infrared emission bands, due to 4T 2 → 4A 2 (Cr3+) as well as 5I 6 → 5I 8 and 5I 7 → 5I 8 (Ho3+) transitions, were observed under excitation of Cr3+. The enhanced and broadband near-infrared emission was obtained for glasses in the presence of transition metal (Cr3+) and rare earth (Ho3+) ions. This prosperity was optimized as a function of donor (Cr3+) and acceptor (Ho3+) concentration. The integrated intensities of emission bands were determined and their values are found to be maximal at 0.25 mol% Cr3+ and 0.5 mol% Ho3+. The energy transfer from Cr3+ to Ho3+ occurs through a nonradiative process with an efficiency up to 23%. • Cr3+/Ho3+ co-doped barium gallo-germanate glasses were studied for NIR emission. • NIR emission spectra of Ho3+ ions in glasses were measured under excitation of Cr3+. • Emission bands are due to 4T 2.→ 4A 2 (Cr3+), 5I 6 → 5I 8 and 5I 7 → 5I 8 (Ho3+) transitions • The relative emission band intensities of Ho3+ depend critically on Cr3+ concentration. • The energy transfer from Cr3+ to Ho3+ with an efficiency up to 23% occurs. [ABSTRACT FROM AUTHOR]

The near-infrared emission properties in low-phonon (805 cm−1) gallo-germanate glasses and their glass fibers co-doped with Yb3+/Ho3+ and Yb3+/Tm3+/Ho3+ have been investigated. Emission bands centered at about 2 μm correspond to 3F 4 → 3H 6 (Tm3+) and/or 5I 7 → 5I 8 (Ho3+) transitions. The spectral widths of emission lines are relatively large and their values for glass samples co-doped with 0.7Yb 2 O 3 /0.15Ho 2 O 3 and 0.5Yb 2 O 3 /0.4Tm 2 O 3 /0.05Ho 2 O 3 are close to 159 nm and 343 nm, respectively. Gallo-germanate glasses characterized by broadband emission at 2 μm have been used for fabrication of glass fibers. The effects of fibers length on their near-infrared luminescent properties have been also analyzed in details. [ABSTRACT FROM AUTHOR]

Near-infrared luminescence properties of Nd 3+ and Ho 3+ ions in barium gallo-germanate glasses have been reported. Several spectroscopic parameters for Nd 3+ and Ho 3+ ions have been determined from the Judd-Ofelt analysis and absorption/luminescence measurements. Quite large luminescence lifetime, quantum efficiency and stimulated emission cross-section have been obtained for the main 4 F 3/2  →  4 I 11/2 (Nd 3+ ) and 5 I 7  →  5 I 8 (Ho 3+ ) laser transitions of rare earths in barium gallo-germanate glasses. It suggests that barium gallo-germanate glass is promising for near-infrared laser application at emission wavelengths 1064 nm (Nd 3+ ) and 2020 nm (Ho 3+ ). [ABSTRACT FROM AUTHOR]

Up-conversion luminescence of Er 3+ -doped oxyfluoride germanate optical fiber is observed under laser-diode excitation. The enhanced green emission line is due to 2 H 11/2 , 4 S 3/2  →  4 I 15/2 transition of Er 3+ . The integrated luminescence intensity related to 2 H 11/2 , 4 S 3/2  →  4 I 15/2 (green) and 4 F 9/2  →  4 I 15/2 (red) transitions of Er 3+ is reduced with increasing temperature. Several spectroscopic parameters of Er 3+ ions in optical fibers were determined. The spectral linewidth is reduced, whereas the maximum of emission peak is shifted to longer wavelengths with increasing fiber length. [ABSTRACT FROM AUTHOR]

Luminescence properties of Pr 3+ ions in germanate glasses modified by BaF 2 were investigated. Several luminescence bands originating to transitions from the 3 P 0 state to the lower-lying states of Pr 3+ were registered under 450 nm excitation. The spectral analysis suggests that the positions of luminescence bands and their relative intensities are changed significantly with BaF 2 content. The relative integrated luminescence intensities of 3 P 0 → 3 H 4 transition (blue) to the 3 P 0 → 3 F 2 transition (red) of Pr 3+ ions strongly depend on fluoride modifier BaF 2 in glass composition. The luminescence bands of Pr 3+ ions are shifted to shorter wavelengths with increasing BaF 2 content. [ABSTRACT FROM AUTHOR]

