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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 silica

0.75% 6 µm × 6 µm SSC @ 1550 nm

Low-contrast 0.75% Δ, 6 × 6 µm waveguide at 1550 nm. The weakly-guided 7.4 µm chip mode is expanded by a gentle segmented taper (duty 1.0 → 0.48) up to ≈ 10.4 µm to match SMF-28. Coupling loss is the mode-overlap integral against the fiber field: 0.057 dB (98.7%), down from 0.494 dB bare — well under the 0.2 dB target. Includes interactive estimator, mode-matching figures, full source code, and GDS 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.

 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.