Phase and envelope characteristics of ultrashort pulses reflected from a two-dimensional silicon photonic crystal
Bibliographic record
Abstract
We experimentally demonstrate how coherent Bragg, and incoherent, multiple scattering influence the phase characteristics and the temporal shape of $35\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ bandwidth, $200\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$ optical pulses specularly reflected in the plane of periodicity from a two-dimensional (2D) silicon photonic crystal with $560\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ diameter air holes and a $700\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ pitch. The pulse center wavelength was chosen to lie (i) inside a $1320--1600\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ photonic band gap; (ii) on the short wavelength gap edge, or (iii) outside the photonic band gap. The shape of Bragg reflected pulses [case (i)] differs insignificantly from the incident pulse as expected, whereas for pulses whose center wavelength is outside the band gap [case (iii)], multiple diffuse scattering distorts the pulse shape, and the pulse width is broadened by as much as 48%, depending on the illumination site. For pulses centered on the band edge [case (ii)], the group delay is reduced by as much as $\ensuremath{\sim}45\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$ in certain spectral regions compared to Bragg reflected light. Bragg scattering dominates other scattering processes and the reflected pulse shape is mainly governed by the asymmetric reflectivity spectrum and the input pulse characteristics such as bandwidth and chirp. The difference between the mean free path of Bragg scattered photons and surface scattered photons is estimated to be $6\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{m}$.
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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 | 0.000 | 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 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".