Development of ytterbium-doped oxyfluoride glasses for laser cooling applications

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.

Photonic properties of novel Yb3+ doped germanium-lead oxyfluoride glass-ceramics for laser cooling applications

“…Comparing our lifetime results with a previous work [18] for oxyfl uoride glasses from the 30SiO 2 -15Al 2 O 3 -(29-x)CdF 2 -22PbF 2 -4YF 3 -xYbF 3 system doped with 2, 5, 8, 12, 16 and 20 mol% of Yb 3+ ions, similar values were measured for 2 mol%; they measured ~1.57 ms and in the present work we report 1.470 ms for heat-treatment at 330°C with a lower nanocrystal concentration than heattreatment at 370°C with lifetime of 1.900 ms. Krishnaiah et al [18] mentioned that the dominant mechanisms for lifetime quenching are the energy transfer among the Yb 3+ ions and multi-phonon relaxation, especially for concentrations higher than 5 mol% of Yb3+. Here, in GPFYb samples, multi-phonon relaxation is probably not because the Yb 3+ concentration is low (2 mol%) and the matrix has a low phonon energy.…”

“…Longer lifetime is not an obstacle for laser cooling, but it is not desirable, since it can slow down the cooling process [18], however, it is necessary to have high iQY values, close to unity (or 100%). In fact, these radiation trapping effects change the iQY and eQY behavior, dependent on the excitation wavelength, which leads us to propose that 50GeO 2 -30PbF 2 -18PbO-2YbF 3 samples are probably good candidates for laser cooling applications.…”

“…All the samples showed the PLQY close to unity (100%). The detailed study on those samples with different Yb 3+ concentrations showed that the 2 mol% Yb 3+ doped oxyfluoride glass with its high PLQY, its low maximum phonon energy and low background absorption is the most promising candidate for laser cooling and solid-state laser applications besides serving as a reference to calibrate the instruments for PLQY measurements [18]. Pump power dependence studies have revealed a linear increase in the PLQY and a decrease in the lifetime with increasing pump power.…”

Non-Linear Optical Properties of Er3+–Yb3+-Doped NaGdF4 Nanostructured Glass–Ceramics

“…This kind of materials combines the incorporation of active rare-earth (RE 3+ ) ions into low phonon energy fluoride crystals (300-450 cm −1 ) and the good thermal stability and high mechanical and chemical properties of an aluminosilicate glass matrix [1][2][3]. Moreover, the different synthesis methods to obtain these materials (melt-quenching, sol-gel, hydrothermal, etc) together with the combination of host matrix, RE doping and NC size allow the luminescent emission to be properly tuned, thus opening the way to different promising applications such as optical fibers, solid-state lasers, three-dimensional full-color displays and solar cells among others [4][5][6][7][8].…”

Cubic and rhombohedral Ba4Lu3F17:Er3+ in transparent glass ceramics: Crystallization and upconversion luminescence

“…Transparent oxyfluoride glass ceramics have been widely investigated for promising applications in photonics such as in solid state lasers [1], optical thermometry [2,3], X-ray imaging [4,5], non-linear optics [6], holographic recording [7], optical cooling [8] and light conversion devices [9,10]. These composites contain fluoride nanocrystals dispersed in glass matrix and combine the good mechanical and chemical stability of oxides with the excellent optical properties of fluorides [11,12].…”