Lead-free oxyfluoride borate glasses singly doped with Pr 3+ and Er 3+ were prepared and next investigated using absorption and luminescence spectroscopy. In the studied glass system, barium oxide was substituted by BaF 2 . Two luminescence bands of Pr 3+ located at visible spectral region are observed, which correspond to 3 P 0 – 3 H 4 (blue) and 1 D 2 – 3 H 4 (reddish orange) transitions, respectively. The luminescence bands due to 1 D 2 – 3 H 4 transition of Pr 3+ are shifted to shorter wavelengths, when BaO was substituted by BaF 2 . Near-infrared luminescence spectra of Er 3+ ions in lead-free borate glasses modified by BaF 2 correspond to 4 I 13/2 – 4 I 15/2 transition. Their spectral linewidths increase with increasing BaF 2 concentration. The changes in measured lifetimes of rare earth ions are well correlated with the bonding parameters calculated from the optical absorption spectra. [ABSTRACT FROM AUTHOR]

• Pr3+/Er3+ co-doped glass based on InF 3 have been studied • Emission spectra of Pr3+/Er3+ were measured under different excitation wavelengths • Energy transfer process from Pr3+ to Er3+ occurs • Pr3+/Er3+ co-doped glass based on InF 3 are promising for white light emission Pr3+/Er3+ co-doped glasses based on InF 3 were synthesized and then studied for white light emission. The emission spectra consist of several bands corresponding to characteristic 4f-4f electronic transitions of Pr3+ and Er3+ ions. The relative intensities of emission bands depend on the selective excitation wavelengths. The energy transfer process from Pr3+ to Er3+ ions was confirmed by the excitation and emission spectra measurements. From emission spectra, the CIE chromaticity coordinates, the correlated color temperature (CCT) and the color purity (CP) were determined. The results indicate that Pr3+/Er3+ co-doped glasses based on InF 3 are excellent fluoride candidate to achieve warm white light emission. Graphical Abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

Spectroscopic properties of rare earths in lead-free oxyfluoride germanate glasses were studied. The absorption and luminescence spectra of Eu 3+ , Pr 3+ and Er 3+ ions were examined as a function of BaF 2 concentration and several spectroscopic parameters for rare earths were determined. The ratio of integrated luminescence intensity of the 5 D 0 → 7 F 2 transition to that of the 5 D 0 → 7 F 1 transition of Eu 3+ decrease significantly with increasing BaF 2 content. The absorption (Er 3+ ) and emission (Pr 3+ ) ‘hypersensitive transitions’ of rare earths are shifted in direction to shorter wavelengths with increasing BaF 2 content in glass composition. Emission spectra and their decays corresponding to the main 4 I 13/2 → 4 I 15/2 laser transition of Er 3+ were also analyzed. Quite long-lived NIR luminescence of Er 3+ is observed for lead-free glass samples with low BaF 2 concentration. [ABSTRACT FROM AUTHOR]

Spectroscopic properties of Er 3+ ions in lead-free oxyfluoride germanate glasses were studied. The absorption and luminescence spectra of Er 3+ ions were examined for glass samples with low and high BaF 2 content. From absorption spectra the bonding parameter was calculated and its value is reduced with increasing BaF 2 content. The maximum of absorption peak due to 4 I 15/2 − 2 H 11/2 hypersensitive transition is shifted to shorter wavelengths (blue shift) with increasing BaF 2 content. Luminescence spectra and their decays corresponding to main 4 I 13/2 − 4 I 15/2 laser transition of Er 3+ are also presented and discussed. Quite long-lived near-infrared luminescence of Er 3+ is observed for lead-free glass samples with low BaF 2 concentration. [ABSTRACT FROM AUTHOR]

This study presented an analysis of the TeO2/GeO2 molar ratio in an oxide glass system. A family of melt-quenched glasses with the range of 0–35 mol% of GeO2 has been characterized by using DSC, Raman, MIR, refractive index, PLE, PL spectra, and time-resolved spectral measurements. The increase in the content of germanium oxide caused an increase in the transition temperature but a decrease in the refractive index. The photoluminescence spectra of europium ions were examined under the excitation of 465 nm, corresponding to 7F0 → 5D2 transition. The PSB (phonon sidebands) analysis was carried out to determine the phonon energy of the glass hosts. It was reported that the red (5D0 → 7F2) to orange (5D0 → 7F1) fluorescence intensity ratio for Eu3+ ions decreased from 4.49 (Te0Ge) to 3.33 (Te15Ge) and showed a constant increase from 4.58 (Te20Ge) to 4.88 (Te35Ge). These optical features were explained in structural studies, especially changes in the coordination of [4]Ge to [6]Ge. The most extended lifetime was reported for the Eu3+ doped glass with the highest content of GeO2. This glass was successfully used for the drawing of optical fiber. [ABSTRACT FROM AUTHOR]

