Optical Assembly Using Cylindrical Rods for Fiber Alignment
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Solution Overview
Problem
Current optical transceivers face challenges in aligning optical fibers with photonic integrated circuit (PIC) waveguides for mass production due to high coupling loss and alignment tolerance requirements, particularly with silicon photonics technology, where precise alignment of optical fibers within ±3 μm is time-consuming and complex.
Innovation Solution
The proposed optical assembly includes a substrate with U or V-grooves and cylindrical rods to align the PIC chip with the optical fiber, utilizing submicron process accuracy and dimensional precision to achieve the required optical alignment, and incorporates through silicon vias for high-speed electrical integration, enabling a compact and low-profile design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If reverse nanotaper or mode converter is implemented to reduce optical coupling loss, then coupling loss is reduced (1.2 dB/facet for TE mode), but alignment tolerance requirement becomes stricter (±3 μm 3 dB alignment tolerance)
Solution Approach 1:
A cylindrical rod with precisely controlled length is introduced as an intermediary component between the substrate and PIC chip. This rod acts as a spacer that defines a specific vertical offset, enabling the coupling waveguide to be aligned with the optical fiber without requiring tight lateral alignment tolerances. The rod mediates the positioning relationship between components, reducing the impact of lateral misalignment on coupling loss.
Solution Approach 2:
The invention transitions from relying primarily on lateral alignment (X-Y plane) to utilizing vertical positioning (Z-axis) through the cylindrical rod spacer. By controlling the vertical offset between the PIC chip and substrate, the coupling alignment is achieved in a different dimensional space, thereby relaxing the stringent lateral alignment tolerance requirement while maintaining low coupling loss.
2Loss of energy
If precise alignment of optical fiber within ±3 μm is performed for mass production, then optical coupling loss is reduced, but the alignment process becomes time-consuming and complex
Solution Approach 1:
The cylindrical rod is pre-positioned on the substrate before the PIC chip is attached. This preliminary action establishes a predetermined vertical offset that guides the subsequent alignment process. By preparing the spacer component in advance with precise dimensions, the actual assembly process benefits from reduced alignment time and complexity, as the vertical positioning is already determined by the rod's length rather than requiring complex adjustment during assembly.
Solution Approach 2:
The cylindrical rod structure provides self-aligning functionality through its precise dimensional control. When the PIC chip is placed on the substrate, the rod automatically defines the vertical spacing and facilitates alignment of the coupling waveguide with the optical fiber. This self-service mechanism reduces the need for complex external alignment tools and procedures, thereby decreasing alignment process time.
3Manufacturing precision
If cylindrical rod with controlled length is used to define vertical offset, then alignment accuracy is improved, but device complexity increases
Solution Approach 1:
The cylindrical rod serves multiple functions simultaneously: it acts as a mechanical spacer to define vertical offset, provides alignment reference for waveguide-fiber coupling, and serves as a structural support element. By consolidating these functions into a single component, the invention achieves high alignment accuracy without proportionally increasing device complexity. The same rod structure that provides precise spacing also facilitates alignment, eliminating the need for separate alignment features.
Data Source
AI summary
Various embodiments may provide an optical assembly. The optical assembly may include a substrate with a first and a second grooves, and a photonic integrated circuit chip with a coupling waveguide, a first and a second grooves. The optical assembly may further include a first and a second cylindrical rods held by the respective grooves of the substrate and the photonic integrated circuit chip. A portion of the first rod and a portion of the second rod define a vertical offset between the photonic integrated circuit chip and the substrate to align the coupling waveguide with an optical fiber.