Optical rectification and shift currents in GaAs and GaP response: Below and above the band gap
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Bibliographic record
Abstract
We present a full band structure scheme to calculate the electronic contribution to the second order susceptibility coefficient pertinent to optical rectification, ${\ensuremath{\chi}}_{2}^{abc}(\ensuremath{-}{\ensuremath{\omega}}_{\ensuremath{\sum}};{\ensuremath{\omega}}_{\ensuremath{\beta}},{\ensuremath{\omega}}_{\ensuremath{\gamma}})$ where ${\ensuremath{\omega}}_{\ensuremath{\sum}}\ensuremath{\approx}0$, within the independent particle approximation for the electron dynamics, and in the dipole limit. This allows us to determine the electronic response of a bulk semiconductor to a femtosecond optical pulse over a range of central frequencies, both below and above the band gap frequency. Particularly interesting is the limit ${\ensuremath{\chi}}_{2}^{abc}(0;\ensuremath{\omega},\ensuremath{-}\ensuremath{\omega})$. In addition to the usual near-dc interband rectification current, shift and injection currents, associated with actual divergences in ${\ensuremath{\chi}}_{2}^{abc}(0;\ensuremath{\omega},\ensuremath{-}\ensuremath{\omega})$, are taken into account. Calculations for GaAs and GaP, in which injection currents are forbidden, are performed. The band energies and matrix elements are computed with the full potential linearized augmented plane wave method. For frequencies above the band gap, and for typically available pulse widths, we demonstrate that the shift current dominates the current response, being approximately two orders of magnitude larger than the rectification current. For very narrow pulse widths, on the order of a femtosecond, the rectification current becomes comparable to the shift current.
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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)
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Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
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