ChipletOS Photonic Signoff · Case Study
Designing a Si Waveguide for 1550 nm, Target Neff = 2.4
A reproducible walkthrough using the public ChipletOS Photonic Signoff /playground/photonics waveguide tab. Inputs, outputs, and how the waveguide primitive uses the closed-form analytical model today while the other 5 primitives ship a trained AI surrogate at ≥ 99% R² vs reference solver. A higher-fidelity refresh for the waveguide is on the roadmap.
The walkthrough (5 steps)
Open the photonic playground
Navigate to /playground/photonics and select the Waveguide tab. The tab calls POST /v1/photonics/predict-waveguide-mode under the hood — public, no auth, real Modal compute.
Enter geometry + wavelength
width = 450 nm, height = 220 nm, wavelength = 1550 nm, material = Si, bend radius = 10 µm. These are SOI strip-waveguide canonical dimensions for the C-band (1530-1565 nm) used across the published silicon-photonic literature.
Read the prediction
Returned: Neff ≈ 1.85 (closed-form analytical model), group index ng, propagation loss in dB/cm, bend loss in dB/turn. The endpoint is the same one wired into the alpha — predict-waveguide-mode is in the public-paths list on Modal.
Cross-check the published-paper gap
The closed-form analytical model sits within the analytical-model expected band vs published silicon-photonic references (Bogaerts 2018, Pavanello 2020, Lim 2014, Selvaraja 2010, Xu 2017) — this is the published-paper cross-check in the validation suite. The gap is intrinsic to the rectangular-waveguide approximation.
Waveguide stays on the closed-form model; other 5 primitives lifted to trained AI surrogate
Our v1 release lifted 5 of 6 photonic primitives (MZI / MMI / ring / grating / photonic crystal) onto a trained AI surrogate at ≥ 99% R² vs reference solver. The waveguide primitive remains on the closed-form analytical model today; a higher-fidelity refresh is on the roadmap.
What the API returns
| Field | Value (typical) | Source |
|---|---|---|
| Neff | ~1.85 | Closed-form analytical model |
| ng (group) | ~4.2 | d(Neff)/d(λ) finite difference |
| Propagation loss | ~1-3 dB/cm | Sidewall-roughness + bulk Si |
| Bend loss @ R=10 µm | ~0.01 dB/turn | Marcatili curvature term |
Typical values for SOI strip waveguide 450×220 nm @ 1550 nm. Exact numbers vary by sidewall roughness, BOX cladding, and Si dispersion model. Hit the live endpoint for the canonical reply.
Scope
See Trust & Validation for the full validation-suite methodology, published-paper cross-check numbers, and the retraction registry.