Bibliographic record
Abstract
Strong field physics, femtosecond (1 fs = $10^{-15}$), and attosecond (1 as = $10^{-18}$) science require intense ultrashort laser pulses for excitation and measurement. Although fs pulses can be generated directly from a laser amplifier, durations necessary for ultrafast science require spectral broadening and compression. The most common spectral broadening technique exploits the nonlinear interaction of intense pulses focused into gas-filled hollow-core fibres [1]. These fibres allow for a long interaction length to generate octave-spanning spectra while maintaining a near Gaussian spatial distribution. However, these fibres can be 1 – 3 metres on an optical table with additional 1 m focusing and collimating optics, and require continuous backfilled gas flow. More recently, the self-phase modulation in thin crystals broadens the spectrum and uses a self-focusing relay to maintain the beam quality [2]. A combination of solids and gases to generate a supercontinuum has been used to generate attosecond extreme ultraviolet (XUV) pulses [3]. Ultrashort pulses can have a wide variety of applications, including disrupting biological processes for medical procedures, observation of electronic processes on an attosecond scale, and generating XUV and soft X-ray pulses via high harmonic generation or terahertz via difference frequency generation [4]. Here, we compare numerically and experimentally the spectral broadening in solvents and crystals to demonstrate the potential for a compact setup for generating octave spanning pulses for ultrafast experiments. We find that passing a beam through several cm of methanol produces a supercontinuum spectrum that can support few-fs pulses. Similar to the multi-plate thin crystal method, we place a series of 1 cm cuvettes of methanol around two foci in order to reduce self-focussing effects and to avoid filamentation within the material. We compress these pulses using dispersion compensating mirrors, and characterize the resulting pulses using frequency resolved optical gating (FROG) and a novel measurement scheme. Our simulations and models predict a sub-10 fs bandwidth-limited pulse resulting from two subsequent compressions using a total of 4 cm of methanol to generate a supercontinuum. Using this method, experimentally, we have achieved a broad spectrum capable of supporting sub-30 fs pulses. [1] E. Haddad, R. Safaei, A. Leblanc, R. Piccoli, Y.G. Jeong, H. Ibrahim,B.E. Schmidt, R. Morandotti, L. Razzari, F. Légaré, P. Lassonde. "Molecular gases for pulse compression in hollow core fibers," Optics Express (2018). [2] Y.-C. Cheng, C.-H. Lu, Y.-Y. Lin, and A. H. Kung, "Supercontinuum generation in a multi-plate medium," Optics Express (2016). [3] T. J. Hammond, S. Monchocé, C. Zhang, G. Vampa, D. Klug, A. Y. Naumov, D. M. Villeneuve, and P. B. Corkum "Integrating solids and gases for attosecond pulse generation," Nature Photonics (2017). [4] M. Cheng, A. Reynolds, H. Widgren, and M. Khalil, "Generation of tunable octave-spanning mid-infrared pulses by filamentation in gas media," Optics Letters (2012).
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How this classification was reachedexpand
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 | 0.003 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".