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SSC (spot size converter)

Spot-size converter designs that expand a small silica-waveguide mode to match an SMF-28 fiber. Each entry below is a specific platform/geometry with its own GA + 3D-BPM result, source code, and downloadable GDS.

1301 nm · 2% Δ silica

2% 4.5 µm × 4.5 µm SSC

Segmented (digitized) inverse taper: chip waveguide 4.5 × 4.5 µm solid → 8.5 µm-wide low-duty SMF facet. Pitch / width / duty / segment count optimized by a genetic algorithm driving a Python split-step 3D BPM. Best coupling loss 0.246 dB (94.5%) at 1301 nm. Includes interactive estimator, result figures, full source code, and GDS downloads.

 1301 nm · 2% Δ silica

2% 4.0 µm × 4.0 µm SSC

Segmented mode-expanding taper on the same 2% Δ platform, smaller 4.0 × 4.0 µm solid chip → low-duty SMF facet at 1301 nm. Pushing the facet mode near cutoff (duty ≈ 0.18, ~10 µm) matches the SMF-28 field; coupling loss by the mode-overlap integral is 0.115 dB (97.4%), down from 2.4 dB bare — below the 0.2 dB target. Includes interactive estimator, mode-matching figures, full source code, and GDS downloads.

 1550 nm · 2% Δ silica

2% 4.5 µm × 4.5 µm SSC @ 1550 nm

Same 2% Δ, 4.5 × 4.5 µm solid chip → 8.5 µm-wide low-duty SMF facet, re-optimized for the 1550 nm C-band (SMF-28 MFD ≈ 10.4 µm). Pitch / width / duty / segment count optimized by a genetic algorithm driving a Python split-step 3D BPM, confirmed by a 6-seed sweep. Best coupling loss 0.326 dB (92.8%) at 1550 nm vs 0.542 dB for the reference. Includes interactive estimator, result figures, full source code, and GDS downloads.

 1550 nm · 0.75% Δ · DRC · 3D-BPM

0.75% 6 µm × 6 µm SSC @ 1550 nm — DRC ≥ 0.6 µm, 3D-BPM

Low-contrast 0.75% Δ, 6 × 6 µm waveguide → SMF-28 at 1550 nm, made manufacturable: a solid 6 µm lead-in feeds a segmented taper (pitch 3.2 µm, duty 0.80 → 0.48, gap-then-tooth) so every tooth (≥ 1.54 µm) and gap (≥ 0.64 µm) clears the 0.6 µm minimum linewidth/gap rule. The coupling loss is cross-checked by three methods — mode-overlap (0.055 dB), a rigorous local-mode EME device loss 0.082 dB, and 3D-BPM field propagation — within the 0.1 dB target, down from 0.49 dB bare. Includes the EME + BPM figures, a DRC-clean device GDS, source, and downloads.

 1550 nm · Si₃N₄ → UHNA3

Si₃N₄ (1.5 × 0.3 µm) → UHNA3 inverse-taper SSC

High-contrast Si₃N₄ (n≈2.0) core in SiO₂ (3 µm BOX / 5 µm top clad) coupling to a UHNA3 ultra-high-NA fiber (MFD 4.1 µm) at 1550 nm. Instead of widening, an inverse taper narrows the core to a 0.23 µm tip so the mode delocalizes into the oxide and matches the fiber. Coupling loss by a finite-difference mode-overlap solve: 0.42 dB (90.8%), down from 5.0 dB bare. Includes interactive estimator, mode figures, full source code, and GDS downloads.

 1550 nm · 2% Δ silica

2% 3 × 3 µm SSC @ 1550 nm

Small 2% Δ GeO₂-silica 3 × 3 µm core → low-duty SMF facet at 1550 nm. A mode-expanding segmented taper reaches 0.15 dB (96.6%) coupling to SMF-28, down from 2.6 dB bare. The thin 3 µm core makes the expanded facet mode elliptical, so a < 0.1 dB target is not reachable with a lateral SSC — the page explains why and the routes that would (larger/squarer core, UHNA fiber, or a vertical taper). Mode-overlap method; interactive estimator, figures, source, GDS.

 1550 nm · 2% Δ silica

2% 4 × 4 µm SSC @ 1550 nm

2% Δ GeO₂-silica 4 × 4 µm core → low-duty SMF facet at 1550 nm. The slightly thicker core gives a rounder expanded mode than the 3 µm case: a mode-expanding segmented taper (duty 0.95 → 0.20, ~11 µm facet mode) reaches 0.114 dB (97.4%) coupling to SMF-28, down from 2.46 dB bare — comfortably below the 0.2 dB target. Mode-overlap method; interactive estimator, mode-matching figures, source, GDS.

 1301 nm · 1.5% Δ silica

1.5% 5 µm × 5 µm SSC

Segmented (digitized) inverse taper: chip waveguide 5 × 5 µm solid → 8.5 µm-wide low-duty SMF facet. Pitch / width / duty / segment count optimized by a genetic algorithm driving a Python split-step 3D BPM. Best coupling loss 0.264 dB (94.1%) at 1301 nm. Includes interactive estimator, result figures, full source code, and GDS downloads.

 1301 nm · 1.5% Δ silica

1.5% 4.5 µm × 4.5 µm SSC

Segmented mode-expanding taper on a 1.5% Δ platform, 4.5 × 4.5 µm solid chip → low-duty SMF facet at 1301 nm. Pushing the facet mode near cutoff (duty ≈ 0.24, ~9.8 µm) matches the SMF-28 field; coupling loss by the mode-overlap integral is 0.098 dB (97.8%), down from 1.7 dB bare — below the 0.2 dB target. Includes interactive estimator, mode-matching figures, full source code, and GDS downloads.