High-power fiber amplifier using a depressed-clad Yb-doped LMA fiber with low photodarkening
Bibliographic record
Abstract
A 225-μJ polarization maintaining ytterbium-doped large-mode-area multiclad fiber was designed and fabricated with an effective mode area of 450 μm2 and a photodarkening maximum excess loss of ~1 dB/m at 1064 nm. The fiber index profile is based on a depressed-clad to obtain a diffraction-limited output. Optimization for low photodarkening and high conversion efficiency while maintaining a good control on the core's refractive index profile has been achieved by adjusting the ytterbium/phosphorus/aluminum concentrations in the fiber core. Concentration ratios of phosphorus/aluminum from 0.12 to 1.25 were experimentally investigated in terms of photodarkening rate and excess loss. Within this range, the photodarkening excess loss was observed to decrease by a factor of 8. The large-mode-area fiber was used in a 10-ns pulse amplifier at 1064 nm with a repetition rate of 100 kHz and 0.5-nm bandwidth. The diffraction-limited output has a measured M2 value of 1.04 when the fiber is coiled to a diameter of 12 cm. The fiber amplifier slope efficiency is 70% with a polarization extinction ratio greater than 23 dB. It is shown how the phosphorus/aluminum ratio reduces photodarkening, and how a depressed-clad design improves higher-order mode filtering for reliable, efficient, and compact ytterbium-doped fiber amplifiers.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 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 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".