Photonic Circuit Coupling Structure for Alignment Tolerance
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Solution Overview
Problem
Existing photonic circuit coupling methods, such as evanescent wave and end-to-end coupling, face challenges with alignment errors and coupling efficiency, particularly in achieving reliable and reproducible coupling between photonic circuits made from different materials like III-V semiconductor and silicon.
Innovation Solution
A photonic circuit structure featuring a main waveguide and four secondary waveguides with specific geometric arrangements, including parallel and diagonal orientations, to enhance evanescent wave coupling and improve tolerance to alignment errors, ensuring consistent coupling coefficients and reduced light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If evanescent wave coupling is used to achieve low light energy loss, then coupling efficiency is improved, but manufacturing precision and assembly difficulty increase due to the need for precise distance control between waveguides
Solution Approach 1:
The coupling structure is divided into multiple secondary waveguides (at least three) arranged around the main waveguide, with each secondary waveguide contributing to the overall coupling. This segmentation allows the system to achieve robust coupling through collective interaction rather than relying on a single critical interface, thereby reducing the impact of precision errors in any individual waveguide positioning.
Solution Approach 2:
The secondary waveguides are arranged asymmetrically around the main waveguide rather than in a symmetric configuration. This asymmetric arrangement, where waveguides are positioned at different orientations and distances, creates multiple coupling paths that are not equally sensitive to alignment errors, thereby improving overall tolerance to manufacturing variations and reducing the strict precision requirements.
2Ease of manufacture
If butt coupling is used for ease of implementation, then ease of manufacture is improved, but coupling efficiency becomes uncertain due to sensitivity to alignment errors
Solution Approach 1:
The invention introduces evanescent wave coupling as an intermediary mechanism between the main waveguide and multiple secondary waveguides. This intermediary coupling method allows optical energy transfer without direct physical contact or precise end-to-end alignment, thereby maintaining ease of manufacture while significantly improving coupling efficiency reliability through the distributed nature of the coupling interaction.
Solution Approach 2:
The coupling structure transitions from one-dimensional end-to-end coupling to a two-dimensional or three-dimensional arrangement where multiple secondary waveguides surround the main waveguide. This dimensional change creates multiple coupling pathways simultaneously, making the system less sensitive to alignment errors in any single direction and thereby improving reliability while maintaining manufacturing simplicity.
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
The proposed structure enhances alignment tolerance and coupling efficiency by maintaining consistent coupling coefficients and reducing light loss, making it more robust and reliable for photonic circuit integration.
Implementation Method 1
each secondary waveguide having a first portion substantially parallel to the main waveguide arranged in the vicinity of the main waveguide so as to achieve evanescent wave coupling between the main waveguide and the secondary waveguide
Data Source
Figure 1A~2D
Figure 3A~4
Figure 5A~5D
AI summary
The invention relates to a photonic circuit (C1) comprising a coupling structure to an external device, this structure comprising a main waveguide (WP1) and at least two secondary waveguides (WS11, WS12, WS13, WS14), each secondary waveguide (WS11, WS12, WS13, WS14) having a first portion substantially parallel to the main waveguide (WP1) arranged in the vicinity of the main waveguide (WP1) so as to achieve evanescent wave coupling between the main waveguide (WP1) and the secondary waveguide, the first portion extending into a second portion, an end opposite to the first portion of which defines a coupling face of the secondary waveguide, opening at the level of an external face of the circuit.