Structural and optical characterizations of Yb3+ doped GeO2-PbF2-PbO glass-ceramics for optical refrigeration
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Bibliographic record
Abstract
We report on the structural and optical properties of 50GeO<sub>2</sub>-30PbF<sub>2</sub>-(20-x)PbO-xYbF<sub>3</sub>, with x = 0.5, 1.5, 2.0, 2.5 mol% glass-ceramics for optical refrigeration. XRD measurements reveal the formation of nanocrystals embedded in glass samples after heat treatment at 360°C ⁄ 20h. Spectroscopic measurements show that samples have near infrared photoluminescence emission due to the <sup>2</sup>F<sub>5/2</sub> − <sup>2</sup>F<sub>7/2</sub> Yb<sup>3+</sup> transition, centered at ∼1020 nm with excitation at 919.7 nm, or 1011.2 nm, and the highest PL emission efficiency occurs for samples with 2.0 mol% of Yb<sup>3+</sup>. The PL quantum yield varies between 95% and 75%, depending on the lanthanide concentration and excitation wavelength, for 1.5 and 2.5 mol% Yb<sup>3+</sup>doped samples being the most efficient under 1011.2 nm excitation. The UV-Vis-NIR spectroscopy shows a transparency as high as 80% in the infrared region, and the absorption between 900-1050 nm increases with Yb<sup>3+</sup> concentration, in good agreement with the theoretical doping levels. Preliminary measurements monitoring the sample temperature dependence using a fiber Bragg grating sensor, as a function of pump laser wavelength and Yb<sup>3+</sup> concentration shows that the heating process approaches zero for an excitation wavelength of around 1030 nm, which is an indication that phonons are annihilated in these glass-ceramic materials, and shows promise for applications in optical refrigeration.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it