Abstract
Oxyfluoride glasses doped with 2, 5, 8, 12, 16 and 20 mol% of ytterbium (Yb3+) ions have been prepared by the conventional melt-quenching technique. Their optical, thermal and thermo-mechanical properties were characterized. Luminescence intensity at 1020 nm under laser excitation at 920 nm decreases with increasing Yb3+ concentration, suggesting a decrease in the photoluminescence quantum yield (PLQY). The PLQY of the samples was measured with an integrating sphere using an absolute method. The highest PLQY was found to be 0.99(11) for the 2 mol% Yb3+: glass and decreases with increasing Yb3+ concentration. The mean fluorescence wavelength and background absorption of the samples were also evaluated. Upconversion luminescence under 975 nm laser excitation was observed and attributed to the presence of Tm3+ and Er3+ ions which exist as impurity traces with YbF3 starting powder. Decay curves for the Yb3+: 2F5/2 → 2F7/2 transition exhibit single exponential behavior for all the samples, although lifetime decrease was observed for the excited level of Yb3+ with increasing Yb3+ concentration. Also observed are an increase in the PLQY and a slight decrease in lifetime with increasing the pump power. Finally, the potential of these oxyfluoride glasses with high PLQY and low background absorption for laser cooling applications is discussed.
Highlights
Ytterbium (Yb3+)-doped glasses have been widely investigated for their potential in solid-state lasers[1,2], downconversion[3], upconversion[4], light emitting diodes[5], athermal lasers and more recently in solid-state laser induced cooling[6]
Glass transition and crystallization temperatures, thermal stability against crystallization and thermal expansion coefficient were determined by thermal analysis
Yb3+-doped 30SiO2‒15Al2O3‒(29-x)CdF2‒22PbF2‒4YF3‒xYbF3 oxyfluoride glasses have been fabricated and characterized from a thermal and spectroscopic point of view. Their glass transition and crystallization temperatures as well as thermal expansion coefficient were determined by thermal analysis
Summary
Ytterbium (Yb3+)-doped glasses have been widely investigated for their potential in solid-state lasers[1,2], downconversion[3], upconversion[4], light emitting diodes[5], athermal lasers and more recently in solid-state laser induced cooling[6]. Basic requirements for laser cooling applications include materials of low phonon energy, low background absorption, high purity and photoluminescence quantum yield (PLQY)[7]. Since 1995 laser cooling based on anti-Stokes fluorescence have been reported in a wide variety of low phonon energy host materials[9,10,11,12] doped with Yb3+, Er3+ and Tm3+ ions[12,13,14,15]. Oxyfluoride glasses based on heavy metal fluorides and silicates may surpass oxide and fluoride glasses by combining their advantageous properties such as low phonon energy, low melting point, high chemical durability and www.nature.com/scientificreports/. The motivation of our work is to develop low phonon energy oxyfluoride glasses for laser cooling applications. The obtained results were compared with those reported on Yb3+: ZBLANP glass[6] and Yb3+: YAG crystal[12]
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