Broadband and Polarization Flexible SOI Grating Coupler Based on Sub-Wavelength Gratings with Low Back Reflections
Bibliographic record
Abstract
Optical couplers play an integral role in coupling of the guided mode from an optical fiber into a Photonic Integrated Circuit (PIC) and vice-versa.Apart from the edge couplers, grating couplers are the most extensively used optical I/O's.While edge couplers couple light within the same plane, grating couplers diffract the inplane guided mode into an out-of-plane radiated beam, thereby changing the direction of propagation.Though grating couplers are easy to fabricate and are wellsuited for wafer-scale testing, they have limited application owing to their polarization selectivity and a coupling bandwidth of only 30-40 nm.This restricts the use of grating couplers in Dense Wavelength Division Multiplexing (DWDM) applications.To overcome, the shortcomings of a conventional grating coupler, we first investigated the fundamentals of grating coupler and studied the principle governing polarization insensitivity for a surface grating coupler.By engineering the average effective index of the grating coupler using sub-wavelength gratings, we increased the coupling bandwidth while maintaining polarization insensitivity.A broadband grating coupler can help eliminate the bottleneck in the coupling of DWDM fibers to the PICs.A polarization flexible grating coupler can realize higher transmission rates by introducing polarization diversity (TE and TM polarization operate independently) thereby resulting in increased data capacity of the Optical Telecommunication Network (OTN).With a uniform sub-wavelength grating coupler (SWGC) designed in this thesis, we attained 3-dB operating bandwidth of 105nm and 121 nm for the iii TE and TM polarization, respectively.The proposed device attains coupling efficiency of -4.88 dB for both TE and TM polarization at 1550 nm, resulting in near zero polarization dependent loss.A 1-dB coupling bandwidth of 57 nm was obtained for TE polarization, whereas TM attained an even higher bandwidth of 69 nm.To the best of our knowledge, the SWGC design proposed in this thesis offers the best reported performance in bandwidth and polarization sensitivity.
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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) | 0.001 | 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".