An investigation of the structural and luminescent properties of the transparent germanate glass-ceramics co-doped with Ni2+/Er3+ for near-infrared optical fiber applications was presented. Modification of germanate glasses with 10–20 ZnO (mol.%) was focused to propose the additional heat treatment process controlled at 650 °C to obtain transparent glass-ceramics. The formation of 11 nm ZnGa2O4 nanocrystals was confirmed by the X-ray diffraction (XRD) method. It followed the glass network changes analyzed in detail (MIR—Mid Infrared spectroscopy) with an increasing heating time of precursor glass. The broadband 1000–1650 nm luminescence (λexc = 808 nm) was obtained as a result of Ni2+: 3T2(3F) → 3A2(3F) octahedral Ni2+ ions and Er3+: 4I13/2 → 4I15/2 radiative transitions and energy transfer from Ni2+ to Er3+ with the efficiency of 19%. Elaborated glass–nanocrystalline material is a very promising candidate for use as a core of broadband luminescence optical fibers. [ABSTRACT FROM AUTHOR]

This work reports on the fabrication and analysis of near-infrared and mid-infrared luminescence spectra and their decays in fluoroindate glasses co-doped with Yb3+/Ho3+. The attention has been paid to the analysis of the Yb3+→ Ho3+ energy transfer processed ions in fluoroindate glasses pumped by 976 nm laser diode. The most effective sensitization for 2 μm luminescence has been obtained in glass co-doped with 0.8YbF3/1.6HoF3. Further study in the mid-infrared spectral range (2.85 μm) showed that the maximum emission intensity has been obtained in fluoroindate glass co-doped with 0.1YbF3/1.4HoF3. The obtained efficiency of Yb3+→ Ho3+ energy transfer was calculated to be up to 61% (0.8YbF3/1.6HoF3), which confirms the possibility of obtaining an efficient glass or glass fiber infrared source for a MID-infrared (MID-IR) sensing application. [ABSTRACT FROM AUTHOR]

Fluoroindate glasses co-doped with Pr3+/Er3+ ions were synthesized and their near-infrared luminescence properties have been examined under selective excitation wavelengths. For the Pr3+/Er3+ co-doped glass samples several radiative and nonradiative relaxation channels and their mechanisms are proposed under direct excitation of Pr3+ and/or Er3+. The energy transfer processes between Pr3+ and Er3+ ions in fluoroindate glasses were identified. In particular, broadband near-infrared luminescence (FWHM = 278 nm) associated to the 1G4 → 3H5 (Pr3+), 1D2 → 1G4 (Pr3+) and 4I13/2 → 4I15/2 (Er3+) transitions of rare earth ions in fluoroindate glass is successfully observed under direct excitation at 483 nm. Near-infrared luminescence spectra and their decays for glass samples co-doped with Pr3+/Er3+ are compared to the experimental results obtained for fluoroindate glasses singly doped with rare earth ions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Holmium singly doped barium gallo-germanate glasses have been studied for near-infrared luminescence at 2000 nm. Near-infrared luminescence spectra corresponding to 5I 7 → 5I 8 transition of trivalent holmium and their decays have been examined as a function of BaF 2 and activator (Ho3+) concentration. The integrated intensities of luminescence bands increase up to 0.5 mol% Ho3+ and then reduce with further increasing activator (Ho3+) concentration. Luminescence linewidths increase with increasing Ho3+ concentration, but remain nearly unchanged with BaF 2 content. The glass samples exhibit the shortened decay curves with increasing activator concentration, which is due to the presence of energy transfer between Ho3+ ions. The luminescence lifetime 5I 7 (Ho3+) is found to be maximum at 5 mol% of BaF 2. • Ho3+ doped barium gallo-germanate glasses have been studied for NIR emission. • NIR emission of Ho3+ was examined with BaF 2 and activator concentration. • Luminescence linewidths and lifetimes were determined. • Luminescence lifetime 5I 7 (Ho3+) is found to be maximum at 5 mol% of BaF 2. [ABSTRACT FROM AUTHOR]