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.
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.
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.
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 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.
New multicomponent titanate-germanate glasses were synthesized and their luminescence properties have been studied. The intense near-infrared luminescence bands are observed in titanate-germanate glass, which correspond to main laser transitions 4F3/2 → 4I11/2 (Nd3+), 4I13/2 → 4I15/2 (Er3+) and 5I7 → 5I8 (Ho3+) of rare earth ions. In particular, luminescence linewidths have been examined in relation to potential broadband near-infrared laser applications.
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