A Scalable, Low-Loss Fiber-to-Chip Packaging Technique Using CO₂ Laser Fusion and Oxide Mode Converters
- deshna2
- Jun 23
- 2 min read
One of the major roadblocks in scaling silicon photonics for commercial applications is efficient, reliable fiber-to-chip packaging. Conventional approaches often suffer from high optical loss, complex alignment, and limited scalability. In this research, we explore a promising solution: CO₂ laser fusion splicing combined with strategically designed on-chip silicon dioxide mode converters.
The Packaging Problem
Photonic chips can achieve remarkable performance — but only if light can enter and exit efficiently. The challenge lies in the mismatch between standard single-mode fiber (SMF-28) and on-chip waveguides with sub-micron dimensions. This mode size difference leads to high insertion losses and limits manufacturability.
A Compact, Efficient Mode Converter
The research introduces an oxide mode converter, a silicon dioxide cantilever waveguide designed to create a smooth, low-loss optical transition. Simulations show that with optimized geometry total transmission losses can be reduced to as low as 0.5 dB.
Permanent Bonding via CO₂ Laser Fusion
Instead of using epoxy or physical fixtures, the proposed method uses a CO₂ laser at 10.6 μm to create a glass-to-glass fusion between the cleaved fiber and the oxide converter. This eliminates Fresnel reflections and improves both optical performance and mechanical stability.
Results include:
1.0 dB minimum coupling loss per facet
Broad 160 nm bandwidth (C-band)
±2.5 μm alignment tolerance, enabling automation and passive alignment.
Scaling Up: Multi-Fiber Packaging
This technique supports single-shot attachment of multi-fiber arrays while maintaining low variation in coupling loss:
2-fiber array: 1.1 dB
4-fiber array: 1.5 dB
8-fiber array: 1.4 dB (±0.2 dB variation across fibers)
Compared to edge coupling without mode converters, this approach improves coupling efficiency by up to 1.85 dB per facet.
Conclusion
This research shows that CO₂ laser fusion splicing, combined with oxide mode converters and integrated alignment features, offers a low-loss, scalable, and automation-friendly packaging solution for high-density photonic integration. It holds strong potential for applications in high-speed optical interconnects, sensing systems, and volume photonics manufacturing.
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