Low photodarkening single cladding ytterbium fibre amplifier
Bibliographic record
Abstract
A single cladding ytterbium doped fibre amplifier pumped at 980 nm that exhibits negligible amount of photodarkening over a long period of time is demonstrated. The output power as a function of time decreased by a very small factor compared to standard single mode ytterbium fibres. To achieve this photodarkening resistant amplifier, a special ytterbium doped fibre has been developed. Codoping with aluminium or other rare-earth such as erbium is shown to decrease the multi-excitation of ytterbium clusters and thus lower photodarkening. Photodarkening was characterized by comparing the amount of excess loss created by core pumping single cladding fibres at high intensity at 980 nm. Photodarkening was found to be directly proportional to the excitation of the ytterbium ions by comparing different pumping scheme and pump wavelength. Core pumping of a single cladding ytterbium doped fibre amplifier at 980 nm represents the worst case scenario for photodarkening. Engineering ytterbium fibres for low photodarkening is therefore critical in pulsed amplification where short length of fibre with high doping level is required as demonstrated with 6 &mgr;m core ytterbium fibre amplifier pumped in the core or in the cladding. Photodarkening was correlated to clustering from cooperative luminescence measurement at 500 nm produced by ytterbium clusters that would emit UV radiation under strong pumping.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.000 | 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 | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".