Fiber Array Coupler With Optical Windows for Passive Chip Alignment
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Solution Overview
Problem
Photonic chips with Through Silicon Vias (TSVs) face challenges in edge coupling due to their thin thickness, which restricts the creation of deep trenches for lens or fiber placement, and conventional edge coupling techniques are not applicable, necessitating a more efficient and cost-effective alignment method for optical components.
Innovation Solution
A fiber array unit (FAU) with alignment features, including optical windows and alignment protrusions, is used to passively align optical fibers with photonic chips, utilizing self-correcting alignment features and cured adhesive for secure coupling, allowing for precise alignment without active feedback, suitable for TSV-compatible photonic chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional edge coupling techniques are used with TSV photonic chips, then optical signal transmission is achieved, but the thin thickness of TSV chips prevents creation of deep trenches for lens or fiber placement, making conventional techniques inapplicable
Solution Approach 1:
Instead of placing fibers or lenses at the edge of the photonic chip (conventional edge coupling), the patent inverts the approach by placing the optical fiber at the center of the fiber array unit with the photonic chip coupled to its side. This inversion allows optical coupling without requiring deep trenches in the thin TSV chip substrate.
Solution Approach 2:
The patent introduces a fiber array unit as an intermediary component between the photonic chip and external optical fibers. This mediator enables optical signal transmission while accommodating the thickness constraints of TSV chips, as the fiber array unit provides the necessary structural support and alignment features.
2Manufacturing precision
If active alignment methods are used, then precise optical coupling is achieved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent incorporates preliminary alignment features (alignment protrusions and alignment receivers) during the manufacturing process. These features pre-establish the correct spatial relationship between fibers and the photonic chip, eliminating the need for complex active alignment procedures during assembly.
Solution Approach 2:
The alignment protrusions and alignment receivers are designed to automatically guide and position the photonic chip relative to the fiber array unit during assembly. This self-aligning mechanism eliminates the need for external alignment equipment or complex adjustment procedures, reducing both cost and complexity.
3Reliability
If wire bond based interconnection is used, then electrical connection is achieved, but peripheral bond pad space is depleted, limiting further interconnection density
Solution Approach 1:
The patent transitions from two-dimensional wire bond connections at the chip periphery to three-dimensional vertical interconnections through TSVs. This dimensional change allows electrical connections to pass through the chip thickness, freeing up peripheral bond pad space for optical coupling and increasing overall interconnection density.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables efficient and cost-effective passive alignment of optical fibers with photonic chips, overcoming the thickness constraints of TSVs and reducing manufacturing costs by eliminating the need for active alignment, while ensuring accurate optical coupling and high signal transmission performance.
Implementation Method 1
The optical window is disposed over the cured adhesive
Data Source
AI summary
Embodiments herein describe a fiber array unit (FAU) configured to optically couple a photonic chip with a plurality of optical fibers. Epoxy can be used to bond the FAU to the photonic chip. However, curing the epoxy between the FAU and the photonic chip is difficult. As such, the FAU can include one or more optical windows etched into or completely through a non-transparent layer that overlap the epoxy disposed on the photonic chip. UV radiation can be emitted through the optical windows to cure the underlying epoxy. In one example, the windows can also be used for dispensing epoxy. In addition to the optical windows, the FAU can include alignment protrusions (e.g., frustums) which mate or interlock with respective alignment receivers in the photonic chip. Doing so may facilitate passive alignment of the optical fibers in the FAU to an optical interface in the photonic chip.