Even though the (75 NaPO3-25 CaF2) (in mol%) glass can be heat-treated into transparent glass-ceramic with Er3+ doped CaF2 crystals precipitating in the volume of the glass during heat-treatment, this glass was found to be a poor glass former, limiting its use as upconverter under 975 nm pumping. In this study, the impact of the glass composition on the thermal, optical and structural properties of the glass was investigated in order to understand how the glass composition can be tailored for the development of thermally stable upconverter glass-based material. The addition of MgO, Fe2O3 and Al2O3 in the NaPO3-CaF2 glass system increases the thermal stability of glass due to the depolymerization of the glass network. However, the changes in the glass composition also impacted on the nucleation and growth process. Indeed, CaF2 and other crystals were found in the newly developed glasses after heat-treatment leading to glass-ceramics with lower intensity of upconversion than the (75 NaPO3-25 CaF2) glass-ceramic used as a reference. Glasses were also prepared with different concentrations of Er2O3 and ErF3. These glasses were found to be promising as not only are they thermally stable, but they also exhibit green and red emission with high intensity under 975 nm pumping due to Er3+ clustering.

Featured Application: The newly developed Er 3+ , Yb 3+ doped phosphate glasses presented in this paper could find many different applications in space, telecommunications, LIDAR, spectroscopy and bioimaging, just to cite a few.Abstract: New Er 3+ , Yb 3+ codoped phosphate glasses with the (98-x) (0.50P 2 O 5 -0.40SrO-0.10Na 2 O) -0.5Er 2 O 3 -1.5Yb 2 O 3 -xZnO (in mol %) composition were prepared by melting process with up to 10 mol % of ZnO. The impact of the changes in the glass composition on the thermal, optical, structural properties was investigated. Using IR and Raman spectroscopies, we confirmed that the addition of ZnO up to 10 mol % leads to a depolymerization of the network without having a significant impact on the Er 3+ and Yb 3+ sites. We also discuss the effect of alpha particles irradiation. The glass with 2.5 mol % of ZnO was irradiated with 3 MeV alpha particles and a total fluence of 10 12 α/cm 2 . After irradiation, this glass exhibits surface expansion (measured at~200 nm, 1.5 months after the irradiation) and an increase in the surface roughness. The alpha particles irradiation is suspected to lead to changes in the spectroscopic properties of the glass. Finally, the photo-response of the glass was found to be reversible.

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Our study advances the development of new ternary silicate glasses for use as a designed cladding for semiconductor core optical fibers using molten core draw process. In order to fabricate high-quality hybrid fibers (homogeneous core shape, low amount of bubbles, low internal stress, no cracking), oxide glasses are the best choice as cladding materials. These glasses should be engineered with tailored thermal properties (coefficient of thermal expansion (CTE) and drawing temperature) so they match those of the semiconductor. Glasses in the system) with x = 0 and 10 and MO and in the system 50SiO 2 -10Na 2 O-(40 − y)B 2 O 3 -yTiO 2 with y = 0, 1.25, 2.5, and 5 were investigated. Their thermal properties were measured and discussed with regard to the glass structure analyzed using FTIR spectroscopy. Due to their rigid network, which leads to beneficial thermal properties including low CTE (~5 ppm K −1 ), the Ge-containing glass with x = 10 is a promising cladding candidate when preparing a Ge core fiber and the Ga or Zn-containing glasses when preparing an InAs core.

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