Nanosized hydrated YbPO 4 •nH 2 O powders were prepared by precipitation from aqueous solutions. It is shown that the structure, optical properties, and size of the raw particles can be further tailored by the subsequent calcination. The raw hydrous crystals transform into the anhydrous YbPO 4 xenotime form after calcination at temperatures above 800 °C. In comparison with the hydrous form, the latter is characterized by a well-defined defect-free xenotime structure and multiple sharp peaks in the absorption and emission bands due to the splitting of Yb 3+ 2 F 7/2 and 2 F 5/2 manifolds into multiple Stark sublevels as well as by a significant increase in the near-infrared photoluminescence intensity. It is demonstrated that the synthesized YbPO 4 phosphors can withstand the corrosive behavior of phosphate glass melts; their reaction with silica glass at temperatures up to 2000 °C is negligible, and thus, YbPO 4 particles can be used to prepare translucent glass−crystal composites.
We report the use of the extrusion technique at highest temperatures to date (975 °C - 1000 °C) for the fabrication of suspended core fibers (SCFs) from glass with molar composition 65 SiO2-20 Al2O3-15 La2O3 (SAL65). Through adjusting die design and fabrication conditions, extruded preforms for fibers with two different core sizes (1.2 µm and 3.1 µm) were successfully produced. Cross-sectional microstructure and material loss of these fibers highlight the potential of the extrusion technique for fabrication of microstructured optical fibers from glasses with high softening temperature and thus high thermal and mechanical stability.
We demonstrate distributed optical fiber-based pressure measurements with sub-bar pressure resolution and 1 m spatial resolution over a ∼100 m distance using a phase-sensitive optical time-domain reflectometry technique. To do so, we have designed a novel highly birefringent microstructured optical fiber that features a high pressure to temperature sensitivity ratio, a high birefringence and a mode field diameter that is comparable to that of conventional step-index single mode fibers. Our experiments with two fibers fabricated according to the design confirm the high polarimetric pressure sensitivities (−62.4 rad×MPa−1×m−1 and −40.1 rad×MPa−1×m−1) and simultaneously low polarimetric temperature sensitivities (0.09 rad×K−1×m−1 and 0.2 rad×K−1×m−1), at a wavelength of 1550 nm. The fiber features a sufficiently uniform birefringence over its entire length (2.17×10−4 ± 7.65×10−6) and low propagation loss (∼3 dB/km), which allows envisaging pressure measurements along distances up to several kilometers.
Large core soft glass fibers have been demonstrated to be promising candidates as intrinsic fiber sensors for radiation detection and dosimetry applications. Doping with rare earth ions enhanced their radiation sensitivity. SiO2-Al2O3-La2O3 (SAL) glasses offer easy fabrication of large core fibers with high rare earth concentration and higher mechanical strength than soft glasses. This paper evaluates the suitability of the SAL glass type for radiation dosimetry based on optically stimulated luminescence (OSL) via a comprehensive investigation of the spectroscopic and dosimetric properties of undoped and differently rare earth doped bulk SAL glass samples. Due to the low intensity of the rare earth luminescence peaks in the 250–400 nm OSL detection range, the OSL response for all the SAL glasses is not caused by the rare earth ions but by radiation-induced defects that act as intrinsic centers for the recombination of electrons and holes produced by the ionizing radiation, trapped in fabrication induced defect centers, and then released via stimulation with 470 nm light. The rare earth ions interfere with these processes involving intrinsic centers. This dosimetric behavior of highly rare earth doped SAL glasses suggests that enhancement of OSL response requires lower rare earth concentrations and/or longer wavelength OSL detection range.
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