Passive Fiber Array–Waveguide Alignment With Gap-Controlled Ridges
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Solution Overview
Problem
The alignment of optical fibers with photonic integrated circuits is challenging due to the need for precise alignment tolerances and the use of active alignment processes, which are costly and time-consuming, and passive alignment methods using V-grooves on the IC consume valuable space and suffer from axial misalignment issues.
Innovation Solution
A passive alignment method is employed using V-grooves in a fiber support substrate that mate with alignment ridges on the photonic IC, ensuring precise alignment without physical contact between the components, utilizing controlled dimensions and extra-array alignment features for larger arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If active alignment process is used to align optical fibers with waveguides, then alignment precision is improved, but manufacturing cost and time increase significantly
Solution Approach 1:
The patent implements preliminary action by pre-forming V-grooves in the fiber support substrate and pre-positioning alignment features on the photonic IC before the actual fiber assembly. This allows the alignment infrastructure to be prepared in advance, enabling rapid passive alignment during assembly without requiring time-consuming active alignment processes for each individual fiber connection.
Solution Approach 2:
The patent applies self-service through the passive alignment mechanism where the V-grooves and alignment ridges automatically guide and position the fibers relative to the waveguides without requiring external active alignment equipment or manual adjustment. The structure itself performs the alignment function through its geometric configuration, eliminating the need for complex active alignment systems.
2Ease of operation
If V-grooves are patterned and etched directly in the photonic IC to passively align fibers, then alignment process is simplified, but valuable real estate is consumed that could be used for optical device formation
Solution Approach 1:
The patent segments the alignment function from the photonic IC by placing the V-grooves in a separate fiber support substrate rather than etching them directly into the IC. This segmentation allows the IC to maintain its full area for optical device formation while the alignment functionality is provided by the external substrate that mates with the IC through controlled interfaces.
Solution Approach 2:
The patent introduces an intermediary fiber support substrate that bears the V-grooves and aligns the fibers, separating this alignment function from the photonic IC. The substrate acts as a mediator between the fiber array and the IC, providing the necessary alignment without consuming IC real estate. The controlled mating interface between the substrate and IC enables precise alignment while preserving IC area for devices.
3Ease of manufacture
If V-grooves are used for passive alignment, then alignment cost is reduced, but axial alignment control deteriorates over time due to bonding epoxy deformation
Solution Approach 1:
The patent extracts the alignment function from the bonding interface by using the V-grooves in the fiber support substrate to establish precise lateral alignment before bonding. The alignment is determined by the rigid geometric relationship between the V-grooves and the IC's alignment features, rather than relying on the flexibility of bonding epoxy. This extraction of the alignment determination from the bonding process eliminates the source of long-term axial misalignment.
Solution Approach 2:
The patent changes the critical alignment parameter from being dependent on bonding epoxy dimensions (which deform over time) to being determined by the rigid geometric parameters of the V-grooves and alignment ridges. The controlled dimensions of these features provide stable, time-invariant alignment that does not deteriorate with thermal cycling or aging, while still enabling cost-effective passive alignment.
Data Source
AI summary
Passive alignment and connection between a fiber array and a plurality of optical waveguides terminating along an edge of a photonic IC (PIC) is provided by a controlled mating between alignment V-grooves formed in a fiber array support substrate and extra-array alignment ridges formed beyond the extent of a waveguide array integrated within the PIC. The height and width of the alignment ridges are formed to engage with the alignment V-grooves upon mating of the fiber array substrate with the PIC, providing passive alignment while maintaining a physical gap spacing g between the components (ensuring the integrity of the passive alignment).