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This paper presents novel multicore fibers with broadband emission in the 1.4–2.1 μm range. Based on our previous work with barium gallo-germanate glasses and fibers, the 4 and 11-core fiber structures, each containing core glasses doped with Er 3+ and Yb 3+ /Tm 3+ /Ho 3+, were developed. Our efforts have resulted in flat emission in 3 dB and 10 dB bands, achievable under excitation at 796 nm, 808 nm, 940 nm, and 980 nm. The measured emission spectra of these fibers are described as a superposition of emission bands from each individual core, corresponding to the transitions of Er 3+ , Tm 3+ , and Ho 3+ ions. Our method demonstrates the potential of emission profiling in multicore optical fibers as a new way to construct eye-safe broadband fiber sources.

Fluoroindate glasses co-doped with Pr 3+ /Er 3+ ions were synthesized and their near-infrared luminescence properties have been examined under selective excitation wavelengths. For the Pr 3+ /Er 3+ co-doped glass samples several radiative and nonradiative relaxation channels and their mechanisms are proposed under direct excitation of Pr 3+ and/or Er 3+ . The energy transfer processes between Pr 3+ and Er 3+ ions in fluoroindate glasses were identified. In particular, broadband near-infrared luminescence (FWHM = 278 nm) associated to the 1 G 4  →  3 H 5  (Pr 3+ ), 1 D 2  →  1 G 4  (Pr 3+ ) and 4 I 13/2  →  4 I 15/2  (Er 3+ ) 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 Pr 3+ /Er 3+ are compared to the experimental results obtained for fluoroindate glasses singly doped with rare earth ions.

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.

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 Tm 2 O 3 and Ho 2 O 3 complexes’ weight concentrations were 0.5% and 0.2% respectively. Numerical analyses show weakly guiding conditions and 42.2 µm of MFD LP 01 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.

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.

The effect of oxide modifiers on multiple properties (structural and spectroscopic) of phosphate glasses with molar composition 60P2O5-(10−x)Ga2O3-30MO-xEu2O3 and 60P2O5-(10−y)Ga2O3-30MO-yEr2O3 (where M = Ca, Sr, Ba; x = 0, 0.5; y = 0, 1) were systematically examined and discussed. The local structure of systems was evidenced by the infrared (IR-ATR) and Raman spectroscopic techniques. The spectroscopic behaviors of the studied glass systems were determined based on analysis of recorded spectra (excitation and emission) as well as luminescence decay curves. Intense red and near-infrared emissions (1.5 μm) were observed for samples doped with Eu3+ and Er3+ ions, respectively. It was found that the value of fluorescence intensity ratio R/O related to 5D0→7F2 (red) and 5D0→7F1 (orange) transition of Eu3+ ions depends on the oxide modifiers MO in the glass host. However, no clear influence of glass modifiers on the luminescence linewidth (FWHM) was observed for phosphate systems doped with Er3+ ions. Moreover, the 5D0 and 4I13/2 luminescence lifetimes of Eu3+ and Er3+ ions increase with the increasing ionic radius of M2+ (M = Ca, Sr, Ba) in the host matrix. The obtained results suggest the applicability of the phosphate glasses with oxide modifiers as potential red and near-infrared photoluminescent materials in photonic devices.

The results presented in this communication concern visible and near-IR emission of Pr ions in selected inorganic glasses, i.e., borate-based glass with Ga O and BaO, lead-phosphate glass with Ga O , gallo-germanate glass modified by BaO/BaF , and multicomponent fluoride glass based on InF . Glasses present several emission bands at blue, reddish orange, and near-infrared spectral ranges, which correspond to 4f-4f electronic transitions of Pr . The profiles of emission bands and their relative intensity ratios depend strongly on glass-host. Visible emission of Pr ions is tuned from red/orange for borate-based glass to nearly white light for multicomponent fluoride glass based on InF . The positions and spectral linewidths for near-infrared luminescence bands at the optical telecommunication window corresponding to the G → H , D → G , and H → F , F transitions of Pr are dependent on glass-host matrices and excitation wavelengths. Low-phonon fluoride glasses based on InF and gallo-germanate glasses with BaO/BaF are excellent candidates for broadband near-infrared optical amplifiers. Spectroscopic properties of Pr -doped glasses are compared and discussed in relation to potential optical applications.

The results presented in this communication concern visible and near-IR emission of Pr3+ ions in selected inorganic glasses, i.e., borate-based glass with Ga2O3 and BaO, lead-phosphate glass with Ga2O3, gallo-germanate glass modified by BaO/BaF2, and multicomponent fluoride glass based on InF3. Glasses present several emission bands at blue, reddish orange, and near-infrared spectral ranges, which correspond to 4f–4f electronic transitions of Pr3+. The profiles of emission bands and their relative intensity ratios depend strongly on glass-host. Visible emission of Pr3+ ions is tuned from red/orange for borate-based glass to nearly white light for multicomponent fluoride glass based on InF3. The positions and spectral linewidths for near-infrared luminescence bands at the optical telecommunication window corresponding to the 1G4 → 3H5, 1D2 → 1G4, and 3H4 → 3F3,3F4 transitions of Pr3+ are dependent on glass-host matrices and excitation wavelengths. Low-phonon fluoride glasses based on InF3 and gallo-germanate glasses with BaO/BaF2 are excellent candidates for broadband near-infrared optical amplifiers. Spectroscopic properties of Pr3+-doped glasses are compared and discussed in relation to potential optical applications.

Inorganic glasses co-doped with rare-earth ions have a key potential application value in the field of optical communications. In this paper, we have fabricated and then characterized multicomponent TiO2-modified germanate glasses co-doped with Yb3+/Ln3+ (Ln = Pr, Er, Tm, Ho) with excellent spectroscopic properties. Glass systems were directly excited at 980 nm (the 2F7/2 → 2F5/2 transition of Yb3+). We demonstrated that the introduction of TiO2 is a promising option to significantly enhance the main near-infrared luminescence bands located at the optical telecommunication window at 1.3 μm (Pr3+: 1G4 → 3H5), 1.5 μm (Er3+: 4I13/2 → 4I15/2), 1.8 μm (Tm3+: 3F4 → 3H6) and 2.0 μm (Ho3+: 5I7 → 7I8). Based on the lifetime values, the energy transfer efficiencies (ηET) were estimated. The values of ηET are changed from 31% for Yb3+/Ho3+ glass to nearly 53% for Yb3+/Pr3+ glass. The investigations show that obtained titanate–germanate glass is an interesting type of special glasses integrating luminescence properties and spectroscopic parameters, which may be a promising candidate for application in laser sources emitting radiation and broadband tunable amplifiers operating in the near-infrared range.

Influence of titanium dioxide concentration on thermal properties of germanate-based glasses has been studied. Germanate glasses varying with TiO 2 content were examined using DSC methods. The DSC curves exhibit two exothermic peaks, when GeO 2 is substituted by TiO 2 . Based on DSC measurements, characteristic temperatures were determined. The studies demonstrate that glass transition temperature increases, whereas thermal stability parameters are reduced with increasing TiO 2 concentration. The DSC curves were also acquired with different heating rates, and the Kissinger method was used to calculate the activation energy. X-ray diffraction analysis for germanate-based glass with TiO 2 indicates that crystallization processes are more complex and several phases are formed during annealing. The absorption and emission spectra of glass samples doped with Er 3+ ions were also examined before and after annealing process.