Curved Fiber Assembly for Low-Error Photonic Chip Edge Coupling
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Solution Overview
Problem
The warpage or curvature of photonic integrated circuits (PICs) due to fabrication processes or bonding with electronic integrated circuits (EICs) leads to misalignment and reduced optical coupling efficiency between waveguides and optical fibers, particularly in edge-coupling configurations.
Innovation Solution
Customized alignment arrangements and mechanical bending of optical fiber substrates to match the curvature of warped PICs, including tailored fiber positions and grooves, and the use of microlens arrays for improved optical coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optical fibers are directly aligned with waveguides on a flat substrate, then alignment simplicity is maintained, but alignment precision deteriorates due to PIC warpage
Solution Approach 1:
The fiber substrate is intentionally designed with a curved surface that matches the warpage profile of the PIC. This curvature compensation ensures that the fiber facets remain optically aligned with the waveguide facets despite the PIC's warped geometry, thereby maintaining high alignment precision without requiring complex active adjustment mechanisms
Solution Approach 2:
The fiber substrate incorporates localized curvature variations that correspond to the specific warpage pattern of the PIC. By tailoring the curvature profile to match the local deviations of the warped PIC surface, the alignment arrangement achieves high precision while keeping the overall structure relatively simple
2Reliability
If the fiber substrate is bent to match PIC curvature, then optical coupling efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The fiber substrate's curvature parameter is adjusted to match the PIC's warpage characteristics. By changing the substrate's geometric parameters (curvature radius, curvature profile) during manufacturing or post-processing, the optical coupling efficiency is enhanced while using standard fabrication techniques
Solution Approach 2:
The fiber substrate is pre-formed with the required curvature profile before the bonding process. This preliminary shaping ensures that when the fibers are bonded to the substrate, they are already in the correct curved configuration to match the PIC warpage, simplifying the overall manufacturing process
3Manufacturing precision
If uniform fiber positioning is used, then manufacturing simplicity is maintained, but alignment accuracy deteriorates due to warpage-induced misalignment
Solution Approach 1:
Instead of uniform positioning, the fiber substrate employs a curved surface profile that compensates for PIC warpage. This curved geometry maintains consistent optical alignment across all fiber-waveguide pairs despite the underlying warpage, achieving high alignment accuracy without requiring individual fiber adjustment mechanisms
Data Source
AI summary
The disclosed technology is generally directed to methods and structures for edge coupling between waveguides of a photonic integrated circuit (PIC) chip and an optical fiber array. The PIC may have a warpage caused by the PIC formed on a substrate. Some methods are directed to bending the optical fiber array to provide a bent optical fiber array having a curvature or warpage generally tracking that of the PIC chip. Some methods are directed to providing the bent optical fiber by application of mechanical force on the optical fiber array. Some methods and structures are directed to fabricating the optical fiber array having fiber core regions rotationally aligned with respect to an optical fiber mount to position centroids of the fiber core regions in a flat plane parallel to a major surface of the optical fiber mount.