Fabrication of fluoride phosphate glass optical fibres for UV applications

UV-transmitting step-index fluorophosphate glass fiber fabricated by the crucible technique

“…However, despite the fact that this method seemed to be successful in the work of Zou et al [17,18], we were not able to draw a crystal-free optical fiber from neither a core-cladding preform nor a single index preform. On the contrary, we rapidly faced serious problems of uncontrolled crystallization at the surface of the fiber during the fiber drawing process, similar to those reported by Kalnins et al [22]. Surface crystallization issues were also reported in fluoroaluminate glass fiber drawing and ascribed to moisture attack followed by surface devitrification along the drawing process [41].…”

“…Work is ongoing to improve the fabrication process and eliminate these striae. In the literature, as above mentioned, only four works dealing with the fabrication and optical characterization of fluorophosphate glass fibers was reported, to the best of our knowledge [17,18,22,23]. In their work, Zou et al from Hoya Corporation reported ultra-low losses in their fibers with a minimum loss in the UV of 0.11 dB/m at 365 nm while extrinsic absorption bands were observed due to the presence of transition metal impurities at 340 nm (Fe 3þ ), 520 nm (Cr 3þ , Ni 2þ ) and 800 nm (Cu 2þ , Fe 2þ ) [17,18].…”

“…Kalnins et al have prepared an unclad optical fiber by drawing preforms produced by extrusion under nitrogen of a commercial fluorophosphate glass (N-FK51A). Although they reported on preform neck-down crystallization issues during the drawing, they achieved minimum losses of 3.05 dB/m at 405 nm after increasing the preform feed-rate and drawing speed [22]. They also showed that treatment of extruded preforms prior to fiber drawing further improved optical fiber loss to 0.5e1 dB/m [23].…”

“…Very few studies on the fabrication of fluorophosphate glass optical fibers have been reported in the literature [17,18,22,23]. Zou et al produced step-index fibers by drawing at the optical tower an ultra-highly pure core-cladding preform obtained by extrusion in the system P 2 O 5 eAlF 3 eYF 3 eMgF 2 eRF 2 eNaF, (R ¼ Mg, Ca, Sr and Ba).…”

Ultraviolet Upconversion Luminescence in a Highly Transparent Triply-Doped Gd3+–Tm3+–Yb3+ Fluoride–Phosphate Glasses

“…To get improved UV emissions of RE embedded in solid-state host matrices upon longer wavelength laser excitation, low-phonon energy hosts as fluoride crystals, fluoride and chalcogenide glasses doped with Nd 3+ , Pr 3+ , Ho 3+ Tm 3+ , and Er 3+ ions have been widely studied. − However, the production of fluoride crystals is expensive and not suitable for large-scale manufacturing, while fluoride glasses usually have poor mechanical properties and chemical stability, and chalcogenide glasses are not transparent in the UV region. On the other hand, fluoride–phosphate glasses offer the prospect of combining the desirable optical properties of fluoride hosts with the favorable mechanical properties of phosphate glasses. − Fluoride–phosphate glasses and optical fibers, when produced with ultrahigh-purity reagents, can be highly transparent in the UV (down to ∼160 nm), contributing to the efficiency of photoemission in this region. − …”