Dual Mechanical Alignment Features for Glass Waveguide–PIC Coupling
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Solution Overview
Problem
Existing passive mechanical mating features in silicon-based photonic integrated circuits suffer from dimensional variations, leading to undesirable coupling losses due to misalignment between glass substrates and silicon photonic integrated circuits, particularly affecting vertical and lateral alignment.
Innovation Solution
Implementing dual alignment features, including alignment protrusions and mating protrusions, to facilitate precise registration of waveguides between an optical interposer and a PIC die, allowing for lateral and vertical alignment, reducing misalignment sensitivity by transforming dominant Y-axis misalignment into X-axis misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If passive mechanical mating features (V-grooves) are used for alignment, then mechanical registration is achieved, but dimensional variations cause misalignment and coupling loss
Solution Approach 1:
The alignment system is segmented into two independent functional components: alignment protrusions for vertical axis alignment and mating protrusions for lateral axis alignment. This segmentation allows each component to specialize in one dimension, reducing the impact of dimensional variations in the other dimension and thereby improving overall alignment precision while reducing coupling loss.
Solution Approach 2:
The invention transitions from a single-axis alignment approach to a dual-axis alignment approach by adding alignment protrusions that operate in the vertical dimension (Y-axis), complementing the existing lateral alignment (X-axis) provided by V-grooves. This dimensional expansion transforms the alignment problem from one-dimensional to two-dimensional, improving overall registration precision.
2Ease of operation
If V-grooves are used for both vertical and lateral alignment, then mechanical registration is achieved, but Y-axis misalignment sensitivity increases due to dimensional variations
Solution Approach 1:
The alignment function is segmented between two distinct features: V-grooves handle lateral alignment while alignment protrusions handle vertical alignment. This segmentation isolates the Y-axis alignment function to a dedicated feature with controlled tolerances, reducing sensitivity to dimensional variations in the V-groove dimensions.
Solution Approach 2:
Alignment protrusions act as intermediary elements that mediate the vertical alignment between the optical interposer and PIC die. These protrusions provide a controlled mechanical interface that reduces the direct sensitivity to Y-axis misalignment by transforming the alignment mechanism.
3Reliability
If tighter tolerances are applied to alignment features, then coupling loss is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
By segmenting the alignment function into specialized protrusions and grooves, the invention allows for relaxed tolerances on individual features while maintaining overall alignment precision. Each feature can be manufactured with standard tolerances rather than tight tolerances, reducing manufacturing complexity while achieving reliable coupling.
Solution Approach 2:
The invention changes the geometric parameters of the alignment features by introducing protrusions with specific dimensional relationships (e.g., height, width, spacing) that inherently provide alignment functionality. These parameter designs allow for robust alignment with standard manufacturing tolerances, avoiding the need for overly tight tolerances.
Data Source
AI summary
An apparatus includes an optical interposer including a first surface, a first mating protrusion extending outwardly from the first surface, and two or more alignment protrusions extending outwardly from the first surface. The first mating protrusion is to be partially disposed within a first recess formed in a second surface of a photonic integrated circuit (PIC) die when the first surface of the optical interposer opposes the second surface of the PIC die and respective distal surfaces of the two or more alignment protrusions contact the second surface of the PIC die. A first portion of an outer surface of the first mating protrusion is to contact a first side wall of the first recess and a second portion of the outer surface of the first mating protrusion is to oppose a second side wall of the first recess such that a second space is to be defined therebetween.