80 Gbps PAM-4 Data Transmission With 940 nm VCSELs Grown on a 330 μm Ge Substrate
Bibliographic record
Abstract
940 nm oxide-confined vertical-cavity surface-emitting lasers (VCSELs) on$330~\mu $m thick Ge bulk substrates were fabricated and characterized, presenting a novel approach to VCSEL manufacturing. The wafer surfaces demonstrated high smoothness and flatness, with a peak-to-valley wafer distortion of$50.3~\mu $m, a root mean square roughness (Rq) of 1.34 nm, and an average wafer bow-warp of$3.77~\mu $m. The Fabry-Pérot dip precisely aligned with the target wavelength, while stopband center mapping exhibited excellent uniformity across the wafer, with a 1.937 nm (0.206%) standard deviation. At 300 K, the Ge-based VCSEL with a$6~\mu $m oxide aperture achieved an optical peak power of 5.5 mW and a maximum modulation bandwidth of 19.8 GHz, with a roll-over current surpassing 16 mA. Furthermore, the device demonstrated successful data transmission at 53.125 Gbps and 80 Gbps using PAM-4 modulation, achieving transmitter and dispersion eye closure quaternary (TDECQ) penalties of 1.36 dB and 4.70 dB, respectively. These results underscore the potential of thin Ge substrates in advancing VCSEL technology for high-speed optical communication applications.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.003 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".