<title>Transverse modal characterization of VCSELs based on intensity measurement</title>
Bibliographic record
Abstract
In many VCSEL applications, it is essential to know the transverse beam characteristics. This paper reports an experiment of transverse modal characterization based on intensity measurement. The beam form a VCSEL is imaged by a microscope objective and intensity profiles are recorded by scanning an apertured detector. The second moment of the intensity profile is found to vary quadratically with the distance along the direction of beam propagation. An effective Rayleigh range is extracted by means of quadratic data fitting. Once this parameter is obtained, Fourier analysis of one intensity profile yields the relative weights of the Hermite-Gaussian (HG) modes, provided that the beam is indeed a superposition of independent HG modes. It is found that a VCSEL driven at low current generates a beam that is approximately HG or a superposition of independent HG modes. At high drive current, however, the transverse modal structure becomes more complicated. The experiment demonstrates that intensity-based Fourier analysis is a convenient method to assess the closeness of approximating the outputs form semiconductor lasers by superposition of independent HG modes without using sophisticated spatial modal filters. The experiment also measures the M<SUP>2</SUP> modes without using sophisticated spatial modal filters. The experiment also measures the M<SUP>2</SUP> parameter of beam quality versus the drive current.
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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".