A Scalable, Low-Loss Fiber-to-Chip Packaging Technique Using CO₂ Laser Fusion and Oxide Mode Converters

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.

To learn more about us and our services visit www.photonectcorp.com, to dive deeper into more such research findings browse Scientific Text | Photonect.

Want to know how we can help you? Email us at info@photonectcorp.com.

---

Research Papers: 

• Fiber-to-chip fusion splicing for low-loss photonic packaging

• Fiber array to chip attach using laser fusion splicing for low loss