High-power femtosecond molecular broadening and the effects of ro-vibrational coupling
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Bibliographic record
Abstract
Scaling spectral broadening to higher pulse energies and average powers is a critical step in ultrafast science, especially for narrowband Yb-based solid state lasers, which have become the new state-of-the-art. Despite their high nonlinearity, molecular gases as a broadening medium inside hollow-core fibers have been limited to 25 W, at best. We demonstrate spectral broadening in nitrogen at ten-fold average powers up to 250 W with repetition rates from 25 to 200 kHz. The observed ten-fold spectral broadening is stronger compared to the more expensive krypton gas and enables pulse compression from 1.3 ps to 120 fs. We identified an intuitive explanation for the observed average power scaling based on the density of molecular ro-vibrational states of Raman active molecules. To verify this ansatz, the spectral broadening limitations in O 2 and N 2 O are experimentally measured and agree well. On these grounds, we propose a perspective on the role, suitability, and limits of stimulated Raman scattering at high average and peak powers. Finally, high-harmonic generation is demonstrated at 200 kHz. These findings can have strong implications for intense, high-repetition-rate, pulsed ps laser propagation in the atmosphere where the dominant species are N 2 and O 2 .
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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