Optimized passive V-groove alignment for low-loss optical coupling in co-packaged systems

Efficient optical coupling between fiber and chip remains a critical challenge in silicon photonics, particularly for co-packaged optics (CPO) applications. This paper presents a novel passive alignment methodology using V-groove couplers that significantly enhances optical coupling efficiency. Through systematic optimization of three key parameters UV glue dispensing position, lid bonding location, and end separation control, air bubble formation is effectively mitigated at the fiber-chip interface. Compared to prior passive alignment method, this work improves optical efficiency by 50~70% while simplifying manufacturing complexity. The experimental results demonstrate an obvious improvement in coupling loss from 11.46 dB to 2.68 dB using the optimized process. Optical simulations validate that strategically incorporating index-matching material in the control of end separation markedly enhances light collection efficiency relative to air-gap conditions. This methodology provides a practical solution for high-performance, cost-effective optical coupling in next-generation CPO systems for data center and high-performance computing applications.